CycleKart Tech Forum

Using the Cable operated reverse gearbox

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moto-klasika Avatar
moto-klasika Zoran R. P.
Bern, Bern, Switzerland   CHE
Hello Denny, Charles and Vic,
Three of you are representatives of three quite different “schools” of writing, then approach to “perfect CycleKart” and finally cyclekartism in general … In spite of that, or just because of that – I really enjoy in writing your posts, and now I found them all at one place at one subject. Even I disagreed sometimes (or often), I respect them as honest and useful for builders, would-be builders or public... Of course, my opinions are irrelevant because I am not building CycleKart and I will not build one. However, I enjoy in following discussions and learning things that I do not know. Even if never used, such experience, information and knowledge are pleasant and joy by themself (and how knows?), but better then to search for pornography in my old age (just watching – no doing, principles are similar).

If ever start to build one, I would have similar dilemmas, about what and how to build “my perfect CycleKart”! Should it be:

1. Original Stevenson Formula - simple and cheap, light, safe and fast, the most fun with the least problems, that I followed trough many years during long and great correspondence with Pete Stevenson?
2. Unorthodox construction of plywood monocoque chassis/body construction (no-welding!), which is my old dream? (aluminium monocoque should be the top-class!)
3. Sofisciatated automobile with front and rear suspension (why not independent?), differential (limited slip or with blockade), chock absorbers around, hydraulic disk-brakes here and there, reverse gear, electric-start – that is exact copy of some veteran/vintage automobile?

If I decide to start buying lottery tickets and have some success there – I should must start to think seriously about what to do! The first variant is the most real and practical, the second is the most interesting and the third is magnificent – almost real racing micro-automobile (just to abound Holly Grail: lawn-mower engine and transmission)...

I suppose that I would be there for long time, maybe more silent sometimes (not an easy task for me!) - as public at 3rd gallery of theater...

Regards to all three of you and to many more active members not mentioned this time!


P.S.: Just not to forget – all this is about fun! Rules and standards are written after doezen of CycleKarts were built and used – not before that! Therefore, relaxed approach is (probably) welcomed and if auto looks and drive as average CycleKart, everything should be OK? Even beter if driver/owner act in a style of average cyclekartist? Spirit and attitude is more important than technique and technology?

Zoran R. Pualić
(mostly living in Bern, Swiss & happy in my Belgrade, Serbia)

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Torro123 Avatar
Torro123 René Wesselius
Amsterdam, NH, Netherlands   NLD
Reading all the before replies i feel like to give a warning.........
The whole stephenson concept CK was to buil a low-cost fun kart with classic design,these karts can be build by almost enyone with limited technical skills and a simple toolbox.
Now reading all of this about gearboxes,diff's and steering boxes i am afraid there would be a different class into the CK world.
Nowadays you can buy a complete CK for the price of a small car or build a CK which cost a lot more using all of the mentioned items,i have also been reading about upgrading the engines upto 20 hp or more.........
I have been involved since 1972 in 50cc bike racing,this was a typical home build racing class untill the factories get involved,then is was all about how more money was spend the faster the bike was.
At first when i started to race in the paddock everybody was helping fellow drivers with parts or technical support and it was one big family,later the bikes stood in a closed tent and everything was a big secret,no more family no more fun.
I am afraid when cyclekarts develop this way it will become a hobby for the rich and (not so)famous,the blue collar CK enthousist will fade away and the event become a high sponsored event with large entry fee's.
There must be a kind of technical freedom ofcourse but i think these must be home made innovations,not off the shelve high dollar items.
Just my thoughts.

gearguy Charles Schultz
Oil City, Pennsylvania, USA   USA
Forward is done via CHAIN; 10 tooth to 13 tooth. Most of the "slop", lost motion, or backlash is from this as there is no chain tensioner.
Reverse is 15 tooth x 39 tooth CUT & Hardened .5 module [12.7 NDP] 20 degree NPA spur gears with a 10 mm face width. 15 tooth pinion is fixed to the input shaft along with the 10 tooth sprocket.
On the output shaft both the 13 tooth sprocket and the 39 tooth gear always rotate. They have needle bearings in the bores. The gear & the sprocket have a toothed "clutch" in them & the rotary shifter arm slides the other clutch member from Forward to neutral and then to reverse. Very clever mechanism with smooth movement and a good level of precision. Both input & output shaft turn on #6003 ball bearings. Housing is a nice die casting with a gasketed & double doweled split line.

My gear rating program projects just under 5,000 hours of life for the reverse gearset at 6.5 HP & 2300 RPM input. The rating limitation is durability not tooth breakage.

A more realistic expectation is 500 hours of operation in reverse which results in a calculated capacity of 7.25 hp durability & 13.3 hp strength. Strength is a measure of tooth breakage limit. Very few gears break at the calculated limits; usual "limit is 1.5 to 2x the calculated value.

