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Old 04-01-2017, 10:46 PM
falshami falshami is offline
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Default stuck on my build need help with BLDC setup 10kw on my buggy urgent!

Ive been building an Electric buggy for myself to daily drive. most of it is complete, charging system works lovely. sound system, lights, everything is fine. However I am and have been stuck on the drive train. I have 35 inch tires. attached to a drive train that is realistically around 2:1 . the whole machine weighs about 900 pounds? I started with a 5kw BLDC motor. it didnt really do the trick. SO i upgraded to a 48v 10kw GM BLDC with a VEC500 controller and now we are moving at least. we got up to 30-40 mph. however acceleration is absolute dog crap i mean from a dead stop she struggles. also it seems the battery never gets taxed for the full 10kw. at peak amperage draw i saw maybe 160, when she should be able to do 200a draw. the controller is rated for 10kw continuous as well as 20kw peak for short bursts, i am no where near that, and with my gearing i should be able to get 60 mph . so what gives? why cant i squeeze all the power from my equipment? also motor hardly gets even slightly warm. controller a bit but since i adjusted a few settings its much better. thoughts? i need to finish this project asap!

Last edited by falshami; 04-01-2017 at 10:49 PM.
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  #2  
Old 04-01-2017, 11:12 PM
Karter2 Karter2 is offline
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Default Re: stuck on my build need help with BLDC setup 10kw on my buggy urgent!

A 2:1 drive reduction is not going to get the motor rpm much above 1200 rpm at 60 mph with those 35" tyres.
You probably need something like 8:1 or more to get the power out of that motor.

Last edited by Karter2; 04-01-2017 at 11:18 PM.
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Old 04-01-2017, 11:29 PM
falshami falshami is offline
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Default Re: stuck on my build need help with BLDC setup 10kw on my buggy urgent!

so are you saying that i should be reducing my motor or gearing it up? currently its 2 spins to ever one axle turn, and it just feels so slow and 30ish isnt cutting it. the motor is rated at 6000 rpm and maybe 4500 under load? so you are saying i should do a much smaller gear on my motor? and maybe by reducing the load the rpms will spin up higher? or is this a controller issue?
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Old 04-02-2017, 12:53 AM
Karter2 Karter2 is offline
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Default Re: stuck on my build need help with BLDC setup 10kw on my buggy urgent!

Yes, smaller gear on the motor.
Calculate the axle rpm at 60 mph.....about 600rpm ?
So if you want besr acceleration with a 60 mph max speed, the you should aim for max motor speed at 60 mph....about 8:1 gearing needed.
That would give you 4 time as much torque at the wheels than your current torque.
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Old 04-02-2017, 01:51 AM
falshami falshami is offline
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Default Re: stuck on my build need help with BLDC setup 10kw on my buggy urgent!

This is so obvious i feel like a moron. This is true. So currently with my 18 to 32 it is a bad combo. the smallest tooth gear i could find is a 10 tooth to 32 which should get us closer. to where we want to be. the next step is increasing the size of the axle gear but the issue there is that not much more will fit i don't believe much more will fit as it will hit the CV boot. but perhaps a 40 may fit and get us to 4:1. where as we will be at a 3:1 now. this should at least put me in a better position correct? and drop my amp usage at the same time?
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Old 04-02-2017, 07:07 AM
Karter2 Karter2 is offline
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Default Re: stuck on my build need help with BLDC setup 10kw on my buggy urgent!

If you cannot get suitable gearing to fit, you may have to build in an intermediate "jackshaft" to get enough reduction.
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Old 04-02-2017, 09:11 PM
nucleus nucleus is offline
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Default Re: stuck on my build need help with BLDC setup 10kw on my buggy urgent!

Quote:
Originally Posted by Karter2 View Post
A 2:1 drive reduction is not going to get the motor rpm much above 1200 rpm at 60 mph with those 35" tyres.
You probably need something like 8:1 or more to get the power out of that motor.
But there's more torque at lower RPM, and everyone knows that torque is more important than horsepower.
















Not.
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Old 04-03-2017, 01:38 AM
falshami falshami is offline
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Default Re: stuck on my build need help with BLDC setup 10kw on my buggy urgent!

well we do want plenty of torque and we will most likely end up playing with jack shafts. my confusion with jack shafts is ratios , ive been researching and i dont quite get them... so if i start with a 10t sprocket and have an ending sprocket of 32 or 35, what do i need the two gears on the jack shaft to get me close to an 8:1 ratio?
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Old 04-03-2017, 03:27 AM
Karter2 Karter2 is offline
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Default Re: stuck on my build need help with BLDC setup 10kw on my buggy urgent!

10T on the motor, driving a 40T on the Jackshaft (4:1 ratio)
Then a 16 T on the jackshaft , driving to a 32 T on the axle (2:1 ratio)
That will give you 8:1 total reduction.
But a 10T motor sprocket is not ideal from a wear or chain life aspect !
What type of chain are you using ?
Can you run 219 pitch chain to get better sprocket sizing ? At least from the motor to the jackshaft.
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Old 04-04-2017, 02:58 AM
falshami falshami is offline
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Default Re: stuck on my build need help with BLDC setup 10kw on my buggy urgent!

I can run any chain you recommend! im currently running a size 50 chain, will other chains and small toothed sprockets wear incredibly fast compared to others?
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