1/5 or 1/4 scale differential for homebuild with 49cc engine
hello forum, recently i have been getting some ideas together of making an rc petrol buggy. currently i have an engine that i will use which is a 49cc 2stroke engine and have got it running. but i just dont know how to go about getting a differential and what ratios they are. i am wanting it to be pretty fast (45mph at least) and i want it to have a drive shaft input. any ideas would be helpful. thanks
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Hello, you! I think i will start by directing you to this thread: http://www.rcuniverse.com/forum/rc-g...st-topics.html for you to take a look at all the threads there. Do you have any ideas on how to make the frame and setup of the car exept from what you have alread planned?
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Currently I am just in the planning stage and thought I should first get an engine,gearing and differential set up and have roughly the right gearing ratios first before I start trying to design a frame to go around parts I don't have yet. But should be just a flat sheet of metal with a engines mounted so the driveshaft would go Into the diff rather that having a chain driven one. And should from that be able to use some dogbones to the wheels and have independent suspension. Ohh and thanks for the link to that thread :)
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Ohh just thot of another alternative.maybe I could use a centre diff as a rear diff and have a chain coming from engine to a sprocket far back on the buggy then on that same shaft have a smaller cog that meshes with the centre(but now rear)diff. Just an idea. Might take a picture of that rough idea and the other one so u can get a better idea of what I mean
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I understand, the latter option you mention here is exactly ( if i understand you correctly) the same as i have made on two of my cars. But i think it will be hard to get a bevel diffgear and pinion that will get the gearing low enough to make it work with a driveshaft directly from the clutch and to the diffgear.
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Well on the minimoto I got the engine from it had an 8t drive sprocket and a 50ish t rear sprocket which gives roughy a 6:1 drive ratio. I was thinking that I should maybe half it and go for a 3:1ish as the won't be thee weight of the driver so maybe a 13t pinion bevel gear and a 43t diff gear. Maybe that would be optimal torque to speed ratio. Still nothing certain though might get a few bevel pinions and try them out. Thanks for the help though
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The 23 ccm engines on stock 1/5 cars has about 6:1 gearing, but 3:1, even if it is a 49 ccm engine, would be too much i think. I don't know the top rpm on your engine, but i think it will get a uncontrollable top speed with lack of torque. When i was constructing my first car i used a 36 ccm chainsaw-engine and 3:1-gearing, this made the clutchbell turn blue and the clutch shoes to glaze, and the theoretical top speed would end up at about 130 km per hour. I am older and wiser now :)
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Originally Posted by Lars from Norway
(Post 11693890)
The 23 ccm engines on stock 1/5 cars has about 6:1 gearing, but 3:1, even if it is a 49 ccm engine, would be too much i think. I don't know the top rpm on your engine, but i think it will get a uncontrollable top speed with lack of torque. When i was constructing my first car i used a 36 ccm chainsaw-engine and 3:1-gearing, this made the clutchbell turn blue and the clutch shoes to glaze, and the theoretical top speed would end up at about 130 km per hour. I am older and wiser now :)
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About 6:1 would be nice to try with first, maybe you can go down to 5:1 if it feels like it has enough power for it.
Yes, you can build a diff, but it takes a lot of work, machining, spinning with lathe, milling and lots of other operations. It would be easier to get a Baja-diff and gear it down 3 or 4:1 with pinion and diff-gear, and take the rest by gearing it down 3 or 2:1 by using the bevel gear to connect to the clutch with an axle. |
Originally Posted by Lars from Norway
(Post 11696209)
About 6:1 would be nice to try with first, maybe you can go down to 5:1 if it feels like it has enough power for it.
Yes, you can build a diff, but it takes a lot of work, machining, spinning with lathe, milling and lots of other operations. It would be easier to get a Baja-diff and gear it down 3 or 4:1 with pinion and diff-gear, and take the rest by gearing it down 3 or 2:1 by using the bevel gear to connect to the clutch with an axle. |
Nice to help, i am ready for more :)
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