The mesh looks fine to my eyes, but all the books have to say is that backlash should be small. Which it is, all the way round. But the measurement I can make is vertical movement from when the bevel is testing on its bush, as it will be when operating, and when lifted snug. As seen in the picture it has 12 thou. This has no shim between the bearing housing and the cam box. There was an 8 thou shim in there. That gave 20 thou lift. I've not seen a measurement, but I imagine a small movement makes the closest mesh, without overloading the gears. Am I fussing too much? If I do fit it as it is, the Oldham coupling will have 30 though play, so will probably need changing....
The smallest amount of backlash is good for quiet running ,but I dont know if there is a clearance needed for any expansion. Have to look it up.
Thanks Robert. I'd like to get this right. With 12 thou vertical clearance, the actual gap between teeth will be about 6 thou.
There seems to be very little written about these things. One says 30 thou vertical movement in the vertical shaft...another says 5 thou! Franks says nothing. Backlash in the bevels has no numbers. Now we take it for granted that we have dial gauges etc. But I don't think that was to be expected in the 1930s!
Can I suggest you contact:-
Barry Stickland email@example.com
He should be able to answer your question, if / when he does. Could you post the response?
I need to build my cambox and will be looking forward to what information Barry can advise.
, I have spent many happy(!) hours setting up the bevel cam drives on Ducati's. The condition and security of the bearings will affect everything . I also found it usefull to test the smooth running of the gears by removing the rockers . A ducati with good gears will run well with no perceptible clearance ,but can produce an interesting almost supersonic whine , they often came from new with the whine.There is an ideal relationship between the gear teeth flanks and a little engineers blue is used on my gears to show the contact point.The gears are pretty everlasting unless mistakes are made ,Hailwoods comeback TT victory was nearly scuppered when his gears exploded at the finish.
I just mailed Barry. I'll keep you posted.
It's probably too much to expect anyone to have the original tolerance data on these engines. I know lots of writers talk and indeed complain about assembly, measure, disassembly, shim, etc - but they've all had their original tolerances messed about with for years. And although the Inter engine looks a bit daunting, at least you don't have to mess about with making sure those push rods are in the right place as you do with the big twins - so each job is actually quite quick. I wonder however if they were ever built in such a way that all parts were interchangeable? The claim that they were built specially in the Competition Shop makes me suspect that nothing fitted properly in the factory, and everything had to be fettled by a skilled mechanic simply to get it together - which is the antithesis of how a mass production factory is supposed to operate.
...you should never buy a Rolls Royce... ( pre BMW ownership..)
On my induction into Ford Motor Company, Product orientation was a big part of it. We were show the processes for machining, measuring, assembly and test. All processes were compared to varying market leaders or high reputation suppliers with samples set up to verify. Needless to say the Rolls Royce V8 for the Phantom VI sat there looking resplendent, and whilst the fit and the finish felt good on measurement no two identical components were measured the same.
Ford were turning out 2000 a day, working to a 5 micron tolerance on size and all was machined measured and assembled (50:50 on assembly) automatically.
Fantastic achievement; alas... we were making the ford CVH motor. A dog then and now! It was a bit of a case of "all the gear no idea"!! The replacement to the Kent pushrod engine with hydraulic tappets, electronic ignition/management, aluminium OHC head... ... producing less power, consuming more fuel and reliability down the pipe was hardy a step in the right direction.
The design was wrong, the carburation atrocious and the market with high expectation tried hard to accept what was in many ways a dud! ...then bought a Vauxhall red top
Sadly the plant closed last month whist still producing some of Ford's finer examples of ICE's (3cyl 1 litre and super efficient V8s).
Back on subject; meshing of bevels is pretty much the same in any application isn't it? Central contact no tight spots on rotation... they all transfer power, generate heat and need to have minimal backlash. Splined or Oldham they are two separate units, straight cut and probably already well used.
Bearing control and lubrication are paramount, the rest is about how you want it to sound; they can whine if you go zero tol... or clatter with wide gaps for extreme temperatures. Its expected use can determine where you go with this but you will "feel" what is right under no load conditions.
Just thoughts before I lock down and strip another project!!!
Thank you Jon. I should never have started this! Leave well alone is a very good motto I'm sure. The gears are smooth and uniform, look good and feel good. I know they were assembled by a man far more expert than I shall ever be, and they have not done many miles since then. Lubrication is plentiful, and they don't make any noise that's audible above the ridiculous exhaust system.
