Dave's 80:1 RC mid drive kit build log

And a thin layer of MG Chemicals 8329TFM securing the stator to the heatsink should yield some serious thermal capabilities...

FastJohnny said:

Leeleeducati said:

Hey FastJohnny,

Nice setup, your mounting brackets don't look like the standards. Did Dave custom make those for your frame, or are they another series offered? Do you have any dimensional details you could share?

Thanks!

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Yes they are custom sized to fit in the frame by our man Dave D. I'm not sure of the dimensions, but I will say the super short mounts are both a gift and a curse. The PRO is that they are short, look cool, and fit just perfectly in the triangle. The CONS are that the mounts are too short to mount the ESC on, and make the simple task of running a chain between the motor freewheel and crank chainring a complete nightmare.

Because the mount is so short you can only run certain chainring/motor freewheel combos. I'm going to struggle to explain this. With a longer mount you can run any chainring you want within reason, just take a link out, or add one to get the chain length and tension just right. With my mount, only certain combos work. For example with the 20T freewheel and a 30T motor chainring, using X number of links on the motor chain, it is so loose that the tensioner can't keep enough tension on the chain to stop it from falling off. If I take out a single link of chain, the chain is now too small to fit. If I swap the 30T for a 32T motor chainring, there is now a length of chain just long enough to fit, and the tensioner can apply tension (pictured).

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What in going to experiment with given that I'm having some of the same issues is using jockey wheels of varying teeth number. I have one as small as 10 and can buy as large as 17, which should make a significant difference. I have also placed a large spring from the tension arm to a fixed point to provide more force onto the chain.

Varying the jockey wheel size is a good idea. I'll make the arm of the tensioner a bit longer as well and use a stiffer spring.

tangentdave said:

Varying the jockey wheel size is a good idea. I'll make the arm of the tensioner a bit longer as well and use a stiffer spring.

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Also I think it might help if the jockey wheel had larger profile teeth on it, more like an actual cog/chainring instead of the smaller/shorter jockey/derailleur profile. I don't think this is common though.... All the derailleurs I've looked at tend to have the exact same tooth profiles....

Is there a better spider/freewheel setup to use? I've noticed a concerning weeble-wobble in mine and I find the clearance of the inner chainring to be very tight with the spider itself. Wouldn't mind swapping it out for something a little higher quality and better clearances. Might be why I've thrown my chain a few times over the last 400km.

A better freewheel crankset is what we're searching for. I forget who has which freewheel, if yours is the White Industries HD, the bearing inside may be working itself loose. The cheaper Cyclone FW with dual rows of open balls is a better choice for us since we're almost exclusively freewheeling. The White FW is the nicer one with a raw steel finish, the cyclone is painted black. Might need to change out your FW. Do you have a 24t motor chainring at the crankset or 32t?

Don't forget to check the crank bolt tight!

Oh, and first 2nd gen kit headed out the door today! A couple more days and #2 will be out for delivery!

I have the black cyclone FW with 24t. I'll go over it all again and make sure nothing is loose. Shouldn't stop me from riding for now.

tangentdave said:

Oh, and first 2nd gen kit headed out the door today! A couple more days and #2 will be out for delivery!

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Oh my god. It is beautiful. Might just have to order one soon

wow it really does look awesome

That is gorgeous machine work no doubt. Increased heat shedding capacity is going to be fantastic.

I just finished the freshen up on my bike along with a new 11t-40t 9s cassette. My chainline wasn't great on the old setup so this time around I pulled a few cogs and pushed the 18-21-24-28-34-40 cogs out (range of 40km/h to 85km/h). Chainline looks better, frame does look like it has been tweaked a few degrees, the price of power I suppose :lol:

I also noticed after a few hundred km of riding that the whole unit wanted to shift over to one side and the torque pushed the tpu spacer all the way to one side. I think a longer length tpu spacer would be good for frames with wide downtube to help keep the unit from 'walking'. I may get a buddy to make one that fits the contour of the glory downtube to see if that helps.

2s pack is ready to add to my two 6s banks for 14s. I was wondering if it made any difference where the 2s pack is connected? I was going to place it either negative side or between the two 6s packs. Does it matter?

You're connecting the packs externally? Not soldering, but plugging the XT connectors in series? The order of the series connections doesn't matter, just make sure all the cells are equally charged when connected.

hi Dave can your gearbox be use. motor clockwise left or right spinging


with new gearbox did you cut the teeth the same shape

if I want to use left hand side drive


thank you

tangentdave said:

You're connecting the packs externally? Not soldering, but plugging the XT connectors in series? The order of the series connections doesn't matter, just make sure all the cells are equally charged when connected.

