Mongoose Envoy Update – Cargo Deck 3.0

When I originally used a double-kick longboard deck to make an XL cargo carrying top for my Mongoose Envoy project, its 33″ (84cm) length and 10″ (25cm) width seemed really big.  Considering I was coming from a world of ordinary bike racks on normal-wheelbase bikes, it was quite large.

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Deck 1.0, shortly after installation. I try to avoid the word “festoon” to describe a bike build so those two little bags in back went away soon afterwards.

The XL deck worked *splendidly*.  I had no complaints whatsoever, and I could have left it like that forever.  However…

The board, by virtue of its 33″ length, only used 4 of the 5 available rows of M5 mounting bosses.  So I had definitely left some available space on the table.   In a perfect world, I would have found a longer version of the same board:  Say a 40″ double-kick.  But alas, at the time, I couldn’t find one.  I also could not find another board that had this same 10″ width.  Everything else was more narrow.  But I could get close with what became Deck 2.0: a 40″ x 9.75″ kicktail longboard.

It installed easy enough.  I painted it with Rustoleum truck bedliner to pebble the surface just right so it held onto gear a bit.  I used the same inverted grub-screws for drill guides like I describe in the Deck 1.0 post.   And the rack was now long enough so it used all 10 mounting points on the frame.  It couldn’t be more solid – the board is 8 layers of Canadian maple – and makes a sturdy handle I can use to pick the bike up and move it around from the rear.

And… its 40″ long.  With that solid center mount kickstand, its handy to have a coffee table with you wherever you go.  From a cargo standpoint I could easily net down a 3-foot duffel bag on top and still have room to spare.

Still, It didn’t work out quite the way I planned.  I thought I wanted to move the rack further forward so I could mount gear under the seat.  So I did that and the idea was to take up the otherwise wasted space just behind the seat.  But once I had it set up, I found the space effectively unusable.  I needed to keep some room back there for the Thudbuster to flex as part of its normal duty cycle, and my legs hit whatever was jacked up all the way to the front.

I also missed the front kick on Deck 1.0, which provided a natural slope to keep gear from sliding forward under hard braking.  As a substitute threaded a couple of M6 bolts directly into the M5 holes (no fixing nuts needed) that existed for the nonexistent trucks. These held down a simple 50-cent L bracket wrapped in my favorite padded rubber mastik tape.  It worked but in the end I removed it for aesthetic reasons. 

Lastly, I mounted the board just a hair too far forward, and occasionally I brushed it with my legs during the pedal stroke.  Not a big deal unless you are a perfectionist. I didn’t want to redrill the holes so I could move it back. It was a minor imperfection. So I left the board on for several months and it worked great.

But I did acquire a 44″x9″ kicktail longboard from Magneto, with the intention of using it on the back of a planned Surly Big Fat Dummy build.  That plan went away, and the 44″ board had no home… so what the hell lets put it on the Envoy.

While I was at it, I decided to make a couple of changes.  First of all, the Magneto board comes with an aggressive, highly abrasive grip coating on it.  I took an orbital sander and smoothed it down some so it would not potentially wear thru duffel bags and bits I’ll have netted down on top of it.

Next, I painted it with the same Rustoleum truck bed coating spray.  This took a little more of the harshness off the grip coating and gave the deck a tough finish.  I also decided to two-tone it with some medium gray paint on the underside.  It turns out this is totally invisible unless you are laying on the ground looking up at it.

Also, instead of re-using the 25mm post spacers, I bought new ones 40mm tall. These required longer 75mm bolts.  Having used the rack already for several months with 25mm between deck and frame, I wanted more room to move my hands in and out attaching/detaching net hooks, passing cinch straps thru etc.

It came out great.  This Magneto board is a sandwich of bamboo and maple so it has a touch of flex to it. This made  bolting to the somewhat uneven frame easier.  Its still rock solid despite the now 4″ longer tail out the back, which I do not notice from a convenience standpoint (its not too long, which I worried about).  The 40mm spacers are an absolutely perfect height to let me get my hands in there without being so long they compromise the solidity of the mount.

The board has a front kick, but it turns out it can’t easily be used, for the same reason I couldn’t use the front few inches on the 40″ deck. However it is slightly narrower than the shorter board so even though it is just as far forward, I no longer hit it with my legs.

As a gear-stop/bumper, I wanted something a bit more substantial than the half-assed L bracket I used on the shorter board, so I used a couple of the leftover 25x13mm M5 spacers, plus some 10x10mm spacers I had in my parts bin, to create some ‘electrode’ stanchions fore and aft.  With the large area washers at top, they either provide a bumper for gear stowed on the deck, solid purchase for a hook, or a place for my net to grab onto in the very back. Silicone grip scraps fit right over them to ensure the edges of the top washer don’t bite into my gear.

The two forward stanchions are extended from the deck mounting holes and go all the way thru to the frame.  They use 110mm M5 bolts.  The two in the rear use the rearmost holes drilled for the trucks. These use matching countersunk bolts and finishing washers like those used with all the other mounting hardware.

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A bit of scrap silicone handlebar grip tucks under the rear stanchions to provide a smooth, grippy place for my net to glom onto. You can stretch the net all the way back and over the kicktail, too.

Compare this pic above to the 40″ board and its clearly longer, but functionally, the increased length is no bother.  If I had to fit the bike on a train or bus then this is not the best solution.  At some point, if I need some extra carrying space out back, its available.  At present, I have an extended amount of space for my round 40″ duffel.

… and a bigger coffee table.

Mongoose BBSHD Update: Musical Chainrings

It seems inevitable.  When I build a bike, I go through front chainrings trying to get the gearing just to my liking.  My Mongoose Envoy build has pretty much set the world record for tweaks in this regard.  But gearing wasn’t the problem so much as chain alignment.  Alignment is one of the most talked about issues with mid drives and up to this point I have not had to work too hard to get it right.  This build, not so much but I think I finally got it (like $350 later).

