Crank build for racing engine
- Thread starter chark_mandler
- Start date
Bruce I'm not sure Maughan's do anything but make parts and some engine work.......their flywheel/main shaft assemblies are pretty much available anytime, perhaps a complete crank assembly might be a special order.......I would say they have a small staff number..... not a full mechanical or restoration shop.
I think that Graham recently struck out on his own.
I agree with Greg about putting the old flywheels aside. Maughan ships the flywheels disassembled, and I have them assembled and balanced here to prevent the wheels from going out of alignment during shipment. I use a Carrillo rod with bronze washers instead of hardened washers. Ensure there is enough clearance for oil to get out of the big end quickly, and it should be good to race. I use new wheels to achieve good hardness and some resiliency to create a bit more grip on the main shafts and pin. I think it is cheap insurance.
David
David, did you ever work out an approximate time frame as to when a race crank should be disassembled.......I vaguely remember John Trease told me at some time around 3000 track miles/kilometers........sounds a lot, but not as much as one might think.......I suppose it depends on the state of tune of your engine as well.
Greg,
That sounds about right. I think the Comet design is excellent, with its narrow crank and beefy design. Your high-compression alcohol engines may have contributed to a slightly earlier demise. David Tompkins has used this engine for five years. and won four national championships. That is normally about 12 races a year as they take the best of 10 finishes (which means you have to win ten races). If you pick an average of 100 miles per race, including two practice sessions per race to get correct gearing and tire pressures, that works out to 1200 miles/season. The rule we used was a rebuild around season three, which would fit John's 3,000-mile rule.
It comes down to how tight the cam spindle was when it was installed. That is the weak link in the reliability chain. The big end will probably last longer, but if you are running at a championship level, it is best to replace or rebuild it after three years. David has 6,000 or so on his engine. It is just a matter of how well the engine goes together and how much over-revving occurs. These engines are so reliable I could probably sacrifice some reliability for more power, but Dave always had the choice to switch to my cam, which has about 4 more HP, and he stayed with the MK2. I think this worked out well for him as a rider, so I have no complaints.
David
That sounds about right. I think the Comet design is excellent, with its narrow crank and beefy design. Your high-compression alcohol engines may have contributed to a slightly earlier demise. David Tompkins has used this engine for five years. and won four national championships. That is normally about 12 races a year as they take the best of 10 finishes (which means you have to win ten races). If you pick an average of 100 miles per race, including two practice sessions per race to get correct gearing and tire pressures, that works out to 1200 miles/season. The rule we used was a rebuild around season three, which would fit John's 3,000-mile rule.
It comes down to how tight the cam spindle was when it was installed. That is the weak link in the reliability chain. The big end will probably last longer, but if you are running at a championship level, it is best to replace or rebuild it after three years. David has 6,000 or so on his engine. It is just a matter of how well the engine goes together and how much over-revving occurs. These engines are so reliable I could probably sacrifice some reliability for more power, but Dave always had the choice to switch to my cam, which has about 4 more HP, and he stayed with the MK2. I think this worked out well for him as a rider, so I have no complaints.
David
The rules from country to country make it difficult........period 3 class here is bikes from 1946 to 1962........not capacity related as they split these up......although the numbers overall are so low that they just throw them all in together now........but here you could be racing against the last of the Manx's or any other bike up to 1962.......this is why I've been trying to get more power......In the Unlimited class, which is what I run in, this is bikes up to 1300 cc.......this could include Triumph's and Norton's that run 810cc's and 920 some of them are very quick, but on the verge of being quite unreliable as well........My mate's Norvin will be a 1200 twin so it will be a very quick bike..........At Broadford back in 2018 Keith Campbell got around there on a 600 cc ESO/Norton doing a lap time of 1.06 this was faster than all the twins including a Norton/Jap twin........This was what inspired me to build my bike......I'm never going to be as fast a rider as Keith.......I just wonder what lap times he could do on my bike........
It will not matter at all but my view about classic racing in recent times is not so positive: The definition of cheating is in my eyes an action that is not obvious to the public or business partner as not openly visible. So on classic bikes big brakes, big carbs and all is not cheating as everybody and the spectators can see what was modded on the racer.
But anything worked on in the engine cannot be checked when applying for entering in racing. Especially way bigger capacity is the most important factor for having a lot more power from that engine. Not a concern when this was checked before and everybody knows about this and is entered in papers. It is just not fair running against 650 singles with a standard 500 cc racer, same with other classes and very different capacities of engines.
If I had some say in regulations I´d want capacity checked at beginning of racing season by simple oil fill checks through spark plug hole - a 10 minutes exercise. So all participants will know what sort of competitors they are dealing with.
