Vintage motorbike

Tony,

Glad you survived to show us the pics of that proud young man and his bike.

I remember some time around then, Bell ran a rather persuasive advert ... something along the lines of: If you have a Ten Dollar head, buy a Ten Dollar helmet.

... a thought that has stayed with me.

MichaelG.

I only vaguely recall from my student days how to calculate the out of balance forces on various engine configurations and it's something I chose not to revisit although it is quite interesting. The closest twin to having perfect primary balance is the boxer (opposed pistons ) with 2 crank pins. Almost any vee is going to shake like a pig unless you use balancer shafts because the primary balance is always going to be poor in both axes. The vertical twin is a pig too, whether you have the pistons going up and down together or 180 degrees apart.

Quite well written article in Wikipedia compares various engines - including a fairly lengthy section about steam engines towards the bottom.

Murray

Vic Willoughby who used to write for one of the motor cycle papers and also wrote some books had a very good insight on balancing engines.

I think secretly it was his pet subject as he always managed to work it into many of his articles.

I'll leave it to our resident Google Child to come up with all the links, references and patent numbers.

Very few engines have a natural balance, straight six is one but many can either be balanced to behave in the rev bracket thy were designed to run in, like racing bikes.

Where the biggest problems occur is when an engine has to behave over a very large performance range and there will always be conflicts. The balance factor when tuning is always a percentage of reciprocating weight, usually between 40 and 60 % but for racing it usually closer than this at 45% to 55%

A good background can be found in Phil Irvings "Tuning for Speed"

A large part of my earlier life was spent working on and making parts for what are now classic racing bikes. In fact my whole workshop came about solely for this reason. Many were out and out exotica and specials but nor the usual spanner specials of putting a triumph engine in a [ fill the blank in ]  frame, but out and out specials where one man made everything including the patterns.

Denis Jones **LINK**

And Ron Phillips **LINK**

Are two of the better know special builders who I had a lot to do with over the years.

Edited By John Stevenson on 09/10/2014 02:36:15

And don't forget that you can still buy a brand new Enfield v-twin today, made from two Bullet top-ends joined at the hip. Google Carberry Enfield.

This has grown to a really interesting thread!!

Seeing the TriGreeves twanged a chord with me. I built a roadgoing one in the early 70s, using a 350 Triumph T21 motor. It wasn't anything like as neat as the one earlier on though! I called mine a Grumph. It was at the time that green road bikes were becoming popular, but most were Bantams or small capacity two strokes. I wonder what became of it, I don't even remember how I got rid of it, but I rode it around for about a year.

I remember Phil Irving had an article about 270 degree cranks in Motorcycle Sport (magazine) in the early 80s, it sounded like such a good idea.............

cheers

Bill

Have to disagree with you on a couple of points Muzzer. A 90 degree V twin has perfect primary balance. It requires a balance weight on the crankshaft that balances 100% of the weight of one piston assembly.

The boxer twin would have perfect primary balance, if the two bores were in line with each other. Usually they are not, since the need for a 180 degree crank makes that difficult. So they do create a couple.

Further to the earlier discussion on parallel twins, the usual thing has been for four strokes to have the 360 degree crank and two strokes to have the 180. That gives even firing intervals on both, but of course neither has especially good balance,,,the 180 feeds a couple into the frame, which a typical motorcycle frame is not well placed to resist. Honda would be one of the exceptions, the CB350 series had a 180 degree crank, giving it a distinctive beat to the exhaust since the firing intervals were not even.

The engine that interests me a bit is the one that Brough tried at one stage. Four cylinders, opposed to each other in pairs, with each opposed pair using the same crankpin. The two cranks were geared together to rotate in the opposite direction, and all four pistons moved in the same direction at the same time. Each pair was balanced by a balance weight on their own crankshaft and so the engine had perfect primary and secondary balance, and an even firing interval. Very clever except for the need for balance weights...but if you make the same style of engine with more slices, you can even get rid of the balance weights. That gets you to an engine that is a bit much for a motorcycle, like the Napier Sabre or the BRM H 16

John

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John,

I don't remember the gory details, but in the mid-70s a friend had a CB350 which he managed to rebuild as a "split single" ... Needless to say, it vibrated like one on those concrete-levelling contraptions ... I do still remember the terrifying experience of my one pillion-ride.

