Commando gear teeth thread.

[B.Rad]

perhaps you are in the wrong forum.

You've only just spotted this ??

gidday Rohan

No mate. Just sometimes I get a bit cranky with replys like that. My shortcoming I suppose.

Gearing on a motorcycle to me is a very serious subject. not like a transmission failure in a car.

get it wrong and the consequences can be catastophic. I would not like to have a tooth break at 80 MPH or more.

You know the consequences. This event could kill you.

all the best Aussie bradley

 

[Rohan]

Gearing on a motorcycle to me is a very serious subject. not like a transmission failure in a car.
get it wrong and the consequences can be catastophic. I would not like to have a tooth break at 80 MPH or more.

No kidding.
We don't know how you sleep at night, Norton boxes always shedding teeth and all that.

We hope you made your concerns known to Norton management back in the 1950s....

 

[B.Rad]

Gearing on a motorcycle to me is a very serious subject. not like a transmission failure in a car.
get it wrong and the consequences can be catastophic. I would not like to have a tooth break at 80 MPH or more.

No kidding.
We don't know how you sleep at night, Norton boxes always shedding teeth and all that.

We hope you made your concerns known to Norton management back in the 1950s....

this is another fine example of unnecessary sarcasm. Totally unnecessary. Does not set a good example of co-operation for new members

I will not degenerate what I consider to be a relevant thread into a slanging match.

can you post without smart arse comments and stick to relevant matters only.. I do try to be civil , it is good manners after all.
best wishes Aussie bradley

 

[Hobot]

Ok while the topic is hot I've 2 observations that fit here. One, only gear teeth Peel stripped nailing it too slow was 3rd gear. Two, Kenny Cummings broke teeth off his Commando pinon gear so found a swap meet vendor with a more robust Atlas version. So that's where I'd start on upgraded teeth profiles. Btw 1st gear wear is d/t the paper thin bush wear that then mis aligns cog on shaft but if that bush kept up with then infinite 1st gear life expected. I can assure you the safety relief of over powering 1st with drag sprint clutch drops are tire spin &or wheelie.

 

[B.Rad]

The small 1st gear on the layshaft is almost always rather worn in Norton boxes.
Can't imagine it actually does too many miles, so the torque kills the surface....

I'd also suspect that LABs mention of the tooth count changing on '4th' gear from
even numbers to odd numbers of tooth counts would be to spread the wear all around the gears.
ie not to have the same teeth always meeting the same teeth....

Gidday mate. a few comments on your post.

1st gear. yes, 1st gear pinion is not a good example of design. refer to my previous post "bad teeth" and you will see an alternative.
the problem is the design is not capable of handling the torque. Not the torque itself .
This mod also has NO interchangeability issues.

4th gear pair. yes , a hunting ratio is sometimes a desirable thing. but there are 3 better reasons than that alone.

1. Cost. by dropping one tooth on the pinion significant advantages can be obtained more cheaply than making 2 new gears. only 1 item needs to be changed and there are NO issues with interchangeability. the modified pinion meshes perfectly with the old design gear.

2. Strength. again refer to my previous illustration. the beam strength has increased significantly. a 20% increase in load carrying capacity can be expected.

3. Longer life. the stronger tooth has significant increase in resistance to fatigue stresses. Something like a 300% increase in expected life.

Hope this helps Aussie bradley

 

[acotrel]

So you would deny that the gearbox is the main limiting factor in the commando design ? I will go out on a limb and state that a standard commando 750 engine with a good six speed box behind it and without any frame mods, would beat any standard Honda CB750 in most competitions. The fifties Gileras had seven speed boxes, and the Brits knew very well about the advantages. In Australia we also have the same disease - we won't spend a dollar to make a dollar - it is self defeating. I don't know what the gearbox is like in the 961, however If you are ever building a race bike if you haven't got the gearbox, forget it.
As far as loads on internal gears are concerned, surely the loads on individual gears in a standard wide ratio gearbox are much greater than in a 5 or six speed CR box when the bike is accelerating hard ? - Everything is spinning faster in the multi-(6)-speed box to deliver the same power against the same resistance .
As far as the commando motor is concerned, for what it is I believe it is perfect, as long as you don't try to rev the tits off it.

