HOME and how to join › Forum › Open Area › General Scott topics › 22 tooth final drive sprocket needed for record attempt
It has long been an ambition to set a much higher maximum speed record for a Scott. I made an attempt a few years ago, but the normally bulletproof engine blew a head gasket during its first proving run. Calculations showed a speed of approx 117 mph at part throttle.
I need a 22 tooth engine sprocket for this task but have loaned mine to Ela Heck for her Scott racer in Germany.
If anyone has a 22T sprocket to sell or loan for a couple of months, I would be much obliged.
For the technically minded, on the previous attempt, the gearing was
22 x 44 x 22 x 34 19″ rear wheel and engine revs at that time to only about 5000 whilst testing dustbin fairing stability. Engine capable of delivering power to 6000 and capable of accepting up to 7500 safely, but I need a different exhaust system to utilise this potential.
The venue would be Woodbridge on July 18
Kind Regards
Roger Moss
Roger,
I have a massive 24 tooth sprocket in good condition. This may not be what you are after, but you would be welcome to borrow it ?
Regards,
Paul
Dear Paul There was I thinking that I had seen everything! I have never seen a 24T engine sprocket! Are you sure its a sprocket? It dos’nt have a tyre on it by any chance? I would not have imagined that a 24 T sprocket would have space to rotate!
I could use such a sprocket, as I have lots of larger rear wheel sprockets.
24T !! I must sit down! I have come over all “Unnessessary”
Thanks Paul!
Roger,
I went into the shed to check and it really is 24 tooth. It’s the sort of thing that you could use as a flywheel if you machined the teeth of. If you email your address i’ll put it in the post to you. If you manage to break the record with it then you can engrave the date, venue and speed on it !
Regards,
Paul
Roger
Cannot help with the Sprocket – but would be v.willing to help on the day – be photographer /spare pair of hands etc.
where is location going to be?
Cheers
Neil Levings
01789 550621 07769834040 😆
Can’t help over the sprocket but best wishes in your attempt.
Personally I believe if you can achieve the same gearing with the 24 tooth front as you are aiming for, then this is a better option. The chain does not turn through as small a diameter and I believe this to be more efficient.
I have just looked out the entry forms for the Woodbridge speed weekend and it is July 31 and August 1st
I must get my entry in soon or I will miss it.
I will post a notice when I get the acceptance. You are right Rod about the radius of the sprocket. I must have a look at one of these.
As a completely different subject, current high strength con rod aluminium alloys are cstronger than the steel used in Scott rods. my checks reveal 34 TT for the Scott steel rod and 38Tt for the alloy rod.
It makes it perfectly viable to make beam section lightweight rods in alloy, perhaps with needle roller small ends and at least reasonably priced compared with Titanium. Why can you not be satisfied Roger! Oh shut up! you never get anywhere standing still!
(You are never alone with Schizophrenia!)
If possible I will try to get to Woodbridge for the attempt. Is it near Ipswich or have I got the wrong one. Can you let us all know the details nearer the time Roger as I’m sure there will be quite a few people interested in how you go on
Sprockets for racing I am probably talking scribble but in my box of Scottbits I have two bizarre objects that have 22 and 23 teeth respectively.
Are these what you are looking for?
Derek
Dear Roger surely if you drive your mag from the clutch drum your timing will never be right? Alan Noakes.
Dear Roger surely if you drive your mag from the clutch drum your timing will never be right? Alan Noakes.
Hi. I got fed up of changing mag chains that had become so stiff that you had a job to bend them straight with your hand.
The Sprint Special drives its mag from the clutch drum and this is a much shorter run than from the crankshaft.
All I did was to replace the sprockets and chain with a timing belt and pulleys. To my memory, I did this in the late 70’s and I am still on the same belt. When I consider the cumulative cost of the mag chains I would have used and the reliability and reduction of chain thrash, then I am happy with something I did for myself. My approch to the Scott is that it must be constructed correctly from accurate parts. With the sole exception of the Long Stroke cranks, the basic design is quite hardy. There is only one way to success in anything and that is to know what you are doing and then do it thoroughly. I will openly acknowledge that to make or rebuild to limit gauge, is more expensive than some procedures that have been used where there was a lack of appropriate accurate machine tools available. I can also dismantle an engine and after measureing the components, clearly demonstrate the reasons for failure.
In my youth, we used to see the description used of “Motor Engineer”. My Uncle Owen Zanker of Loughborough was one. I want to see Scotts restored to the esteem that they deserve and will do my best to help wherever I can. Perhaps I should offer to host a meeting of the rebuilders, so we can consider where we can help each other in the best interest of Scott owners
Roger, sorry for not explaining my previous question, it had nothing to do with how you drive your magneto, in fact I applaud any innovation, my question was asked because somewhere along the line your request for a larger gearbox sprocket became overtaken by the possibility of fitting a larger engine sprocket which would move a standard clutch drum into a different position at every turn along with your mag drive. Please keep up the good work. Alan Noakes.
Hi both!
I have not figured out yet precisely how to post a reply specifically to one contribution, so please forgive a joint reply.
To Alan. It would seem that you are unusually observant! What happened was that, as I am producing considerably higher output than normal, I was having clutch slip problems. My response was to fit stronger springs and then a new clutch release system to lower lever pressure. I also stiffened the pressure plate that can deform under load.
To lower the torque that the clutch must transmit, I chose to replace the normal 20 tooth engine sprocket with a 22 tooth item. This is about as big as you can get inside the case profile. The ratio of flywheel is then 22 to 44 ie 2:1 It then was necessary to fit a 60T L section belt pulley to the outside of the clutch basket and make up a flanged 30T pulley for the mag. Hence 2:1 x 1:2 we get the synchronous timing we need.
There is a photo of the kit on the website.
To Derek.
If you do not anticipate using the 22 and 23 T sprocket and would consider selling them, this would be great. If you do not want to sell them, then I would greatly appreciate the loan and would naturally pay all postage. I am presuming from this that you are not located near the East Midlands UK
I have just rebuilt the brakes with new linings so if we lose a little on the straights, we can outbrake the opposition into the corners!
Kind Regards
Roger