CycleKart Tech Forum

Knock Offs and Friction Shocks

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Denny Graham Silver Member Dennis Graham
Sandwich, Illinois, USA   USA
Brian, the friction shocks that Rhys has made and are discussed at length in the
thread that Vic posted, are about the best example that I've seen.

Selecting the proper friction material is the biggest hurdle one has to get over
with a friction damper. Friction is just a term for the force that has to be overcome
in order for something to slide or come away from another object. In that sense,
it doesn't matter what is causing an object to adhere to another, there is a
frictional force associated with it. We've all observed how it takes more force to
get the sofa moving when the wife wants to vacuum under it, but once it's moving
is slides a lot easier.

The same thing is happening with a friction shock each time it transitions from its
static state to its dynamic state. The stickiness of the two surfaces in contact with
each other is very important in the way the damper will perform. Almost any material
will work as a damper but how smoothly it transitions will have a big bearing on how
effective it is. During each cycle that the damper reverses direction it is transitioning
from it's static to its dynamic state, in other words, it will take more force to get it
moving, then that force will taper off once its in motion.

I'm going to make my own dampers, and I'll want them to work just as the original
Hartford's did. As far as the "spider washer" is concerned I'll get some 1095 from
McMaster Carr and cut and dish my own. Oil quench to harden them and temper
them in mothers oven if I can get her out of the house for the day. The cleaning
cycle I'm hoping will get them up to 500°F.

I can calculate thru experiment, the coefficient of friction for the various friction
materials available. But to find the actual area needed for these light front ends
that we're dealing with, I need a good idea of the average weights. This was another
reason for my futile attempt to get some real CK front weights when I was working out
the spring rates. So I'm expecting that I'll get a ration of $#!@ about over complicating
the building of the friction shocks also, but, that's my bag. So it looks like I'll have to
get there by the old trial and error method of engineering for my dampers also.

I think I'll look into possibly laser printing of the labels once the area of the disc
is finalized. Without re-reading back thru two dozen pages of that previous damper
thread, if I recall correctly, Rhys posted that the art work was the most costly part
on his version of a friction damper.

This is another project where I wish I had a buddy with water jet or laser or just a
CNC plasma table. I quickly gave up the idea of having anything done with these
processes after asked around about the costs for having a shop make them,
Even in short run quantities of a few hundred pieces the cost was out of the
ball park around my part of the country.
Denny Graham
Sandwich, IL

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Woodysrods Brian Woods
Westbank B.C., Canada   CAN
Thanks Denny
What is special about 1095?

Pierro Taruffi Rhys Nolan
Tamworth, Staffs, UK   GBR
1923 CycleKart Vintage "Voisin Laboratoire"
The photo etched labels are available on their own if you want. As full size ones now use Masonite for the discs, and as I know that it works well for the cycle karts, I would suggest that you give it a try. It's very easy to replace with something different some time down the line if you feel the need. Brake type material DOES NOT work. It has too much friction. The star is simply there to spread the load out to the edges, nothing more. By selection of the material thickness you can leave that as a decoration.
I spent a lot of time researching, I have shared it all. I am happy if folks want to re-visit.

Knock offs, I have never seen anything like the wing nuts on any full size car. Before the ones we all know there were just very large hex nuts, much like what was legislated to replace the eared ones when Health and Safety got involved.

Edited 1 time(s). Last edit at 2017-02-21 11:46 AM by Pierro Taruffi.

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Denny Graham Silver Member Dennis Graham
Sandwich, Illinois, USA   USA
Nothing special about 1095 Brian, just that I've used it to make springs for some
radio parts when I was into restoring old radios. 1074/1075 would also work just
fine, both are readily available from McMaster Care, where I buy a lot of my
stock and hardware.
Masonite will definitely be one of the materials I'll try when I set up to chart the
friction coefficients Rhys. Of course it's the least expensive and most
readily available also.


gearguy Charles Schultz
Oil City, Pennsylvania, USA   USA
AISI 1095 is an excellent material for springs that are heat treated in the home shop. The last two digits signify the carbon content, in the case of 1095 that is .95% [a bit below 1%]. Carbon equivalency determines the hardenability of the material; the hardness vs thickness ratio. The higher the carbon equivalency the hardness. The higher the hardness the higher the strength.

Take your dished AISI 1095 stars, heat them with a torch until orange hot, and dunk them in oil. Remove from oil after a few minutes and air cool. Once they are room temperature you'll want to temper them a bit before using. Maybe heat to 350F for an hour. Just don't leave a stink in the oven for the better half to discover!

For those interested in materials and thermal processing I recommend the late Carroll Smith's book "Engineer to Win." Better exlaination than we got in engineering school. Steve Smith Motorbooks or Amazon will have it and its companion volumes, Prepare to win & Nuts, Bolts, & Hardware. The publisher would not let him title the later "Screw to Win."

Pierro Taruffi Rhys Nolan
Tamworth, Staffs, UK   GBR
1923 CycleKart Vintage "Voisin Laboratoire"
But do you know what friction coefficient you are looking for? Greased willow was used in the day, but splits!

Denny Graham Silver Member Dennis Graham
Sandwich, Illinois, USA   USA
Actually Charles, drawing the 1095 back at 300°F would leave the material
very close to it's hardest condition, about 65 Rc and quite brittle. What I'll be
looking for is more like 46-50 Rc, which will require more like tempering at
around 700°F. I'll probably have to temper them with a light propane feather
to a light blue and air cool them. Testing some samples will put me in the
ball park.

