Gruber
HobbyMasters
M.L. Toys
KidsWheels
Gruber
HobbyMasters
M.L. Toys
KidsWheels
HobbyMasters M.L. Toys
Gruber
KidsWheels
Need new motors? Grind a gearbox? Adding teeth to a pinion?
#146156
Hey, guys...I joined a while back but have been lurking since. I'm still working on a scratch-build ride-on project (never-ending though it may be), and have finally gotten the fiberglass body done to the point that I want to start on the steel frame and mechanical stuff.

I've looked at a bunch of threads, going back to the old forum, of how others have modified their Power Wheels vehicles. There are tons of good-looking ideas, but not all of the threads had a lot of parts details, in terms of size, mounting, etc. I'm hoping that someone can help clue me in about what parts I need to be collecting...

My plan is to use a 24V (500W) scooter motor with a chain and a live axle. I've found a hand truck wheel/tire that I think will work for me (10" Marathon pneumatic, not knobby). I can't go larger on the tires without really lifting the car to fit them under the wheel openings, and I don't want to do that. As far as weight, I'm guessing that the finished car (not counting the wheels and driveline) will probably be comparable to the PW Boss 302 Mustang. I'm hoping for 8 - 10 mph top speed, but want to have enough torque for my daughter to drive it in the back yard. My yard isn't perfectly flat and level, so it will need at least as much torque as the stock PW gear boxes on the Mustang (hers does fine in the yard).

With all of that in mind, what gearing should I use? I'll be mounting the axle sprocket behind one of the rear wheels rather than in the center of the axle. From posts I've read, I know to go for 420 chain and stay away from 25. As for the axle, the bearings in the Marathon wheels are available in 3/4" and 5/8". Which do you recommend I go with, bearing the axle sprocket in mind (mounting it)?

Is there a particular vendor or type that you recommend for the sprockets and chain?

I'm probably going to go with EastCoastPowerUp's kit for the electronics; but I want to nail down what I absolutely need for getting the driveline mechanically squared away.

Sorry if this sounds scatter-brained...I'm trying to learn, but still kind of don't know what I don't know about this stuff. Thank you for any information you can share.
#146157
I don't think that coop will be much help as to what vendors to use, but he's certainly able to help with the build. And Wesley from eastcoast would probably be able to guide you to the vendors?
But remember, this is an international site, so how about providing a location.
I'll see if I can get their attention.
#146164
**Disclaimer: adding rubber traction and speed can greatly increase roll over risk!!**

Heynow and welcome. This is a large topic, one that I plan to make a video about since there are a lot of factors to consider. The most important is power delivery configuration. 3 options - one motor one wheel drive, one motor solid/locked axle, two motor two wheel drive. Solid axle is great for the dirt, will not turn on the road unless you have really soft tires that will scrub but then have to change tires often. One motor one wheel drive is great for the road but will have one wheel peal on the dirt. Or two motor two wheel drive which is the best of all worlds and will work on all surfaces. This is also the cheapest option.

If you choose a solid axle you will use go kart parts, you need an axle (1" is normal), bearing hangers, hubs or keyed wheels, sprocket hub or keyed sprocket, BMI is popular: http://www.bmikarts.com/Go-Kart-Parts-Kits_c_668.html I can make a shopping list but this is going to add up quick. Something to consider here is you are mixing metric scooter motors with standard parts. You can find a 420 scooter sprocket http://www.ebay.com/itm/262121957166 but this is a 14t so meeting your speed will be harder, more on this in a bit. Here is another #40 sprocket http://www.staton-inc.com/store/index.p ... ct&id=1788

If you choose single motor single drive or dual motor dual drive you can use a wheel/sprocket combo which will reduce your parts, here is a bargain: http://www.ebay.com/itm/332019150252. This has a metric sprocket which is good, these motors often come with them but this is a 14" tire so you would need to change those. Sprocket looks like a 54t. I have used a 10mm shaft and inserted it through the factory shaft location and used 10mm shaft collars to locate the parts https://www.mcmaster.com/mv1498231302/#catalog/8927K36 https://www.mcmaster.com/mv1498231302/#catalog/57485K68

To mount the front tires choose a 5/8" bearing and use Flanged Sleeve Bearings https://www.mcmaster.com/#catalog/123/1185/=18937e2

To find your gearing use a calculator: http://www.diygokarts.com/speed-calculator.html Use 80% of the no load motor RPM. For example a 3,000 rpm would be 2,400, sprocket size 11t, 54t axle, 10" tire = 15mph. 72t would be 11mph.

For chain size #25 is good because you will find it in the metric and standard worlds but sensitive to low chain tension. Small scooter motors come with them and small scooters have them too. I have gotten the wheels for my projects from scooters. I found a few BladeZ's which have a fixed wheel/axle http://www.ebay.com/itm/182638849235. If you get one with a free wheel you will not be able to brake using the motors. You can find #35 sprockets http://www.ebay.com/itm/152522837451, or go with the T8F. I think #40 is too large and overkill. Here are some tools I use to do chain math https://www.rbracing-rsr.com/calcsprocketdiam.html https://www.rbracing-rsr.com/chainlength.html

For motor size I find 500w total is a healthy amount of power. 250w x2 would be good. I have built cars between 500-2000w, here are some examples
Single 24v 500w:

Dual 24v 500w @ 36v:

Single 1,000w solid axle:

Dual 36v 800w @ 48v:

Dual 48v 1,000w @ 60v:

Single 48v 5,000w:


That escalated quickly, didn't it?

The controller is like a carburetor in a car and is critical and will define the characteristics the car. Here is a Kelly controller vs a high performance 4QD. The Kelly's I have had all have a very mild ramp up which is great for golf carts but not much else IMO.
Kelly:

4QD:


There are two factors to rate of acceleration, ramp up rate and amp throughput. Here are some results of the common 500w 24v controller vs the controllers I have:
775 No Load low.jpg


One of the biggest wild card and unknown here is mounting the motors. You must maintain the motor and axle relationship to maintain chain tension and the motor mount must be strong or it will move under load. A tensioner is sometimes required and having a way to easily adjust chain tension is a very important unknown you have to figure out. The easiest way is to build a subframe to work all the out and bolt the whole assembly on the bottom of the car.

I'm sure I have forgotten something but I hope this gets you started, I will add more later
#146169
That is a wealth of information--thank you!

You've got me thinking about the dual motor setup. With the gearing, though, what can the scooter motors handle? I'm wondering where that " line" is, when I've geared too much toward speed and the car can't accelerate on its own on grass anymore (or works way too hard to get moving). What sprockets did you use on the 36V/dual 500W Mustang setup? That looks about the performance that I'm going for at this point.

Concerning the 25 chain, have you had any issues with it breaking?

What do you do for brakes with a dual motor setup? If electric, does it work like a stock Power Wheels with letting off of the accelerator; or do you use a separate brake pedal?
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