My science and engineering club at school is working on a motorized wheelchair project. The wheelchair will have four wheels. We have calculated torque for the two back wheels; it is 245 Nm. The back wheels will hold 70% of the mass, which is 87.5 kg (total mass is 125 kg - person and chair). We need to decide if we should use one motor for both wheels, or a single motor for each wheel. We are having trouble converting the torque to the wattage needed on the motor, and we also would like help identifying the rpm for the sprocket on the motor.
We spoke briefly to support on the phone Friday and the recommendation was to use a single 24 V 450 W motor. We want to understand "why" that motor is the correct motor and try to apply it to the math we completed. We would like to use your Tech Forum for this assistance.
We have used your on-line gear ratio calculator and believe we will use a 26 inch wheel so a 2:1 gear ratio can be used to connect one of the back wheels to the suggested motor.
Would also like to discuss controller selection and possible battery selection as we continue to design our project.
The team decided to use a single 24V 450W motor in the design. We will not be able to use the suggested 36V motor for this project. For timing issues, we will not be able to wait for the delivery times you mention but feel we have found a motor to purchase on-line and will take this route for the motor.
We do wish to work with you and purchase the controller from you, plus any throttle control recommendations you have for items that are currently in stock with your company.
Any additional recommendations, parts list, etc. are appreciated! Thank you!
Yes - reverse
Twist throttle (unless you can make a better case for thumb throttle)
Yes to key switch
ESP Support -
We received the parts order mid- March and worked to compile the electrical system for the project. All the electrical system components worked well once we made modifications to the throttle connector. We are able to run the unmounted motor using the purchased electrical system. The project is progressing and the team is working to mount the motor and connect the motor to the sprocket on the axle.
We have a question concerning how tight the bicycle chain we purchased from ESP should be between the motor and the axle sprocket. We have tried looking for information on your site concerning chain tension. When we first tried to connect the motor to the sprocket, we continued to have the chain slip off. We actually think the tension is too tight but don't know for sure. The motor wants to pull towards the sprocket and we fear damaging the motor - this is why we think the tension is too tight.. We are working to re-enforce the motor mount but need to better understand the tension necessary for the bike chain.
Can you advise regarding the tension requiring on the chain when the motor and the wheel sprocket are connected? What is this for a typical motorized bike or trike?
A picture of the work in progress is included. Thanks!
The chain should definitely have slack and should not be 100% slack-less or else too much pressure will be placed on the motor's bearings and they could wear out very quickly.
Having an overly tightened chain should not cause it to fall off though, in fact it should help to prevent it from falling off. Usually when a chain falls off it is from the sprockets being out of alignment, or from new and used sprockets and or chain being used together.
If all of the sprockets and the chain are new then it has to be an alignment problem. However If a used chain and or used rear sprocket are being used with a new motor sprocket that could be causing the
chain to falling off. As sprockets and chains wear out during use
the chain stretches and that causes the sprocket teeth to wear out along
Here is an illustration that shows the most common sprocket alignment
problems and what perfect sprocket alignment should look like.
I like to check sprocket alignment by eyeballing one of the sprockets against the other one like this.
Please let me know if you have any questions.