CycleKart Tech Forum

I don't have room for 3 Cyclekarts so I sold my T-bucket to make some room. I wanted to build a car that had a softer ride after my daughter complained that her back hurt after riding in one of my first two cars. I'm not sure if what I am doing is an improvement but time will tell. I also wanted to build the car a bit wider to make it easier for me to get in and out. I haven't firmed up my inspiration car but am leaning toward a MG body type. Here are some pictures of the frame which I now have on wheels. I still need to install floor pan, steering and hydraulic brake lines before it will be a driving chassis.

Looking good.

Great innovations.

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Steve Vinson
Arizona CycleKart Club

Design-Build-Race-Repeat

Very clean-looking build, that is very close in design to the unsprung originals. It will certainly be a huge comfort improvement over every hard-tail cyclekart.

However, of all the sprung rear-ends it is the least desirable design, as the whole engine sub-frame is unsprung mass, and the heavy engine is even behind the wheels looking from the pivot point. When the wheels are pushed up 5 cm, the engine will move 10 cm up. For those who also want a sprung read-end I would advice to place the engine as close as possible to the pivot point. The closer to the pivot point, the more the heavy engine will behave/feel as sprung mass.

Technically a bit more complex would be the put the engine on the frame with the output axle very close to the rear wheel sub-frame, the way motorcycles have the drive axle - pivot point - wheel axle positioned in one line. But that's another step on the evolutionary path away from the original hard-tail design.

Please don't read my comment as criticism, but as technical advice. Your current design is already the biggest improvement from the hard-tails, and any further fine-tuning like I described will never generate as much improvement over this design as your design was over the hard-tail.

That is slick! Any chance you can upload more detailed pics on the articulated section of your chassis?
With my back and neck issues, this would be right up my alley and my Grand-daughters as well.

Can you talk a bit about the front axle? Is that and I-beam or C-channel?
What size is it?
tks
dg

Cas, I hope you are correct about that. That is all I am trying to achieve.

Randy, I've attached a picture that shows a bit more detail of the pivot points. I originally wanted to use pillow blocks for the pivot points but couldn't find ones in the size I was looking for unless I paid big dollars. I used 8 interlaced welding tabs, 4 on engine frame and 4 on front frame. Side to side movement is restricted. When I get the chassis running, I'll probably find that I need to beef this point up some. It's all an experiment. I have no idea if the shock/springs I have are too soft or too stiff. I just purchased some inexpensive ones off ebay or Amazon.

Denny, the front axle was cut off an old high lift jack. Picture of ruined jack attached. The cross section is I-beam, 2" high by 3/4" wide on the flanges. Another concern I have is if my welds penetrated this hard axle metal. Time will tell. But it's no fun unless you find a problem and address it.

Ah yes, of course. Never would have thought of that. Wish I would have
noticed that before I went t all the trouble of bending up my 1 1/2" tube.
I just went out an took a file to mine and it appears to be plain old mild
steel. Of course it's not a casting that wouldn't work for that tall of a jack.
From the way it files, I would say it's not high carbon steel either, so a
weld that was properly prepped, i.e., Vee'd out should be fine.
However, there is always a but...... when welding an unknown material,
but you really don't know the alloy of the parent metal.
Keep us informed on this one, If you don't have any trouble with
it that could be a good choice for front axles in keeping with
that era racing car.
Thanks
Denny Graham
Sandwich, IL

I thought that looked like that's what it is. Pretty clever!!!

I decided to replace the bolts in the pivot joints with clevis pins. It only took me a few minutes to disconnect rear drive assembly from the front frame and reinstall. That might come in handy in the future if I want to work on the drive train.

I also installed an aluminum floor pan using .063 5052. It was much harder to shape this floor than I thought it would be. A big break would have made it much easier. The floor pan weighed 11.3 lbs which was heavier than I expected.

Nice Floor!

The front end got a bit busy. All I need to do is bleed the brakes and it will be time to drive the chassis for the first time.

So, my question would be about "King Pin Inclination"?
I looks like your new spindles had camber put into them (unlike the ones I got from Jack last year, that have zero camber) but are upside down for correct KPI????
Suspension system looks great.........it will definitely be easier on your spine!
Keep up the great work and Thanks for posting pictures.
Good Roads
Woody

I don't see much camber but lots of caster.

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S'all for now!

It has about 12 degrees of castor, not much of any camber. My second car didn't have any castor and handled poorly. I may have put more caster on this one than needed but will know soon.

This suspension has no KPI. Correct king pin inclination is where you draw a line though the king pin, it should intersect the ground at the center of the tire. So the king pin needs to be approximately 14 degrees from vertical.