26" BMX DK Legend Build

[neptronix]

I see the listing here.. didn't even know this existed until now.
BMX 26 inch 48V 52V 1500W rear hub motor - electric bike conversion kit

What an oddball motor.. this is a huge mistake by Leaf.. they need to know about it and accept a return.

DK Legend 26
Also, your bicycle is chromoly. This means you could have the appropriate dropouts welded to it. Then, add torque arms on top.
A frame builder could do this for you.

But this would mean the frame and a rare mistake of a motor are married for life.

 

[2old]

Actually that probably won’t work. The dropouts on my bmx are 110mm and the motor won’t support much wider than that. I think all the mtb dropouts are at least 135mm.

What a mess…

You're correct; I thought your bike had 135mm dropouts because that's what the motors that I've dealt with have. The best you could hope for would be mid 80's five-speed MTB's which had 125 or so. My 1984 Fuji which had a BBS02 at the time and the 1984 Schwinn I restored for my granddaughter.

 

[BallHarder]

What an oddball motor.. this is a huge mistake by Leaf.. they need to know about it and accept a return.

Thanks for that. I emailed them asking what my options are. It seems like this motor was made for a bike that doesn't exist!

Every 26" BMX bike I've found online has 14mm or 3/8" rear drop outs.

 

[amberwolf]

This is intimidating. I have no idea where to find a machinist who would be willing to do such a small job. I’ll ask around.

There's plenty of online places that do this kind of stuff for prototyping. Some of them are listed in threads linked in that picture thread, for instance. There's even some in the online market section of this forum here and there.

It might not be all that expensive, though it probalby isn't super-cheap.

Some of the torque-plate designs in that thread can be hand-fabricated if you're up for that sort of thing and have enough patience.

 

[BallHarder]

I'd still recommend making something to support the axle in the dropout itself (to fill the space around it), even if it's just a stack of "axle washers" that have the double-D shape at their core (instead of round) that you grind or file so they do that.

On a scale from 0-10 where 0 is certain death and 10 is... a Volvo how do you all feel about this, along with two of the v7 torque arms?

 

[neptronix]

I'm thinking you need about 2x of the total metal you have to prevent that wheel from loosening over a relatively short period of time, and that metal needs to be bolted or welded to the frame.

Please be wearing appropriate safety gear for the time that the rear wheel falls out the back while you're riding it with the current idea.

 

[BallHarder]

The dropouts are about 1.5x the thickness of these washers they gave me and I only have two spares (that I sacrificed).

 

[amberwolf]

I give it 3 schmoos.

It's much better than nothing, along with the v7 clamping torque arms (assuming those get properly mounted to the frame), but not as good as a torque plate bolted to the dropout would be, on each axle end.

Remember that you want to immobilize the axle in all directions, not just rotationally. If it can move around at all, even a tiny amount, that causes a difference of position on one axle end vs the other, the wheel that's much farther away will magnify the difference. Just a little bit of skew from one end to the other can cause the tire to rub on the frame, for instance.

So...whatever you can do to immobilize the axle is what you want to do.


If you have the time to spend paging thru my various buld threads, you can see various iterations of things I've tried over the years to do this job, usually by misrepurposing some other part not really suited for the job.

The best things I've made for the purpose were the most recent clamping dropouts on the right side of the SB Cruiser, which could be much better designed and most certainly better-fabricated. :lol:

 

[BallHarder]

I appreciate everyone's help. Unfortunately Leafbike says there's nothing wrong and they've never had complaints. They told me to fabricate a part when I asked about a return...

 

[neptronix]

Not good.
I wouldn't use that part. Look at how thin the tubing is..

I would seriously bolt or weld some chromoly dropouts on. Examples:

chromoly track dropouts - Google Search

 

[Chalo]

The problem is I can’t find a single 26” BMX bike that has 10mm rear drop outs. They’re all 14mm or 3/8”.

