M.L. Toys
M.L. Toys
HobbyMasters M.L. Toys
If you have a cheap supplier for motors, batteries, or anything that is of use for a scooter or E.V. (BPRO) list it here for all to enjoy!
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By M.L.Toys
We're happy to announce that today we officially launched R&D on a true automatic slipper clutch for Power Wheels 7R gearboxes. A slipper clutch will allow for things like rubber tires, brushless motors, and much higher speeds. It's too early to say any more about it. They have a test vehicle and will need several months to create, test, re-create, retest, etc. Hoping that in the end we have an affordable and reliable product.

It's too early to say any more about it
Willing to at least tell where the slipper lives? At motor? Out drive? Somewhere in between?

On another note, I had initially considered using a ball differential in my Wrangler build to act as both a diff and a slipper. I ended up going with a conventional bevel gear arrangement up front and a spool in the rear, but if the kid manages to fry the 500 watt motor, I'll be revisiting the idea. The beauty of them is that they can be adjusted to act like a posi as well. Roger Curtis of Associated Electrics pioneered them, but they were adopted by numerous other RC car makers.

The plan right now is to put it on either the 2nd, 3rd, or final drive gear. That gear would be replaced with a new one of course.
The ball diff design is best for lightweight vehicles. And in the case of a Power Wheels would create a situation where the inside face of the gearbox would always spin and the wheels never turn because there is an uneven load on either side of the gearcase. If you're into RC, this will more resemble the clutch design that Traxxas uses except I imagine the clutch pad will need to be a large ring, not 3 little pads. Keep the ideas flowing though as I will pass them along to the design company.
Ball diffs can be scaled up. Getting them to work right in any application is about the preload adjustment; too loose, they slip, too tight, they are basically spools. Now I'm gonna have to do it as proof of concept for ya ;)

Of course, I'm not talking about using one in a PW gearbox which drives only one wheel. Only way that would work is to have a shaft that mechnically couples the gearboxes. No, I build live axles for BPROs. This is the rear axle for the Wrangler build, upgraded this week with a 500W MY1020 can:


The gears, motor, bearings, wheels/Tires and brake parts were purchased and modified. The entire housing, the differential, the axle shafts, etc. were built from raw stock.
this will more resemble the clutch design that Traxxas uses except I imagine the clutch pad will need to be a large ring, not 3 little pads.
Traxxas is the oddball, using pads or friction pellets. Most makes use a single or double friction ring design. This is an Associated V2 slipper, which would probably be more easily incorporated into a BPRO gearbox:



If I were going to incorporate one into a BPRO, I'd put it as close to the motor as possible. Hard part is going to be tuning it right so that it does what it's supposed to without getting burned up by little people who don't let off the throttle when the vehicle stops moving! This is what caused repeated motor failure in my Wrangler build; the thing was powerful enough to carry >200 lb adults with ease, but the really grippy Kenda tires wouldn't spin when the kids ran into something or otherwise bound them up, locking the rotors and smoking brushes & commutator segments.

I think to make this a workable design, it's going to have to be adjustable by the end user, and adjustment no more difficult than removing a wheel. The preload is going to have to be adjusted for different vehicle and payload weights. If I had an extra 7R assembly here, I'd be able to offer more input, but going off of memory and images only, I'd say you'll want to use first gear, and it's gonna need a threaded hollow shaft that will fit over the stock stud in the GB, but allow you to have a spring with nut adjustment for tension. Going to have to make an inboard hub, and make the outboard hub part of the 1st gear pinion. To further complicate things, you'll need to have a bearing surface on the portion of the shaft that contacts the outer case half, meaning you'll need some kind of sleeve that exists on the outside of the tension spring with a flanged bearing to ride in the case.

This would be easy to accomplish with a totally custom gear box, but making it compatible with a stock housing is gonna be a little tricky. I think you'll end up having to sell it as a gearbox assembly rather than just a gear that the end user installs.
Last edited by 66deuce on Thu Jan 14, 2016 9:47 am, edited 3 times in total.
Sweet live axle assembly!

Yes, full pad design is what we're talking about. Even Traxxas doesn't use the pegs anymore. How they incorporate it into the gearbox is the magic we're waiting to see. They already make slipper clutch systems and seem highly confident that they can design one into a 7R gearcase. Don't know if that will mean the consumer purchases a pre-assembled gearcase or if they'll just be able to replace on of the existing gears with a slipper clutch mechanism/gear. We'll have to wait and see the prototype.
Sweet live axle assembly!
Thanks! You should check out the rest of the build. I just finished modding the front axle for the 500W can tonight, got it reinstalled and tested. With my 190 lbs in it, it'll crawl over the arms on my 9,000 lb lift, which are 4" square tube sitting about 1" off the ground.

This is the build thread:

We'll have to wait and see the prototype.
If you don't like what you get, I wouldn't mind volunteering my time to prototype one, although I'd need parts covered.
Just a thought. .....

Ever cosnider clutches from a chainsaw? Small and heavy duty enough and just trial and error spring tension until the right rpm is found... no idea if it would work but pipe dreams start somewhere

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