While dealing with this I have fooled around with three different sets of crankarms (160’s, 170’s and 175’s).  Not the subject here so if you notice the different crankarms in the pics, I am ignoring them on purpose.

The Right Tool For The Job

The Mongoose build is a first for me in many ways.  One thing in particular:  the BBSHD fits the frame really well.  Its a 68mm bottom bracket with absolutely zero chainstay obstruction for the secondary housing.  So I can butt the motor right up against the bottom bracket.  Further, its a lonnnng way back there so chain alignment and misalignment – an inevitable concern with an HD build – is a lot more forgiving since the angles are gentler thanks to the longer reach.  On this bike, if I want I can even forego the offset non-drive side crankarm and the pedals are still easily centered under me.  So the HD is a great fit here.

About That Job…

The Mongoose is a cargo bike.  So it hauls heavy stuff (usually groceries).  It has a secondary job as an unladen backup commuter, but primarily it needs to be optimized to start from a stop while the entire system – with me – weighs 400-450 lbs (180-204kg).  I have really loaded it that heavily so this is not a theoretical exercise.  So I want a big-ish chainring for when I am pedaling fast and light, and still need to be able to get to the big cogs in the back for when I am loaded up and chugging along like a two-wheeled freight train.

Plan A:  Luna Eclipse (42T)

The Luna Eclipse is one of the best BBSHD chainring setups on the market, with a unique ‘wicked’ tooth profile meant to eliminate the possibility of a chain drop under extreme use.  It also has the most extreme internal offset of any chainring option.  This will do the most to overcome the grief visited upon the BBSHD builder by that drive’s secondary housing sending the chainring way out to right field.

Its also gorgeous.  The gunmetal finish I chose matched beautifully with the dark grey frame.  Unfortunately 42T (which is the standard for full-offset chainrings as any smaller and you can’t clear the secondary housing) was not large enough to keep me from clown-pedaling when riding the bike as a commuter.  There was another problem:  Chain alignment.  Running that smaller 42T ring with the smallest rear cog resulted in, after only a few weeks, a whole lot of wear on the inside.  This is why mid drive builds demand the most out of the builder in terms of thinking things thru.  Time for Plan B.

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Its not ruined yet, but its lifespan sure has been shortened.  this was only a couple hundred miles of wear.

The Eclipse is a proprietary chainring platform, but fortunately other sizes are available.  the largest of which is what I tried next.

Plan B:  Luna Eclipse (48T)

So Plan B was to swap in a Luna 48T ring onto the Eclipse center section to fix the clown pedaling, and to stay the hell off the 12T small rear cog to deal with the alignment issue (I am using a welded together steel cluster for durability and the 12T is alloy and not a part of the welded cluster, so its better to stay off it for the sake of longevity anyway).  I thought that 48T/14T on this bike was the perfect sweet spot.  A small front ring is best when its on cargo duty, and a large one is best when its a commuter.  48T, when used in conjunction with upshifts, gave me pretty much everything I needed.

Pretty much but not everything.  First of all, remember the deep offset of the Luna ring?  It moves the chain inboard 24.8mm which *usually* eliminates the damage the BBSHD does to chain alignment.  Not on the Mongoose, whose narrow bottom bracket effectively papers over all of the sins committed by the motor (at this time I had not yet fully figured this out).  So, as I found with the 42T ring, it was inset too far, even when I stayed off the smallest cog.

So Plan B helped, but it didn’t solve the problem.  After only a couple weeks (I am now checking carefully and frequently) I saw the beginnings of the same wear on the inside of the chainring.  Like the 42T, I had to retire this thing fast so I could use it on some future project.

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Not as bad as the 42T, but still bad.  Both this one and the 42T looked perfect on the other side.

Sidebar: A mid drive chain powered by a 1500w motor is a chain saw when it comes to components rubbing against it.  That is just a reality of a mid drive and you have to deal with it as part of your design/build process.  When you get it right, you are golden for thousands of happy miles.  Get it wrong and you are sawing thru chainrings and cogs like nobody’s business.

Plan C: Lekkie Bling Ring (46T)

So now what?  42T was too small.  48T was more or less just right.  And the chainring offset that lets me use the inner cogs at great alignment still needs to be reduced or I can’t use anything but the lower gears.  Lekkie has a Bling Ring available in 46T.  It has the same internal offset their 42T ring has and, since I use them on two other bikes I know they are top quality.  At 18.3 mm its offset is quite a bit less than the Luna.  So I got a 46T.  I also added a 2mm spacer underneath it, further reducing the chainring offset to 16.3mm.  That is a whopping 8.5mm less than before so I hoped I would be good on the smaller outer cogs and still let me use the big inners.

And, pretty much, it was.  Chain alignment didn’t seem to be much of an issue, although it still wore down a bit more on the inside.   I was also able to shift up to the biggest cogs in the rear for very low gearing options.  Those are important on a full cargo load and if I am dealing with hills.

But… I flat out missed that 48T high gear for commuting.  And I was still seeing – very slight but noticeable – wear on  the inside of the chainring teeth from the chain, which was still visibly angling outboard a fair distance.

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This one was on for a few months and had 8.5mm less offset.  But it still shows signs of premature aging.  This was undesirable but livable.

I decided to try an extreme option I had not previously considered.  But on this bike, where all of the normal chainring offset stuff doesn’t seem necessary, it might actually work.

