8am-5pm Pacific Time Monday-Friday
Start a new topic

Electric dolly project


I am an engineering student and my capstone project is to design and build and electric cart to transport two welding cylinders. We have the cart designed and now we are trying to determine a motor size. Calling manufacturers hasn't gotten me anywhere.


~ 600 pounds

walking speed (~3 mph)

15 degree max incline

Can anyone provide guidance ?

We can help and have practically all of the parts that will be needed. Figuring out the gear ratio for a 3 mph top speed is the first step. We can figure out the correct gear ratio and sprocket sizes using our gear ratio calculator. Do you know what size tires (outside diameter) the dolly has or will have?

Yes. The front two wheels on the drive axle are 13 inch diameter


13" Drive wheels

3 MPH max speed

15 degree max incline

600 pounds max total weight

Any help with spec'ing out parts will be greatly appreciated!!

We need a better option for batteries, a throttle, controller, motor and brakes

(82.5 KB)
(47.2 KB)
(57.1 KB)
(71 KB)
I ran a gear ratio calculation using our 24 Volt 350 Watt gear motor which has a 420 rpm under load shaft output speed and found that with a 50 tooth sprocket on the axle or wheel the top speed would be 2.93 mph. Here is the calculation.


 A 24 Volt 350 Watt motor pulling 600 pounds up a 15 degree incline at 3 mph is very close to the motor's power limit. I think it would work however it does not leave much room for occasionally pulling up steeper inclines. If you want to overbuild the machine, a 36 Volt 600 Watt motor would be a better choice, however the cost of electrical parts would be more if using a 36 Volt 600 Watt gear motor and electronics compared to using a 24 Volt 350 Watt system.

Here is an example of a 24 Volt 350 Watt gear motor kit that sells for $300.00: https://cart.electricscooterparts.com/ProductDetails.asp?ProductCode=KIT-145-C

And here is an example of a 36 Volt 600 watt gear motor kit that sells for $635.00: https://cart.electricscooterparts.com/ProductDetails.asp?ProductCode=KIT-149

We can modify these kits with different parts such as larger or smaller batteries, different size sprockets, different style throttles, etc. For example if the kit with 36 Volt 600 Watt motor was modified to have smaller 22Ah batteries and a smaller 2.5 Amp battery charger then its cost would be decreased by around $200.00.

Please let us know your thoughts and we will take it from there.

Hi, I'm in this class designing with Rachel.  The issue we are running in to is that the cart needs to go up a grassy hill.  The calculations we ran say that we need 1400 in* lb of torque from the motor to ensure we can avoid getting stuck on the hill. 


Our 36 Volt 600 Watt gear motor has 112 inch pounds of torque at its output shaft. To increase 112 inch pounds of torque at the motor to 1400 inch pounds of torque at the wheel, a gear ratio of 12.5 to 1 (12.5:1) would be needed.

Our MOT-36600G 36 Volt 600 Watt gear motor has a 10 tooth sprocket for #420 chain. If a 125 tooth wheel or axle sprocket was use then there gear ratio would be 12.5 to 1 and the wheel would have 1400 inch pounds of torque.

However with this motor and this gear ratio the top speed would only be 1.38 miles per hour. To double this top speed for a top speed of 2.76 miles per hour, two 36 Volt 600 Watt gear motors could be used along with two 62 tooth wheel or axle sprockets.

Here is the gear ratio calculation for one 36V 600W gear motor with a 125 tooth wheel/axle sprocket and 12 inch tires.


 Please let us know if you have any questions.

With your experience, do you foresee any issues with our cart having two motors which are powered independently or would you suggest us having both motors on the same controller

Having two motors powered independently with two controllers would not cause any issues at all, and one throttle could be connected to two controllers so they are both regulated with a single throttle. Using one controller for two motors would also work without any issues. Either way would work great.

This is very helpful and we really appreciate it. We will most likely be ordering a kit from you for our project so we will probably make some changes to what it includes.

-Do you guys carry the #40 60 tooth sprockets and chains we would need? 

-We only need this thing on and running for maybe 10 minutes at a time between charging... I have someone looking into what that actually means mathematically for batteries, but off the top of your head what would you recommend for two motors running for that long?

-We would still need the throttle, controller and a fuse but now we will need provisions for the duel motors and also we would like a circuit breaker instead of a regular fuse.. is that possible?

-Would you know off the top of your head what we would need for a "dead man switch" to wire in to our circuit? 

