Daytona first gears

I would be interested in hearing the experiences of owners employing in their AMC / Norton gearboxes a set of 'Daytona' first gears.
For those unaware they were originally produced for use on the Nortons being raced at Daytona in the late 40s and were 20t - 34t and retained the kickstart facility. Part numnbers 8607 and 8608.
I have heard / have been told that the teeth strip but that it could possibly be the result of the use of the incorrect grade of steel and /or incorrect hardening of the gears being produced these days. Mind you i have recently heard of gears(NOT produced by Andover Norton... I REPEAT NOT PRODUCED BY ANDOVER NORTON))where the centre spline is not concentric to the outer teeth leading to quick tooth failure. It must take real skill and zero quality control to manufacture such gears !!
Of course as the 'Daytona' gears were originally designed for use with 500cc motors then failures could well be the result of people employing them with larger far more grunty motors.........
Unfortunately I and a friend only have one good second hand set left and are thinking of having a small batch manufactured. YES of course we know the correct material to employ, depth and hardness required of the case hardening.
There are recently manufactured sets available but one dealer with a few sets on his shelf refused to sell me a set and I quote "because they break".........I can think of a dealer in the past who would of still flogged them!

Got any photos of these.

That sounds like a fairly high tooth count ?
Norton gears always summed the gear pairs to 42, or thereabouts.
A lot more must mean the teeth are something entirely different ?
And close ratio boxes usually go for a SMALLER tooth count on the kickstart,
more teeth would mean its a wider ratio box ?

I believe Ludwig used this first gear didn't he? I seem to recall reading a post of his on the subject, which was, as usual for him, very well written and very informative.

What he pity he left after being hounded out by 'Pointless'... or was it 'Needless'... oh no, I remember, it was 'Needing'.

Rohan said:

Got any photos of these.

That sounds like a fairly high tooth count ?
Norton gears always summed the gear pairs to 42, or thereabouts.
A lot more must mean the teeth are something entirely different ?
And close ratio boxes usually go for a SMALLER tooth count on the kickstart,
more teeth would mean its a wider ratio box ?

Click to expand...

Pictures of RGM's Daytona 20/34 first gears here:

http://www.rgmnorton.co.uk/dept/gears-s ... _d0156.htm

Ken

Thanks Ken.
Can't say I've been paying attention then.
They are small teeth, aren't they.

I thought it was L and h that had clashed....

Kind of an interesting choice, 20/34. None of the other first gear sets I've seen use anything like it. First gear pairs for the AMC box with kickstart provision seem to range between 13/29 and 15/27, except for the Daytona set.

Ken

The pitch circles for yer average Norton gears kind of dictate that the gear teeth should sum to 42,
so obviously to get so many more on there they (someone !) has reduced the tooth size, considerably.

They'd have to be good steel to survive that...

Norton gears and, if memory is correct, the more highly stressed(??) BSA gears were(and I believe Andover Norton gears are) manufactured using EN36B a 3 1/4 % nickel chromium case hardening steel which after correct case hardening gives a very hard wear restant surface wihilst developing an extrewmely tough shock resistant core. BSA used to stamp EN36B on the side of these gears.
I suspect some people manufacturing norton gears employ other steels.........En24 for example.
There are some dealers whose products I would NOT touch even with a very long barge pole as, having friends in the trade who have to repair Nortons which have used these dealers products, I hear all about their failures......

The use of theis 20 -34 tooth gear set was because Norton wanted to fit a high first gear to their Daytona race bikes in the late 40s and the regs required a kick start be fitted and usable. The std manx first gear was not of a size to allow a std kickstart mechanism so someone must of been tasked with coming up with a set to do so which required a smaller depth tooth form and more teeth.
As for the std gear sets adding up to 42 teeth my money is on this being because that is how Sturmy Archer designed their 4 speed box in the early 1930s and the basic box design never changed when Burman began manufacturing the box for Norton (after Sturmy Archer stopped producing them) and later when AMC probably did so. My money would be on the earlier Sturmy Archer 3 speed boxes having the same centre distance between the shafts and total number of teeth per set of gears. I have no doubt someone will correct me if required!! So basically Commando owners are running around on a box designed for 350 -500 cc singles producing about 25 HP and probably a max torque output at the crank of 25 ft lb........ Best count your blessings that they used real safety factors in their design calculations in those days!! Not that I suspect many Commando owners will know the history of their gearbox.....or engines come to think of it......Tee hee!!

