manual clutch for horizontal shaft engine

[briggsscooter2]

Hi all.

I used to post on here quite a bit a few years back under the username "briggsscooter". I forgot my damn password and no longer have the email account that that user name was linked to. Oh well.

I've surfed the internet and this forum and cannot find info on any manually operated clutches that are commercially available. Why is that? I might be biased from my dirt bike and street bike experience, but i would take a manual clutch over a centrifugal clutch any day of the week. Its surprising to me that this basic technology hasn't carried over to the mini bike and go kart world.

Fast forward a few months and I am 90% complete with designing a manually operated clutch for a horizontal shaft engine. I will be starting the prototyping phase in a few weeks once I get a few minor design details worked out.

Some specs:

-Completely bolt on unit
-Actuated by standard lever and brake cable
-Does not apply a thrust force to the crank shaft bearings
-3.25" diameter
-Needle bearings used throughout


Some bad specs:

-Sprocket center line is farther outboard than a conventional centrifugal clutch by about 3/4" (this is when the centrifugal clutch is mounted such that the sprocket is close to the engine). I can't figure out a way to get around this. This would require shifting the engine by 3/4" to account for it.
-Minimum sprocket size is 15 teeth for #35 chain. I MIGHT be able to get it down to 14 teeth but i doubt it. My thought, though, is that since launch RPM will be higher than a standard setup, this wont be as big of any issue as one might think. Still unfortunate.


What do you guys think? I am trying to gauge interest level to see if this is something i should pursue as a product instead of just building one for my scooter. Price would probably be comparable to a Comet TAV2.

Thanks for the feedback.

 

[rmm727]

Let's see some pics.

 

[trailhopper]

"Sprocket center line is farther outboard than a conventional centrifugal clutch by about 3/4" (this is when the centrifugal clutch is mounted such that the sprocket is close to the engine). I can't figure out a way to get around this. This would require shifting the engine by 3/4" to account for it."

So that would require drilling new holes in the engine plate? :shrug:

 

[oldsledz]

The sprocket center line may not be a problem if you have a jack shaft.

With the 15 tooth sprocket will you be able to put along at 5mph when you need to with out slipping the clutch or will the engine stall?

How many do you need to sell to make it worth while?

With the price difference it will never replace the centrifugal clutch.

 

[briggsscooter2]

"Let's see some pics."

Wasn't sure if this was a smart thing to do, but since you asked. See link below. Please note that i have not designed a provision for mounting the cable housing yet.

clutch picture



"So that would require drilling new holes in the engine plate?"

That is one option. As another said, one could use a jack shaft.



"With the 15 tooth sprocket will you be able to put along at 5mph when you need to with out slipping the clutch or will the engine stall?"

My scooter is currently set up with 12 front, 53 rear and uses a 10 inch rear tire. At 1200 RPM, I would be doing 10 MPH. I would have to slip the clutch to go slower. Keep in mind, though, that you also have to slip your centrifugal clutch to go 5 MPH as well.




"How many do you need to sell to make it worth while?

With the price difference it will never replace the centrifugal clutch."


Pretty tough to replace the centrifugal clutch- probably impossible. It is incredibly simple and cheap to manufacture. I am not really sure how many i would need to sell to make it worthwhile- I'll have a better idea after I get through the first prototype phase.




A few more advantages of this clutch:

-you can bump start your mini bike
-wheelies would be very easy. Could probably spin the tire as well.
-better off the line acceleration.

 

[Newoldstock]

"Let's see some pics."

Wasn't sure if this was a smart thing to do, but since you asked. See link below. Please note that i have not designed a provision for mounting the cable housing yet.

clutch picture



"So that would require drilling new holes in the engine plate?"

That is one option. As another said, one could use a jack shaft.



"With the 15 tooth sprocket will you be able to put along at 5mph when you need to with out slipping the clutch or will the engine stall?"

My scooter is currently set up with 12 front, 53 rear and uses a 10 inch rear tire. At 1200 RPM, I would be doing 10 MPH. I would have to slip the clutch to go slower. Keep in mind, though, that you also have to slip your centrifugal clutch to go 5 MPH as well.




"How many do you need to sell to make it worth while?

With the price difference it will never replace the centrifugal clutch."


Pretty tough to replace the centrifugal clutch- probably impossible. It is incredibly simple and cheap to manufacture. I am not really sure how many i would need to sell to make it worthwhile- I'll have a better idea after I get through the first prototype phase.




A few more advantages of this clutch:

-you can bump start your mini bike
-wheelies would be very easy. Could probably spin the tire as well.
-better off the line acceleration.

I might be able to help you with a manufacturer in China.
Trouble is once the Chinese get their hands on it ( if they pick it up for producution ) it will be cloned.....

 

[bigrob]

It is a great idea , and I have often wondered how hard it would be to produce one.
There are a few of us on here that have lathes and mills , when you get the design worked out would you consider selling a plans package for home builders.

 

[scootercat]

I can't remember what iss. of mini bike guide it was in, but there was a man.clutch story it used a three disc setup, one on the outside with fiber pad on the surface,two,a sprocket/disc then another disc on the inside..|||...held together with tension springs like a cycle clutch...>|||<the sprcket/disc spun on a large dia.bearing and the engine was chained to this for the primary drive...the hub that the in and out discs road on a jackshaft that had a center hole for the release shaft to pass through...I'm going to try and find what I'm talking about and get some pics scaned...It looked like a speedway bike clutch,Thats what You need to fab up!...Would be fun for doing burnouts and hole shots!....Scootercat....

