PDA

View Full Version : custom, unorthodox build. ideas?


CaliusOptimus
11-12-2006, 04:03 AM
hey everyone! im new to these forums, and R/C for that matter, aside from some cheepo walmart toys ive modded out.

im posting this in the general discussion because, well, my ideas dont fit into 'nitro', 'electric', 'monster trucks' or any of the other categories (aside from online builds which only had 4 friggin threads.....well anyway. ill start with what i do know, im ordering a couple pieces of machenery (small lathe and vert. mill) to make some special parts for a gokart i built a few months ago. its pretty cool as far as gokarts go, 13hp, legroom for a 6' plus person, +40mph and a comfy seat! lol, heavy as hell and no susspesion though, i dont have the experience with the application specific physics of an r/c car, truck or gokart for that matter. SO.

i figure ill design an r/c car in small scale (sorta) before i go off spending hundreds of dollars machining chromo parts only to find out i f*cked something up. im going to use a g230rc+expansion pipe (5+hp) for my engine, go-ped style aluminium wheels and a briggs&stratton gokart centrifugal for the neccesary parts of my drivetrain.

i was hoping someone could post some detailed pictures of steering components, halfshafts, disassemled differentials, suspension components or anything else that might be helpful for my design. i do not have the tools to make intriacte parts like bevel/miter gear differentials, oil dampened shocks or ball end style half shafts. im aware of a differential design that uses standard spur gears inside a rotating case without anything fancy like a ring and pinion. theres a small one in one of my cheepo r/c cars although i cant get to it because of a stripped screw. thats one thing i am really hoping to learn about, seeing as how i would be able to cut the gears and components myself. well hey, im open to ANY ideas that might take some of the trial and error out of my build!!

thanks!

fasterthanspeed
11-12-2006, 11:53 AM
Heres a pretty simple differential (click on link)
http://www.rctek.com/general/differential_ball_description.html

Heres an idea for the front steering and suspension.
http://www.geocities.com/dave_beeby/frontsuspension.html
For the rear sorta copy the front suspension. use cvds to get the power to the ground.

balang_479
11-12-2006, 11:57 AM
Look at this entire build, you might learn something.

http://forums.radiocontrolzone.com/showthread.php?t=167129

CaliusOptimus
11-12-2006, 08:03 PM
speed, it seems to me like the differential design in the link relies mainly on the friction between the 2 sets of thrust bearings to transfer motion. am i missing something or is this correct? :confused: the link for steering helped a lot, ill probally go with something similar for my front end.

btw, new question. this r/c is probally going to be in excess of 40 lbs, im not sure what to do about a servo for steering. browsing through the Hitec catalog the servo with the highest torque had 416.6 oz-in at 7.4 volts (HSR-5995TG), i dont know if this is enough. if i were to use to identical servos side by side with a y cable would there be an issue with them beeing missaligned to eachother or moving at different rates?

fasterthanspeed
11-12-2006, 08:30 PM
Thats more than enough. Thats about 26 pounds of force.
You are right about the diff. it works on alot of rc cars. you may want to go with out a diff. and and have the angle of the steering bocks at an angle so when you turn one wheel is off the ground.

CaliusOptimus
11-13-2006, 12:11 AM
ill probally put two anyway :D just for piece of mind.

is this what you meant by 'angle the steering blocks'? the knuckle pivots in this pic are at a 10 degree angle, should put the wheel itself at 5 deg. in maximum turn. this is kinda of a block diagram prototype. ill machine everything to be purdy, and not so square. the wheels wouldnt turn much as the knuckles are anyway, so it is for representation only.

http://img167.imageshack.us/img167/8250/wheelknuckle1ug2.jpg

CaliusOptimus
11-13-2006, 09:11 PM
hey guys, whats the average angle for front wheels in maximum turn? if i use two of the servos i mentioned above at 26 lbs-in i can attain double, maybe quadruple that at the wheels, if i can work out the steering linkage to double the force. if so, the servos rotate to 180 degrees total, leaving my final wheel angle at 45 degrees. with somewhere around 100lbs-in of torue, that seems about right considering how much force a 40 pound car would get in a sharp turn at decent speed. gimmie your 2 cents! ill post some pics, maybe a video so ya'll can see what im trying to acomplish.