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Building a trike mobility scooter

My wife currently has a Zappy made by Zap and loves it except for when going up a hill or in grass the front wheel loses traction.  I am building her a similar design but I want to drive from the rear wheels.  My question is drive motor options.  If a live axle will it turn?  Would a transaxle be better or dual drive motors?  She like the speed of this one at about 13 MPH and the light weight design so want to keep it similar.  She also like the freewheel going down hills when in a campground and running the dogs.  Any thoughts or suggestions would be appreciated.

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The trike will be difficult to turn if it has a live axle because most of the weight is on the rear wheels so they have a lot of traction. A transaxle or dual drive motors would be better. Since a transaxle only provides power to one of the wheels, and to the wheel with the least amount of traction at any given time, a dual drive motor design would provide the highest amount of traction and would also allow the trike to turn well because the motors will speed up and slow down depending upon how much load is on them. When making a turn with a dual drive motor system the outside motor will have less load and will speed up and the inside motor will have more load and will slow down.

Adding freewheeling sprockets to the rear wheels would allow for even easier turning with a dual motor system because the outside wheel could freewheel when going faster than the inside wheel. 13 MPH is a very reasonable speed to achieve with a single or dual electric motor drive system. Depending on how steep the hills are that you are designing it to go up I would use two motors rated between 250-500 Watts each. A dual 250 Watt motor setup would be able to climb moderate hills with a 13 MPH top speed gear ratio, and a dual 500 Watt motor setup would be able to climb fairly steep hills with the same gearing.

Appreciate the advise.  Can you start to work up a kit to include 2 motors, controllers, charger, freewheeling sprockets and anything else needed.  Planning on a 36V system but have room to do 48V if needed.  Would also like it to have reverse.  I have a new twist throttle, 3 wire, but will need everything else. Since you recommend 250-500 watt lets split the difference and go with 350.  Wonder if I should install one motor to a switch so it could be turned off, then turn on if traction is needed?  Assume battery life would be increased and turning would really be good then.


I am also a bit confused on drive wheels at this point since my initial plan was a live axle.  Do you have any recommendations?  Was hoping for a 5-6 inch wheel that would accept a 4-5 inch wide tire that has some traction and being 12-13" overall height. I have not started to fabricate anything at this point since purchasing the drive kit should be step one so any options would be great.



I recommend inquiring with a store that sells go cart parts for the wheels and axle. I think that would be the best place to try to find those parts.

I like your idea about having the motors switchable so either one can be turned on or off at anytime. The best way to do that is to have two speed controller and then each controller could be turned on and off as needed. Reverse is no problem we have controllers with reverse. I can start working on a kit for the electrical parts and motors. Running the scooter on 36 Volts would be required in order to have 350 Watt motors, as we do not have 350 Watt motors available in 48 Volts. For the kit do you have any idea which throttle and motor you would like to use, and what size batteries?

36 Volt Motors:
36 Volt Throttles:

Please let me know if you have any questions.

I think I have located wheels and axle so will be going with a 3/4" axle.  6" wheels so overall height should be in the 12-13" range so you can gear it accordingly.

Motor I want to change up and go with the 450W item MOT-SD36450.

Throttle - I have a brand new half twist 36V throttle, three wires on it so don't need that.

Batteries would be three of - BAT-12V22A.

correction.  5" wheels, 1" axle with 11 inch overall diameter.  72 tooth to an 11 tooth looks like it should be good,


I just finished making a kit for your project. Please look over all of the parts in the kit and let me know if you need any changes made to it.

Here is a link to the kit item # KIT-151:

Couple of questions.  We spoke about freewheel clutches for both sides, do you still recommend these?  If I send you a nice little headlamp, key switch and horn assembly off of a Zappy 3 Pro-Flex can you add connectors so it will plug into this module as well?  If you could do that I would need only one of the handlebar power switches but would need to add one of a SWT-32.  I also need the following if you wish to add to your kit for ease of ordering.



1 WHL-1053

1 BRK-480L


I am sure there is more but would like to get these items and start fabrication around these.