A 3/8"' axle is 9.5mm in diameter, and I think you'll find that pretty much all "3/8 inch" frame ends will fit a 10mm axle as well.

 

[BallHarder]

A 3/8"' axle is 9.5mm in diameter, and I think you'll find that pretty much all "3/8 inch" frame ends will fit a 10mm axle as well.

I misspoke. I thought 3/8 and 14mm were approximately the same size.

 

[Cryingmadman]

I misspoke. I thought 3/8 and 14mm were approximately the same size.

I misspoke. I thought 3/8 and 14mm were approximately the same size.

Hi,

Sorry about your misfortunes I am not a welder but I do have tons of e bikes parts and goodies no charge if they can help you salvage your build.

Ideas are easy execution is a bitch

Cryingmadman@gmail.com

Regards

Cryingmadman

 

[99t4]

It's far from a lost cause. Here are the positives:

1. Large flat dropout platform makes it easy to securely attach (fabricated) clamping dropouts outboard.

2. Plenty of extra axle extension to easily accept thick fabbed clamping dropout (thicker is better-- more secure).

I am envisioning a large 1/4 inch thick plate in the same triangle shape of the existing dropout, laying flat on and securely bolted (3 bolts, spaced apart?) to the existing dropout. This will locate and secure the axle with a clamping dropout end.

Have you studied the TA picture thread AW suggested above?

torque arm picture thread

Cross-posting these two threads so a search will turn up both: "Found an awesome torque arm" (3 pages) https://endless-sphere.com/forums/viewtopic.php?f=1&t=11570 xxxxxxxxxxxxxxxxxxxx Original thread died. Figured I'd help out and repost what I saved. Here is the album link...

endless-sphere.com

So, something like this:

Here are some more pictures of others (some crude but to give you ideas):

"ScootBike"Build.

This build will be based on "Strong GTS." and a "Baja Motorsports 500E". I had started to customize these as two separate platforms. "Strong"http://www.endless-sphere.com/forums/viewtopic.php?f=6&t=34672 "Baja Rat"http://www.endless-sphere.com/forums/viewtopic.php?f=10&t=34624 I am...

endless-sphere.com

 

[BallHarder]

I am envisioning a large 1/4 inch thick plate in the same triangle shape of the existing dropout, laying flat on and securely bolted (3 bolts, spaced apart?) to the existing dropout. This will locate and secure the axle with a clamping dropout end.

Something like this? It's a steel plate with a 10mm notch and three bolts that go through the existing dropouts? I tried drawing it on my computer but couldn't figure it out.

 

[BallHarder]

Oh, would these work? I would just need someone to weld them to the existing drop outs?

"FISH HEAD" BMX/CRUISER HORIZONTAL DROPOUTS - 10MM HUB SLOT — BICYCLE FABRICATION SUPPLY

BFS “ FISH HEAD” BMX/CRUISER HORIZONTAL DROPOUTS THESE DROPOUTS ARE GREAT FOR, 20/22/24/ 26” BMX FRAMES OR KLUNKER BUILDS 10MM HORIZONTAL HUB SLOT 22MM (..875”) LENGTH SEAT STAY SLOT FOR 19 TUBING , CHAIN STAYS 19MM TUBING ANGLE OF CENTERLINE BETWEEN SEAT STAY AND CHAIN STAYS IS 32° MADE FROM 3

www.bikefabsupply.com

They're 3/16" thick steel and have a 10mm slot.

 

[neptronix]

Please see this post.. get some quality dropouts, they're not expensive:

Not good.
I wouldn't use that part. Look at how thin the tubing is..

I would seriously bolt or weld some chromoly dropouts on. Examples:

chromoly track dropouts - Google Search

 

[99t4]

Something like this? It's a steel plate with a 10mm notch and three bolts that go through the existing dropouts? I tried drawing it on my computer but couldn't figure it out.

View attachment 345303

Yes something like that. At least 1/4" steel. 3/8 would be better. For ease of access extend the "tail" out past the existing rear edge for unimpaired access to the pinch bolt.



