DH Comp Rotomax Mid drive

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Feist92   1 mW

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DH Comp Rotomax Mid drive

Post by Feist92 » May 02 2019 9:15pm

Ive been absorbing info from this site for quite some time but figured it was about time I posted what Im trying to do.

I got the ebike bug a couble of years ago and made a rushed decision to buy a Rotomax 150 from hobby king.
Almost as soon as I got the motor things got busy at work and life and has sat in a box buring away in the back of my mind. Ive finally decided this should be a priority for me as the traffic getting to work is getting worse.
Excuse the rough CAD (btw I didnt draw any of the base bike parts)

Im not sure what to do with the batteries but I have a bunch of prismatic lipo cell that Ill probably use and I want a Lebowski based motor controller coz they're awesome. I bought a couple of his chips around the time I bought the motor but never did anything with them. The biggest Issue I think Ill have will be with making a power stage capable of running this motor up to it limits.
Im fairly keen to see how this thing does as Im yet to find anyone else running this motor.
Updates will unfortunately be sporadic and infrequent
Attachments
Drive train L.PNG
Drive train R.PNG

Feist92   1 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » May 18 2019 3:39am

Ive tidied up the cad a bit and started machining the main drive train block. Ive still got 3 opps to go on this so its a wee way off yet.
Drivetrain R2.PNG
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DanGT86   10 kW

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Re: DH Comp Rotomax Mid drive

Post by DanGT86 » May 18 2019 9:14am

Nice plan and work so far. Controllers for these large RC motors have proven challenging for bike use so far which is why you don't see a whole lot of them run to full potential. Looks like a nice compact mounting solution.

Have you given any thought to using the swing-arm pivot as the jackshaft location so you can eliminate all chain tensioners? Did you place the jackshaft in that location to promote any particular suspension behavior like anti-squat?

I'll be keeping an eye on this build. Good luck and again nice work so far!

e-Sprocket   1 mW

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Re: DH Comp Rotomax Mid drive

Post by e-Sprocket » May 18 2019 7:28pm

Love the CAD and machine work! I use Fusion 360 for all my builds. Geek time.


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e-Sprocket   1 mW

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Re: DH Comp Rotomax Mid drive

Post by e-Sprocket » May 18 2019 7:37pm

Feist92 wrote: Im fairly keen to see how this thing does as Im yet to find anyone else running this motor.
I thought about using the larger RC motors. You may have issues with cooling. I think you also may run into problems with it being open to the ferromagnetic elements.



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Feist92   1 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » May 20 2019 2:41am

DanGT86 wrote: ↑
May 18 2019 9:14am
Nice plan and work so far. Controllers for these large RC motors have proven challenging for bike use so far which is why you don't see a whole lot of them run to full potential. Looks like a nice compact mounting solution.

Have you given any thought to using the swing-arm pivot as the jackshaft location so you can eliminate all chain tensioners? Did you place the jackshaft in that location to promote any particular suspension behavior like anti-squat?

I'll be keeping an eye on this build. Good luck and again nice work so far!
The controller will be the limiting factor for a long while, Im thinking that Ill have to be fairly progressive with my expectation due to my lack of money/ knowledge. Ill probably have to start with a generic chinese controller then work my way up.

That was what I was hopping to do but unfortunately this swing arm is remarkably hard to clear with a chain. I wish I had but how it is, is the only way I could get it to fit and Ill still have to do some weird things with the lower part of the chain line. At some point Ill build my own frame but this will have to do for now at least
e-Sprocket wrote: ↑
May 18 2019 7:28pm
Love the CAD and machine work! I use Fusion 360 for all my builds. Geek time.
Thanks, Im using solidworks for the CAD and Fusion for CAM. Ive not been able to get my head around the modeling side of fusion yet. Im putting it down to being too thick :lol:
e-Sprocket wrote: ↑
May 18 2019 7:37pm
I thought about using the larger RC motors. You may have issues with cooling. I think you also may run into problems with it being open to the ferromagnetic elements.
Even if i only get 6kw peak out of this motor Ill be fairly happy and if not the stator on these motors have very convenient cut outs which I might use for water cooling

Feist92   1 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » May 25 2019 9:46pm

I got the lower block mostly finished and made a couple of clamps to see how they fit up
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Feist92   1 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » May 30 2019 4:27am

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e-Sprocket   1 mW

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Re: DH Comp Rotomax Mid drive

Post by e-Sprocket » May 31 2019 10:50pm

Killer!


