Cush Drive Crankshaft Pulley
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SeeleyWeslake said:
I don't think Norman is planning to retire yet....
He told me that he would make one, no problem but a one off price. The reason for starting this thread was to see if anyone else is interested, to maybe find another supplier (comnoz might get around to it, but...lots of projects...) or to maybe get a small batch price rather than one off.
Part of the issue will be spec, width number and profile of teeth, but assuming the Hemmings clutch is popular (and available in 68 tooth to give your 1.89!) (and that Bob Newbys clutch would also work?) and as you say there is a belt supply that can support various shaft centres (my Rickman will be around 26mm for example as the engine is upright). And recognising that with a 68 tooth drum a 1.79 ratio could be acheived with a 38 tooth pulley to the profile you have, it would be a good option for a number of racers who would definately give their transmission an easier time with this set up, even if they had to change their choice of gearbox sprockets, but hardly a big deal, certainly not the same investment as a new wheel, cush drive and set of rear sprockets.
I had in mind a 40 tooth to work with a 70 tooth drum and get close to 1.72, because back in the day, as they say, I ran a 57 tooth triplex drum with a 33 tooth sprocket and 17 tooth gearbox sprocket, so 1.72 primary, but the engine was an 850 revving to between 6200 and 6700 depending on actual spec, and now I am building a short stroke 750 to rev over 7500, so the 1.79 with the 38/68 could be a better choice! Certainly back then I did not remove the gearbox cover in 4 seasons whilst others were removing the box every week.....must be worthwhile looking after your investment, it so much more fun to finish races!
So, if a few guys agreed on spec, maybe Norman would build a batch at a better price, it would be real nice to have a Norman White trick part, or someone else would like to?
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Hi there, just found that dated 2006, in britbike forum, and written by BDM......., let's go:
If you change the material in what Norton called a transmission shock absorber you alter its shock absorbing characteristics and IF we assume that it actually was a shock absorber in the first place you may well be making it into a shock load increaser
Personally I believe the clutch shock absorber introduced in 1934 by Norton for a single sylinder bike with different shock characteristics to a twin or even betwen a 500 and 350 plonker was as was the one when Triumph later junked their crank one and put one in the clutch..which was , accoeding to the ex Triumph Gent I talk to who was one of Mr Turners assistants at the time it was done...'a copy of one that had been around in 1919'. This may well of been a copy of one from 1805 or even AD60!!!
I once said to a few British Buike Industry people such as Mr Hopwood, Mr Hele, Mr Cave etc to see what their reaction would be 'In my opinion you spent less on clutch and shock absorber development than you did in feeding the D.O. cat' and NOT one has dissagreed!!!!
Talking to a few clutch designers over the years ALL have stated to me that there is NO way the same transmission shock absorber can work correctly fitted to anything from a 350 single to a 750 twin and by others to 1000 cc V twins etc etc so I suspect it is in fact a shock increaser and could explain why it one was NOT included on the Commando..but I doubt it, probably a case of 'Its only a ******** two year stop gap model lets not bother designing developing and fitting a proper one'. Developing such things CORRECTLY costs money AND time. I believe Triumph farm such work out to a Jap company who probably look at a Honda one and copy it.... with the odd change so it looks new.......????
Harley had a so called shock absorber fitted to their lumps for years....When in the 70s they and The Gates Rubber Co developed the all belt driven Harley they had a problem with primary belt failures ....this was eventually traced back to the so called shock absorber putting rather large shock loads into the transmission system because it was NOT working correctly. This was all told in an SAE paper of which I have a copy or two somewhere. The so called shock was redesigned to work something like correctly, the shock loads were reduced and the belt failure problem went away!!.I just do not understand why anyone would assume our so called shock absorbers work anything like correctly and it could well be the case that in NOT having one Commando transmission is given an easier time!!
In his 1949/50 A4 size 350cc 7R and 500cc E45 twin design note book Mr Jack Williams wrote that the clutch mounted transmission shock absorber did not have enough movement available within it to work correctly and that he wanted a crankshaft mounted car type one......Now I very much suspect that his request that such be fitted was based upon testing that he had done to determine how well or badly the std lumps worked.
Mr Hayward used to sell different Triumph shock absorber 'rubbers' so that all Triumph owners could become transmission shock absorber exspurts and individually tune theirs.....Ha Ha Ha. Suggest you consult such Mr Hayward and seek his advice!!!
Dont Andover Norton supply the rubbers...I suspect they will at least be to the original spec.