 

[B.Rad]

Ok while the topic is hot I've 2 observations that fit here. One, only gear teeth Peel stripped nailing it too slow was 3rd gear. Two, Kenny Cummings broke teeth off his Commando pinon gear so found a swap meet vendor with a more robust Atlas version. So that's where I'd start on upgraded teeth profiles. Btw 1st gear wear is d/t the paper thin bush wear that then mis aligns cog on shaft but if that bush kept up with then infinite 1st gear life expected. I can assure you the safety relief of over powering 1st with drag sprint clutch drops are tire spin &or wheelie.

gidday hobot. thanks for your comments.

Firstly, infinite life cannot be expected Mate. On any gear pair in our boxes. The stresses involved exceed the endurance limit of the steel needed for an infinite life. the expected life is finite. I have mentioned this previously in this thread and gave an explanation of why this is so.

yes, you may be correct in saying 3rd gear can be improved. I have not got to the nitty gritty yet as to studying any more than the first gear pair. so 3rd may indeed be a weak point.
best wishes Aussie bradley

we will see after I have disgested the information LAB provided as to model changes..

1st gear pair: mate, please look at my"bad teeth" post illustration. the design flaws are obvious.

look at the standard profile and the alternative. the difference in shape is obvious. misalignment may be a problem, but is not the primary cause of trouble. the design is everything a good gear should NOT be. the main problem with this pinion is undercut. weakens the beam strength considerably.

remember the main objective of this post is to compare changes on early and late gears to determine how much advantage the changes had over the old design. and see where the existing gear may be improved as to strengh and life. And of course the intention to educate lay people about gearing.

I still have not had any solid evidence that Atlas 1st gear pair is stronger or more robust. all so far are unsubstansiated claims. I would really welcome some technical evidence for this claim. facts and figures will convince me. increased beam strength, less undercut, stuff like that.
Thanks for your comments. Aussie Bradley

 

[Rohan]

I still have not had any solid evidence that Atlas 1st gear pair is stronger or more robust.

If you are simply going to post replies like some pompous git and rubbish all who reply to you,
seemingly without knowing anything about Norton boxes at all, we are not going to advance very far.
At all. ??

 

[B.Rad]

So you would deny that the gearbox is the main limiting factor in the commando design ? I will go out on a limb and state that a standard commando 750 engine with a good six speed box behind it and without any frame mods, would beat any standard Honda CB750 in most competitions. The fifties Gileras had seven speed boxes, and the Brits knew very well about the advantages. In Australia we also have the same disease - we won't spend a dollar to make a dollar - it is self defeating. I don't know what the gearbox is like in the 961, however If you are ever building a race bike if you haven't got the gearbox, forget it.
As far as loads on internal gears are concerned, surely the loads on individual gears in a standard wide ratio gearbox are much greater than in a 5 or six speed CR box when the bike is accelerating hard ? - Everything is spinning faster in the multi-(6)-speed box to deliver the same power against the same resistance .
As far as the commando motor is concerned, for what it is I believe it is perfect, as long as you don't try to rev the tits off it.

Gidday Alan. This is a relevant query from you. so I will adress your concerns.

yes, I would debate this. There are lots of things about the Commando design as a whole that have or can be improved upon.. However as this opens up a whole new can of worms, and is off topic to this thread I would suggest starting another thread on this subject.

please read my stated intentions of this thread. I wont be distracted by red herrings. Comparisons between Gileras and Hondas have no place in this thread. Start a new one please.

No, when designing a gear set, obviously the ratio has some consideration but does not play the most part . The ratio is just another consideration to be accomodated but is not the biggest factor.

However pitch line velocity is very relevant. So if pitch line velocity is based on ratio, you could say yes, ratio has an influence. I would agree with that.

But again this is such a complicated subject that I can say with confidence that there are far more important considerations than ratio.

The loads do depend on speed, but other considerations are more important.

regarding you query on loads, the loads on individual teeth are not necessarily higher in a 4 speed than a six speed.

The loads can be mitigated to a large extent by varying input speed, profile modifications such as tip relief, involute mods like getting the base circle away from the pitch diameter, ( this has a huge influence) long addendum pinions, face width and much more.

It is the designers job that when given a fixed ratio, to mitigate the loads so that they are within acceptable limits. So to me ratio is not the prime consideration.

