[joakim]

I have just seen another post in this forum "Who wants to help build a racing simulator" This will be somthing like that i hope...

And i have made a dwg of an rc car chassis (a starting point)

If its somone out there who have had the dream to build an rc car, it would be nice if we all could put our heads together and design it... (2 heads is better than 1)

So, download the dwg then do the changes you think is the best way to go, then upload it again. And in the end maybe we have a car that is worth trying to build.

I have wanted to try to fitt a chainsaw engine or something like that into it.
its 50cm long, the steering and things like that i didnt think so much about.
I guess its up to you guys to include it in the drawing...

The drawing was made in autocad 2007, but i saved it as 2004, so i hope as many as possible can open it. If there will be problems, i can post it as dxf (if that will help).

[joakim]

Here is the same file in DXF

[joakim]

I was thinking maybe it would be best to make it a 2wd...
Without diff, that way it would be real easy to make, and alittle more room
for the engine.
And since the chainsaw motor allready have a centrifugal clutch, that problem is solved. Or will it still spinn alittle without resistance?
The brakes are a different story, any sugestions?

[SORCHEROR]

the brakes are usually done with disc brakes similar to a cars,using a single disk that is activated by a servo,theres one stationary pad and the other floats the servo pushes them all together with a lever,theres a spring to open it back up again when released,or you couls use a drum with one pad the servo pushes against the drum,works but less power,the disks are better
steve

[joakim]

As you wish... Some brakedisks will be added.
I guess this would be 1 disk, since we dont have any differential.
Is it hopeless to just have rear brakes? or should it be front also?

Another thing....
Anyone know if its possible to use electricity from the chainsaw engine
to drive the servos? that would give a real advantage. (dont have to be conserned about low batteries) Since the engine have a coil, it must also
have a smal alternator, but will it be powerfull enough? I dont know the the normal voltage used in chainsaws, but i guess 6V or 12V

[joakim]

I have removed the 4wd, and put in a simple rear diskbreak (didnt make all the detail, but i guess its not that important at this moment)

[joakim]

I added some cool rims that i found here on the forum
the rims are made by UNCLE BUCK

But sadly i found a flaw... the car actualy seems wider than it is long...
hmmm... with the rims on, it was easier to see...
well, i post the drawing again beacuse of the cool rims...

well i seem to have made a few revisions so i will leave it alone
for a while, maybe someone else would like to do something...

Hmmm... seems like i have a problem...
the dwg file is now to big to upload (zipped)
I tryed to first devide it with rar na then zip it, but winzip doesnt alow that.

Atleast here is some pics, til i figure out what to do...
Any advice?

[pastera]

The coil in the chainsaw directy fires the plug - no low voltage.

You could wind another low voltage coil and mount at the flywheel to help with power drain but would still probably need batteries.

Aaron

[keebler303]

I have a 1/10 scale nitro truck and a little bigger version of that is basically what you have going. 2wd is a definate. I think you might want a differential, it will not turn as well without, but it will do mean burnouts and get better traction (2wd vs. 1wd). You will probably want some gearing between the chainsaw and the axle. A belt or chain from the engine to the gearset (or jackshaft with another sprocket set) would be in order. The commercial units use a disk brake on the input to the gear box. The brake is generally actuated by the same servo that operates the throttle. This setup is probably the easiest. A little linkage and springs make things work out well. I may have a few minutes to give you some help from time to time.

Good Luck
Matt

[joakim]

I think you are rigth, maybe its not that easy to get low voltage from a chainsaw, i will see what to do with it... first i need the motor.


I was thinking about using a chain as drive from the motor, maybe also try without a diff at first so it doesnt get so complicated to build...
It can be added a diff at a laiter point i guess. Atlest i want to build it so it can be added...

[Switcher]

Maybe this link will help you?
http://home.howstuffworks.com/chainsaw5.htm


.

[joakim]

Still haven been able to post the laitest dwg
Its to big... what can i do?

[RotaryNut]

....2wd is a definate. I think you might want a differential, it will not turn as well without, but it will do mean burnouts and get better traction (2wd vs. 1wd).

Best of both worlds with a ball diff, allows differential while turning, while acting as a locker, all power provided by motor goes equally to both wheels(with correct adjustment). It's also very easy to make.
See description here: http://en.wikipedia.org/wiki/Ball_differential

A bonus of its design is it's also an LSD with an adjustable slip rate, anywhere from free-spin to locked.
Adjustments can be made without removing the diff from the car, just drop out one axle.

Be sure to check This Link (from above wikipedia article) which shows photo's, graphics and an animation(req. DivX).(Site in German)
Use Google Language Tools to translate, or Click Here.

[joakim]

Thanx...

I will defenetly go for a ball diff, now that i have read about it...
And you are right, looks like it can be made without big problems.

[RotaryNut]

...looks like it can be made without big problems.

MUCH easier than cutting bevel gears.
And works a million times better too.

I've been using ball diffs for 20 or so years(Kyosho, Yokomo/Associated etc etc), still amazes me that they haven't been used in full-size vehicles yet.
Must be a issue with wear that doesn't affect small-scale light load use.

[iggk]

I used to race RC cars back about 15 years ago i got an associated RC12L, first time i ever seen a ball diff. there amazing in the simplicity and efficiency.

I'm just starting to learn solidworks so i doubt i can be much help but I'll be keeping an eye on this thread.

[BiggerHammer]

The chainsaws I've used have been rather stronger than I would expect to use for an RC car. I haven't looked at your plans in detail, so if I'm off-base please tell me but would a smaller IC motor such as one from a weedwhacker be a possibility? It would have less power but would be much less bulky.

Also, chainsaws (again, in my experience) are built so that the motor is integral with the frame, which means that you'll get much thicker, stronger, heavier engine casings than you may need for this application.

[mrcodewiz]

I have heard that ball diffs aren't sufficient for high-torque applications and that is why you don't see them on 1/8th and larger r/c vehicles. I have nothing to back that up - just what I have heard.

[maxpower RC]

Hi guys,

I am hoping to build 1/4 scale 30cc upwards cars but the basics are the same. I have some rules i hope to abide by in my project;
1. Car design must use ""real car like"" features
2. Must have full chassis- roll cage based chassis, (maybe including flat chassis pan also)
3. petrol engine - front mount or mid mount.
4. A Arm front suspension - fully adjustable for camber, caster, toe, springs, ride height, shocks etc.
5. multi link rear suspension - adjustable springs, ride height, shocks etc.
6. multi-speed gearbox - auto shifting (adjustable shift points).
7. adjustable centrifugal clutch (adjustable take up point).

The basic approach will be to build a base car without many of these points and add-in a feature until the full project aims are reached. I have had a few dramas trying to get help with the construction of a diff or components to do so without breaking the bank.

This is in an ongoing ""design faze"", ""component sourcing"" stage at the moment and I too hope to get some help on this.

I have come up with a couple of things so far, eg;
1. Chassis/roll cage will be build from high carbon light weight 10mm round steel tubing as used for large vehicle brake systems etc.
2. Local Steel/cladding company has a laser cutter and CNC Milling machine that i can get an ""Alloy flat chassis plate"" cut with all holes and detents in place - done relatively cheaply. That is until I can get my own milling machine.

I am glad to contribute some ideas etc.

[maxpower RC]

Guys,

I have had a lot of answers by studying sites like this one in the link.
http://www.rctek.com/general/cunha_f...e_pb_dart.html
I suggest you study each image (larger image form each link) it will answer lots of questions for you.

Plus I am seriously thinking about building a ""ball diff"" in 1/4 scale - hell why not !