CORRECT OIL for the chain case is straight SAE10 mineral (or SAE 20 if you cannot find SAE 10).....So Mr Phil Heath told me decades ago and he was part of the original pressed steel oil bath chain case development team along with Mr Franks and others Correct filling precedure being, so he told me ..Remove spark plug/s. Fit oil level plug and remove inspection cap. Find wife or son or anyone handy. With them operating the kickstarter and you watching the chain as it flies past your nose SLOWLY fill the chaincase and AS SOON as you see oil is just touching the chain STOP filling. He did make the comment that doing it this way would stop the problems of clutch slip and drag due to oil but that it did little for chain life.. BUT it was a lot better idea than the previous open run chain idea as on my Late Fathers Nortons of the 20s and early 30s.... Mind you if you bother to read chain manufacturers bumph there is no way to correctly lubricate chains at the speed we use them at in our primary drives anyway. Probably the best way being an olde Triumph idea where the system was enclosed within a chain case along with some oil but at the top of the chain case they had a oil collection area from where it was piped down to fall on thew inside of the chain on the side plates (As Manx /G50 Etc) so some at least was forced between the plates as the chain flew round the clutch and some even stood a slight chance of reaching the many plain bearings within the chain.
That way you probably picked some up to cushion the rollers (unless things were cavitating) and got some into the plain bearings. Not long ago a UK University did some reaearch into the dynamics of using high speed chain for auto cam drives... I spoke to a couple of the people in charge of the project and both said how amazed they were at the lack of knowledge they found within the chain industry regarding high chain speed use.As chain is an industrial item and industry rarely used chain at anything like even 2000 ft per min and we use it at up to 8000 ft per min why should industrial chain manufactures of done lots of expensive testing.... If you want a laugh try finding ANY test data showing the power losses that occur in say your singlex chain runing at even 5000 ft per min. Mr Jack Williams also stated in his design note book that a primary chain was probably no more than 90% efficient at high chain speed and lower with incorrect lubrication. Personally I saw a lot of zero efficiency ones laying in Manx roads after a TT in the 50s and 60s.
It should be rememered that chains were employed to replace flat belts on motorcycles but NOW we have toothewd dry running belts that we can use to replace industrial chains. ANd dont forget that TT winning Rotary Norton employed a 25 or 30 mm wide Gates belt on its primary drive.....
If you change the material in what Norton called a transmission shock absorber you alter its shock absorbing characteristics and IF we assume that it actually was a shock absorber in the first place you may well be making it into a shock load increaser
Personally I believe the clutch shock absorber introduced in 1934 by Norton for a single sylinder bike with different shock characteristics to a twin or even betwen a 500 and 350 plonker was as was the one when Triumph later junked their crank one and put one in the clutch..which was , accoeding to the ex Triumph Gent I talk to who was one of Mr Turners assistants at the time it was done...'a copy of one that had been around in 1919'. This may well of been a copy of one from 1805 or even AD60!!!
I once said to a few British Buike Industry people such as Mr Hopwood, Mr Hele, Mr Cave etc to see what their reaction would be 'In my opinion you spent less on clutch and shock absorber development than you did in feeding the D.O. cat' and NOT one has dissagreed!!!!
Talking to a few clutch designers over the years ALL have stated to me that there is NO way the same transmission shock absorber can work correctly fitted to anything from a 350 single to a 750 twin and by others to 1000 cc V twins etc etc so I suspect it is in fact a shock increaser and could explain why it one was NOT included on the Commando..but I doubt it, probably a case of 'Its only a ******** two year stop gap model lets not bother designing developing and fitting a proper one'. Developing such things CORRECTLY costs money AND time. I believe Triumph farm such work out to a Jap company who probably look at a Honda one and copy it.... with the odd change so it looks new.......????
Harley had a so called shock absorber fitted to their lumps for years....When in the 70s they and The Gates Rubber Co developed the all belt driven Harley they had a problem with primary belt failures ....this was eventually traced back to the so called shock absorber putting rather large shock loads into the transmission system because it was NOT working correctly. This was all told in an SAE paper of which I have a copy or two somewhere. The so called shock was redesigned to work something like correctly, the shock loads were reduced and the belt failure problem went away!!.I just do not understand why anyone would assume our so called shock absorbers work anything like correctly and it could well be the case that in NOT having one Commando transmission is given an easier time!!