Plan D: Luna 130 BCD Adapter and Wolf Tooth 48T Ring

BBSHD chainrings are generally all proprietary to the platform.  Not so in the cycling world, where chainrings are universal, needing only to match the proper Bolt Circle Diameter for the chainring bolts.  Match the BCD between crankset and chainring and you are good to go.  There are adapters out there in the world that allow a Bafang motor to use standard 104mm and 130mm BCD chainrings.  The problem is they don’t give you anywhere near as much inward offset.  But given my experience so far, maybe I can live with that.  They should fix my alignment on my ‘commuter’ cogs, but will I still be able to use my ‘cargo’ cogs?

In addition to the LunaCycle 130 BCD adapter, I also chose the Wolf Tooth Drop Stop chainring as those rings are best-in-show for this sort of thing on a mid drive.  Attachment to the adapter was a little different than the usual chainring-to-crank operation in that its backwards.  The chainring goes bolts onto the inside.  I was able to play some games to good effect:  I reversed the chainring so it is logo-side-inward.  Not as pretty, but doing that lets me take advantage of the countersunk bolt holes on what is normally the outboard side.  The countersinking let me mount a bolt so it is almost flush with the ring, which in turn is butted up almost on top of the secondary motor housing.  With the countersinking it now has plenty of clearance.

Plan D Results

FINALLY.  Everything is working right.  The reduced chainring offset means my 14T cog (still not using the 12T for the reliability issues mentioned above) lines up straight back.  This outboard shift did affect my inner cog alignments but I can still get to all of them but the biggest 32T.  I’m comfortable with the angles on all but the second-largest 30T for long term use, and in a pinch, that 30T will work fine.  I just don’t want to stay on it for a week.  So this 9-speed is now a 7-speed and as DIY mid drives go thats still better than a lot of builds can manage.

And worth mentioning, like a lot of what they do, the CNC-machined Luna adapter is freaking gorgeous, and very precisely manufactured.  So much so it really stands head and shoulders above another adapter I got my hands on and was able to compare it directly to.

Honorable Mention: USAMade 130 BCD Adapter

I was surprised at how well this worked and how nicely it was made.  The part only cost me $29.99 on Amazon.  Still, it was Made in USA, well machined and rock solid.  The only things I didn’t like about it was the fact it was machined a bit too heavily, which meant it placed the chainring a millimeter or two further outboard than was necessary, and in this game millimeters count.  Further, as you can see above I was able to reverse the WolfTooth ring and take advantage of the bolt head countersinks.  That didn’t work with this part as USAMade countersunk the outside edge of their part, which made the bolts too long to allow my trying the same trick on the inside, where I needed it.  For a different build it might work fine so I am keeping it for my parts pile.

As for the Stone chainring seen on the USAMade adapter (scroll up to the title image at the top of the page), thats a Chinese Special that ran less than the godawfully expensive Wolf Tooth.  Its noticeably lighter in construction than the WT and I’m not sure I am sold on the tooth profile.  This ring will sit in my parts pile waiting in the wings as an emergency replacement.

Great Big Bags (an important afterword)

Some time ago I made a post about Big And Cheap: DIY Cargo Bike Bags.  On that post I noted on the build sheet this last item:

Therm-a-Rest Classic Foam Pad        Amazon   29.95

And then never mentioned another word about it.  I still ignored it in the Cheap DIY Cargo Bags: Update follow-on post.

Oops

So, that item is actually sort of a big deal for these bags.  Why?  Because the padding lines the inside of the otherwise floppy ol’ canvas parachute bag and gives it a soft but firm structure.  It also of course pads the interior so your carton of eggs stands a better chance of making it home in the same number of pieces it started out in at the grocery store.

Without further ado:  Here’s a look at the end result:

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And here’s what it looked like before I took a knife to it:

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This is a “Therm-a-Rest RidgeRest Classic Foam Camping Sleeping Pad” in its Large size, which is 77″ long by 25″ wide.  The important measurement is the width:  25″.  Thats only 1″ wider than the measured 24″ width of the Rothco Parachute Bag we are using for this project.  In actual practice, stuffing it into the bag, the width is perfectly sized to the bag.

What about length?  Well, I found all you have to do is cut one of these sleeping pads in half, widthwise.  This will give you two 25″ wide by 38.5″ long pieces.  That 38.5″ is pretty much perfect insofar as lining three sides of the bag (rear, bottom and front face).

Having this sturdy but padded liner inside the bag, you can pile stuff on inside and the bag retains its squared off shape.  Further, when using the straps to lift up the bag off the lower rack, the liner allows those straps to carry some of the bag’s weight without flopping down onto the rack in its center.  Without the pad as a liner, none of that good stuff happens.

Here are a couple of shots of the bags, empty, and folded up.  Here again the pad on the inside gives these monstrous panniers shape so they can fold up and stay neat/tidy.

 

You can see from the pics above how useless those big straps would be without some sort of internal structure (also notice these are still the early 2″ straps).  That internal padding is crucial to making these bags work.  Now lets look at the bags loaded:

 

See that grocery cart in the background?  Well, it was mostly full and now its loaded up into the Mongoose.  Filling both the 25L (each) front panniers and these almost 77L bags in the rear.  Those bags are still well-loaded but as you can see by no means full.   They are loaded mostly with 2L juice bottles, a case of 500ml coca cola bottles and a slew of soup cans and such.  With all that weight, the straps can still hold the bags up and partially off the lower rack and retain their shape (although I did add a third 2″ strap in the center to supplement the two outer 3″ straps… this load was *heavy*).

So… thats why you need the pads.

Finally, what do these bags look like when truly, fully filled out?  Recently I took some old XL sleeping bags out of the house.  A city park was midway to the drop off point and I pulled over for a quick set of pics.

