GrayK's RC Mid-Drive (Deathbike)

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GrayK   1 mW

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GrayK's RC Mid-Drive (Deathbike)

Post by GrayK » Apr 29 2019 11:52pm

I have been using CAD so much more recently and decided it was time to make a crazier bike than my old Denzel motor. When I had the fund I started to work on an extremely compact solution. I am using 3 VESC all in a CAN array powering 200kv 6384 sensored motors. Pictures do most of the talking. I was extremely lucky and had a friend of mine waterjet the plates for me. I can hit 40mph on 1st gear and its so much power I worry that I will break the controllers. Still building confidence on it. If there is a big enough demand for these motor assemblies I might start selling them. They are super compact and still can output 100Nm of torque at the drive sprocket. The hardest part now is finding batteries that will be happy to push out 240+ amps so, for now, its 12s Lipo. I also can't get FOC to work on VESC because of a "Flux leakage"
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thorlancaster328   10 W

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by thorlancaster328 » Apr 30 2019 12:07am

That's quite the build!
Have you considered putting a chain guard over the mid-drive chainsaw mechanism?
Find weakest component, upgrade it, repeat until satisfied. Rome was not built in a day.
When in doubt, get bigger MOSFETs / Batteries / Motors / Etc.

GrayK   1 mW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by GrayK » Apr 30 2019 12:42am

Hahaha thats so funny yeah kinda have been busy recently with school but for now i'm wearing shorts and tucking in laces

fio   1 µW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by fio » Apr 30 2019 12:46am

:warn: :warn: :flame: :flame:

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icherouveim   1 kW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by icherouveim » Apr 30 2019 1:11am

Great project!
Do you have some videos to share with us?
I can see some LG 18650 cells, is this your backup power to get you home when you run out of lipo power??

GrayK   1 mW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by GrayK » Apr 30 2019 10:34am

icherouveim wrote:
Apr 30 2019 1:11am
They arent 18650s they are large Caps I think you are talking about the VESC noise protection but im not sure. I will post videos soon

billvon   1 GW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by billvon » Apr 30 2019 11:50am

GrayK wrote:
Apr 29 2019 11:52pm
I can hit 40mph on 1st gear and its so much power I worry that I will break the controllers.
I'd worry more about breaking the chain/cluster. That's a lot of torque for a bike chain designed for ~250 watts.
--bill von

GrayK   1 mW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by GrayK » Jun 06 2019 3:11am

billvon wrote:
Apr 30 2019 11:50am
GrayK wrote:
Apr 29 2019 11:52pm
I can hit 40mph on 1st gear and its so much power I worry that I will break the controllers.
I'd worry more about breaking the chain/cluster. That's a lot of torque for a bike chain designed for ~250 watts.
I put a torque curve on the motor controller for that reason. It ramps up the power from 10% to 100% in a given time independent from the position of the throttle.

billvon   1 GW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by billvon » Jun 06 2019 2:30pm

GrayK wrote:
Jun 06 2019 3:11am
I put a torque curve on the motor controller for that reason. It ramps up the power from 10% to 100% in a given time independent from the position of the throttle.
That doesn't sound like it limits the torque, just reduces the ramp rate.
--bill von

GrayK   1 mW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by GrayK » Nov 03 2019 3:37pm

billvon wrote:
Jun 06 2019 2:30pm
GrayK wrote:
Jun 06 2019 3:11am
I put a torque curve on the motor controller for that reason. It ramps up the power from 10% to 100% in a given time independent from the position of the throttle.
That doesn't sound like it limits the torque, just reduces the ramp rate.
Yeah its a current ramping limit. Basically a torque limiter

Grantmac   10 kW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by Grantmac » Nov 03 2019 4:17pm

That's a really good frame to run as left hand drive since the rear drop out is 150mm. With a 40mph first gear that's all your need. That would also let you run more of the reduction on the rear wheel via 219 chain.
Plus your be able to pedal and chain breakage is much less likely.

I bet it sounds wild!

billvon   1 GW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by billvon » Nov 04 2019 10:10am

GrayK wrote:
Nov 03 2019 3:37pm
Yeah its a current ramping limit. Basically a torque limiter
But it doesn't limit the torque; just limits how fast it rises. Your powertrain still has to withstand all the torque the motor can put out.
--bill von

GrayK   1 mW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by GrayK » Nov 04 2019 9:37pm

I disagree since Torque generated = (60 * K * I * flux)/ 2pi where K is the armature torque constant and I is the current. The torque generated is directly proportionate to the current being fed into them.
billvon wrote:
Nov 04 2019 10:10am
GrayK wrote:
Nov 03 2019 3:37pm
Yeah its a current ramping limit. Basically a torque limiter
But it doesn't limit the torque; just limits how fast it rises. Your powertrain still has to withstand all the torque the motor can put out.

billvon   1 GW

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Re: GrayK's RC Mid-Drive (Deathbike)

Post by billvon » Nov 04 2019 11:28pm

GrayK wrote:
Nov 04 2019 9:37pm
I disagree since Torque generated = (60 * K * I * flux)/ 2pi where K is the armature torque constant and I is the current. The torque generated is directly proportionate to the current being fed into them.
Agreed. So if you limit the current, you limit the torque. If you let the current ramp up to maximum, then you ramp up to maximum torque.
--bill von

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