Should be able to fab most of this with common homeowner tools: vise, jigsaw with metal blades, drill, file, c-clamps. Can you find somebody local to weld tubes to the rear edges to serve as the pinchbolt housings?

If you want to avoid the welding on the tubes part, you could instead shape the plate so the tails extends out in a parallel shape instead of triangular, and use some common HW store steel cable clamp pieces like this:

Tip: Make the axle slot slightly tight as first. Open it up only as needed with the file. Only enough to allow the axle to slide in with some minor force. ANY possible axle rocking movement here is the enemy.

I forsee the tricky part to be achieving vertical alignment of the rear wheel. Horizontal alignment you have some adjustment because of the long horizontal slots, but once the bolt-on plates are mounted you are stuck with the ultimate vertical alignment. So take your time when marking and drilling the mounting holes. Shouldn't cause too much trouble if you securely clamp the plates to the frame while the wheel is in the in the dropouts and aligned correctly. Then drill thru both the plate and frame at the same time, checking that the wheel alignment hasn't moved. Or maybe easier, drill the mounting holes in the plates first, then clamp them on, verify the alignment, and use those holes as guides to drill the frame's existing dropouts. Make your job easier by obtaining good high quality drill bits, don't drill steel at high speed, and use lube.

 

[2old]

The last dropout looks excellent (to me). However, if you decide to weld anything, AFAIK welding chrome produces toxic gas(ses); the welder should already know this though.

 

[E-HP]

Here's a couple pictures of the axle and drop out. Is there a universally recommended torque arm for bikes that don't have the disc brake nuts welded to the subframe?

View attachment 345135


View attachment 345136

I never pulled the trigger on a BMX frame build because nowhere on the Leaf website does it provide the axle diameter of the 1000W or 2000W "BMX" hub motor kits. At one point, I was ready to assume that they were cut for 14mm axle flats since that's the standard, but decided not to take a chance. I would buy two of these Grin torque arms, and only use the part that fits on the axle. Orient the axle so the flats are vertical and the axle is supported; fit the torque arms and drill an anchoring hole in the existing dropout. That should provide plenty of support.

V2 Front Torque Arm

GRIN Front Torque Arm for Mounting on Forks with Fender Eyelets. Thick 1/4

ebikes.ca

If you look online, there are very few BMX ebike builds and the ones that are have oddball frames made for 10mm axles.

 

[Blankman2100]

I can offer only experience. Go forward it cand done

 

[Blankman2100]

And just for good measure .... I'll raise you a lever and include .........DIY BELTDRIVE
On your homemade bmx ebike sir

 

[BallHarder]

And just for good measure .... I'll raise you a lever and include .........DIY BELTDRIVE
On your homemade bmx ebike sir

I love it. I don't understand it, but I love it.

Do you also have a 10mm axle and 14mm dropouts?

 

[BallHarder]

I never pulled the trigger on a BMX frame build because nowhere on the Leaf website does it provide the axle diameter of the 1000W or 2000W "BMX" hub motor kits. At one point, I was ready to assume that they were cut for 14mm axle flats since that's the standard, but decided not to take a chance. I would buy two of these Grin torque arms, and only use the part that fits on the axle. Orient the axle so the flats are vertical and the axle is supported; fit the torque arms and drill an anchoring hole in the existing dropout. That should provide plenty of support.

V2 Front Torque Arm

GRIN Front Torque Arm for Mounting on Forks with Fender Eyelets. Thick 1/4

ebikes.ca

If you look online, there are very few BMX ebike builds and the ones that are have oddball frames made for 10mm axles.

This is such a helpful reply. Thank you very much. I also couldn't hardly find any information on a 26" BMX build which is why I started this thread. I figured someone might want some detail. If nothing else it will educate people on the differences between BMX and most every other bike's axle diameter!

 

[calab]

Sheldon Brown website is a good resource.