IMHO this is a very nice piece for those of us who need or want a reverse gear capability.

Purists, please note this thread is in the Custom Kart Forum. For those who are building outside the published formulas.

One little jab though, a parade of (40) professionally built $11,000 toy cars hardly says "economical hobby" to the average tinkerer. That is cheap compared to many forms of motorized fun but it isn't "chump change" either. Perhaps we should have a challenge to build the cheapest cycle kart every year. I have a wood chipper motor out in the shed to contribute along with some scrap plywood and old 1-5/8" diameter galvanized fence rail & old bed frames.

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FNRcover.JPG    30.4 KB

FNRgears.JPG    30.9 KB
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Denny Graham Silver Member Dennis Graham
Sandwich, Illinois, USA   USA
1950 Chevrolet 3600 "Old Blue"
1954 Chevrolet 3600
A chain???? who'd have thought.
I would have bet all of it was done with
spur gears. Still don't quite get the forward
engagement, but that's not important.
Thanks for doing that autopsy Charles.
I'ts nice to know what's inside of that.

So, everything inside 'is' replaceable
after all, as long as the case isn't damaged.
I couldn't make out the chain in the photo,
to dark, so I opened it in Photoshop and lightened
it up, now I can clearly see it.
Looks like it might be #35, hope it's not some
special Chinese chain.
Brgs are common and inexpensive and the spur
gear looks to be a common one which one could
find a blank for.
Thanks again

I wonder if that answered Bob' s question?????
I'd say that gearbox got a pretty good going over
in this thread.

Edited 1 time(s). Last edit at 2017-02-17 06:17 PM by Denny Graham.

CmdBentaxle Avatar
CmdBentaxle Silver Member Dave D
Federal Way, Washington, USA   USA
1950 CycleKart Italian "1950 Ferrari 166 F2"
I am not a cyclekart purist. That much is plainly seen in my choice of a 1950 car.
I used to spend more time defending the traditional cyclekart formula, but have come to realize that it doesn't need defending.
Simple, lightweight, cyclekarts need no advocate. They are, and will continue to be I believe, the most appealing
of the type for the majority. They are fast, nimble and go together quickly.

However. If some people are attracted to the idea of more sophisticated systems, who am I to begrudge them their fun?
Unless someone wants to come over and install 40lbs of additional hardware on my car, why should I care?
If that same equipment makes the car more enjoyable to it's builder, why should anyone discourage him from
using it.

Build for your intended use, I say.
My only caution is about weight. As some of these well equipped karts are eventually completed, I suspect there may be some startling scale readings.


moto-klasika Avatar
moto-klasika Zoran R. P.
Bern, Bern, Switzerland   CHE
Gearguy Harles Schultz
Winfield, Illinois, USA USA

Feb 13, 2017 12:58 AM

I copied this from the Arizona Kart Club FB page this morning in anticipation of someone complaining that diffs/brakes/ F-N-R boxes add too much weight.
Weights of each car.
Lowell Roemke
Red alpha 303 pounds
Yellow t-bucket - 288 pounds
Blue car - 369 pounds
Copper car - 339
Steve Vinson
Red ford - 269 pounds
Steve Jo car - 260 pounds
Dennis mono car - 255
Jon chassis - 236

In reply to # 22312 by Pierro Taruffi I have just been checking weights and sizes of the cars on the Gittreville site, the Bugatti Tank on there is as below.

For those curious about weights: the frame is 27.4#; rear axle/wheels/sprocket/brakes 53.9#; front axle/springs/Panhard rod/steering rods 41.5#; steering shaft/wheel/bearings 7#; GX200 and Comet drive 40.3#. Birdcage, floor pan, pedal set, etc., bring the total up to just under 200#. Bodywork added 70#.
Overall length 120"

My ERA dimensions
Wheelbase: 62”
Ground clearance: 5” (front axle)
Front track: 39”
Rear track: 39”
Overall length: 96”
Body width: 16.5”
Radiator width: 14”
Height: 33”
Height at scuttle: 31”
Weight: 196 lbs
Hello Rhys,
It looks that your first CK is one of the lightest known up today? You didn't write a lot about it - but what was experience and impression from drving it?

Any more facts about your all-wood built Austin-7 special? What happend to it? I suppose that it was built strong and light with your experience in building boats!


Zoran R. Pualić
(mostly living in Bern, Swiss & happy in my Belgrade, Serbia)

bluesdocbob Avatar
bluesdocbob Bob Paterson
Darlington, Victoria, Australia   AUS
Thank you to everyone who has commented this train of thought I started and as a result I'm going
to ad one of these units to my build of a cyclekart and I'll def make sure to add photos here on in a
new build thread.
And yet again thank you again for the inspiration to go ahead.......

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