commando balance shafts?

That's my thoughts, if the crank wants to push/pull the crankcase fore/aft,causing the "lump" to transmit this im-balance to the frame ,then a equal offset lump going the other direction will reduce the im-balance energy? basic balance shaft useage :roll:
These "armchair" thoughts shared with you lads are interesting.
I guess the Commando in its dieing years was played out for any good amount of cash to be thrown at it...fact as we all know the cash pot was allmost empty,and the rubber iso's where just good enough...at pennies to make.
I watched Jay leno on his john player ,he excepts machines for what they where..and enjoys the quirks....but saying that he doesn't ride them far,or often..just enough to put the 5 minute video together.
Kawasaki with the A10 bsa copy where not impressed with the bikes quirks ,and quickly re-designed it!

I will never forget "30 years ago" assembling a interstate not aware of the iso set up i just tighted the engine into the frame..bolted up tight! The bike vibrated like crazy and caused double vision...luckly the owner sorted it out
Madass" Donald" is correct in the idea that a balance shaft can be external, driven from the crank via chain...
Might spend some retirment time playing...keeps the old grey matter healthy, better than mowing the lawns.

Al-otment said:

Rohan said:

Indeed Aco - balance shafts and rubber donuts do NOTHING towards giving the mechanical parts an easier life.
The main bearings and cases still have to be strong enough to hang together, no matter what...

Click to expand...

I agree isolating the rider from vibration using rubber means the out of balance forces still exist and therefore components need to strong enough to cope with the stresses, but balance shafts cancel out the vibrations and therefore reduce stress.

Click to expand...

Build the motor light enough and the pistons stay still while the motor goes up and down . :lol:

Generally development of engines sees the crankcase weight increased as they improve the stttrength to contain the power development inevitably unleashes . :?

BALANCE SHAFTS would be SECONDARY to the mass / shake / ' vibration ' , the resultant with shafts being to cancel the osscillation of the CASES .
But the shafts themselves induce FURTHER stresses to the cases , Thus they need more strength / weight per horse power .

Therefore power to weight the ' Isolastic ' set up isnt to bad at all .

Though the nasty BMW Twin uses a counterweight at the crank , increaseing the streeses & inertia there , whilst cancelling the vertical displacement / vibration .
This is possably a development of the dual rod Ducati 500 set up .

" The Supermono inherited many of its features from 888 Racing. Liquid cooled double overhead cam shaft with four valve desmodromic cylinder head. A horizontally placed 550cc cylinder utilized a "dummy connecting rod" that acted like a second piston. This ingenious piece of engineering was the key to overcoming vibration problems. "




B M

All You Need is a Good Dentist . ! :lol:

Of corse the Velo Fellows mayve got it right , despite the price of silver or whatever it was ;

Heres a pirated artical that may be a load of tripe on Irvings parrallel V twin , or 270 degree crank . Asumeably reduces bearing loadings by countering forces AT the source .file:///C:/Documents%20and%20Settings/Windows%20XP/My%20Documents/Downloads/Crank%20(1).pdf
or go here http://www.triumphrat.net/twins-technic ... crank.html then there .

Theres more info from the obstroperous Triumph brigade here http://tioc.org/1993-3PM7.pdf on displaced journal crankshafts ,

You might consider this an attempt at ' Balanceing ' , the Original IRVING article is Somewhere . :x First Id seen was the Aussie BSA / Honda with the NORTON crankshaft ,

more drivle : http://www.xs650.org.au/Technical%20Info/smoothness.htm



Peak to peaks...
360 deg. crank = 19,116.34 N (100%)
292 deg. crank = 15,767.87 N (82.5%)
285.3 deg. crank = 15,151.86 N (79%)
270 deg. crank = 13440.74 N (70%) apparently .

http://victorylibrary.com/brit/offset-c.htm never find the pither your wanting . :x heres the little sucker , a Norton Crank - offset crankpins in a B S A in a Honda RS or somesuch 250 . True non partisan Er artisty um .



" When people started selling S/Hand rolling chassis it looked like just the home for the latest incarnation of the BSA motor, this time with an altered Norton crank built up on a new centre that offset the pins to 90deg, this also made it 818cc. "
http://www.dotheton.com/forum/index.php?topic=6756.0 and elsewhere .