-We have a mechanical brake system that is basically a bar held tight across the wheels by springs . The thought is that the bar will be actuated until the operator pulls a lever to disengage the bar.. adding a sort of "safety" feature if the operator should remove his hands from the handle bar the cart will stop. Would any of the brake lever kits here work for a system like that? I can provide a sketch if it does not make sense. We are still working through the design so theoretically we could make changes to accommodate for the kit available.

I will probably think of more components that we will need for our assembly but that is a start for our purchasing process.

The MOT-36600G gear motor has a 10 tooth sprocket for #420/#41 chain factory installed onto it. #40 chain has a slightly larger roller than #420 and #41 chain so I recommend to use either #420 or #41 chain so the original sprocket on the motor can be used. #420 chain is 50% stronger than #41 chain and usually costs the same so I would use #420 chain if possible.

We do sell #420 chain and it is available on this page: https://electricscooterparts.com/chain-420.html

We just started selling #420 chain and sprockets last year so we do not have a good variety of #420 sprockets yet - we only have a 34 tooth sprocket right now. However virtually all stores that sell go kart parts have 60 tooth sprockets for #41/#420 chain so that sprocket will be very easy to find.

Regarding battery size the maximum discharge rating of the battery is the most important thing to consider first because that will determine if the battery will have enough power in it to run the machine at full power. Since your electric powered dolly will have two 36 Volt 600 Watt motors the maximum power draw will be 1200 Watts. A 1200 Watt 36 Volt load equals a 33.33 Amps so a battery pack with a 34 Amp maximum load rating would be needed in order to provide enough power to run the two 600 Watt motors at full power. Here is a chart we have showing maximum discharge current ratings for sealed lead acid (SLA) batteries.


Looking at the chart you will notice that a 12Ah battery pack can output 36 Amps for 7 minutes. Unless you are planning on driving the dolly up a steep hill for more than 7 minutes at a time then a battery pack made from three 12 Volt 12Ah batteries would do the job and would provide a 10 minute or longer run time.

We can switch the fuse in our kits over to a circuit breaker, that is no problem at all.

For a dead man switch one of our handlebar mount momentary switches such as SWT-25 could be used as the main power switch, or in conjunction with another main power switch. It can be viewed on this page: https://electricscooterparts.com/handlebarswitches.html

We carry brake levers and cables that could be used to disengage the bar brake. They can be viewed on these pages: https://electricscooterparts.com/levers.html    https://electricscooterparts.com/cables.html

We can start making a kit for your project once all of the parts that you want to have in it have been chosen. If you could let us know the part numbers of the parts for the kit we could go ahead and make it.

If you have any further questions or need any information about our parts before choosing which ones to include in the kit then please let us know, and we will be glad to help.

 These are the items that we need for the kit:

36 Volt 600 Watt Electric Scooter Gear Motor (MOT-36600G) x 2

10 Feet of #420 Chain with Master Link (CHN-42010LF)

#420 Master Link (CHN-420ML)

BAT-12V12A, 12 Volt 12 Ah Battery Model WP12-12/T2 With 12 Month Warranty x 3

3 Pin Black Nylon XLR Charger Port with Cover and 12" Wires (CNX-XLR05W)

Full Length Wuxing Twist Throttle with 36 Volt Power Meter (THR-110)

36 Volt 800 Watt Speed Controller (SPD-36800B)

Handlebar Mount On/Off Power Switch (SWT-21)

36 Volt 2.5 Amp Automatic Battery Charger With 3-Pin XLR Plug (CHR-36V2.5AXLR)

we would also like a circuit breaker - whichever you feel is appropriate

I included a 40 Amp circuit breaker with the kit. We would normally recommend using two 36 Volt 800 Watt controllers with a kit like this so each 600 Watt motor had its own controller. Two controllers would be best if the cart was going to be used industrially on a daily basis. However if the cart will only be used for demonstration then one controller will be okay. If you decide to use two controllers then please let me know and I will modify the kit to have two.

The MOT-36600G motors are currently on back order and will be back in stock in around 10-14 days. After the kit is ordered we will go ahead and make it, so as soon as the motors arrive it will be ready to ship out. I apologize that we do not have these motors in stock today and hope that this time frame works for you.

I made the kit and here is the link to it: https://cart.electricscooterparts.com/ProductDetails.asp?ProductCode=KIT-157-B

Please have a good look at all of the parts in the kit to make sure that I included everything that you want. I can modify the kit if anything needs to be changed or added to it.

Please let us know if you have any questions.


I believe this kit will work for us I need to confirm with my team.  Can you give me a shipping estimate on the kit as well.  Shipping to Newark, DE 19713


The best shipping rate for this kit to Newark Delaware 19713 is $41.66 with FedEx Ground delivery.

Please let us know if you have any questions.

Login or Signup to post a comment