 

[Oldsalt]

A manually controlled clutch would be a very desirable item on a drag machine because the rider could peg the throttle and apply the clutch so that the engine was always at its peak torque. In other words...you are always in the 'correct' gear.

I had the third Van Tech 125 scrambles bike produced in Visalia CA. It had a manual clutch and with my rider, Joey Petz, could not be beat. The engine was revved to the moon and the clutch used as a 'torque converter'. The first 5 or so built had go kart type centrifugal clutches but mine was retro fitted by the factory to have the better manual. They were a single plate as I recall but that has been a long time ago. The clutch was on a jackshaft close to the swing arm.

I too have looked at all the sources I could think of to locate an existing clutch that would be reasonably sized for a minibike motor...I'm with you, it doesn't exist.

I would say that your clutch will be the high zoot set-up even for a stock 5 HP briggs. I'm interested! From my experience with the Van Tech it would not merely 'replace' the centrifugal...it would be a serious upgrade. Van Techolt used three small, round friction 'pucks', rather than a full 'plate' to keep the co-efficient of friction as high. The body, and even the #35 primary sprocket, was aluminum. The only thing that would wear out was that sprocket.

A jackshaft with a flywheel could be looked at. It would 'store' energy and make the clutch easier to manipulate without bogging or over revving the motor.......I think.

DO IT!

 

[Stangrcr1]

I would be up for one for a 1" shaft 390....

 

[RADustin]

I been trying to get my hands on a used vortex clutch. I think I could manually operate it very easily.

 

[Beal]

Manual clutch sounds like fun.
If I can afford one, wouldnt mind having one...

 

[Dave_In_Florida]

I'm listening

 

[KustomKartKid]

I've surfed the internet and this forum and cannot find info on any manually operated clutches that are commercially available. Why is that? I might be biased from my dirt bike and street bike experience, but i would take a manual clutch over a centrifugal clutch any day of the week. Its surprising to me that this basic technology hasn't carried over to the mini bike and go kart world.

It sounds interesting and would be fun to fool around with. To answer your question though, probably the biggest selling point of the original mini bike and what made them so popular was their simplicity.......gas and go with a simple scrub brake or drum brake. The centrifugal clutch is a fascinating piece of engineering...simple, cheap, and effective. It allowed folks of all ages and skill levels to just hop on and have fun.

In my opinion, it is the single most important feature that contributed to the sale of millions of mini bikes and go karts.



.

 

[Artrockets]

... The centrifugal clutch is a fascinating piece of engineering...simple, cheap, and effective. It allowed folks of all ages and skill levels to just hop on and have fun.

In my opinion, it is the single most important feature that contributed to the sale of millions of mini bikes and go karts.



.

Well said. On a vehicle without gears the centrifugal clutch is a must. You can let your engine warm up without having to hold the clutch. I can't imagine trying to pull start an engine while holding a clutch lever in. For the drag racing circuit I can see real value but for everyday riding I'm on the fence.

Although... I'm working on an old trail mutt right now that will have a manual clutch but it's just engaging/disengaging(tightening/loosening) a fan belt basically. It will be a big lever coming up from the floor that will just stay at whatever position you leave it at ie.. open, closed or somewhere in between.

 

[Beal]

Well said. On a vehicle without gears the centrifugal clutch is a must. You can let your engine warm up without having to hold the clutch. I can't imagine trying to pull start an engine while holding a clutch lever in. For the drag racing circuit I can see real value but for everyday riding I'm on the fence.

Although... I'm working on an old trail mutt right now that will have a manual clutch but it's just engaging/disengaging(tightening/loosening) a fan belt basically. It will be a big lever coming up from the floor that will just stay at whatever position you leave it at ie.. open, closed or somewhere in between.

I supose there could be some sort of lever/lock to keep it disengaged.
Like a lawnmower parking brake usually has some sort of lock to keep the brake engaged. And Im sure there are plenty of ways to do so with a clutch lever...

 

[briggsscooter2]

"I supose there could be some sort of lever/lock to keep it disengaged.
Like a lawnmower parking brake usually has some sort of lock to keep the brake engaged. And Im sure there are plenty of ways to do so with a clutch lever... "

That is exactly what I am doing, I'm modifying a standard clutch lever to have a push button that keeps the clutch disengaged for starting.




Sorry I havent had time to answer everyones questions, been working quite a bit lately...

 

[Stangrcr1]

Just thinking...

For drag, what about reverse operation...?

It would be normally released and when the lever is pulled, it engages. Change spring loading to change slip... Or hydraulic like a brake that can easily be modulated.

 

[briggsscooter2]

Just thinking...

For drag, what about reverse operation...?

It would be normally released and when the lever is pulled, it engages. Change spring loading to change slip... Or hydraulic like a brake that can easily be modulated.

No reason you couldn't do this, can you go into more details on the benefits?

 

[briggsscooter2]

Chugging away at this design.... I've been able to reduce the distance between the casing's 4 bolt pattern surface and the sprocket center line to 1.0 inch. Can someone please measure their engine setup and tell me what this value is?