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  • homemade drive differential

    im among other things making a remote control 1/4 scale dune buggy, ive got the chassis and the suspension sorted but im having a little trouble with the rear drive assembly, i was going to make the rear axle in one piece solid form but if there is a simple way round to split the axles it would be a better option, anyone had this problem?

  • #2
    A rear "differential" would certainly aid control when turning. One simple method used by some Karts is to use a slip clutch between the two axle halves. This requires the axle to be supported inboard as well as outboard. Another option would be to just drive one wheel and have the other free wheeling.

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    • #3
      "Another option would be to just drive one wheel and have the other free wheeling."

      Billyboy- That's a very easy solution which many karts use; when i first saw a one wheel drive kart i thought it was pretty funky. I didn't have alot of faith in its performance but, to be honest, when i got to building karts, i found that most of my single drive karts handled much better and accelerated better or as well as the ones with differentials...now taking them off-roading is a different matter. But for a r/c vehicle i would think one would be ok...

      Otherwise a differential isn't horribly difficult to make. The go-kart ones have a cylinder that houses the four gears. Instead of a ring gear and pinion gear, the sprocket is bolted to the outside of this cylinder so its easier to change. Inside the differential you need one shaft perpindicular to your axles with two bevel gears on it. The bevel gears are free to spin. The shaft, however, sits in a pocket in the cylinder so when the cylinder turns, the shaft turns. Then, meshed to the two gears on the shaft are two bevel gears, one keyed to one axle, the other keyed to the other axle.

      And then - its time to test it! ( i stripped the teeth of of three of the gears on the first differential i made...i had a homemade tranny and i slipped from third into reverse...yikes!!)

      I assume you already knew all that about the basic construction but you probably had trouble finding a bevel gear. Take a look at ebay and google it - when i was looking for go-kart sized bevel gears all i could find were dinky ones that would be good for r/c cars. Infact i saw some especially for r/c cars! If you need i'll do some poking around and see what i can turn up.

      Oh - check out "martin gears" - i think that may have been one of the places that had some small bevel gears in anything from steel to brass to plastic. not sure though...they also make sprockets i think

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      • #4
        FT, I think my wife and I will adopt you! Our grandsons just don't have your common sense. If I had enough work, you would be in business. Hard to find a young guy that's interested in being the best! I think you are going to make it.

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        • #5
          You could also try a ball bearing diff which is used in smaller scale RC . Fairly simple to make, easily adjustable and hard to break.
          Coming from a drag racing back ground I would do a solid axle and the hell with turning corners.

          Steve

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          • #6
            Originally posted by S_J_H
            You could also try a ball bearing diff which is used in smaller scale RC . Fairly simple to make, easily adjustable and hard to break.
            Coming from a drag racing back ground I would do a solid axle and the hell with turning corners.

            Steve

            LOL, I could "park" my old drag car on an incline just by turning the front wheels all the way to one side or another and lock the steering column!

            Anyway, on the dune buggy RC car if you plan to run it in dirt and the like just put a solid axle in. If you really want to get carried away you could make a detroit locker, just need some time and a rotary table.

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            • #7
              Stock drive makes some pre-fab diffs that might work and if you dont mind dealing with metric Quality transmissions is who i use for my bike cranks, There gears are great, they are in an annealed state for machining and then you can quench harden yourself and they turn out really good with very little deviation and a super hard skin, if you want a tough differential spyder gear set up dont use just two, build a cross yoke and throw in two more...

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              • #8
                See here:

                http://www.sherline.com/tip27.htm
                Weston Bye - Author, The Mechatronist column, Digital Machinist magazine
                ~Practitioner of the Electromechanical Arts~

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                • #9
                  If you wanted to keep things simple, why not look for a used diff out of a smal lawn tractor and modify it if need be. I'm not sure how big a 1/4 scale buggy is but these diffs aren't very big so it might work.
                  Jonathan P.

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                  • #10
                    How is the machine powered?
                    Free software for calculating bolt circles and similar: Click Here

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                    • #11
                      Small world. I too am working on such a project. And the differential is part of the problem. It just has to have one.

                      At first I was going to scale up a ball type out of a smaller car. Not very complicated and as stated, adjustable for slip.

                      However I wanted to build something that could be put together with as much off the shelf parts as possible so I have decided to go with a small differential made for a small lawn tractor. They have also been used in some of what they call mobility chairs here.

                      I won't go for suspension at first, just a basic chassis to hold the engine and steering in place until I can be sure of the one thing that might be a problem. The steering.

                      What to use to steer the thing? Mine might come out a little bigger than 1/4 scale. I'm using wheels and tires from HF here. And I don't think what they are calling 1/4 scale servos (for aircraft) will be strong enough. I am considering two options. 1. using two of the biggest servos Hi Tech makes and gearing them down or 2. there is a way to hack a regular servo to drive a larger geared motor.

                      For power I have an engine off one of those stand up scooters. They have a very tidy reduction gear/clutch on them that will be easy to adapt.

                      Good luck, and some pictures would be welcome.

                      Here's a pic of the differential I'm going to use.

                      http://www2.northerntool.com/product/35768_35768.htm

                      I think the carrier is about 4 inches in diameter.
                      Last edited by topct; 09-23-2006, 11:19 AM.
                      Gene

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                      • #12
                        I have one of those Northern Tool diffs I got in an E-Bay deal with some other parts that I'm not planning on using. It's just taking up space. I could be persuaded for next to nothing ....

                        Bill

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                        • #13
                          Diff.

                          pntrbl, check your mail.
                          Gene

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                          • #14
                            thanks for the reply's and advice, Argos (general houseware store in england)was selling some real cheap petrol hedge strimmers off for آ£50 so i couldnt resist buying one just for the engine, when i stripped it all down the engine seems to be the same as a zanoa but is un-named, evan its a 34cc with a built in clutch assy, i did want to buy the FG marder r/c buggy which uses a standard 26cc zanoa engine but at آ£500+ its a little out of my budget so im having a go at making my own version of the buggy, a few little obsticles to get over first like drives, steering, ect but these shouldnt prove to hard, i like the idea of a northern tool diff and thanks pntrbl but i think i may be able to lay my hands on one, topct these modern high torque servos for scale a/c should perform your needs if just for the steering, ill post some pictures when it starts to take shape.

                            bill

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                            • #15
                              Once again, thank you Millman! I was having a bad day until i read that...

                              Billyboy - post pics when you get a chance! Sounds like an interesting project.

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