Actually, nothing in a Sturmey Archer box will fit a Norton box, or vice versa, that I have seen anyway.
Parts for the 3 speed boxes look nothing like the later boxes, and SA 4 speed parts look similar (sort of) but are not the same.
Thankfully, someone is reproducing the SA main bearing, a complicated multi part thingy, but its somewhat expensive. (VERY !).
So, JM, you don't entirely know your Nortons gearbox history either ?!

Someone once commented that the gears in Massey Ferguson tractors are small, but must be extremely good quality to survive.
Now I've seen inside some MF gearboxes, and the gears (and shafts) are small - not that much bigger than Norton gears really.
They must be made of tough stuff indeed to last so well. And have a good reputation.
Anyone know what they are made of ?
Or who made them.

If I was going to have some gears made, I'd investigate if their manufacturer was still around.
Those people really knew their oats....

I use a 20/34 set from RGM, I know others on the forum use them also, I havent heard of anyone having issues with these , they may have , maybe I missed the reports.

RGM look to be still showing/selling these, so thay can't be too much of a problem ?

Do you give it the berries when you hit the launch button, or just amble away from the lights though ?
That may be the nub of the matter.
The small 1st gear is often quite worn in std gearsets, and thats going back into Norton gearbox antiquity....

BTW, has anyone worked out (mathematically) what ratio these give.
And how do they match up with the stock AMC 2nd gear, does it noticeably narrow the gap ?

I have a spread sheet with about 12 different combinations worked through. But posting a pdf here with photobucket is too much like hard work and I can never remember the password !! Including work I must have at least 10 different passwords and half them are forced to change ever 6 weeks so I give up !!

I used the RGM 20/34 first gear pair in my 500 Dommie race bike without any issues.

But we found that for short circuit sprint racing on NZ racing circuits the start was so important we went back to pretty much a standard Mk 11 Mk 111 Commando set for the 500 Dommie. Full close ratio was hopeless - everyone had vanished by the time you were off the line. And even the lower 20/34 pair wasn't that great. Longer races and circuits where the start and first into the first corner isn't such an important part of the race it would be different.

Late Commando with a RGM kickstart CR first gear
Top Third Second First
Main 23 21 18 20
Layshaft 18 20 23 34

1 1.22 1.63 2.17

% 0.22 0.34 0.33


Late Commando (M11 A and MK111)
Top Third Second First
Main 23 21 18 14
Layshaft 18 20 23 28

Ratio 1 1.22 1.63 2.56

% 0.22 0.34 0.57

One of the best racing compromises for a 4 speed box is to use the 23 19 CR top gear pair combined with Mk 2 nd gear pair and the standard 3rd and first gear set. This give you a bit of close ratio but still gets you off the line. We tried about 3 different sets of clusters before we settle on this for our circuits plus using an early 60s cotton real type Triumph wheel with bolt on rear sprockets to get the overall gearing.

Close Ratio RGM top pair. Rest late Commando M2A on
Top Third Second First
Main 23 21 18 14
Layshaft 19 20 23 28

1 1.15 1.55 2.42

% 0.15 0.34 0.57

I've previously posted some tables of gearbox data, including the Daytona gear ratios, here:

commando-gear-teeth-thread-t21304-60.html?hilit=gearbox%20data

Ken

Thanks Ken.
You always seem about 10 steps ahead of us....

If you are using EN36B in high sress situations the sulphur and phosphorus concentrations need to both be less the 0.010%. Those two elements are indicative of whether the steel is dirty or has inclusions. You could also do 'sulphur print' off the end of the bar. Often there is an inclusion running down the middle, That grade of steel is used for making NATO 105mm gun barrels, in Australia Comsteel 4130 is not clean enough.

Rohan said:

Thanks Ken.
You always seem about 10 steps ahead of us....

Click to expand...

Kind words, Rohan. Mostly though, I've always just been a little obsessive about accumulating data. And now that I'm in my dotage, it feels good whenever I can pass some of it on.