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Feist92   1 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Jun 01 2019 12:36am

Thanks mate
I thought I wanted to put the controller behind the seat post but Im thinking it would be better in the triangle so now the hole for the phase cables is on the wrong side. Aside from that Im fairly happy with it
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Merlin   1 MW

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Re: DH Comp Rotomax Mid drive

Post by Merlin » Jun 11 2019 6:10pm

p0rn!

Feist92   1 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Jun 14 2019 11:21pm

Ive modified the rotor and made a new shaft to extend out the back of the motor. The pulleys are just 3d printed for now, Ill make some proper ones at some point but Im rather curious to see how the printed ones hold up.
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aCeMadMod   1 kW

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Re: DH Comp Rotomax Mid drive

Post by aCeMadMod » Jun 18 2019 8:54pm

What controller will you use?

Great job. Upgrade motor bearing it will help

Looking forward to end ebike😎
Do you have 135mm or 150mm rearend for comp frame

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Drunkskunk   100 GW

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Re: DH Comp Rotomax Mid drive

Post by Drunkskunk » Jun 19 2019 4:11pm

That thing is seriously awesome. Any plans to make a few and sell them?
Buy the ticket, take the ride.
Monster Bike:http://endless-sphere.com/forums/viewto ... =6&t=38667

Feist92   1 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Jun 21 2019 9:23pm

aCeMadMod wrote: ↑
Jun 18 2019 8:54pm
What controller will you use?

Great job. Upgrade motor bearing it will help

Looking forward to end ebike😎
Do you have 135mm or 150mm rearend for comp frame
Im not sure, there are a couple on the cards atm. I was looking at a lebowski, mobipus or one of the beefed up vesc 6 controllers but Ive just found out about Vasili's 12f Nucular controller which seems like a really good fit.
Rear on this frame is 150mm
Drunkskunk wrote: ↑
Jun 19 2019 4:11pm
That thing is seriously awesome. Any plans to make a few and sell them?
Thanks. Not really at this stage. If I do it will be a lot simpler that what Ive got currently, the jack shaft block in particular is a pain in the ass to machine

Grantmac   10 kW

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Re: DH Comp Rotomax Mid drive

Post by Grantmac » Jun 22 2019 12:38pm

Correct me if I'm wrong, but you are going to drive the sprocket side of the wheel right?

Feist92   1 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Jun 22 2019 3:17pm

Na disk brake side

Grantmac   10 kW

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Re: DH Comp Rotomax Mid drive

Post by Grantmac » Jun 22 2019 4:23pm

Correction: I mean disc side.

Regen for brakes or keeping the disc too?

larsb   100 kW

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Re: DH Comp Rotomax Mid drive

Post by larsb » Jun 23 2019 5:28am

The controller will be the limiting factor for a long while
I've looked at this myself: http://teamtriforceuk.com/a200s-v2-1/
Nice power in a small package, VESC.

Maybe also a Kelly high speed option controller could work (even though i have blown too many kellys to really recommend them.)

Is BEMF sine or trap-shaped?