Having freewheel clutches on the rear wheels will allow the scooter to coast with the motors off. They will allow the scooter to be easily pushed when its power is off. Freewheels will also allow the scooter to coast when going down a hill or incline which will require the brakes to be used more often. The scooter will be more efficient with freewheels so the ride time may be a little longer in between battery charges, however the freewheels will make the scooter coast so the brakes will need to be used more often. If the scooter will be used to go down hills or inclines then I would recommend not having freewheels so the motors can provide braking, this will make the scooter a lot more predictable to ride and easier to control.

We do not have a wiring diagram or pin out for the Zappy 3 Pro-Flex headlamp, key switch and horn assembly so I am not sure which of its wires are for what functions. That makes it risky to wire to the harness because we would have to guess which LED light wire is positive and negative, and if we guessed wrong that could burn out the headlight LEDs. I am not sure if the assembly is held together with screws or glue. If it is held together with screws then we should be able to take it apart and see where its wires go to. We could definitely give it a try if it is held together with screws but I am not sure how long it would take us so we would need to charge hourly for that part of the job. My guess is that it would take us around 60 minutes to take apart and reassemble the headlight assembly to figure it out, and to make a wiring harness for it that attaches to the switches and controller. Our shop labor fee is $60 per hour.

I can add the additional parts to the kit once the decision to use the headlight assembly has been made. Would you like to send the headlight assembly in and swap out a SWT-23 for a SWT-32?
We do want freewheels for sure so please include those as well and the other parts requested included swapping one of the one power switch out.  As far as the headlamp combo I will ship that your way tomorrow.  The one I am sending you is one that Zappy warrantied due to a little plastic part on the ignition switch that broke and allows the key switch to spin but it is still functional and is held together with screws so you can examine it.  Don't worry if you hurt it as I will buy a new one anyway for 40 bucks.  The first key position is ignition on and the second it headlamp on.  Ready to place the order as soon as possible.  Appreciate all you assistance! 


We do not have 70 tooth sprockets that fit onto freewheels. The sprocket sizes we have that fit onto freewheels are 55, 65, and 80 tooth. I ran a gear ratio calculation and found that with the 65 tooth sprocket the top speed will be 17.07 MPH, and with the 80 tooth sprocket the trike will have a top speed of 13.88 MPH. Here is a screenshot of the gear ratio calculations.

The freewheel will be significantly more difficult to mount to the wheels than a plate sprocket. We have freewheels that catch in both clockwise and counterclockwise rotations so that is not a problem. However these freewheels thread onto hubs with M35X1.00 left hand and right hand threads. That is something to consider when choosing whether to use freewheels or not. Before I make a new kit with freewheels and different size sprockets could you please investigate whether you have the resources to mount the freewheels onto your rims? Also if you decide to use freewheels please let me know which size sprockets you would like to use.

That does make it a bit more challenging.  Do you have any type of hub or wheel that these would thread onto?  Are the clutches made of steel and if so could I weld an adapter plate to them or would this hurt internals?  Have done some looking for RH and LH dies of this thread pitch and find many RH but not LH.  The 80 tooth sprockets will be fine.  I did ship the headlamp module we spoke about on Monday via UPS so you should be seeing that any time now.

The right hand thread freewheel will thread onto any of our rims and wheels with threaded hubs. The left hand freewheel is not very commonly used however we do have one rim for 12-1/2" tires that has a hub with reverse M34X1 threads. The rim for 12-1/2" tire that we have available with both right and left hand M35X1.00 threaded hubs looks like this.

The clutches are made entirely out of steel and should hold up to careful welding as long as they were re-oiled after they cooled down. They can be re-oiled externally without taking them apart.

Left hand M35X1.00 threads are rare so I am not surprised that a die can not be found for it. Welding the freewheels onto 35mm OD steel pipe may be the easiest way to attach them if you want to use them with steel rims.


I am sure I can chuck up something in the lathe and make a nice adapter plate for the clutches so not overly concerned, just thought you might have something available I could adapt or use to work.  I will look at the price of this wheel later, might be able to destroy it for adapters cheaper than spending my labor building them.  

I did insert a note in my shipment to you about possibly in your wiring harness installing in line connectors from any wires running from the handle bars so I can easily install them in the plastic body that will be used with this build just in case I need to separate the fork and handlebar section in order to travel on airlines.  I also left my phone number in there so you can call and discuss in person.

Thanks again.

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