 

 

Heat Sinks For the BBSHD Ebike Mid-Drive

Not so long ago, someone asked whether heat sinks had ever been applied to the BBSHD with any success.  This reminded me to document what I have done for posterity’s sake.  I turned a motor whose casing temp was 165 degrees fahrenheit and reduced it to 135.  Still pretty warm but a 30-degree reduction nonetheless.

Whats The Problem?

Well, there isn’t one, actually, unless you are really beating on the drive.  Even then its only going to be an issue under specific circumstances.  The fact is, these motors are pretty well built and they generally don’t suffer from heat issues.  Unless…

  • You are running the motor on the street, say, on long city blocks, and either laying into a high level of continuous pedal assist, or the throttle

AND

  • You are running the motor on a 52v battery, in its max 30 amp configuration

AND

  • It is REALLY hot outside.  We are talking 100-110 degrees fahrenheit (38-43 Celsius).

So, we’re talking summer commutes or midday shopping runs in Central California on streets like this, where my bike – which I geared for proper pedaling at 28+ mph – is putting out 100% power from the motor, continuously in between stoplights… and its a long way to the next light.

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I’m riding in the Class 3 lane on the street, not the Class 1/2 shared use path just to the right

Put all of these things together and now you have a motor that gets hot.  How hot?  My Stormtrooper – A rescued Motobecane Lurch frame with carbon fiber 90mm deep dish wheels, 52v 30a BBSHD, and a Luna Lander front air fork – was seeing motor casing temps of 165 degrees.  Yikes.

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The Stormtrooper – Now living the good life in Pacific Grove, CA where it is never hot, unless its on the inside of a freshly baked cheddar bagel.

So…. what can you do?  On this bike, I added a whole slew of 8.8mm x 8.8mm x 5mm heat sinks – purchased with thermal adhesive already applied so they are just peel-and-stick.  Here is a link to the source I used.  You can find them quite a bit cheaper buying direct from China but you will wait a couple of months for them to arrive.  When done, the motor casing looked like this (I completely encircled the motor so there are many more of these things on than you can see here):

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The small heat sinks are placed in rows, 4-across.

Next, I put on another large round heat sink on the end cap.  Since it was sold to me in bare alloy, I used radiator paint (for minimal impact on heat transfer).  I also had to apply my own heat transfer adhesive.  I chose this style as it had the large center area that could be used for adhesive.  Note I also had to fill the very center of the motor where there is a gap thanks to the laser etching for the logo.  I did this with 3+ layers of thermal adhesive, cut to fit flush.

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You can see the thermal adhesive I applied to the center alloy section of the end cap, just at the top.  Hand cutting the adhesive strips to fit was a pain.

Here is a different motor where I used different heat sinks.  These are 8mm x 30mm x 8mm in size.  So they fit – again almost perfectly – in the smooth channel on the BBSHD motor casing.  This time you only need to stack them as they fit the channel 1-across.  Much easier.  Also they are a bit taller, with more room between the fins.  Is that better or worse then the little 5mm units?  I haven’t done any testing so I don’t know.  On this motor, I did the same end cap as pictured above.

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These 30mm-wide sinks were a lot easier to apply as you only have to go 1-wide all around the motor.

Here is a link to the 30mm heat sinks I used.  I can’t find a domestic source for these so if you decide to go this route you just have to order them from the source … and wait.

By the way, these identical heat sinks work extremely well on a mini-Cyclone… Those motors overheat if you give them a dirty look.  The same combination of 30mm adhesive sinks mounted radially, plus the same end cap.  Takes the surface temperature down to the point where the motor can be used with relative confidence once you learn not to overdo the throttle and cook it… The heat sinks cool the motor from the outside literally as much as is possible under the circumstances.

 

Cheap DIY Cargo Bags: Update

Recently I posted up about how I made some Big And Cheap DIY Cargo Bike Bags.  Since I made that post, I have made a couple of improvements worth mentioning (including learning to lock my front wheel… look closely at that pic above… doh!).

The Straps

While I discussed them in my original post, my use of 3″ wide straps hadn’t actually happened at that time.  The straps were in transit.  They have since arrived and been installed.  I do prefer the wider size, and the shorter length of just under 60″ (I’m using two 30″ straps connected together).  You can see them in use in the picture above.

It is worth noting the clumsiness I experienced with the longer 2″ x 72″ straps went away with a couple of days’ use.  I simply got used to them, so as I mentioned in my original post, there is nothing wrong with 2″ straps.  1-piece, 2″ x 60″ straps should work just fine, will cost a bit less and be a hair less complicated.  Although they will give a little less support.

The Hooks

Discussing the improvement to the hooks is a bit more involved.

Lets backtrack a step: Originally when planning this project I ordered some AN970 Large Area Washers from Pegasus Auto Racing Supplies.  I intended to use them in conjunction with the M5 mid-frame braze-on bosses on the Mongoose Envoy to permanently anchor the bags to the side of the bike.  Later on as the project matured I decided to just use the straps and not bolt the bags to the bike.  So I never utilized these washers.

I bought the 1/4″ size which have an outside diameter of 1.125″ (28.6mm).  Inside diameter is suitable for an M6 bolt, and usable with an M5.  Washer thickness is 1.6mm so these are very beefy.  Additionally they are made with Grade 8 heat treated steel.  These washers are VERY strong.  I have used the 1/2″ size, unsupported except for a nut, to secure end link bushings on a track (race) car and they held firm without bending in that very extreme job.  If you toss your bike out of an airplane, these washers will probably be the only thing not bent on impact.

So… I have a bunch of unused washers.  So what?  Well, as you can see from the original build, the S hooks fit inside of a fairly large 13/16″ hole.  The hook has plenty of lip to hang on thru bumps and bonks while going down the road, but it still moves and there is a little rattling.  I hate rattling.  When I build a bike it doesn’t rattle.  I don’t care how big of a cliff you ride off of.  No rattles.  So… I took steps.  Afterwards, the bags remain easy to remove from the bike.  You just do it differently.

