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Best gearing for speed

Discussion in 'Norton Commando Motorcycles (Classic)' started by Champy72, Jun 30, 2019.

  1. acotrel


    Jun 30, 2012
    I had to laugh. I was at Calder Raceway one day in about 1970, and Barry Marshall was there with his 750 two stroke Kawasaki H2 and needed a passenger, so I got into the sidecar. Barry's idea of tuning was methanol with the biggest possible ports. He stretched me out in the sidecar and I had to keep climbing to stay on board. I accidently stood on his foot which was on the pedal for the rear brake. After we stopped doing that, we reached the end of the front straight going like the clappers and he almost shot me over the front.
    Barry ended up with O'Dell's Windle Konig sidecar. So he also became the Junior Sidecar Champion.
  2. storm42

    storm42 VIP MEMBER

    Jul 20, 2011
    Excellent, see you at Chimay if I can get an entry. Will try now.
  3. Champy72


    Nov 30, 2018
    That will be good! Turn right as you go through the gates, and keep going just about as far as you can. That's where we usually park and hook up...
  4. storm42

    storm42 VIP MEMBER

    Jul 20, 2011
    I think I am in, but the website is a nightmare, the drop down for the class of machine only went up to 750cc so I used that and now I am in the 750 class with a 920, I have emailed them and asked for the mistake to be rectified but not heard anything yet.

    So you will be at the side of the straight that runs into the last corner? I have been to Chimay to watch for a good few years but haven't taken much notice of the paddock, would it be possible to pitch a frame tent and what day will you be arriving? I am thinking Thursday lunch time.
  5. Champy72


    Nov 30, 2018
    Wouldn't worry too much about class, they sort it out no matter which class you have put down! You may well be in G2, hopefully not in G3!
    We'll be basically inside that corner - you can see the bridge easily from where we are. Plenty of grass in that area for a tent. Planning on getting there on Wednesday lunchtime-ish.
  6. johnm

    johnm VIP MEMBER

    Feb 26, 2008
    I stayed out of this discussion because sidecars are way out of my experience but I have a couple of thoughts based on my solo riding.

    1. More gears are better so the six speed may mean you can sacrifice top gear if you get the gearing wrong. (or the wind decides to blow)
    2. If you dyno the bike and get a torque plot versus rpm then make a spread sheet which tells you where you will be in the torque curve for each gear change. For example if you change from 3 rd to 4th at say 6500 where does that put you on the torque curve in fourth gear? A G Bell discusses this in his book Four Stroke tuning. This gives you the optimal gear change points for your gearing spacing. With a six speed you should have lots of flexibility.
    3. That gearing site given above is the way to go. If you know spreadsheets you can easy make your own and incorporate the torque curve data.
    4. I keep a record of the lap times and gearing performance at each meeting. A Gopro camera which can see the tach and where you are on the track is good. You should be able to determine the gear your in from the sound track if you cannot remember. This is good if you not the rider but still useful as an accurate record even if you are.
    5. I have an aerial photo or scaled map of each circuit and mark it up with lenght of straights, gear shift points , rpm etc.
    6. Once you have got a good database from 4 and 5 This can give you a good starting point for gearing if you go to a new circuit. Dont forget about hills or wind however !!
    7. I converted my Norton to a detachable sprocket rear hub and have a set of sprockets with matching chain lenghts. On a solo 18 " wheel I can change sprockets in maybe 20 mins. Longest time is doing the lock wire on the bolts.

    Main thing is to keep a good record.
    Last edited: Jul 10, 2019
  7. Champy72


    Nov 30, 2018
    Appreciate all your comments. Unfortunately, I am still 'feeling my way' and really do not have the time to video where and when I change gear, at what revs and where I am on the circuit. I am really having too much fun racing with my peers...
  8. acotrel


    Jun 30, 2012
    As you raise the overall gearing, the internal ratios become more spaced out A close box makes the motor less likely to bog down. So as you raise the overall gearing, the acceleration rate as you come up through the gears is slower. It means that you don't change gear as rapidly as you are accustomed to doing on shorter circuits.
    I was reading something the other day about less powerful bikes needing more gears. With a Commando engine, you have to do something. The standard gearbox is pathetic. If you wait for throttle response, you will wait forever.

    What is this stuff about keeping records ? I never do that and every time I use the bike, I have to reinvent the wheel
  9. johnm

    johnm VIP MEMBER

    Feb 26, 2008

    " really do not have the time to video where and when I change gear, at what revs and where I am on the circuit. "

    Ummmm. Thats why you use a Gopro :)
  10. Champy72


    Nov 30, 2018
    Didn't know GoPro had so many lens...;)
  11. johnm

    johnm VIP MEMBER

    Feb 26, 2008
    You set it up to see the tach and part of the track. Its not hard.
  12. johnm

    johnm VIP MEMBER

    Feb 26, 2008
    I get the feeling you think what I wrote was a waste of time.

    I havn't raced my bike for a few years but this is a video of my Dommie #500 ridden by Tony McQueen at the 2010 Burt Munro.

