Update: Steering & Throttle linkage & Ring Roller
Hello wise karting elders; here's my latest update.
Last time we spoke, I had a basic frame and a few half-baked ideas. Now, instead, I have a frame and some badly-implemented ideas!
Anyway, take a look at my steering system; I've really just been winging it; I did read some derpumentation about steering geometry. However, it was all very boring, so I built out what looked simplest based on what I could find online.
Also, I tried to have as much adjustability as I can so hopefully I can correct the inevitable geometry cockups later. Hence lots of holes on my pitman arm and spindle arms.
NOTE: No axles yet as I'm having trouble finding some suitable front wheels at a price I'm prepared to pay (ie. zero). Once I find something, I should be able to get some axle bolts of the correct size.
Steering Questions for you wise elders:
1. I bent my spindle arms up to roughly match the angle of the pitman arm. Is this a good idea? I feel like it might limit my maximum steering angle or something.
2. Currently (using holes 3 of 5 on my pitman arm and spindle arms), I get maybe 80 degrees of steering wheel movement. That feels low to me. What's normal for a kart? What should I adjust to improve this?
Next up, is my throttle/tensioner clutch setup. You may remember that I'm using a lawnmower engine which is set to run at a certain RPM. You guys recommended that I just forgo a traditional throttle and just have a tensioner clutch instead of a throttle pedal. That way, I don't have to modify the crappy carb or govenor on the engine and just let it run at whatever RPM it wants and I get power by tensioning the clutch. Sounds simple, so that's what I'm doing.
So here's v1 of my tensioner... I found these heavy duty control cables at PrincessAuto for $5, so I bought 2. The tensioner has a pair of rollerblade bearings on the end; those will push the back of the v-belt in towards the center of the loop whenever someone hits the throttle. I made a mounting plate out of some sheet metal to hold the cable and tensioner arm pivot. Once I have my engine position finalised, I can figure out how it will fit under there.
I also built a pair of pedals out of some rebar and a small tube hinge. Check em out; I attached one to the tensioner cable to see how it would look.
Questions:
1. In a tensioner clutch, how much movement is normal for the idler that pushes on the belt? With the above setup, I can make the idler move 6 inches or so... that's way overkill, no?
2. There will need to be a return spring on the throttle and brake; do I put it on the pedal end or the other end?
Small side-project!
I've been trying to find a suitable small steering wheel, so I looked online and discovered that it's impossible to get a simple crappy kart steering wheel sent to Canada for less than about $80. Even the cheapest, crappy $20 wheel from BMI Karts becomes extortionate once you factor in exchange rate, shipping, holding fees and import taxes. It's very depressing sometimes, living up here in the cold north.
So I figured I'll just make my own out of some rusty rebar instead; zero-dollars is the goal after all! Imagine something cool like out of MadMax FuryRoad!
Math says that a 3foot piece of rebar will give me an 11inch steering wheel; perfect! All I need to do is bend it into a perfect circle, weld it together, add the middle bit and bob's your auntie. But how can I bend a bit of rebar into a circle? Aha! Let's make a Ring-Roller!
So I put this together with a few bits of angle, some half-inch flat, a couple of bolts and some more roller-blade bearings. I made the handle out of more rebar.
I drilled the angle iron with some holes that line up with the holes on my vise, so I can screw them in there to add tension.
It worked good for some thin flatbar that I had lying around, but once I put my rebar in there, the angle iron started to bend up, forcing the rollers to twist and letting the bar pop out.
Version 2 will mount the rollers to the face of the angle iron; not the top. That should allow the force to be transferred into the work piece and not into bending the mounts.
Anyone built anything similar? Any tips?
Cheers!
Jan.
Edit: looks like I hit the pic limit... sorry, no room for more pics of my ringroller!