MichaelG.

Hi Michael G, It seems to be a confusion in terminology, you call them parraleel twins because the cylinders are side by side, I had always considered that in a parrallel twin the pistons went up and down together, and in a 180 twin, they were opposed, hence the vibration problem was always referred to as a problem "inherent in parralell twins" wheras 180 twins are balanced much better. Now I stand back and reconsider it all, I take your point!

Phil

The Tri-Greaves reminded me of a trials bike I built and rode about 30 years ago A "Tri-Field"

It was a 500cc unit Triumph engine in a Royal Enfield, very low compression ratio and special wide ratio gearbox internals etc. The tank was from a BSA Victor.

Phil

Hi all, Just read back and see that Michael knew about the queens chickens, and also probably AllJunkSpares and BitsStuckAnywhere.. My Friend Richard had a greeves with the cast frame and leading link forks, but it had a 197 villiers engine (9E?) like this one

http://commons.wikimedia.org/wiki/File:Greeves_20DC_197cc_-_Flickr_-_mick_-_Lumix.jpg

Them were't days tha knaws!

Phil.

In my, ;Yoof' I had an Ariel NH 350 which had the rigid frame converted to one of the first McAndless rear springing.

All the, 'Tramp' of the rigid fraame was gone and the ride was nice and soft. I reconditioned the engine with new bearings and piston and cylinder and a new carb. It had to go when I was posted to Hong Kong.

My next bike was a Triumph Tiger 100. The engine was good but the ride a bit twitchy, later I had a Norton 500 Dominator, duff engine but a nice ride. I wish i could have put the Triumph engine in the featherbed frame of the Norton. That would have been a bike of interest.

Clive

Innards of a Jones engine.

Not bad for coming out of a 12' x 10 shed.

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Thanks, Phil

MichaelG.

.

This thread is developing nicely ... Well done Nick, for starting it.

What with all those straight cut gears and ball races, I'll bet that there was quite a racket when it was started!!

cheers

Bill

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Great to see that one, Phil

One of my [all-too-many] abandoned projects was to build a Tri-Field ... I had picked-up a Crusader Sports, with a reasonable chassis and an engine that had been "worked on with a Hammer and a BreadKnife" ... unfortunately I couldn't find a Triumph engine at an acceptable price, and I moved it on.

Somewhere "in the Archives" I may still have a set of sketches for the engine plates ...

MichaelG.

Triples seem to be quite smooth, my T150V was much calmer than my mates Bonnie. My Hinkley Trident has balancer shafts and has a slight left right rock when idling at lights etc. the T150V did not seem to do this as I recall. I had a 250 desmo for the weekend once and the vibration was fierce, the other thing that made that bike hard work was the rh reverse pattern gear change, I had mastered swapping from left to right but the reverse pattern threw me completly so I almost came to a stop before I had decided which foot and which way to change, glad to give that back to my mate.

Mike

Vibration was a major problem with the Britten motor cycle built in Christchurch, the bike, motor and frame(what there was of it) were scratch built, John was more an artist that engineer, but he had a great team, pity the big C got him, he was full of ideas right to the end.

Ian S C

Tony,

Those 'crash' bars reminded me that they where compulsory in SA and pretty useless at any speed over walking pace.

I found out when I T-boned a drunk vagrant who had wondered into the road during a Transvaal cloudburst, and I was tippy toeing as well speed wise.

The only time I rode without my race car full face Bell was the day I bought the bike, and then only because I just didn't feel happy with it on.

One thing the dealer didn't tell me was that the gearbox was sequential, so I floundered for a while before I somehow found out.

During one particularly spirited ride, changing up at maximun revs third to fourth I think, my left hand was jerked free from the grip due to acceleration forces, and in a LH sweeping bend, leaned well over.

Now that caught my attention somewhat!

Did have a good Robot 'dice' with an American muscle car, side by side all the way into top gear, before I had to turn off.

Ahh, the adrenaline days. Good memories.

Geoff - Got lost last night trying to find that effing pub! Useless SatNav!

So a European designed 1200 cc car would have totally cained you then.!

Nick