Mounting / Connecting The Fisher Price Motor

Any one out there know of some quick and easy ways to adapt the fisher price transmission to 3/8" shaft or a sproket ? In the past first used to provide a hub we do not have any such thing this year and being rookies we dont have back stock to pull from.

Last year my team used two FP motors bolted on either side of a spool for an elevator system. All we did to mount the spool to the FP was: we took out the final gears from the gearbox (the ones with the wierd hubs), cut the hubs off, drilled holes in the gear, and bolted the gears to the spool itself. Then we put the gearboxes back together around the spool, and it worked quite fine.

The main concern with mounting stuff to the outputs of the FP gearbox is that the output hubs are plastic. Some teams have done the bolt-on method, some teams make hubs that will fit over the other ones.

Hope that helps.

This is a picture of one of the CD robots with an OK view of an example of how to mount to the FP. We used the tophat that goes with the transmission and just mounted a thin plate with a sprocket welded to it.

There are other ways as well. But here is at least one example.

Joe J.

There is another thread around here somewhere describing the planetary gearbox from Banebots. It is probably the quickest and simplest way to mount the FP motors. Order on-line and for less than $50 and about an hour to adapt the motor to the gearbox, you’ll have a compact, lightweight transmission with your choice of gear reduction, a variety of mounting points and, I believe, a keyed 3/8" shaft.

We’re using a couple on our robot… maybe three if we need to mount the Mabuchi as well.

Either that, or check out the white paper on “Nothing but Dewalts” that shows how to adapt a DeWalt drill to an FP.


Yes I agree. I assumed that you wanted to use the stock FP transmission for some reason. If you are open to changing the gearbox, I whole heartedly recommend using the low cost gearbox discussed here or using a Dewalt XRP transmission modified to accept a FP motor.

The first is cheap and easy. The second is more involved but gives a better result for some applications.

Joe J.

You were correct, we are planing on using the stock FP Transmission… is there anyway you can order those hubs they gave us in the past that just fit in and have the flange on the outside end ?

I don’t have the part number but believe that the hub is an item you can order from F-P service parts.

Joe J.

If you look carefully at the inside end of the flange coming out of the FP transmission, you will notice it isn’t round, but octagon shaped. (It took me a year to notice this) You could cut an octagon (just under 1.5" across the flats, approx 3/4" thick) drill the center out, and attach a shaft. Hoseclamp and/or pins around the outside to hold it on. I would probably bore out the hole in the case also, and use that with a bushing to help support the shaft.

I know that others have done this with some success. If you do, be sure to put a ring or a hose clamp around the OD of the 10 fingered output shaft with the octagon on the inside. In many cases, the fingers are not strong enough to transfer the torque without splaying and or breaking.

Even though others have had success, I will be honest, this method sort of creeps me out. I much prefer the tophat method.

Joe J.

We did this last year with great success, using the motor onder high loads. The hose clamp even slipped off from time to time with no ill effects. see the linked picture:


The octagon method works great but my team’s part was a cnc’d metal chunk that weighed close to a pound. Not that efficient mind you. Thankfully you can attach to that big ring in many different ways. Just about anything you can stick through it and screw on should work great. Last year we used it as a pulley and we literally just put a flange thing on the end and wrapped string around the big plastic output ring. It worked perfectly for our application. Things don’t always work out so nicely though.

What we have done for several years now is make a round part that fits into the octagonal hole and feeds all the way through to the back hole. We use either steel or aluminum and screw the round part through the slots in the octagonal part. It makes for a very strong connection and allows you to put a potentiometer on the back side. A picture says 1,000 words so I will find a picture in the next hour or so. I will send another post with this picture.

This connection held up even when we broke our output shaft at Chicago two years ago (sorry 93 and 107).


Here are the views I was talking about. I couldn’t find any pictures, but I have the solid model views. The real parts were made directly from the model so the views are accurate.


Paul, today we did something very similar, and it works beautifully. Much better than trying to use the black coupler. One thing we found, is that by using 5mm bolts, which are larger in diameter than the slot is wide, and then drilling the slot out slightly to accept the bolt, makes for an extremely strong connection, even without the bolts tightened down.

Are their any lighter ways to make these FP gearboxes usable?

My team is trying to use them, but without being able to make the output shaft able to hold sprocket, they will be “useless”.

This really is an easy (with access to a lathe), light way to do it. The entire aluminum slug with bolts weighs maybe a few ounces, and the necessary shaft support can be as light as you want to make it.

How about a proven method to take power off from the next-to-the last gear? IIRC, this stage is about 450 RPM.

Are you talking about making a metal “slug” to fit in the octahedral shaped plastic piece?

I’m still a bit confused how this would work? Would the slug have a shaft on it like the whole thing milled/lathed out of one aluminum rod?

We did that last year, cutting the gearbox to eliminate the last stage. I don’t remember exactly how we did it, tomorrow I’ll take a good look at the robot and post the results here. :smiley:

Well, really whatever you want. Heres how it breaks down:

On the white output of the fisher-price, there is an octagonal hole formed by tabs. It appears to be round at first glance. So, by maching a round slug that fits in this octagonal hole closely, you have now effectively “Plugged the hole”. Between the slots of the FP output, you drive bolts through, into holes tapped on the Aluminum slug. So, the slug can then have whatever you want on it. Want to drive a 1/2" shaft with it? Machine and broach a 1/2" hole into the Al slug! All it is is really plugging the output hole with something that is easy to interface.