    The bike he beat was built by Nick Thomson. He built the 250 Velo that lapped at the Manx at 90 mph last August and the 350 Velo that lapped at 95 mph in practice in the Manx. The 350 is being packed to go back to the Manx this week.

    The rider who Tony beat is Chris Swallow. Who got 4 th in August 2018 Classic Manx senior at a race average of about 107 mph.

    So you may not think much of my ideas but they have worked.

    This one at Puke shows the track and the tach. The blue Goldie he passes on the front straight of Pukekohe at 4.04- 5 seconds in has also lapped the IOM at 100 mph. In this you can also see what happens if you dont mount the camera properly. I should say Tony is a very good rider and when he was young won against Aron Slight in production racing in Oz. The bike that picks him up at the end of the back straight is a G50 while the Dommie is just a Clubmans class bike with a faring on.

    It also illustrates very well the problem of getting a 4 speed bike off the line against a bunch of 5 and 6 speed race bikes. Once he is moving its not so bad especially on a more open track like the old Pukekohe pre the new chicane in the back straight.

    Or a Tony racing his Kawasaki at the Burt Munro street track. Not my bike but you can see the tach Gopro setup

    I used these tapes to work out gearing improvements. It was a poor mans data logger but now days that could be a better plan.
    Last edited: Jul 14, 2019
  13. Champy72


    Nov 30, 2018
    I don't believe your ideas are a waste of time at all, and if I raced in MotoGP or F1, I am sure my pit crew would have all you suggest plus a lot more to hand!
    However, I race in a very amateur class, where none of us have a bottomless pit of money to spend on trying to get and extra 5mph. I race for the pure thrill and excitement of being on the track with my friends and peers, not to mention the social side.
    I know of no racer in the classes who would go to the lengths that you outline, and very few go to the IoM to actually race. Our tracks are generally short, and as we ride them each year, I believe we are fairly au fait with their braking points, bend layouts and quirkiness.
    Thank you for your input.
  14. johnm

    johnm VIP MEMBER

    Feb 26, 2008

    Definitely not at MotoGP or F1 level.

    I was just answering your question in your first post.

    " I have an 850 Mk 2 Commando engine with Maney stage 2 head and a belt drive, running in a classic kneeler sidecar racing outfit.
    Just about to install a 6 speed gearbox (Hemmings), and need to work out the best gearing (sprockets) to get highest speed at 6,500 to 7,000rpm.
    Don't want to watch the rev counter hover on 6,000 because the engine won't pull anymore.

    Any ideas, experience, calculations out there??? "

    My bikes an old 1956 Dominator Clubmans class with GPM pistons, an SS head and a 4 speed box. No Maney heads or 6 speeds so way way less $ than yours I imagine. I actually found spending less money on high spec parts but time spent analysing to be a very cost effective way of gaining hp and improving lap times.

    You can get a refurbed GoPro here for less than US$100. Plus a bit of velcro to hold it on.

    I improved the bhp of my Dommie by almost 20 % just by tuning what I had, cutting and welding pipes. No new parts.

    Read, observe, experiment, tune provides very cheap hp.

    I don't take my bikes to the Manx. I share a workshop with the Manx bikes but they are on a whole other planet to mine. Just the trip to the Manx with one or two bikes costs more than NZ $20,000 from here.

    This is the one which is leaving this week. Last years story when it got a 95 mph lap in practice and cracked the exhaust in the race. Hopefully it will finish this time


    There is a fair bit of money in this bike but again mostly its time. 90 % of the engineering was done by a mate in his shed. Casting and pattern making were outsourced. It has a Nova six speed cluster but the longer mainshaft for example was made in the shed.
    Last edited: Jul 15, 2019 at 7:49 PM
  15. acotrel


    Jun 30, 2012
    People who keep records make me sick. I don't do it, but commit everything to memory, then pay the price for being indolent. I only ever ride on one race circuit these days - that makes things easier. I never have to find my way.
    John - I like the way you think. It is a recipe for success. Anything I do with my bike is usually a continuation of what I have done previously. When building my 850, I was able to go directly to many things. If I spent $20,000, I might get another 5% out of it. - The law of diminishing returns applies.
    Last edited: Jul 15, 2019 at 8:13 PM
    johnm likes this.
  16. acotrel


    Jun 30, 2012
  17. johnm

    johnm VIP MEMBER

    Feb 26, 2008

    The Diener Velos - Eldee 1, 2 and 3 are 250s.