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Fig. 1:  Here’s everything we need to get the first part of the job done (stabilize the connection of the hook to the bag)

Step 1: Attach the big washer

These washers are big.  1 1/8″ wide in fact (essentially the same size as a headset stem cap).  They are so wide they cannot fit inside of the narrow end of the ‘S’ hook unless we spread it a bit.  So lets do that.

Take your pliers and spread the small end of the ‘S’ just barely enough so the washer will fit inside of it.  Fit the washer in and then again being very careful not to over-crimp the ‘S’, take it back to being the same shape (parallel) it was originally.

When you are done, you can stop here and fit the resulting product onto your bag grommet to see what you have accomplished.  You will fix the hook by putting the big end thru from the inside of the bag.  It will look like the picture below.  At this point the connection is much more solid and when on the bike very unlikely to come undone unless you want it to.

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Fig. 4:  If you over-crimp the hook it will be too tight and will no longer fit.  If you leave it spread out, it will rattle and move around.  Just put it back the way it was before you put the washer in and everything will be fine.

So, we could stop here, but if you recall, I said no rattling.  So lets take this another step to further solidify the hook into the hole and, as a bonus, make it silent.

Step 2: Add mastic tape to washer

Everyone knows duct tape is a gift from the Gods.  A million uses.  For bicycles and particularly ebikes, 3M Moisture Sealing Tape, Type 2228, is even more useful.  This stuff is available at your local hardware store for about $10 a roll for the 1″ wide stuff.  Its magic comes from the fact it is 65 mils thick (five or six times thicker than what you think tape thickness should be) and is a soft, adhesive rubber that can be stretched, bent, squished and molded as you see fit.  And when it sticks to itself it literally welds together.

For this job, for each hook I snipped three snips of tape, each about 5mm in length.  I didn’t actually measure – no need to be so precise.  I just eyeballed it.  Two of the snips went to the inside side of the washer, pushed inward to hold the hook in place and more or less fully face the washer with thick, soft rubber tape (3 guesses on how that affects rattling).

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Fig. 5:  Do a better job than I did here and cut yourself a little more tape so it goes edge to edge on the washer.

Step 3: Add tape to hook

With the above complete, plant the hook in the grommet hole – now you have to do it from the inside of the bag – and use the third snip to wrap around the hook, so the tape is between the hook and the grommet face.  Like so, below.  This will be a snug fit, but the tape’s tendency to weld to itself makes this job certain despite the fumblefingering that will ensue during job completion.  When done, you have this:

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Fig. 6: The 3rd strip of tape silences the hook rattling against the grommet.

Repeat the process with all four hooks.  Here’s a peek inside the bag.  Notice the washers completely cover the grommet hole.

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Fig. 7:  View from inside.  Pretty sturdy connection compared to poking a hole in fabric with a hook.

The hooks worked fine as conceived in the original build.  But these are now a  more secure, stable mount.  For long term use this is a better way to do the job, and the cost to do it is about 80 cents.

FYI its fine if you don’t use these Grade 8 uber steel washers… look for something similar at your hardware store, probably a 1/4″ zinc fender washer.  Cheaper, too.

Upgrade The Hooks

This is not such a big deal but it works just a little better.  All of the pics above use the black steel hooks that presently retail for $8.99.  These hooks are powder coated so the black is on there pretty good,  But its not going to be perfect, and rubbing paint (bike frame) on powder coat (hook) means you get some rubbing off on both the frame and the hook.  Plus that powder coat isn’t as smooth as polished steel.  These hooks come in a polished steel option for an additional $1 for the 30-hook pack.  I got a pack of these and they seem to fit more smoothly against my frame (where the hook is exactly the size of the frame rails, so fitment is always rubbing-tight).

There is a slight cosmetic difference as they are slightly visible now whereas the black ones were not.  I’ll leave it to you do decide if you care.

These hooks, in the best tradition of Chinese marketing, are described as “premium metal steel” so we’ll have to see whether either behaves differently.  I am using polished on one side and powder coated on the other.  Time will tell if either will rust.

I Hate Ebike Torque-Sensing (maybe you should too)

Well, I don’t actually hate it, but I have no love for a technology rooted in cycling’s past, and whose existence, in my opinion, is primarily owed not to the fact that torque-sensing is a better system, but instead as a tool to help persuade an existing customer base (recreational cyclists) not to hate the product (ebikes) quite as much as they already do.

Say what?

What is Torque-Sensing Pedal Assist?

On an ebike, when a torque sensor is used, it applies a strain gauge to the drivetrain (located either inside the bottom bracket, or in the back of the bike near the gear cluster).  This measures the amount of force you apply to your pedaling stroke.  If you pedal (work) harder, the assist you receive is dialed up.  If you pedal more softly – regardless of your cadence – the assist level is reduced or eliminated.

I have heard it said that torque-sensing “rewards pedal effort” and this statement is both correct and indicative of the root problem with its advocacy.  Old school cyclists hate Hate HATE the fact ebikes can allow someone to make forward progress without using their muscles in the first place.  By restricting/keying the assist to physical exertion levels, the fact that a motor exists at all is less difficult to accept – and more easily sold to the existing cyclist population.

It is unfair to say torque-sensing is ONLY about this.  Its not.  You will also hear people say torque-sensing results in the most ‘natural’ bicycle riding experience for them, since you still have to work hard on the pedals.  And the assist increases in proportion to your effort, just like a real bicycle.  An ebike goes faster of course, but a physical work ethic is still demanded.  So to be fair, torque-sensing does indeed give cyclists a familiar experience, and one that they may specifically want.  There is nothing wrong with that.

