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Old Jan 14, 2013, 02:03 PM
Emress
sirbow2's Avatar
United States, SD, Rapid City
Joined Nov 2011
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Question
diy rc vehicle design

I plan on designing my own RC SCT or truggy with aluminum or CF/GF only (a few exceptions) and wanted your opinions. for ex: what parts should be which material. CF would be the best for the base plate. Aluminum for the shafts. steel gears etc. waterproof.

another thought was having steering in the front and back. has anyone done this or bought one? I think i'd improve turns, and general stability. Although, it would need some tuning for the separate servos.


I am new to cars, but i have done my fair share of reading and watching youtube videos. Plus, im awesome at CAD.
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Old Jan 14, 2013, 02:10 PM
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Quote:
Originally Posted by sirbow2 View Post
another thought was having steering in the front and back. has anyone done this or bought one? I think i'd improve turns, and general stability. Although, it would need some tuning for the separate servos.

Nice idea, quite an undertaking, but you sound like you could be up to the challenge.

4 wheel steering is nice for tight slow turns, but when going fast, it can actually work against you. First, you need to have the rear steering assy fully slop-free, or the car will do unwanted 180s at higher speeds. Also the added steering might increase the chance on grip-rolls, in fast corners.

Technically it's a nice feature, but if you want to go fast, it's not recommended.
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Old Jan 14, 2013, 02:30 PM
Emress
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United States, SD, Rapid City
Joined Nov 2011
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im probably taking this part to seriously, but i could use the servo to "lock" (use a tx switch to keep them at the correct channel value) the rear wheels. or maybe even add a mechanical lock (some sort of pin?) to protect the servo. could add some nice versatility.
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Old Jan 14, 2013, 02:43 PM
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Keeping the servo centered is only a partial solution. The steering mechanism also has slop, and this can't be locked.
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Old Jan 14, 2013, 03:49 PM
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Are you building this to race, or just as a fun thing to do? If you want to race you'll have to look at the rules for dimensions and what is and isn't allowed.
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Old Jan 14, 2013, 03:50 PM
Emress
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United States, SD, Rapid City
Joined Nov 2011
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now, its just for fun. maybe 1/10 scale. although that would be interesting to read. nevermind. found the roar rules
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Old Jan 19, 2013, 10:33 PM
Emress
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United States, SD, Rapid City
Joined Nov 2011
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ok, i need some help :P i dont know nearly enough about rc design. i know the theory, just not the size of everything, i guess.
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Old Jan 20, 2013, 12:58 AM
Did you check the FAQ already?
SoloProFan's Avatar
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You have the means and knowledge to manufacture your own gears etc? Did you ever build an RC car kit for instance? Perhaps you are trying to run before you can walk, at least that's the impression I get a little.

How about altering the ambitious plan of building a vehicle from scratch to modifying an existing car to 4 wheel steering instead? That way you can also see if it improves the handling by first making it stock, then starting the conversion.
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Old Jan 20, 2013, 02:04 AM
Emress
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United States, SD, Rapid City
Joined Nov 2011
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means: not currently. looking for a good machine shop for my college choices as im currently a senior in high school. i have taken the PLTW courses (basically the intro eng courses in college) so i know about gear ratios, stress, strain, etc. id need small gear on the motor, big on the trany, and then maybe that same ratio again in the trany-> wheels to lower the speed. no specifics yet.

knowledge: working on it now

I was think of that with my tuirnigy SCT. the front and back are essentially the same. just no steering rods on the back. id need another front end assy and maybe some front->back drive shaft mods. and another servo. and then i thought "oh what the h*ll, i have a week before it gets here, why not do something fun"
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Old Jan 20, 2013, 02:17 AM
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Quote:
Originally Posted by sirbow2 View Post

I was think of that with my tuirnigy SCT. the front and back are essentially the same. just no steering rods on the back. id need another front end assy and maybe some front->back drive shaft mods. and another servo. and then i thought "oh what the h*ll, i have a week before it gets here, why not do something fun"
Soms cars feature identical front and rear bulkheads. The LRP Blast series for instances are pretty much identical front and rear, such a vehicle would be more easy to convert to 4 wheel steering.

As for gear ratios, you could look at existing brands. Some print the final drive ratio for each pinion gear in their manuals, combined with pinion teeth count and spur gear count you can calculate the transmission ratio for the section after the spur. Mostly this is around 2.92 : 1 but it can vary a little, depending on wheel size for instance. Bigger wheels require more torque.
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Old Jan 22, 2013, 06:27 AM
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remondo's Avatar
Joined Nov 2005
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It seems your skills may be valuable to the OpenRC project- an almost fully printable RC truggy. I have just posted a thread trying to gather some great minds to help finish the project, is this something you would be interested in? The design files can be downloaded here http://www.thingiverse.com/thing:42198
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Old Jan 23, 2013, 08:06 PM
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are you going for four wheel drive or rear wheel drive
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Old Jan 23, 2013, 08:10 PM
Emress
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United States, SD, Rapid City
Joined Nov 2011
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i haven't even got to where it matters whether i do or not in my design, but it would be significantly easier for designing. might as well do rear only now. good tip
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Old Jan 23, 2013, 09:46 PM
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your welcome and i would think a mid mounted or rear mounted trans would be easier too
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Old Jan 23, 2013, 10:36 PM
Emress
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United States, SD, Rapid City
Joined Nov 2011
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going off that. i have a question. in a typical rc SCT, rally or whatever, is the diff used for gear reduction also, or is just the spur gear?
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