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We havn't updated this page in a LONG time. But the
season is almost over and when we have time, we will be updating this page. A lot has changed since we built our first 2 cars! We hope to be able to do a full photo spread on every car
in our group. So check back often! And if you are
building, make sure you send in your photos along with updates so we can get them posted.
Send us your photos and we'll post them up.
Jola's Roller
The plan was to build 2 identical cars
that would use interchangeable parts. This would allow us to also build a spare
parts inventory so crash damage could be repaired easily and quickly. We also
wanted to build a chassis that would allow for easy modification and upgrades as necessary.
We built from scratch with no real plan,
just sort of pasted on another tube where we though we needed one as we went along.
In the long run, this probably is not the
way to go. By the time we collected the materials and worked things out, we spent
more money then we would have if we would have purchased a ready built go kart and ditched the engine. And we spent a lot of time building parts and components that are available from the go kart suppliers
for probably less money then we spent on materials.
But we are having fun and we are
improving things as we go.
We started with a cheap set of wheels and
tires not really suited for high speed. We had 4 wheels to use as fronts, so
we only needed to buy 4 others for the rear. The idea was that this would get
us started and we could latter step up to some high speed wheels and tires with little modification to the chassis. The rear wheels came from Harbor freight and cost about $10 each.
We didn’t have a lot of time to spend on building if we were going to
get in a few races before the end of the season. So this wheel and tire package
would save time and get us started. It would also allow us to maybe build a few
extra loaner cars without spending a lot of money.
In the initial mock up, we started by building
a rectangular chassis out of 1¼ inch square tube.
2 feet wide and 4 feet long. In retrospect, this was a little short. Future cars will be at least 5 or even 6 feet long.
The extra foot or two will allow us to lay the driver down a bit more, lowering the center of gravity and reducing
wind drag, and will also improve some of the steering geometry problems since we will be able to lower the steering shaft.
Another issue with the short chassis is the weight
bias. Most of the weight of the driver is on the rear axle. This makes the front light and may result in an understeer situation as speeds and cornering loads increase.
To this basic rectangle chassis, we added a step
up in the rear with 1¼ tube that is 1½ inches above the bottom rail. This is
where our 5/8” axle is mounted allowing the bottom of the chassis to stay level and keep the center of gravity low.
The next thing was to figure out what to do for
steering. We built a straight axle again using the heavy wall 1¼ inch tube. This was cut to 26” and then we made tabs out of ¼ x 1½ strap. These had a ½ inch hole drilled in them for the king pin bolt. These
tabs were welded to the main tube and gave us our steering pivot point.
For the spindles, we used 1 inch square tube cut
to 8 inches long. 1 inch back from the front end we drilled a ½ inch hole for
the king pin bolt. Then 1 inch farther back, we drilled a 5/8 hole through the
sides for the spindle. The 6” long spindle was then welded into this hole. On the rear end of the Ackerman, we drilled a 3/8 hole for the mounting bolt for the
tie rod end.
The spindles were mounted to the axle with 1/8”
UHMW plastic washers sandwiched top and bottom to take up space and give us a nice lubricious joint.
Figuring that the front axle and steering assembly
would be the parts that took the most abuse and needed the most repair, we mounted the front axle with bolts to the chassis. In this way, the entire assembly could be removed and replaced in a matter of minutes.
We also weren’t too sure if the 1 inch tube would be tall enough for this application. Bolting the front axle assembly on would allow us to build another front axle using
taller spindles if necessary and then simply bolt it into place latter without having to cut and grind welds.
The steering assembly was fabricated and also
bolted into place allowing for quick and easy replacement should damage occur.
We made our tie rods out of 5/8 hexagonal stock
with rod ends to make wheel alignments simple and quick.
The seat came from JC Whitney. It is maybe a little too high and too big for what we are doing, but it does hold you in pretty well and
is a comfortable seat. Maybe a racing type Go Kart seat would work better and
keep the frontal area of the car and driver package a little smaller.
The next thing to tackle was the brakes. We didn’t want to have to use hand brakes.
The thinking was that you may need the brakes at the same time you need to have both hands on the wheel. We wanted foot brakes.
Using 1 inch square tube, we fabricated some pedals
and linkage for the brakes to push a flat plate against the tire. One of the
problems was the lack of ground clearance and in initial testing this proved too low.
But we eventually got things worked out where
the linkage gave us the ground clearance we needed.
After the initial mock up, everything was disassembled
and painted. Then reassembled for final testing.
On our first test runs, we found the steering
to be too quick for comfort and the brakes to be lacking the stopping power we wanted.
Back to the drawing board.
The short chassis coupled with the long pitman
arm and short Ackerman on the spindles made for a very twitchy ride. We had to
slow the steering down.
We shortened the pitman arm by 1 inch. And then raised and lengthened the Ackerman by 1 inch. This
should help to slow down the steering. We may replace the steering wheel with
something of a larger diameter as well, but this might cause other problems with space when the body goes on. If it does, we will need to install a detachable steering wheel to facilitate entry and exit of the car.
We had mounted the brake plates with the hinge
anchor at the top. We found that we were able to roll the car forward with the
brakes depressed, but the car would not roll backwards. Would the direction of
the rub plate against the rotating wheel have that much effect on the braking of the wheel?
We didn’t know, but we had to do something as the brakes just didn’t stop the car even at low speed no
matter how hard you pressed.
We reversed the rub plates
and mounted them so the hinge anchor was on the bottom. We needed to fabricate
new brake arms to reach the relocated rub plates.
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