What is Cadence-Based Pedal Assist?

In its simplest form, its nothing more than this:  Your assist level goes up or down based on how fast the crankarms are turning.  The amount of effort you expend could even be irrelevant if your gearing is low enough.  The only thing that matters is the rotational speed of the pedals/crankarms (strictly speaking it is the spindle’s rotational speed that is measured, but thinking ‘pedal rotation’ is easier to visualize).

So if you want more assist, you just turn your legs faster – not harder.  Again in simple circumstances this means you can get into a low gear and easily ‘ghost pedal’ your ebike, without expending any effort.  So you are breezing right along right up to either the speed limit of the ebike or the road/path you are riding on. 

Such a thing is utterly anathema; deeply, personally hated in the cycling community.  There, your progress and ability is hard earned through what can only be described as prolonged, personal, stoic suffering whose level outsiders neither understand nor hope to match.  Despite the spandex, funny hats and silly shoes, cyclists know they are truly badasses.

Except, fate has dictated these solitary warriors suddenly have to share the road with the Griswolds, blowing past them in their two-wheel Trucksters.  Ebikes democratize cycling so that now… anyone can do it?  WTF!?!

… not a shock the response of cyclists to ebikes has been negative.

Its not so simple

I said above the description of cadence-based pedal assist was in “its simplest form”.  There are some cadence-sensing ebike motors that have settings both complex and rather profound in how they impact the riding experience.  Notice I did not say ‘cycling experience’ because a central tenet of my rejection of torque-sensing is that ebikes are not bicycles.  It is a mistake to treat them as if they should behave the same (unless that is something you expressly want).

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Some cadence assist options are at left, and this isn’t even the Pedal Assist screen for this particular motor.  The settings determine assist strength and at what point, based on both speed and rpms, that the assist gets cut back.  Other screens have settings to determine how much the cut-back is, how fast it kicks in and more.  Not at all the simple concept most internet experts describe as their idea of cadence assist.

Torque-Sensing Can Be A Disaster

If you have a physical limitation, torque-sensing doesn’t necessarily help you get past it.  It does help you go faster while working hard.  Studies have shown that ebikers in fact can work nearly as hard as, or even harder than bicycle riders… they just don’t realize it.  Possibly this is due in part to the exhilaration of being able to go faster, and stay in the saddle for longer periods.

Myself, I am a lifelong cyclist.  Or rather, I was.  I commuted daily for decades.  For many years I eschewed the use of an auto.  I commuted and even shopped for groceries by bike (being poor and single had nothing to do with this 🙂 ).  But after a couple of heart attacks, my cycling life was over.  To stay alive, I gave up the intensely personal activity I most valued.  Bummer.

A few years ago, I discovered ebikes, and the one I bought had cadence-based torque sensing.  I had no idea there was another kind of system at the time.  I did something many old-schoolers do not:  I treated the ebike – which looks like a bicycle but is not one –  as a new animal.  I threw out much of of the knowledge on cycling I had acquired, and started over on riding technique.

At the start, pedal effort very quickly led to chest pain and an immediate need to stop doing that.  But I could go on if I dialed up the assist and incrementally lowered my pedal effort, while maintaining forward progress.  This doesn’t work with torque sensing.

I learned to treat the ebike like an exercise machine.  An exercise machine that went places… and was practical transportation.  This approach to riding an ebike and incrementally notching the assist level up and down as needs of the moment dictated solved everything.  The procedure in a nutshell is as follows:

  1. Set a preferred cadence
  2. As heart pain occurs (heart pain /= being tired) click up the assist level so I get closer to or completely ghost pedal the bike – and keep moving
  3. On recovery – I’m good after maybe a half block – ramp down the assist level a click at a time and start working harder again
  4. All the while – maintain the same cadence
  5. Rinse and repeat as the miles click off.

Again, to belabor the point:  This is transportation.  My bike has somewhere to go, so the point of cycling is to reach a destination.  If I was a recreational cyclist then maybe its fine to stop and sit on a bench for awhile.  But the point of riding for me is to get somewhere.  So I must maintain forward progress while managing my exertion level.

Only cadence sensing is going to let you do that (and I know this from experience.  See Afterword below).  Its a totally different riding experience.  In the end, described most simply, you have an exercise machine that is moving.  Again… not a bicycle.

Over time and thru repetition, I scaled back the point where pain occurs to where I was able to change my bike’s gearing.  Now I’m running at top assist speed while maintaining pedal pressure and exertion at all times during the ride.  On my Class 3 daily driver I cruise right at 28-30 mph (legal in my jurisdiction) and I get to those higher speeds above the assist limit by myself.  All along doing so by maintaining a set, preferred cadence.

And if I overdo it, since I am now running this auto substitute at full power, I can just upshift (maintaining cadence on the easier gear) to take a break while only losing a mph or three.  This is a different way to use cadence-assist.  I am not dialing back power: I’m always running at full blast.  Instead I am just varying my pedal effort up and down via gear changes.

What happens to a rider with physical restrictions who tries to depend on a torque-sensing ebike for transport?   You ride, you need a break and an assist and… the bike tells you to fuck off.  Its not going to help unless you work hard enough to deserve a reward.  So much for dependable transportation.

Broadening The Use-Case

Cadence sensing isn’t just for recovering invalids.  For the healthy rider, successful use of cadence-based assist as a hard-exercise tool is easily possible, and rooted in that rider not coming into the experience with pre-conceived ideas.  Don’t treat it like a bicycle (yes I am repeating this over and over on purpose).