Ken

In the early 80s??(long time ago and a very distant memory) a friend and I decided to go play so called classic racing with an in bits Atlas he had bought rather cheaply. In those days of bump starts it was interesting to note how slow close ratio box bikes got off the line when really riding a very cheapo overweight underbraked under powered Atlas it is a help if one were with the leaders into the first bend and not at the rear of the field.... I cobbled together a box employing a set of 14-28t 4ths modifying them to give a set of firsts which with std 28-14t 4ths and 20-22t and 22-20t 2nds and 3rds enabled a reasonable quick get away off the line(assuming the bump start was not uphill as on one side of the track at Brands Hatch for example) and the rev drop between the gears was, IF (and I repeat IF), memory is correct between 1200 and 1500 rpm ensuring the motor was constantly withing its max grunt range.

I(ncidentally a friend turned up the other day with a set of unused 15-27 first gears. Apparently he bought 10 sets from Ray Petty decades ago and they were part of the batch Peter Williams had manufactured for the works Commando race lumps.......He said 200 sets had been manufactured.

Very sorry but as I look at the sectioned drawing of the Sturmy Archer 4 speed box I found on the web I see the basis of the Commando box. It would NOT even suprise me if the broaching tools used these days to spline new Andover Norton gears is maked PROPERTY OF STURMY ARCHER!!! Ok so the number of teeth on gears changed over the years etc along with the lift mechanism and shell etc changed but I bet the centre distance between the shafts is identical as is the tooth form and shaft sizes. Even the spline for the clutch centre was the same....it was also employed on Ariel mainshafts and later plunger BSA main shafts thus allowing owners to fit belt driven 3 friction plate Commando diaphragm spring type clutches easily to Gold Stars...you simply change the main shaft....
I note in my copy of the book Gear Lubrication (published by Wakefield Lubricants many decades ago) that it states the Burman 4 speed box was and I quote 'The box is guarenteed for 50 b.h.p. at 2,500 clutch shaft input'. Now I bet that this figure is including a safety factor of x2......so...playing silly buggers......
50 b.h.p. at 2,500 r/p.m. = a torque of 105 ft lb. Assuming a 2-1 primary ratio this equates to 52.5 ft lb at the crank. Assuming the designer was a sensible chap and employed a good safety factor of say x2 then the box was designed for use with motors producing 26.25 ft lb MAX......remind me how much grunt Norton claimed for their 750 and 820 motors!! No wonder the boxes rarely completed a lap of the TT before failing......tilll Peter Williams did a few rather inpurtant modifications and why ex NVT friends told me they wer fully aware of Commando gearbox problems....mind you with all the problems of the motors......
The early history of the gear boxes used by Norton is given by Titch Allen in his Norton History epistle published over many months in Motor Cycle Sport in the early 1970s.(the January 1972 issue page 36 is well worth reading although so is the complete epistle).
No spelling or grammer checks done. Got to watch football.

[quote="J. M. Leadbeater" but I bet the centre distance between the shafts is identical as is the tooth form and shaft sizes. [/quote]

Are you just guessing here, or saying for certain. ?

I am resurrecting this old post in light of the fact that I have just ridden my bike, which now has the Daytona first gear set from RGM, after a full restoration. I am running a 20 tooth countershaft sprocket and a Norvil belt drive kit - which I understand raises the primary drive ratio by a little.

I rode the bike in the Macau GP 50th anniversary parade this weekend, it was all pretty slow stuff and I only got the bike into 3rd gear once or twice. The gap between 1st and 2nd was noticeably tighter and a fellow participant on an 850 electric start model was constantly changing between 1st and 2nd. I found myself searching for a lower gear on a few occasions when the 50 bike parade bunched up. I think it is a good modification for general road riding (i have the set that keeps the kickstart) but I think if I was to use this in heavy traffic with any frequency I would rapidly get tired of being unable to ride at a walking pace without constant clutch slipping.

Re “Daytona first gears”
These were originally fitted to a 500 Manx Norton in which the AMA rules forbid the close ratio box and high compression engine of the Manx - hence they had to have a kick starter fitted to the Manx g/box( meaning a highly modified 500 Norton international.) the Yanks didn’t like this bike being raced against their beloved H D. The Daytona bike/car race was a sand/beach race originally.