In his 1949/50 A4 size 350cc 7R and 500cc E45 twin design note book Mr Jack Williams wrote that the clutch mounted transmission shock absorber did not have enough movement available within it to work correctly and that he wanted a crankshaft mounted car type one......Now I very much suspect that his request that such be fitted was based upon testing that he had done to determine how well or badly the std lumps worked.
Mr Hayward used to sell different Triumph shock absorber 'rubbers' so that all Triumph owners could become transmission shock absorber exspurts and individually tune theirs.....Ha Ha Ha. Suggest you consult such Mr Hayward and seek his advice!!!
Dont Andover Norton supply the rubbers...I suspect they will at least be to the original spec.
CORRECT OIL for the chain case is straight SAE10 mineral (or SAE 20 if you cannot find SAE 10).....So Mr Phil Heath told me decades ago and he was part of the original pressed steel oil bath chain case development team along with Mr Franks and others Correct filling precedure being, so he told me ..Remove spark plug/s. Fit oil level plug and remove inspection cap. Find wife or son or anyone handy. With them operating the kickstarter and you watching the chain as it flies past your nose SLOWLY fill the chaincase and AS SOON as you see oil is just touching the chain STOP filling. He did make the comment that doing it this way would stop the problems of clutch slip and drag due to oil but that it did little for chain life.. BUT it was a lot better idea than the previous open run chain idea as on my Late Fathers Nortons of the 20s and early 30s.... Mind you if you bother to read chain manufacturers bumph there is no way to correctly lubricate chains at the speed we use them at in our primary drives anyway. Probably the best way being an olde Triumph idea where the system was enclosed within a chain case along with some oil but at the top of the chain case they had a oil collection area from where it was piped down to fall on thew inside of the chain on the side plates (As Manx /G50 Etc) so some at least was forced between the plates as the chain flew round the clutch and some even stood a slight chance of reaching the many plain bearings within the chain.
That way you probably picked some up to cushion the rollers (unless things were cavitating) and got some into the plain bearings. Not long ago a UK University did some reaearch into the dynamics of using high speed chain for auto cam drives... I spoke to a couple of the people in charge of the project and both said how amazed they were at the lack of knowledge they found within the chain industry regarding high chain speed use.As chain is an industrial item and industry rarely used chain at anything like even 2000 ft per min and we use it at up to 8000 ft per min why should industrial chain manufactures of done lots of expensive testing.... If you want a laugh try finding ANY test data showing the power losses that occur in say your singlex chain runing at even 5000 ft per min. Mr Jack Williams also stated in his design note book that a primary chain was probably no more than 90% efficient at high chain speed and lower with incorrect lubrication. Personally I saw a lot of zero efficiency ones laying in Manx roads after a TT in the 50s and 60s.
It should be rememered that chains were employed to replace flat belts on motorcycles but NOW we have toothewd dry running belts that we can use to replace industrial chains. ANd dont forget that TT winning Rotary Norton employed a 25 or 30 mm wide Gates belt on its primary drive.....
Hortons Norton
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Does anyone know how he's doing?? I liked reading his stuff, It was a bit easier than others. lol Hope he's ok.
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SteveA said:swooshdave said:
Can you name the supplier, (PM if not in public) I do want one! Of course I am in the UK not US, I am told there is a supplier in The Netherlands or similar!
Steve
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marinatlas said:
Sorry if this was written by someone you respect, but its a rant running from 1907 to the 1990! And in fact it tells us little and contradicts itself....
First it says that the Commando does not have a transmission shock absorber, and then it tells us who supplies rubbers for them.....the rear wheel cush drive rubbers, which is still a transmission shock absorber to me....OK, we hear from many Commando owners that they don't work too well, and using better rubbers in good condition is surely the minimum action you should take to try and rectify this....adding a crank shock absorber on a stock road bike is probably the last thing you should do...I am not advocating it....
Personally I want a crank cush, because I don't have a rear wheel one, or a clutch one, which of course is a viable option except that it adds undesirable complexity and mass to the clutch and mainshaft, and the suppliers of Commando belt drives do not make one, you need to adapt something from a Triumph!
You may well not want to add a cush drive to the crank a stock Commando, if it aint broke don't fix it...Norman White is well respected and has produced some, but it is likely they have been used mainly in rigid mount frames with no rear wheel cush...though I don't know this...
Several people have gone to some length to add cush drives to bikes with either Norton Commando derived engines or gearboxes, so I guess they have a reason. giving the transmission an easier time may be important, but you are most likely also reducing shocks transmitted to a rigid frame.