Using the ebike as an exercise machine as you roll down the road, you’ll be getting fit during time otherwise spent sitting in your car and exercising nothing.  A torque-sensing ebike can do this too… but if the ebike is meant to also be practical transportation, your physical condition of the moment will have a direct impact on whether you make it to your destination.  Not so with cadence assist.

The Future

It took 34 years for the Tour de France to allow bicycles with derailleurs — because not grinding up a slope in the Alps on a single-speed was cheating.

… Isn’t it better to triumph by the strength of your muscles than by the artifice of a derailleur? We are getting soft.

-Henri DesGrange, world-renowned cyclist and original TDF organizer

If someone tried to make that same case today, their opinion would be discarded as fringe idiocy.

So lets take that same interval: 34 years from now, when ebikes have long-since become the accepted norm (just look at the sales figures) as derailleurs did a century ago… will we be espousing technology or methods rooted to the norms of the past?  Will a couple of generations of riders who have known nothing else continue to think of torque-sensing assist as giving a bike a ‘normal’ feel?

My money is on ‘no’.  Or more accurately… sorta-kinda-no.  I think for higher end bikes a dual system could become commonplace, letting riders choose one or the other as they see fit in the moment.  One mode for recreation.  One for transportation.

But if it has to be a this-or-that binary choice, then torque-sensing won’t survive the test of time.  Why?  Sheer weight of numbers, and the growth of the automobile replacement market.  Look at global ebike sales.  Only a small fraction of ebikes are sold in the European and North American markets, where recreational cycling is a thing.  Instead look at the Far East, where bicycles are simply utilitarian transportation and there is no stigma attached to effortless travel.  Whats the norm there?

Cadence-based assist.

 

Afterword

Lest I give the wrong impression… I have an ebike that uses torque sensing, and frankly I love it.  But its a recreational bike, not suited for a bike that has a job.  Going for a fun ride, where I don’t have a problem stopping and sitting down on a bench or a rock for awhile and enjoying my surroundings… Its almost perfect for that.  I wish I had time to ride it more.

But by its nature it can’t be a serious transportation tool.

 

Big And Cheap: DIY Cargo Bike Bags

There is another post that shows later-improvements to these bags.  And here is another one that covers a hole I left in this article below.

I have a Mongoose Envoy that I turned into a project bike.  I essentially took a very inexpensive bike with low end components (but a fantastic frame, with a good fork and wheels) and rebuilt it into a high power, heavy duty cargo bike with better components than I’d get if I paid for one from a major manufacturer.

The Envoy comes with two almost-38L-each panniers (24″ long x 16″ tall x 6″ deep).  Thats one hell of a lot for a bag on a normal bike.  But on a mid tail cargo bike frame, they’re smaller than what they could be.

The stock bags look skinny, and are no thicker than a normal pannier.  But I’ve had them loaded with a complete Costco grocery run where the bike ended up well past its 140-lb rated cargo capacity.  Using an elastic bungee net to make sure everything stayed tight to the bike, all I had to do was lumber home without killing myself.

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Figure 1.  A light shopping run – not using front bags.  The bags we’ll make here are about the same size as the ones shown, but more than double the width.  Note the cargo net used here as insurance that those bags stay put.

So… the bags work great and are essentially free.  But I’d like something that better suits the capacity that the mid-tail cargo frame can handle.

I managed to score a brand new set of Surly Dummy bags for a great price.  I found they were great bikepacking bags not suited to bulk grocery hauling.  Whats needed is a giant hole you can dump stuff into and zip closed.

It looked to me like the Yuba Go-Getter bag ($300 plus shipping for the pair) was the closest fit to this idea, and to my frame (It is meant to fit their popular Yuba Mundo cargo mid tail)  I contacted Yuba about the exact size of the bags, and that they would be going on a non-Yuba bike.  They promptly got back to me with this:

  • Length – 29″ / 74 cm
  • Depth – 10″ / 25cm
  • Height – 17″ / 43cm
  • Volume comes to about 84 quarts or 79.5 liters.
  • It is important to note that we designed the Go-Getter to be specifically compatible with our Yuba Mundos and we cannot guarantee its compatibility with non-Yuba bikes.

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Figure 2: A single Yuba Go-Getter bag mounted on a Yuba Mundo cargo bike.

Thats pretty awesome in terms of capacity.  However, those dimensions are just enough to worry me on my bike.  The Envoy’s bags are 24″ long.  29″ might end up pushing into my heel clearance.  The height of 17″ is for sure an issue.  Envoy bags are 16″ tall, and its already a problem that those bags essentially sit directly on the lower rack.  While the bike frame is rated for 90 lbs, the lower rack is only rated for 20 per side, or 40 lbs total.  Now, they can handle much more than that in real life, and I have reinforced the lower rack’s attachment to the frame (Supplementing the factory’s four connections with an additional six that are each stronger than the simple factory bolt), but still a bag that basically sits its weight on that lower rack is not ideal.

What would be better would be a bag that is a little shorter, that bows downward under load, putting strain primarily on its hanging hooks, so only partial weight is borne by the lower rack.  Add in a couple straps to help take the load off those 4 hooks and its better still.

I think my solution accomplishes that.  Bear in mind everything I did here was done specific to this bike.  You can take these ideas and make adjustments so this basic concept fits to yours.

The Budget

Lets call the number I am trying to beat the cost of the Yuba Go-Getter bags, which were my benchmark for capacity:  $300.  So I wanted this project to come in as far under this number as possible and still get a quality bag.  As you can see from the build sheet below, I came in well under the commercial product’s price point.