    Les Diener built Eldee -1 in the 1950s and it was a real weapon winning the Australian 250 TT in about 1956. It also cleaned up the works Moto Guzzi ridden by Fergus Anderson when it visited Australia. It is a gear driven DOHC built off a MOV crankcase. (gear driven so nothing like a bevel drive Manx engine) The frame was also Diener and a light weight featherbed style frame. This bike is in the Australian motorcycle museum. Diener had a bad crash and gave up on bikes for a while. But in the 1980s he came back to racing and built Eldee 2. A replica of Eldee 1 but with an International featherbed frame, so a bit heavy really for a 250. This bike is now owned by a friend in NZ. The boys raced Eldee 2 for a while and then built a replica engine with internal improvements. They call it Eldee 3. They are still using the Eldee 2 rolling chassis but with belt drive, 6 speed Nova box etc. This bike went to the Manx and last year got a 90 mph lap in the hands of Bill Swallow. It ran out of gas on the last lap because of a leaking float bowl. Much unhappiness all around. The whole story of these bikes is elsewhere on the website I posted

    But the link I put up is a totally different machine. The boys decided to build a 350. And this time they followed the Velo works 1930s bevel motor layout. The whole story is on that website. This bike got a 95 mph lap in practice at the 2018 Manx ridden by Chris Swallow but cracked the exhaust pipe on the first lap of the race. Take a good look at the girder front forks. They are something special. Improved geometry and a modern damper system. Works extremely well.

    That bike will be packed up for the 2019 Manx on Thursday this week. Hopefully this time it will stay in one piece.

    I should add I have no personal interest or input into these bikes. The builder has been a friend since university days but my only help is a bit of fetch and carry.
    Last edited: Jul 16, 2019 at 6:05 PM
  18. Chris

    Chris VIP MEMBER

    Jan 21, 2008

    Love your input.
    All the things I should have done!
    But never did.
    I photographed my builds had a file with my notes & parts/ specs. A book to take to circuits to give me settings.
    I have never understood what happens to all the time during a meeting. Love being there love riding the bike. I am only now 30 years on getting a bit more organised.
    Laid back to the point of horizontal.
    What a great sport.
    johnm likes this.
  19. acotrel


    Jun 30, 2012
    The last time I raced, I had two good rides in which I was up with the leaders. Because I was using the CR 4 speed box with the high first gear, I could not get a decent start - however it was perfect everywhere else. In my third and final race, I decided to go for it - so I revved the tits off the motor and dropped the clutch. The bike jumped without destroying the gearbox and I was fourth into the first corner. On the second I turned under and passed the three leaders. I was just ahead when the fuel line popped-off. I'd forgotten to tighten the clip. Those other three guys were riding methanol-fuelled 1100cc CB750 Hondas. I still have not raced with the 6 speed box, and I cannot see myself being able to afford to race again.
    It was really silly. I have got standard Commando first gears sitting on my shelf. I could easily have fitted one to the 4 speed CR box and lived with the jump between first and second.
  20. johnm

    johnm VIP MEMBER

    Feb 26, 2008
    I messed around a lot with gearing setup options.

    For a 500 Dominator on tight club circuits I finally comprimised on

    The Daytona first gear pair which are a bit higher than standard 14 28

    The Mk 2 A Mk 3 second gear pair - again a bit higher than the original Commandos and Dommies 18 23

    Commando third gear pair 21 20

    The Norton close ratio top gear pair. 23 19

    A four speed box is never going to be perfect but this gave me a reasonably even spacing between gears matched to the rev drop on the torque graph.

    A standard CR box is totally useless on NZ tight club and street racing circuits. By the time you get going in first the rest of the pack is half way round the first lap.

    The standard first gear pair is a bit low for solo racing really

    Sorry the following is so messy. I have it on a spread sheet but never remember how to post pictures and photo bucket is out these days

    This sheet lists all the Norton AMC gearbox gear alternates that I have been able to find. All gear pairs were for sale at either Andover Norton, RGM, Norvil (Emery) and or British Spares in Early 2003.

    Latter Dominator, Atlas and early Commando
    23 21 18 14
    18 20 24 28
    Standard RGM Close Ratio
    23 21 19 * 17 * No kickstart
    19 20 22 * 25
    Late Commando MK 11A onward (1974-75)
    23 21 * 18 14 * Must be changed as pair
    18 20 * 23 28
    RGM Close Ratio Pair Alternatives. third second first
    22 20 * 20 * Can use kickstart
    20 22 * 34

    Combinations of Close Ratio and standard gears to Suit NZ Tracks
    These are various options I have tried or thought about using the gears I have or are available.
    Close Ratio RGM top pair. Rest late Commando M2A on Close Ratio RGM late Commando M2A second RGM kickstart first
    Top Third Second First Top Third Second First
    Main 23 21 18 14 Main 23 21 18 20
    Layshaft 19 20 23 28 Layshaft 19 20 23 34

    1 1.15 1.55 2.42 1 1.15 1.55 2.06

    % 0.15 0.34 0.57 % 0.15 0.34 0.33

    The first set is what I finally used finally in my Dominator race bike
    It gives slightly higher first and second and the best steps I could get between standard gears

    I used the second set up for a while . It is good but too tall for very fast starts. Good once moving.
    It is the same step between first and second as a late Commando.

    another option 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
    I havnt tried it because I don’t have a standard Norton top gear pair and they are expensive.
    Last edited: Jul 16, 2019 at 8:36 PM

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