26" BMX DK Legend Build

[BallHarder]

Edit: Got a slab of 3/8" steel, a pack of bi-metal bits and some cutting lube but my jigsaw couldn't handle it.

I found a couple mobile welders/metal fabricators that I'm going to call next week. I've got a cardboard template and I'll see what they say. Will post an update once I get the dropouts modified.

Still upset at Leafbike for marketing this as a "BMX" hub motor when all BMX bikes have 14mm rear drop outs...

 

[BallHarder]

I'm going to have a mobile fabrication/welder come to me and do it right.

Here's my nude dropout


Now here's a potential template.







Any thoughts on the design? Should I beef up the beak of the bird? Or, should I go vertical like this?

 

[99t4]

Looking good.

If you go vertical slot you may lose the ability to correctly tension the chain. Presuming BMX = one speed/no derailleur?

Do you have reasons for extending the "beak" out so far past the original dropout?

Don't forget the slot and small hole (stress reliever) at the inner end of the slot.

You will want to use a higher quality grade bolt/nut than that one pictured.

 

[E-HP]

Any thoughts on the design? Should I beef up the beak of the bird? Or, should I go vertical like this?

Make sure to keep note of your brake pad alignment if your final design changes the normal axle location or adjustment range.

 

[BallHarder]

Looking good.

If you go vertical slot you may lose the ability to correctly tension the chain. Presuming BMX = one speed/no derailleur?

Do you have reasons for extending the "beak" out so far past the original dropout?

Don't forget the slot and small hole (stress reliever) at the inner end of the slot.

You will want to use a higher quality grade bolt/nut than that one pictured.

That settles it. I’ll do a horizontal drop out so I can still do chain adjustments.

I figured the longer the beak, the more leverage on the axle when tightening the nut.

 

[99t4]

I figured the longer the beak, the more leverage on the axle when tightening the nut.

Yes that certainly makes sense to our logical mindset, but not sure it is necessary. Hopefully some who have successfully built and used clamping dropouts will share more info.

 

[BallHarder]

The metal fabricator estimated $480 to cut two pieces and weld/bolt them to the existing drop outs. That's more than I paid for the bike.

 

[NateTN]

The metal fabricator estimated $480 to cut two pieces and weld/bolt them to the existing drop outs. That's more than I paid for the bike.

I highly suggest you check out Onshape and SendCutSend.

Spend a week learning basic CAD, design some drop outs that will bolt to your current setup and/or draw up your current dropouts so folks that are more familiar with CAD can help, and then have it all laser cut by SendCutSend.

Having mild steel cut by them is very economical and honestly, with that fabricator quote in mind stainless is still dirt cheap as well.

Cheers, hope that’s helpful.

 

[NateTN]

Just to throw it out there, I just quoted for some very similar sized (roughly) items as your dropouts in 0.250 304 stainless and it came out to less than $20 for a set, I think you could easily and economically solve the issues with your frame going this route.

 

[Hummina Shadeeba]

Maybe too late but I had a bunch of adapters made so can fit that hub in a 14mm bmx dropout. Nice machined steel pieces.

Give u two for ten bucks.

 

[neptronix]

The metal fabricator estimated $480 to cut two pieces and weld/bolt them to the existing drop outs. That's more than I paid for the bike.

A lot more expensive than bolting those ~$10 dropouts i mentioned to the bike eh!

 

[Hummina Shadeeba]

I had a bunch made back when I thought everyone needed an ebmx

 

[Cryingmadman]

I had a bunch made back when I thought everyone needed an ebmx

Hi,

I will take 2

just email me how you want payment

cryingmadman@gmail.com

 

[Hummina Shadeeba]

I found them. PayPal humminashadeeba@gmail.com
20$ with shipping and expenses. Add ur info there
They almost ended in the trash so u get a great deal. I made a couple different kinds. Some need a bit of filing to get the motor axle/shaft in: nice tight fit.