Build Sheet ($111.50, or $55.75 each)

Rothco Parachute Bag (2)             Amazon   45.98
3"x30"velcro cinch straps (8)        Amazon   21.54
C.S. Osborne #6 13/16" grommets (8)  Amazon   11.36
Stainless 0.3"/0.78" S hooks (8)     Amazon    2.67 
Therm-a-Rest Classic Foam Pad        Amazon   29.95

The Bags

I want something more durable than the fabled, dirt cheap Ikea bag.  But really those bags got dropped as candidates because the zippered version is so short at 11″ that it would be putting the load unnecessarily high.  Also its 28″ length is again just enough to worry me.  And how sturdy is it?  The zipper in particular?

I had a candidate already in my hands in the form of a Rothco Parachute Bag.  These are simple, cheap $23 bags made of reasonably thick canvas and strong, smooth zippers with a snapped storm flap.  Dimensions are 24″ long (identical to the Mongoose stock size), 15″ tall (1″ shorter than stock, so addresses my height/weight concerns) and 13″ deep.  Work out those measurements to cubic inches (4680) and convert to liters and you have a 76.7L pannier bag.

Since I already had one of these bags in my closet, I was able to toss in some full size pillows (it ate 3 of them and still wasn’t quite full) and sized it to the bike.  Looked like a perfect fit.  So I bought two more for testing.

Attachment

After a fair bit of fussing around, trying to figure out exactly how I wanted to attach the bags to the bike (it actually took a few weeks), I settled on primary support being grommet holes in the bags, which will connect to simple S hooks mounted to the frame.  These will be further supported by straps.

I used the C.S. Osborne #6 grommet, which has a 13/16″ hole.  Why this brand and size?  Well, there are drapery grommets, shower curtain grommets and outdoor tarp grommets.  The grommets for curtains are nowhere near strong enough to work on a tarp… or a pannier.  I knew from experience the Osborne grommets are solid and will distribute the forces involved as well as possible.

I chose a 13/16″ size because… I had the grommets and the grommet tool already.

20170218_143537Sidebar:  The #6 grommet size is the smallest size commonly available that will let you fit an XT90 connector thru the hole.  Thats why I have the grommets and tools in my garage – from building battery bags for my custom ebikes.  I grommet the pass-thru holes in the bags.  And since I have been using them for years, I know they hold up.  The bag on the right was made in early 2017 and is still in use today.  This $12 Amazon bag with reinforced holes is way cheaper than a custom ebike bag.

 

  • You can see in the first pic below, three of the four grommets’ upper edges match the seam of the bag, while the forward-most grommet is lower.  Oops.  My second bag had them all even and all in the lower orientation.  Despite the different mounting, you can’t tell the difference in how they sit on the bike.
  • The single brass grommet was deliberate as I wanted a quick visual cue to help me orient the bag.  Brass = rear for both bags.

Straps

Not wanting to rely totally on the hooks, there are two dedicated three-inch velcro cinch straps.  These are actually made up of two 30-inch straps combined to make one longer strap.  I had to do this as there does not appear to be a 3″ wide velcro cinch strap in a 60″+ size on the market.  If you wanted to save some money and use a narrower strap, 2″ cinch straps are widely available.  In fact, the pics below show an early test fitment where I was using 2″ x 72″ straps, which worked OK but were so long they were a bit unwieldy.  Shorter straps were more convenient and the wider 3″ version provided more support.

The right way to use the straps:  Loop over the rack at top, and the very bottom, directly underneath.  But do NOT loop under the lower rack and then go up over the bag.  Instead, from the bottom of the bike frame, loop the strap directly under the bag and then back up to the top.  The top loop over the rack helps support the bag’s weight.  The bottom loop onto the lower portion of the frame (or rack depending on your bike) helps hold the bag close to the frame so it won’t flop around.  And the remainder of the strap, directly up against the bag and not under the lower rack, holds up the bottom of the bag, preventing – along with the padding – the bag from sagging.

Hooks

These are pretty straightforward.  I wanted an S hook with beveled edges that allows quick attach/detach, but at the same time is shaped in such a way that the bag will not easily come undone from it as I bounce from pothole to pothole.  I searched for months for such a hook for a cargo net and fell into the ones I am specifying in the build sheet.  Originally meant for my cargo net, they are also perfect for this project as well.  I have the painted black versions but I am spec’ing the unpainted stainless versions.  For your own personal bike, you may need something different.  Follow the link above and note the seller offers three sizes.

More Options

  • Most of the reason I used pre-made cinch straps rather than buying webbing and fastex-style buckles is that hook/loop strapping is much easier to adjust.  This makes it easy to cinch up the straps when the bags are empty, and fold the bags up quite nicely.  There is even a deep, wide pocket formed by this process that is a decent candidate for stuffing in whatever fits.
  • During testing of the bag when fully loaded, I ran a 15″ x 30″ cargo net from my top rack, over the bag and underneath to the bottom rack.  It provided great support to keep the bag from sagging, and held it firmly, close to the frame.  For really heavy loads this looks like a smart thing to have available; especially since it can lay flat in the bottom of the bag and take up no extra space.
  • I have a 24″ x 36″ cargo net (see it in action in Figure 1 above) that I can use to stretch over my entire cargo area.  Up over a side bag, the loaded upper deck and back down over the other side.  For big, heavy loads, a net like this can put a gentle, compressing and enveloping grip over the entire load in the rear.

Where Do You Go From Here?

Unless you have a Mongoose Envoy then your bags will need to be tailored to whatever your bike fittings are.  Expect to put the grommets in different places.  Maybe use a different size of S hook.  Don’t expect my project to work perfectly for your bike although the parts I am using should be mighty close to universal once you space things out per your bike’s needs.

In the photo above: I had so much room in the new bags after loading up my shopping cart, I never even used the 36″ x 12″ duffel that sits atop my 40″ rear deck.  There is almost 154 liters of pannier space in those bags, and after dumping that whole shopping cart into them (the front bags helped too)… they still aren’t full!