Next idea for returning some more democracy back into hobby racing in classic bike sports - like it was at the beginning long time ago in opposition to sponsored millionaire GP racing - is to have engines sealed for one racing season, no exchanging components in between . So when your engine has gone into some defect you are out for the rest of year. That way mechanics will do their very best to produce solid engines and spare them exotic extreme modifications for short time advantages that a less wealthy competitor cannot find the money for.
Same idea was applied on Six Days offroad racing when engines were sealed and any repairs done after racing each day.
This does not drive all fun out of the hobby racing as it applies to all racers the same but saves costs - like they did in GP racing many decades ago, so no first in this approach. Remember the supercharger ban post war, the limit of four cylinders or less in GP engines in mid-sixties, plus number of gears to 6 max. from two digit boxes. This may lead to more honest competition and lowers costs in hobby racing.
In my country the regularity racing with classics has - or had some positive effects by introducing a lot more diversity of machines, even a quantity of real old racing machines when preserving old material as you can go fast or slower , does not matter for qualifying for first places - for some personalities with too much ego, narcissism or whatever motives for going racing. After all, as Greg puts it, it should be all good fun in a hobby activity. But in reality too much aggression has crept in this , so no wonder not many "precious" Vincents are raced today, even when they basically are not really rare or expensive compared to new production Manxes or G 50s . So instead many rather go for ready-to-race Manxes or Matchlesses without having to deal with all these quirks with Vincents to turn them competitive in all out racing. With all that aggression not many owners will be willing to risk genuine old racing machines entering into that sort of racing, so you will see them in parades only at best - a sorry state.
Certainly big respect to Greg for his dedication in all his engine tricks but I do believe this is no good approach and politics in the long run for keeping classic racing attractive as money will drive out many people and a variety of machines at same time. With extreme money spent on maximum power you will end up seeing only faked lookalike classics on the track , headscratching about what you see there in reality.
Vic
But anything worked on in the engine cannot be checked when applying for entering in racing. Especially way bigger capacity is the most important factor for having a lot more power from that engine. Not a concern when this was checked before and everybody knows about this and is entered in papers. It is just not fair running against 650 singles with a standard 500 cc racer, same with other classes and very different capacities of engines.
If I had some say in regulations I´d want capacity checked at beginning of racing season by simple oil fill checks through spark plug hole - a 10 minutes exercise. So all participants will know what sort of competitors they are dealing with.
Next idea for returning some more democracy back into hobby racing in classic bike sports - like it was at the beginning long time ago in opposition to sponsored millionaire GP racing - is to have engines sealed for one racing season, no exchanging components in between . So when your engine has gone into some defect you are out for the rest of year. That way mechanics will do their very best to produce solid engines and spare them exotic extreme modifications for short time advantages that a less wealthy competitor cannot find the money for.
Same idea was applied on Six Days offroad racing when engines were sealed and any repairs done after racing each day.
This does not drive all fun out of the hobby racing as it applies to all racers the same but saves costs - like they did in GP racing many decades ago, so no first in this approach. Remember the supercharger ban post war, the limit of four cylinders or less in GP engines in mid-sixties, plus number of gears to 6 max. from two digit boxes. This may lead to more honest competition and lowers costs in hobby racing.
In my country the regularity racing with classics has - or had some positive effects by introducing a lot more diversity of machines, even a quantity of real old racing machines when preserving old material as you can go fast or slower , does not matter for qualifying for first places - for some personalities with too much ego, narcissism or whatever motives for going racing. After all, as Greg puts it, it should be all good fun in a hobby activity. But in reality too much aggression has crept in this , so no wonder not many "precious" Vincents are raced today, even when they basically are not really rare or expensive compared to new production Manxes or G 50s . So instead many rather go for ready-to-race Manxes or Matchlesses without having to deal with all these quirks with Vincents to turn them competitive in all out racing. With all that aggression not many owners will be willing to risk genuine old racing machines entering into that sort of racing, so you will see them in parades only at best - a sorry state.
Certainly big respect to Greg for his dedication in all his engine tricks but I do believe this is no good approach and politics in the long run for keeping classic racing attractive as money will drive out many people and a variety of machines at same time. With extreme money spent on maximum power you will end up seeing only faked lookalike classics on the track , headscratching about what you see there in reality.
Vic
Our twin racer that won the race at Goodwood is as near standard as you could expect its 998 4 speed mk2 cams etc the only clever bit is a programmable ignition. Our brakes are 7" as we have to keep the original drums but we are allowed to have TLS so we had a set cadded up with standard shoes still pretty poor on stopping. we also are restricted to 19" tyres which on a twin is not to bad a restriction since it keeps the clutch cover in one piece
I dare say this autumn we may come across that heavily modified BMW mentioned a few posts back
I dare say this autumn we may come across that heavily modified BMW mentioned a few posts back