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Yep just 3 parallel groups, two are 6s x 6 and one set of 2s x 6. Didn't know if there was a best practice. I took it out today but had derail issues. Forgot to take suspension travel into account when I setup the new cassette and derail. Shifted great on the bench, decided to wrap itself around the cassette when I loaded it up on the 40t Might make it single speed while I wait for parts, getting the itch to ride!

The gearbox works same either direction, teeth are symmetrical. The backlash is increased compared to a 'professional' cycloidal box to allow higher speeds so it's not ideal for positioning, but bikes only go in the forward direction so we don't really care about that.

Don't cut it too close on the derailleur tension...I've found this style of guide to be easy to implement and helpful






-dave

Mugenski said:

Is there a better spider/freewheel setup to use? I've noticed a concerning weeble-wobble in mine and I find the clearance of the inner chainring to be very tight with the spider itself. Wouldn't mind swapping it out for something a little higher quality and better clearances. Might be why I've thrown my chain a few times over the last 400km.

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I have the previous gen setup and I have desigend a new spider in CAD. I was thinking of having it fabbed.

It allows the use of standard chainrings instead of the unorthodox 5 bolt setup from sickbikeparts. This way one can use a wide variety of tooth numbers, materials and makes it easier for maintenance in my opinion. It retains the 5 bolt fixture for the freewheel but uses standard chainring bolts for mounting the drive and driven chain rings.

The things that will still need to be fiddled with a little bit for each individual application would be the spacing possible for the driven chain ring from the face of the spider. This may also change with chainring to chainring depending on how thick the chainring is at the mount locations compared to the teeth thickness, but I don't think that varies much from manuf to manuf. Also chain ring bolts may need to be shaved down a bit since the lengths might be off compared to stock bicycle components. So, like with any custom project, a little bit of tinkering.

What I still need to do is buy a chainring so that I can confirm the standoff distance from the face of the spider to the driven(inner) chainring. Then I think it should be ready to fab.

I have attached the screen capture of the cad.

If anyone is interested in these please let me know, as it would save on per unit cost when getting it machined.

Dave, if I'm hijacking your thread and you want me to take this out of your thread please let me know.

This thread is for the development of the kit, bring all the ideas.

I tried a spider like this so I could use standard chainrings with less than 32 teeth, but then I got tired of modifying each flanged freehweel to allow the chainring bolts to pass through the flange. And the White freewheels do not cut easily at all, even in the mill. You are thinking this spider to be used with the freewheel crankset, right?

I've made it so that the chain ring bolts will be flush and there is no need to modify the free wheels.

Ah, excellent. Since there are features on both sides, maybe think about standoffs of the flat side to space the small ring off the spider for chain clearance. Can also buy chainring spacers for cheap, that might be the more versatile approach.

Nice, I didn't know about chain ring spacers, I'll look into that. I was just planning on having it machined so that it provides the right clearance between the two chain rings. Spacers will definitely make it more versatile.

Looks like https://wheelsmfg.com/products/crank-pedal-parts/chainring-spacers.html
Has lots of sizes. 10mm and 8mm id which works well since I'm trying to stick with a24t ring and this size in a 74 bcd ring means that it's usually the granny ring and has 8mm bolt holes.

That looks good 12-C. If I can use off the shelf sprockets and just shim it up myself that would be the ticket. Tinkering with the chaining bolts/spacers is no big deal and I feel it's a better option than using custom sprockets. Let me know when you're going forward with this.

how much life should i expect out of a front sprocket?

tangentdave said:

This thread is for the development of the kit, bring all the ideas.

I tried a spider like this so I could use standard chainrings with less than 32 teeth, but then I got tired of modifying each flanged freehweel to allow the chainring bolts to pass through the flange. And the White freewheels do not cut easily at all, even in the mill. You are thinking this spider to be used with the freewheel crankset, right?

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Lots, at least 500 miles of abuse. Surly makes a steel narrow-wide which would last a few times as long as aluminum. Just make sure the front ring is a narrow-wide, chain drops under load suck.

I get about 400 miles out of a raceface 32t aluminum narrow wide. It’s not even totally shot when I replace it. I recently switched to a stainless steel drop stop 32T from Wolftooth. It’s the only steel narrow wide I know of. 100 miles or so on it and no signs of wear yet.

I'm looking to use a wolf tooth steel Chuck ring. It's 24 t like stock but 74bcd to fit my spider.

The sick bike parts steel one lasted about 500 miles for me. I did damage it by dropping the chain a few times and jamming it. I'm pretty sure it's also a mild steel not stainless.