No I don't Rhys, but if I compare a variety of material against the cold rolled finish
that I'll be using for the arms I'll be able to choose the one that is the least sticky at
As I posted to you last summer, I took a willow down and have been drying it. I also
posted some pictures at that time of the pucks that I cut:
As you also posted earlier, the willow or beach would need the brass retainers because
the wood discs eventually would split.
When I get to it, my plans are to experiment with not only different friction materials, but
different greases and oils and compare them for the lowest CoF.


Woodysrods Brian Woods
Westbank B.C., Canada   CAN
Time to reel you guys in again.
"CycleKarts" ......simple little under powered nostalgic looking toys for old fat guys!
Lap times of 2 minutes at the Grand Prix in Tieton, with the longest road course race 17.5 miles,
taking around 35 minutes.
This is not the 24 hours at LaMans.
But thanks for all of the input, I know it will help me make my decision when setting the oven??

Denny Graham Silver Member Dennis Graham
Sandwich, Illinois, USA   USA
Sorry Brian, you got that right. We have veered off course from the heading that
you set off on originally.
My curiosity is very rarely in line with my hot rod and restoration buddies over at
the also.
During the "restoration" of my '50 Chevy I've always asked, just exactly how did
the GM engineers design it and how did the guys on the assembly line put it together.
I've gone on for months just trying to get a color or texture to match just perfectly
in an attempt to duplicate their methods as well as I could in my home shop.

I'm having the same problem with the CK's, "good enough" simply isn't good enough
for me, I need to know the how and why of it, which brings up a lot of questions
on my part and leads me down roads in many different directions.
Being a man of limited means all of my life, that's been my method of education,
which almost always opens many doors that most people don't care to look behind.
Again, sorry.
Denny Graham
Sandwich, IL


Woodysrods Brian Woods
Westbank B.C., Canada   CAN
Good Morning Denny
No apology was necessary.
I was fully aware of where you were coming from, as my forte is reading between the lines.

Woodysrods Brian Woods
Westbank B.C., Canada   CAN
Still researching this info for my Miller build?
Have yet to come up with Knock Offs or a suggestion that I think would work well.
I think I have the Shocks covered now.
Good Roads

Pierro Taruffi Rhys Nolan
Tamworth, Staffs, UK   GBR
1923 CycleKart Vintage "Voisin Laboratoire"
In reply to # 23147 by Woodysrods Still researching this info for my Miller build?
Have yet to come up with Knock Offs or a suggestion that I think would work well.
I think I have the Shocks covered now.
Good Roads

Ask Mike Thorpe for Knock offs, he cast them and has taken several to Seattle on his previous visits, and is going again this year I believe.

joshgoreworks Joshua G
Mchenry, IL, USA   USA

I had to make some springs for a power tool design and formed them in an annealed state. I was having a hard time tempering them with a torch because hot spots were causing failure. I stumbled upon a recommendation that I heat some large blocks of steel and place the spring on the steel or between steel which is at the right temperature or nearer to the temperature. This way I could saturate the steel blocks and wait for them to cool to the desired temperature before setting the yet to be spring on them. This may not work as well on larger parts but the small parts I was making ended up in the test fixture and passed lifecycle testing just like the production ones. I was lucky I was able to lay my spring on its side and see it become saturated and slightly open from its bent state before quenching.

I still would have preferred a tabletop heat treating furnace.

Denny Graham Silver Member Dennis Graham
Sandwich, Illinois, USA   USA
The friction shocks look easy Brian….but the knock off, knock on nuts, depending on which side of the
pond you’re from….that could be a problem unless they’re only to be cosmetic. I did order a Left handed
¾ tap and die last year with the intention of using knock off’s for the front and rear axles but now.. many
months later I’m questioning whether they would be more trouble than they’re worth. After all…..we ain’t
gonna be making any timed pit stops are we???

Thanks Josh, I've gathered up most of what I need to make a fire brick kiln large enough
to take the springs. Planning to make it about 36" long. I'll be using one by and two by
fire brick in an angle iron frame with two propane burners. I hit a snag last week when
I was turning a large taper in my 100 year old L&S 16” lathe. Had to stop pull the head
stock to get at a broken bearing support for the power feed. That eat up the whole week
end plus a couple more days to get it back together. That taper is to form the bell shaped
flare for the SS burner nozzles.
Also been looking for the rollers for my compact bender which I’d like to use to roll the
eyes. They got misplaced during the BIG move I made out to the new place, as did many
of my other tools and items. Doesn’t help that this 75 year old brain isn’t as organized as it
once was. Climbing up ladders to search thru shelves full of boxes has slowed a bunch
since my right hand has been rendered useless since Christmas morning.
But….we’ll get around to those springs eventually, one way or another….that is….if I live
long enough.
Then I gotta figure a way to get 6.55 acres of trees and grass cleaned up and mowed in a
couple of weeks also. First day of spring has come and gone, the grass is greening up and
all the plants and bushes are budding out. Loads of work most of which requires a two
fisted handy man.
In other words…..I’m gonna have a plate full this spring, hope I’m able to digest it all.

Denny Graham
Sandwich. IL

Woodysrods Brian Woods
Westbank B.C., Canada   CAN
So look at the picture and remember my frame is 1 x 3" rectangular tube.
What do you think of 4" for these Knock Offs (2" round centres with 1" spikes)
I do want them to look exactly like the Miller ones.

f99d49c2fcf7433b73c2b9a235a5d467.jpg    48.3 KB

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