motor directly to driveshaft or use sprocket and chain?

[Quinc]

For those of you that have played with both setups which did you prefer? Is one better then the other? Depends on the motor?


Attached examples from other threads of both.

 

[SlowCo]

It depends on the whole system.
And what parts you can and are able to buy or use for the application you want to build.

So what do you want to build or achieve?

 

[Quinc]

Nothing too crazy. Small craft (100lbs 7ft long) for a 4 and 8 year old to play around on at the lake. using a jet pump for safety. I am thinking of the QS-120 motor with 72v li-ion 200a battery. I would like them to be able to do at least 20mph. (I will govern the speed through controller depending on which kid is driving.)

 

[SlowCo]

With a jet you can probably go direct drive. But it still depends on impeller size and pitch, I think. Do you still have to buy all components or are you using some you already own?

 

[Quinc]

With a jet you can probably go direct drive. But it still depends on impeller size and pitch, I think. Do you still have to buy all components or are you using some you already own?

So far I have the 72v 16ah 200a li-ion battery ordered.
I have 148mm and 144mm pumps out of a jetski. I have multiple impellers and pitch guides and can bend the impellers as needed.

and a boma 60v 5900rpm motor I might try @ 72v with 150a kelly controller before I order the QS. (QS because if its a major failure or the kids board of it I want something I can run in a pitbike.

 

[SlowCo]

That cheaper Boma motor isn't a bad idea. You could build a water cooling jacked around it to be able to get higher peak power without burning it out. It will take some experimenting with the impellers to get the motor operating in right rpm range at speed. Nice project!

 

[Quinc]

That cheaper Boma motor isn't a bad idea. You could build a water cooling jacked around it to be able to get higher peak power without burning it out. It will take some experimenting with the impellers to get the motor operating in right rpm range at speed. Nice project!

Appreciate the help! Any chance is there a place that sells a water jacket for these little motors? I was thinking about wrapping it with copper tubing and using thermal paste. But if something already exists that would save a bunch of time.

 

[SlowCo]

I'm not aware of a ready made solution. So the copper tube wrapped around it would be my choice as well. But most important would be to first get the motor running in it's most efficient (higher) rpm range at speed by matching the load of the impeller on the motor in the speed range you want the craft to go.

 

[Quinc]

Getting closer with the build and thinking if I want this thing to get out of its own way I am going to need at least 5500rpm and preferably 6500 rpms.

Has anyone had experience with over driving electric motors? (running larger motor sprocket then axle sprocket)

My plan:
QS-120 motor and 72v 16ah li-ion 300amp battery

Motor: 2800rpms 4400 with flux weakening *or* 3600rpms - 4600rpm with flux depending on which website you read.)
Motor sprocket: 17T (still looking for a 20T)
Driveshaft sprocket: 10T

I am thinking craft with kid will weigh around 200-220lbs.

 

[goatman]

you will lose half the motor torque, it will go from 45nm to 22nm
i should be sea trialing the da-85 this weekend, it has 54nm
http://eastgem.net/da85.html

15000 rpm
https://www.youtube.com/watch?v=MtCIc6Kpo38

72v 16ah, what batteries?

 

[Quinc]

you will lose half the motor torque, it will go from 45nm to 22nm
i should be sea trialing the da-85 this weekend, it has 54nm
http://eastgem.net/da85.html

15000 rpm
https://www.youtube.com/watch?v=MtCIc6Kpo38

72v 16ah, what batteries?

Battery pack is SPIM08HP with 300amp ANT bms.

15k rpm is insane! Prices arent bad either. Keep me posted on how your testing goes!