Potential project

[A RC Dude]

ok, a friend's family at school bought a 25cc leaf blower but got tired of trying to crank it, paying for fuel, all the normal gas engine stuff and bought an electric one without using the gas one much at all. they were about to throw it in the dump and my friend knew i like to build stuff so he gave it to me. The engine looks bran new, even on the inside, but i feel like making some kind of basic, very cheap, fast, on road/baseball field type RC car, probably without any kind of suspension, out of it. But the biggest question is how to do the drivetrain. the shaft comming out of the motor is 7mm thick and has a flat spot.

All I am planning is to basically to slap the engine, tires, gas tank, and very basic steering system on a peice of steel, i don't have much money, don't plan on going off-road (maybe a flat dirt field) or hitting any bumpes at speed. But i have a few questions:

1. Would a Baja pinion gear be the right size? i can't find the I.D. of it anyware

2. Would i be able to do a direct drive from the pinion to a spur and out to the tires, without a clutch?

3. Would cutting the engine off work as a decent brake? i'm not looking for much and i wont to keep it lightweight

4. What kind of tires/driveshaft could i use?

5. What kind of speed would that give me and would it have enough torgue?

6. Would i be able to use a steering servo that doesn't cost much?

7. Could i even build it only using a drill press, grinder, and my friends band saw that can cut metal?

[What's_nitro?]

1. Would a Baja pinion gear be the right size? i can't find the I.D. of it anywhere

I don't know. :)

2. Would i be able to do a direct drive from the pinion to a spur and out to the tires, without a clutch?

A single reduction could work. You need a clutch...otherwise the wheels spin as soon as you start the engine, and would probably cause it to stall a lot.

3. Would cutting the engine off work as a decent brake? i'm not looking for much and i wont to keep it lightweight

Yes, if you only want to stop once.

4. What kind of tires/driveshaft could i use?

I'm picturing a giant pan car in my head... Any wheels/tires could be used depending on which hub adapters you put on the driveshaft.

5. What kind of speed would that give me and would it have enough torque?

With a single reduction you could go 20-50 mph... Acceleration will probably be slow since it's not a "performance" engine but it'll work.

6. Would i be able to use a steering servo that doesn't cost much?

How much do the Baja servos cost? You'll probably need something just as rugged.

7. Could i even build it only using a drill press, grinder, and my friends band saw that can cut metal?

Probably. What material(s) did you have in mind?

[A RC Dude]

thanks!

Originally Posted by What's_nitro?

What material(s) did you have in mind?

whatever is laying around the house and gunkyard stuff lol im poor

[Overdriven]

Take a look over on RCUniverse, in the large scale section. There are quite a few homebuilts that are built the way you are talking about. Lots of good info.

[A RC Dude]

thanks, i had some free time in second period today and found a few projects online (mostly on RCU) and i ran by the hardware store afterschool and think i have it figured out

[reno911]

Fun sounding build. I would def go clutch. Look at some of the scooters and moped sights they tend to have stuff for that size motor in terms of clutch and gears/pinions. I would think some plywood or plexiglass would make a decent cheap chassis. Maybe check your loc craigslist for random junked go carts and stuff for tires/wheels as well as axles/gears/etc.

I have to find the site again, but I stumbled upon a Robot electronic site that had large servos for around the 50-100 dollar marker. Not incredibly fast, but it will work.

I look forward to this going forward!

[Overdriven]

Most f the homebuilts I've seen in built in this style use pocket bike parts (wheels/tires, sprockets etc). Gokart stuff would be heavier and more expensive.

The worst part is the motor choice. Depending on the blower the pullstart can be on the wrong side with no way of adapting a clutch, I had that problem with a blower I found. Blowers also usually don't have as much power, so 20-30mph with slow take off is probably going to he case. Direct drive with no clutch would make take off worse since the engine wouldnt be anywhere near the powerband at slow speeds. A clutch let's the engine rev up near or into the powerband from a stop and slow speeds. Not saying it couldn't be done, but I wouldn't invest much in it, I'm waiting for a chainsaw or weedwacker to come along before attempting my gasser project.

[What's_nitro?]

Originally Posted by Overdriven

The worst part is the motor choice. Depending on the blower the pullstart can be on the wrong side with no way of adapting a clutch, I had that problem with a blower I found.

That's a good point. Most blowers will be hard to fit a clutch to for that reason. If you can put a bit more money into it, look for a weedwacker with a "full crank" engine. The recoil will be on the opposite side of the motor as the output, and they have clutches, too.