Hope this answers your query. best wishes Aussie bradley

 

[Rohan]

Now we are confused ?
The entire torque from the engine has to go through the gearbox.

Torque loadings can be calculated directly from rpms and the reductions thereof in the primary drive and gear ratios.
There is no escaping from this ....

 

[B.Rad]

I still have not had any solid evidence that Atlas 1st gear pair is stronger or more robust.

If you are simply going to post replies like some pompous git and rubbish all who reply to you,
seemingly without knowing anything about Norton boxes at all, we are not going to advance very far.
At all. ??

gidday mate. the way i read that was indeed a cheap shot. and here it seems is another one.

I would have thought I have demonstrated plenty of knowledge of Norton boxes. I have defended every claim so far and answered all questions with sound reasoning. I think. And I dont riubbish all who reply to me, including yourself.

However if I misread your post I will accept that.

if it was meant to be a humorous reply, then I misread it and will sincerely and publicly apologise.

But you may need to give consideration yourself to the tone of some replies. Humor is very hard to recognise in written communiacations. Will you accept that. Some of your replies do seem overly aggressive. And not just to me.

As far as if you think I am very very wrong about my ideas and answers, and have NO Norton gearbox knowledge , please cut me down with sound technical arguement showing exactly where I am wrong.

I would really welcome this. I really would. Actually anyone is very welcome to correct my reasoning.

So if I misread your attempt at humor, I do sincerely apologise.
We must keep this civil
Best wishes Aussie bradley

 

[B.Rad]

Now we are confused ?
The entire torque from the engine has to go through the gearbox.

Torque loadings can be calculated directly from rpms and the reductions thereof in the primary drive and gear ratios.
There is no escaping from this ....

gidday Rohan. I am very sad to see you confused.

Of course there is no escaping from this. the torque and ratios are a given in a lot of cases. they may not be changeable.

gear ratings are based on maximum torque for a given number of cycles. This is the torque used in calculations.

It is then the designers job to mitigate the loads by using a lot of different available methods to get the loads within acceptable limits.. This is certainly what I was explaining to Alan. to explain this technically there is no simple way .

Ratio is not the prime consideration. loads may be mitigated. therefore loads on a 6 speeder may not necessarily be lower than a 4 speeder.

I read Alan's post as saying the loads in a 6 speeder must be lower than a 4 speeder. This, for the above reasons, is not necessarily the case.

And I have not seen justification to support the claim that Atlas gears are stronger or last longer. In fact if this was so, I doubt the factory would have modified the 4th gear pair. you cant just say they are stronger and leave it it at that.

If asking for justification is interpreted as arrogance and pomposity, then I am indeed guilty.

hope this clears up any confusion Best wishes Aussie Bradley

 

[Rohan]

Well, when I pointed out that Nortons solved their noise emissions problem by changing the 2nd gear ratio,
NOT by your quoted 'tooth form' reducing the noise, you replied with some great big long spiel.
I think it was denying what you said, and rubbishing my point of view (which corresponded with known facts, BTW)
but the logic was difficult to fathom, no 2 sentences were connected together.

Norton boxes have a reasonably good reputation in the old brit bike industry, and as Aco pointed out have been and still are used in a lot of specials.
Reading your spiels, it sounds like they are not fit for a moped....

There is a large gulf between these 2 points of view.
If Norton boxes were really that bad, someone would have noticed by now....

 

[Rohan]

Gather your thoughts, and put together a short article on gearboxes, and the technicalities thereof.
You obviously know something about them ?
Demonstrate all these phrases bandied about.
One diagram or piccha for every 200 or 300 words would be nice...

Thats kinda what we expected when you said you were starting a gearbox thread.

 

[Cheesy]

The small 1st gear on the layshaft is almost always rather worn in Norton boxes.
Can't imagine it actually does too many miles, so the torque kills the surface....