EDIT: It's sine! viewtopic.php?t=48580
Ride on :D

Feist92   1 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Jun 25 2019 12:05am

Grantmac wrote: ↑
Jun 22 2019 4:23pm
Regen for brakes or keeping the disc too?
Im mounting the sprocket to where the disk would be mounted on the hub so will have to rely on regen or just the front brake
larsb wrote: ↑
Jun 23 2019 5:28am
I've looked at this myself: http://teamtriforceuk.com/a200s-v2-1/
Nice power in a small package, VESC.
Maybe also a Kelly high speed option controller could work (even though i have blown too many kellys to really recommend them.)
Is BEMF sine or trap-shaped?
EDIT: It's sine! viewtopic.php?t=48580

I had seen that one along with the BESC. The problem with the a200 is its limited to 16s and I was hoping to go up to 20s altho I havent decided if thats the best idea, 16s might be easier to work with.
Id rather not go to a kelly, theyre rather big for what they are. Id like to try a mobipus but I have no idea what erpm they go up to.
This motor in WYE should be around 33mOhm, 54microH and 86.5kv which (I think) is 62,300erpm (based on 10 pole pairs and 72v pack) And yes, quite a nice sine wave :D
Last edited by Feist92 on Aug 18 2019 3:31am, edited 1 time in total.

Grantmac   10 kW

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Re: DH Comp Rotomax Mid drive

Post by Grantmac » Jun 25 2019 1:14am

Regen only could be very elegant if the chain routing doesn't cause weird suspension loads and you come up with a good way to modulate it.

Feist92   1 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Jun 25 2019 3:00am

Thats one thing that Im not too sure on actually. I had planned this routing initially
Chainline2.PNG
But like you mentioned it wont really work with regen. Because both sides of the chain are above the pivot point of the swing arm when the suspension compresses both sides of the chain will shorten and therefore need a chain tensioner that is capable of taking a lot of slack.
The routing below fixes that issue because when the chain on the top shortens the bottom lengthens removing the need for a chain tensioner. The problem with it is theres almost nothing to to mount the lower idler on, the wrap on the drive sprocket isnt great. Not to mention that it looks a bit weird
Chainline1.PNG

larsb   100 kW

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Re: DH Comp Rotomax Mid drive

Post by larsb » Jun 25 2019 6:56am

Feist92 wrote: ↑
Jun 25 2019 12:05am
I had seen that one along with the BESC. The problem with the a200 is its limited to 16s and I was hoping to go up to 20s altho I havent decided if thats the best idea, 16s might be easier to work with.
Id rather not go to a kelly, theyre rather big for what they are. Id like to try a mobipus but I have no idea what erpm they go up to.
This motor in delta should be around 33mOhm, 54microH and 86.5kv which (I think) is 62,300erpm (based on 10 pole pairs and 72v pack) And yes, quite a nice sine wave :D
I think with 10 pole pairs, kV 150 and noload consumption of 250-300W at 14s you'd get quite high eddy losses at 20S. It'd be higher than hobbykings speced rpm by a lot.. "To have flying magnets or not to have" as shakespeare would've said :D
Ride on :D

Grantmac   10 kW

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Re: DH Comp Rotomax Mid drive

Post by Grantmac » Jun 25 2019 5:13pm

What about relocating the jackshaft to the front of the downtube inline with the pivot? Yes it would require a rework but you should be able to put batteries in the frame then.

Feist92   1 mW

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Re: DH Comp Rotomax Mid drive

Post by Feist92 » Jul 13 2019 8:54pm

larsb wrote: ↑
Jun 25 2019 6:56am
I think with 10 pole pairs, kV 150 and noload consumption of 250-300W at 14s you'd get quite high eddy losses at 20S. It'd be higher than hobbykings speced rpm by a lot.. "To have flying magnets or not to have" as shakespeare would've said :D
Youre probably right. I think Ill be sensible for now, Ive got a couple of 16s4p packs which I should make use of anyway.
Grantmac wrote: ↑
Jun 25 2019 5:13pm
What about relocating the jackshaft to the front of the downtube inline with the pivot? Yes it would require a rework but you should be able to put batteries in the frame then.
Im way past the point of no return, that and its the only way to route the chain, the swing arm gets in the way of every possible good chain line.

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