I do however agree with the basic premise that a badly designed part might not have the effect you want. Which probably means that if the rubbers are too small or too soft, rather than absorbing any energy, they just delay the shock....and possibly generate damaging harmonics or oscillations...
In a previous job I designed a few pieces of equipment that had 8m HTD sprockets and used the GT2 30mm belts. At the time according to Gates this was a no no but was done with the blessing of the importer, granted the power was much less although I cannot remember the torque, this may have been right up there though. There were no issues with this setup. The reason for the GT2 belts was because belts with fibreglass cords do not survive in wet environments, the kevlar belts are fine.
The pictured sprocket would be pretty easy to make on a manual mill, I would question its effectiveness though. The tension from the belt will pull the inner and outer metal parts together and the resulting friction may eliminate any cushioning affect, when the rubber is being compressed from the belt tension it will get slacker on the non tension side. If I was doing it I would put a bearing of some sort between the inner and outer part (maybe this has one that cant be seen).
That said it seems to work so I might be right off the mark.
The pictured sprocket would be pretty easy to make on a manual mill, I would question its effectiveness though. The tension from the belt will pull the inner and outer metal parts together and the resulting friction may eliminate any cushioning affect, when the rubber is being compressed from the belt tension it will get slacker on the non tension side. If I was doing it I would put a bearing of some sort between the inner and outer part (maybe this has one that cant be seen).
That said it seems to work so I might be right off the mark.
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Cheesy said:
I understand your point, but as you also said it appears to work....
The mechanism is very similar in concept to the Triumph clutch cush section, there is a video on Youtube, somehwere, of a guy changing the rubbers...they may be squidgy as has been said, but you will need to have some tools to do the job....you need to compress the rubbers you have already put in to make space to get later ones in....by holding the centre static and rotating the outer....in the end I think it becomes quite rigid...and surely the available torque would quickly overcome that little bit of friction? as only one vane of the outer would be in contact with the inner at any one time.....
Though you point does illustrate that it needs a bit of design tweeking to get it right and be a positive rather than negative addition.
SteveA said:
Looking at it again the crushing of the rubber from the tangential force due to the torque transmitted by the belt isnt a problem as there is always a metal to metal contact in the radial direction. Im still not convinced on the friction though (incidentally the friction force is not dependent on the contact area)
, thinking more, any rolling element type bearing between the two parts would die a quick death. A low friction coating on the metal surfaces or maybe even a bit of moly grease might do the trick.
So after questioning the original design, going round in circles a few times it looks like it may be close to the best solution anyway, part of the fun is questioning these things though!
rotorwrinch
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I have not gotten to disassembling the cush sprocket that is currently on the Commando Framed Race Bike. This piece is the first attempt that was upgraded after a few outings. The piece is made out of A2 tool steel. The decision to change the spider was due to the crank nut fracturing and the unit moving on the taper of the PTO shaft. Some of the non-intended modification will be visible on view of the back of the piece. I will post some photos of the 8mm spockets (blanks) tomorrow evening if I can get back out to the garage.
Rj
rotorwrinch
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Well that was not what I wanted. A chance to learn new skills @ my age.
rotorwrinch
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rotorwrinch
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One would think one of these things would need the facility to compress / preload the rubbers , while assembling .
In the manner of the Cush being rotateable hard against one set ( Very Hard ) so as to be able to insert the second set ,
So both are in a Pre Tensioned ( pre-COMPRESSED ) condition installed .Therefore the oscilation is within thw working
LOAD , rather than swinging across and bumping at the ends ( of travel )thus a gentle damping , rather than a bump stop.
In the manner of the Cush being rotateable hard against one set ( Very Hard ) so as to be able to insert the second set ,
So both are in a Pre Tensioned ( pre-COMPRESSED ) condition installed .Therefore the oscilation is within thw working
LOAD , rather than swinging across and bumping at the ends ( of travel )thus a gentle damping , rather than a bump stop.
rotorwrinch
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The spider was positioned in a clover leaf cut out in the sprocket and cushioned by epoxy that filed the void and provided a cush, The product was flexane 80 with a softening agent. Worked well until the crank nut fractured.
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Matt Spencer said:
As can be seen in teh last 3 or 4 minutes of this 10 minute video where aguy changes the rubbers on Triumph clutch hub.
With the Norton crank pulley....you are going to need a Norton crank to hold the taper section and probably you will need to create a tool using an old belt to rotate the outer whilst fitting the rubbers...
http://www.youtube.com/watch?v=ASe67Al5Mfo
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