Horstman twin disc questions

Brian is correct.......

Twenty years ago, when karting was popular, there were several companies making conversion drums.

Tomar made their BLUE three tab drums in Big (Horstman) pattern and Small (Tomar, SMC, Bully) pattern.

Big pattern is 1.0" across the flats.

Small pattern is .800" across the flats.

TS Racing made a vast assortment of drums with all combinations of Small and large pattern, mixed with 3 tab, 4 tab, and later 8 tab rims.

They also made a 3 tab and 4 tab drum for their own bolt on belt drive sprockets.

The Reaper and X5 took a square drive for the 7/8" ID drives.

The Red Hawk was the same square pattern but had a different ID and bushing for the outboard mounting on a Mini Cup.

Buller also offers a Turbo Pattern for the high HP stuff.

It was an inventory nightmare, let alone trying to figure out what the customer wanted, which was usually compounded by them not knowing the exact model of clutch they owned.

Viper/Gator made over 30 different drums at one point after TS and Tomar quit offering their broad selections, but even they have toned it down to only 21 different Small pattern drums and two Turbo Pattern drums.



Long story short...........get a Viper Style 8 tab small pattern drum and two new 8 tab linings with the gear tooth count you need.

Money well spent in the long run until you decide you need a new clutch. Any good kart shop in the USA can supply you with the parts needed.
 
...and now you have...the rest of the story. :)

Thanks, Mike!

BTW, I happen to know a shop that carries the Viper style 8 tab baskets, friction discs, and Bully "style" drivers, (as well as genuine Bully, SMC, WMS, and several others.)


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🏁Thanks and God bless,
Brian Carlson
Carlson Racing Engines
Vector Cutz
www.CarlsonMotorsports.com
Carlson Motorsports on Facebook
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34 years of service to the karting industry ~ 1Cor 9:24
Linden, IN
765-339-4407
bcarlson@CarlsonMotorsports.com
 
The precise width across flats in the drum is .7955 minimum. The precise width across flats on the sprocket is .7955 maximum. That dimension is not an arbitrary number but a calculation using geometry or trigonometry to minimize contact stresses between the two parts.

Thomas Fehring
Structure Mechanics Corporation (SMC)
 
Now that is all the info you can possibly need thank you so much man really appreciate it. I actually scored a 12 tooth right from horstman themselves guy named scott said yeah I think I got one for ya and already sent it to me and it fits mint Only need a little shim for it to be perfect and already got that. Also found a website with fibers and the steels that go in between for super low price. Great little clutch noticed though once you get down to 12tooth in the front they don't run a needle bearing since there's not enough meat on the drive gear for one to fit in there. Guessing just keep that part lubricated well with conventional oil someone said run 30w and just a little but as long as you keep a little there every rip your good. Or if you drive with the clutch primarly locked up you don't really have to worry.
 
Thank you for the warning. What guys used to do racing super moto with dry clutch set ups on there bikes anytime they needed to lube the clutch arm they would just tape parts of a zip lock by it's cooling openings. I know Not to get any oil on the dry clutch. LOL. I used to race MX and built a ton of race motors back when pitbikes were big in the early to late mid 2000s. Working with less CC's but making more HP. A ton of power could be made with port work and a really good cam usually Takegawa, ran like 12.5 to 1 compression. If you want to see a video I know it's totally not related to go karts but it is an engine I built only 150cc's with a Tak head that I machined to make it fit and put bigger valves in it etc. heres the link of a top speed run in my scoot long time ago. If this isn't supposed to be posted here just let me know or remove it since I know it's not go kart related but is engine related cool. lol.
 
So I know I been prolly wearing out this thread on horstman clutches but as people have mentioned you can make a hybrid. Has anyone tried putting the guts of a horstman clutch in a Norman cheetah barrel? They look so darn similar wish I had a Norman. Or I'm gong to guess they are just so slightly different because of patents etc.
 

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It could or should work .
The majority of clutchs are 3.5 " diameter . So if thats the cheetah dia . It should. Though you maybe in the same situation with drivers , if its not the bully/smc pattern .
If yor buying a drum simply get a bully. Everyone has bully drivers .
 
The Cheetah was an absolute blatant knock off of the Greased Lightning.

The original batch came with metric hardware instead of 10-32 SAE bolts and adjuster screws. I think that has since been corrected.

We have used the Cheetah pressure plate as a replacement for GL pressure plates for several years, and recently in a few Bullys due to shortage of OEM Bully pressure plates.

For what a Cheetah cost, you can get a Viper/Gator/Goldilocks for much cheaper and end up with a better piece.
 
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