Or more accurately the hertzian contact stress causes sub-surface fatigue and it is that which can destroy the surface (assuming it isnt a lubrication problem), torque is but one of many factors in determining the magnitude of this stress

 

[acotrel]

That suggestion that Norton attempted to comply with the noise regs. by changing the gearing on the commando raises a question in my mind. Perhaps they also tricked up the cam timing to get the exhaust noise quieter ? Max torque doesn't seem to be in the right place with the 850 cam, if you move it backwards and forwards. My bike is extremely torquey, also very loud even with the two into one exhaust.
Bradley, I appreciate what you are saying about the gear ratios. It is an area which has always confused me. I found that the effects of changing gearing can be very deceptive. We have a very good engineering shop in Euroa which can do gear hobbing at about $150 per pair. I've looked at Phil Pick's CR conversions for the 5 speed Triumph box. Dave Nourish sold a stronger case for that box.

http://www.triples.co.uk/products/gearbox/index.htm

 

[Rohan]

Perhaps they also tricked up the cam timing to get the exhaust noise quieter ?

I think that might just be wishful thinking, or pipe dreaming.
The 850 cam is the same one as in earlier Commandos,
and I don't see any offset keys or anything trick like that..
This had to be in PRODUCTION bikes....

do gear hobbing at about $150 per pair.

That sounds a very good price.
They are generally about $200 a pair and up for Norton stuff, that I've seen quoted anyway.
Does that include dogs.....

 

[Rohan]

Or more accurately the hertzian contact stress causes sub-surface fatigue

We knew this was going to get complicated, fast,
but wasn't expecting quite that fast.

Until we've had the preliminaries, anyway...

 

[Cheesy]

Or more accurately the hertzian contact stress causes sub-surface fatigue

We knew this was going to get complicated, fast,
but wasn't expecting quite that fast.

Until we've had the preliminaries, anyway...

"We" are you royalty?
Contact stress is one of the many variables involved, (the smaller the radius of the flank/face the higher it will be). Google is a pretty good source for the preliminaries "spur gear design" will get some pretty pictures showing the geometry and nomenclature if you are really interested.

Personally Im more interested in hearing the little tricks to improve the gear strength while working around the limitations of what is there already, or alternatively finding out what was done wrong

 

[B.Rad]

Rohan, here we go.
I have had an absolute gut full of your stand over thuggish bully boy tactics. not copping your shit any longer.
this thread was started in good faith with the idea of genuine research, and also a possible education of the lay people.

I never claimed to know it all and certainly invited correction by people who know the subject.
i do know my betters and you do not qualify
I even asked for help in posting.

The whole point was to share knowledge.this is there in the first post for all to see.
I was going OK I thought till you showed up. it quickly descended into most improper behaviour.

Your brutish personal attacks only further demonstrate your complete lack of kowledge of the subject.
and look at the bloody title. gear teeth for Commando's. not shells, not shafts, gear teeth.

And what did I get for my trouble. Vile and vicious personal attacks.

personal abuse is no substitute for reasoned argument. It is the refuge of the purile mind.
I mistook your first cheap shot as maybe an attempt at humor. How wrong I was.

I have been ridiculed, accused of pomposity, arrogance, illiteracy, incompetence, stupidity, speaking crap and who knows what else.
if I am so stupid, how did I complete a trade.

I bent over backwards to placate you.
even publicly apologised when I gave you the benifet of the doubt by mistaking your first cheap shot as humor.

What did I get, even more vile personal attacks. Your behaviour is similar to trolls on social media.

You have ridiculed my replies as fanciful, yet all of your attempts at technical rebuttal have been wrong.
You cannot speak with any authority about gear design or manufacturing.

You demonstrate no knowledge of the art of reasoned polite debate and rebuttal.

Even my legitimate request for evidence was met with a withering personal attack of accusing me of arrogance and pomposity.. again just reinforcing your ignorance.
I am of the opinion that you never let the facts get in the way of a good argument.

so to be consistent, have a go at the poster who wrote about hertzian contact stresses and sub surface stresses. That post is just as technical as mine.

So I am not copping your vile abuse any more.

If you cannot contribute in a positive manner dont contribute at all.

If you cannot identify any errors by me and think everything I say is shit, why open the thread.

this could go on forever .
it disturbes the harmony of this Forum and is not good behaviour.

So it can end now, no ifs no buts. this is really the best option for both of us.

total withdrawl of your vile allegations will be the first step.

I offer you the hand of genuine peace and friendship.

to set a fine example of behaviour to new members.

but if we have to go toe to toe forever so be it.

my offer is unconditional and genuine, The call is yours. bradley Westfall