 

[neptronix]

Hey guys.. you may want to use PMs in the future and not publicly post your email address on here.
There's bots scraping email addresses all over the web which will pick these up and then spam you.

 

[Cryingmadman]

I had a bunch made back when I thought everyone needed an ebmx

Sent let me know if you receved funds

Thanks again
Cryingmadman

 

[Cryingmadman]

Hey guys.. you may want to use PMs in the future and not publicly post your email address on here.
There's bots scraping email addresses all over the web which will pick these up and then spam you.

Sorry my bad

Cryingmadman

 

[NateTN]

I had a bunch made back when I thought everyone needed an ebmx

Those sure look like an excellent solution for OP, were you running them without a torque arm successfully?

 

[Hummina Shadeeba]

Those sure look like an excellent solution for OP, were you running them without a torque arm successfully?

Yea they are a solid torque arm. Doing regen and vesc6 set to highest amperage.

 

[BallHarder]

Maybe too late but I had a bunch of adapters made so can fit that hub in a 14mm bmx dropout. Nice machined steel pieces.

Give u two for ten bucks.

You are not too late. I am so pumped to see your post and the pictures you posted look like exactly what I need. Thank you so much. Sent you a PM with shipping info and once you tell me how much you want for two sets I'll send the Paypal.

 

[BallHarder]

Thanks to Hummina I got some nice dropouts installed and the axle is nice and tight.

Unfortunately the bike isn’t working to propel me forward and I’m at my wits end with Leafbike.

I have everything connected like in their diagram.

The screen turns on and if I twist the throttle with the rear wheel in the air, the wheel spins with a lot of power.

As soon as I put the wheel on the ground and try twist the throttle the motor will jerk for a split second and then cut out.

Is this a faulty motor? Controller? Voltage mismatch?

I have gone back and forth with Leafbike sales. They have suggested resetting the hall sensors by plugging and unplugging a wire pair. That didn’t work. Then they suggested I unplug the hall sensor wire harness. That didn’t work either.

I’m attaching a video of the behavior in case anyone can help me troubleshoot. Motor Issue

 

[neptronix]

I'm happy the dropouts fixed but have no experience with their controllers ( i always tell people to not buy then ).

Possibilities:
- incorrect low voltage cutoff setting or some other kind of protection
- battery is super saggy due to some defect and you hit low voltage cutoff for that reason

Does the screen cut out when the power cuts out? is there a voltage meter of some sort that could indicate the battery voltage dropping?

 

[BallHarder]

The screen does not cut out, fade or die at all during the tests.

 

[neptronix]

Hm,, you have a 30ah battery so this should be beefy enough for the load even if the battery is screwed up.

They say their motors are capable of running sensorless, so if it won't run with the hall sensor unplugged, i don't think we can blame the hall sensors.

If you bought this kit, it's designed for "52v". They may have sent you a 52v controller with an upper voltage limit.
BMX 26 inch 48V 52V 1500W rear hub motor - electric bike conversion kit

A 60v battery is about 71v fully charged, which is beyond the limit of 36v-52v nominal controllers, 63v. A 14S "52v" battery will charge up to 61.1v, and is just below that threshold.

It could be that they sold you the wrong controller. An ideal one would be rated for 60v up to 80v, and have programmable upper and lower limits to account for the uncommon voltage you're running.

TBH the controller is the crappiest part of the leafbike kit. AFAIK it is not programmable and uses low quality FETs, which is why they need 18 of them instead of 12.

What voltage is your battery currently at? if you could figure out a way to discharge it, and you could get the battery down to 62v, we can see if my controller voltage theory is correct. A cheap discharge technique might be to run it upside down or on a stand with the throttle pinned for possibly an entire day because the battery is so big.

 

[Cryingmadman]

The screen does not cut out, fade or die at all during the tests.

H,

I have a couple new controllers and a new 48 volt battery if you want to bring bike over we can see what’s going on.. no charge of course

You have my email

Cryingmadman