Universal joint questions

I'm starting to gather parts, and had a question about UV joints. I was thinking it would be most desirable not to have any 'play' in them at all as far as twisting goes? I read that the ones from steering columns are the way to go. Are certain makes or sizes that are better than others?

Also, I guess it is best to have them as short as possible as well? The closer your butt is to the joint the better?

Thanks

jim

some people use steering knuckles, most seem to use cut down drive shafts.
Best to over engineer the job.
Look for a drive shaft from a rear wheel driven car, make sure the uni joints have no noticeable play in them, cut them to size.
Keep the actual uni joint part as close to the underside of the seat as possible.
Yes, keep is as short as you can within reason.
To give you an idea, the shortest I can get from a cut down tailshaft, id bet as short as 120mm overall length.
http://img212.imagevenue.com/img.php?image=609333164_uni1_122_760lo.jpg
although , the desk racer was 220mm overall length,
http://img176.imagevenue.com/img.php?image=012211124_2014_03_2111.04.15_122_219lo.jpg
but that was a different setup.
If you are planning a more traditional seat mover, the shorter is the better.
Cheers, David.

Bought on eBay for 23.00 - cut them, welded to plates - 0 play in the journals.

Nice job! I like the boston gearboxes too! But if your Boston gearboxes are as heavy as the ones I have that handle about the same torque as yours, you must have over 200 lbs of them! Mine are stainless steel models however so I don't know if that makes them heavier or not. But they cost about as much to ship as I paid for the gearbox itself! lol

Hi BlazinH,
Yes, those Boston Gearheads on eBay (new ones) are 600 - 750 each + shipping. LIST new over 1000.00 each. ALL 3 of mine, including shipping (all New) on eBay, cost a little less than 1000.00. (took about 7 months of searching) The stainless steel ones are outrageous in price.
Good gosh yes, they're heavy - 77 lbs EACH - w/0 electric motors. My 1hp MotorMax Inverter Duty Motors list for 289.00 ea - got all three of mine new for less than 300.00 - and again, NEW.
Those gearheads are built like a friggin tank. I took one apart to change shaft sides and just couldn't believe how well they're built inside......should last a LOOOOOOOOOOOOOOOOG time.

Tom

Hey cthiggin, if it's not a secret, what kind of spring and piston/shock setup do you have in that picture? I was thinking of having a setup like that under the seat for the heave axis.

jimmcquade,
After I finished with u-joint, plates, and my round tube with spline collar, I attached the assembly spline shaft/into/ spline collar, then measured the distance from base to the bottom plate holding u-joint.
Took that base measurement - and added 8" - as my up/down movement is a total of +4" -4" for a total of 8" - then I could compute my spring length - CLOSED - add 8" + 2" more for load -
In my case, I needed a 22" spring.............with the help of @speedy, here, and his use of a spring calculator, came up with the exact spring I needed. I only found 1 Spring Manufacturer here in US that would
build me one. 325.00 US for one, 345.00 US for 2.... it was terrible expensive but it matches my platform, and top weight. This is an ASSIST spring and only helps relieve some load on the motor/gearheads.
It is Matched to "my" platform.
You cannot just go to a junkyard and pick up a used spring, as they will NOT match your heave movement in inches, nor will they match your top frame load.

This was the most technical aspect of my build....but expensive - but I do know it matches my sim and works.

Tom

As far as finding the cg of the seat ,I will use the broomstick idea, and I'm guessing that I should have my feet on the pedals and my hands on the wheel when I do this?

Yes , have a mate hold the back of the sim and roll it back and forth to find its balance point.

I found some motors on ebay canada near where I live, and they have this spec on it
FEED 75-80RPM 50:1

are these the right ones?

http://www.ebay.ca/itm/GEAR-MOTOR-1...483?pt=LH_DefaultDomain_0&hash=item51bed470a3

how heavy are you? how heavy is the seat planned?
I forgot, what frame are you starting with? Was it a seat mover or full frame?

I'm 95k. A non reclining bucket racing seat. I'm going to go with 2 frames, a seat mover and a full frame mover under it. I plan to fly sims as well so I'm going to run with both. My budget is good so, I'd rather go overboard on power to ensure success. What can you recommend?

the 50:1 then for sure.
How much actual travel - throw - angle on the sim did you have in mind?
What do you plan to run more of race or flight?

I will mostly race. 90/10 ratio. I believe I will use the full frame for the pitch/roll of the track mostly. The seat will be for all the bumps and acceleration and braking effects. I have bass shakers already which I can add for curbs? and engine vibration maybe.

I guess as much throw as possible for the frame within a safe limit for the motor. I'm thinking I will want a snappy seat action, and can have slower action for the frame. I don't really know what that would be as far as throw. Can you give me some ideas? Thanks .

ok for snappy action, use a long lever say 65mm with a short throw, total maybe 8-10 deg total, and with a harsh profile, that should snap it motion wise well.
I was thinking suggesting faster motors for seat mover , 25:1 , and the full frame 50:1 , but I think the motion might be a tad different in speeds. Best stick with the same on both, 50:1 if you plan the sim in mind.

OK, great. The last question for a while... What gauge and dimension of steel would you recommend for the full motion frame? I have a clubsport wheel and CST pedals(which are pretty heavy). Since I am having a moving seat on the moving frame, it should be sturdy enough to withstand the extra movement of the seat. thanks again for all the advice.

jim

jimmycquade,
I did a lot of research (2+years) before I built mine - plus checked with my local steel co. etc.

Full platform: 1.5" Square Steel Tube - 1/8" thick - not the 1/16" thin crap........with good welds, you will be in great shape - and this is NOT necessarily "over-built or over-engineered"....it's just very safe for a full platform and the weight and stresses it will encompass.

Blessings,

Tom

Hey I have an non-build question. When the rig is not powered up, and you sit on it, is the seat all loose, or are the motors fixed, so it doesn't move?

Motors IMHO, should be fixed. In all probability, you may have very little play in your heims & Rods, but over-all, (depending on "your build") movement should be minimal.

With my DC motor setup , the motors are free moving until powered on so I just simply power the sim on before climbing in, with the Jrks I use <221><63> on the Shutdown Output so that the sim holds in a centred position for when Im changing games. Some wipers with the right gearing in them will hold positions after power down but for my seat mover I haven't really found a need for them as they are way to slow to be any good for the quality and speed of motion that I prefer.

Steel size I use is 1"x 1" at 1/16" thick, but its just a simple seat mover , come to think of it my old full frame was built from the same steel, but braces in the right place kept everything nice and rigid so it comes down to design, and with DC motion you need to keep the weight down to it min without comprising the strength of the design, with 240v sims a lot different as they have the power to twist the frame hence the stronger construction is needed. Really depends on the motors and the end weight it will carry.