The previous owners didn’t have the luxury of the information we can access. First mobile phone remember it.: like a brick and a car battery... 1983
Commercial word processors....1980’s
Commercial world wide web 1995 and on wards. I am indebted to the late George Cohen, and Stu Rogers for their preservation of the old school knowledge of these machines. As you say we can all have access to the old engineering tools and measuring devices, but if you can’t marry the ability to the problem without them you are creating a false status.
I am far from being skilled in this area but I read the advise of our members and tread gently as I ease my bikes into life, improve their status, and enjoy the thrill of a run around the locality. Or a weeks pleasure on the island, races or no races ( as and when we can).
best of luck Dave.
Look forward to your next run out. PS: is this bike new to you. It is quite a special looking machine.
Wasnt it always a case in much of the brit bike industry of "Selective Assembly" for the best stuff? Joe Craig would have been able to pick all the good stuff for the racers, what was left went onto the assembly line!
PS as a former owner of several Cortinas in various states of decrepitude in my impecunious past, I just loved those crossflow engines! Perfect- in my eyes anyway! Add on a twin-choke webber and the 4-branch GT exhaust manifold.......
for those that don't know, there is a lot of useful information in:-
and in particular:-
Thanks for all your comments.
I just spoke to one of our experts - I'm going to put it all back together as it is. According to Ian Bennet engineering - it's all fine. It was put together by Stu Rogers back in 1990 - (is he still in the field?). I'm sure he made a better job of than I shall.
Since Jon asked - here are a few details.
I inherited the bike a year ago last August. It was owned by the late Bernard Harding who collected cars and bikes. His list of vintage bikes owned and mostly sold included several Nortons, including flat tank models 18 and 16H, 1932 Inter (which I now have); 1902 Quadrant and 1937 16H (also both now with me); and at least 35 more including a brief ownership of 650SS and a NorImp. He bought this one from a colleague who was probably glad to get rid of it - it had been ridden into the ground and almost everything was worn out. That was 1989, and it took best part of 15 years (and a lot of money and lots of making of bits) to get it back on the road.
It's 1932 engine and frame. Later magnesium racing cam box with hairsprings. Also later magneto chain cover with rev counter drive. I only took the cam box off because the weather is horrible and I was worried about whether the Oldham coupling was the correct length because he inserted compression plate after he broke his Achilles tendon failing to start it one day at the late George Cohen's place where George had done some work mostly (I think) on cycle parts. I think in retrospect he wrongly 'remembered' it was slack wire advance (which is correct for the Inter) but actually it it tight wire advance. The result was crippling...
The picture is of it at a Brooklands event in 2005. The Amilcar behind was his pride and joy - date 1927, 1100cc straight 6, twin overhead cams, supercharged, fastest lap at Brooklands in about 1937 at 123mph. Must have been terrifying. The other is his 'chain gang' Frazer Nash. Quickest car gear change I've ever met.
...how interesting. He had a real passion for the prewar scene. I used to help a guy at Prescott with a supercharged Alvis of this period,very competitive guys.
Ian Bennett and co do some great stuff. Stu Rogers as of last year was still busy and did a fabulous repair to my Elektron casings when the Mag Platform gave way. Of course the simple weld became a full blown strip and rebuild with pasivated casings, replaced rings and bearings and renewed the worn bits. I'll send you his number, he was still sprinting though helping more with his son Aaron's rebuilds and tuning tweaks now. He has a huge wealth of knowledge and would probably have record of the work on your bike. He either has, or can get everything for a Cammy Norton. Was creating a museum at back of his home for his personal collection of some absolute thoroughbred bikes. He'll talk all day about the cammy Nortons'; just wish he would write a book.
George C enhanced his knowledge by staying there for a week or more to carry out some rebuilds, sleeping in the workshop... but then again I slept in Georges while he cured an issue on a 54 Manx I owned. I learned not to take him a bottle next time!!!! Great people...
Thanks for your mini history there David. Most interesting and a collecting to preserve from a personal and technical perspective.
... It was a hard act to follow. I raced a Formula Ford for a few seasons with a trusty 1600cc Kent that would pop out 107BHP 6000RPM and do it all day long, any more and you were not running within the regs. Great Days!
I have before me George's notes on the assembly of cammy Norton engines. Under 'cambox fitting' he wrote in item number 11 and 28 "...and remember the shim on number 3...". I think that's a piece of mischief! I certainly hope it is.
...is that they apply to a specific engine which he has assisted in building for someone with its own peculiarities. So it seems to me. Not to say his notes haven't been a great help in my first go around with one of these motors. Salt applied.
..that explains it...thanks