Mark Parker from Bega N.S.W. ,
" Tenginee,
Yep, the crank is cut in half losing 5mm in the cut then pressed into a new centre flywheel 5mm thick and bolted up, where the original flywheel slides on and is bolted up is turned true with the crank when manufactured so this ensures accuracy when it spigots into the centre section, the bolts where they are, in a fairly big circle, including up the centre of the crank pin, I think give a better, stronger assembly than even the Norton shaft which was designed as, and works well, as a bolt up. This crank is more true than most std cranks we also checked. And was used regularly by my son for some years. The cyl I had cast in Melbourne, after making some patterns, the problem I have is finding someone to machine them, the one on my bike I had part machined and ended up buying a drill press and doing all the holes and threads, pushrod tunnel etc myself with assorted tools including a file to finish the tappet block area! If you wanted one and can machine it I'm sure we could arrange something. I haven't tried a shorter block as needed for a 750 but cannot see why it wouldn't work. I'd love to build up a 750 version for someone to race and see what it would do.
I had this thought to-day at work; with the std BSA crank set up, when it shows excessive endfloat why pull it all down to fix? Why not put an outrigger bearing on the crank and control it with that, it could even be set so that the roller doesn't need to run against the lip. This is what I have controling end float and it gives more support to the crank and primary, and fits under the case. "

seems like theres some advantage to unit construction afterall . :lol: :lol: :lol: :roll: :wink:

Any kind of balance shaft or extra con rod an dummy piston would mean new engine cases and many new internal parts by the time you had made it all then it would not look like the original motor and may not even fit back in the bike.
Balancing is not just about the weight of moving parts but as cylinders fire they try to move the engine not just the piston. I owned a VTR1000 Honda if you stalled the motor you could feel the whole bike jump up an go forward. I asked the dealer he said many owners had reported this an Honda felt it was the front piston stopping on compression but then because it then fired with the rod almost straight instead of the crank turning the cylinder moved up an piston stayed still. That was a 90 degree V twin which is supposed to have better balance than a parallel twin but it did vibrate. Not anything like a commando though.
The point I am trying to get across is the engine will vibrate no matter how much you try to stop it an add more parts to cancel it out will only work up to a point but in the end you would have a hole new type of engine. If you where to do all that just go out an buy a different bike it would be much easier so all you can really do is make the best of the engine an ISO system as many many owners do.

Stan Keyes gets a great launch on his 1972 Norton Commando during an AHRMA race at Road America in Elkhart Lake, Wisconsin, in June of 1989.
Keyes went on to beat Pete Watson and Rob Tuluie to win the 750 Sportsman class that day.
(Larry Lawrence photo)

:mrgreen:

Thats Not a Combat ? is it . :wink: :lol:

'But then the balance factor is all about the rider too, not forgetting that bearing loads are least at 53 % BF.'

At what revs ? If the shaft is out of balance at 3,000 RPM, it doesn't matter as much as if it is out of balance at 7,000 RPM. At 7,000 RPM an out of balance shaft exerts much greater forces on the bearinngs and cases. As you are we ll aware, commandos tend to split their cases through the main bearing housings if revved to 8,000 RPM with the standard 53% balance factor. The standard motor is probably designed to operate at up to 5,000 RPM and the isolastics used to cope with the rest up to 6,300 RPM. That doesn't mean that at even 6,300 RPM the bearings and cases are not copping a beating however it is probably tolerable. The forces increase as the square of the velocities. My 850 runs 72% balance factor rigidly mounted and is extremely smooth at 7,000 RPM. If it vibrates at those revs it is doing damage. When idling the bike rocks backwards and forwards. I've never seen a motor destroy itself while idling.
As far as the rider is concerned, he/she is constrained by the environment and the law. If on a race track the revs are at max until the next gear change, then there is a drop proportionate to the gear spacing. With a close 4 speed box, I don't believe mine drops more than 400 RPM on every gear change even when pulling very high overall gearing.
For a road bike 53% BF is probably OK, however I would not rev it high even with the isolastics. The bearings and cases might have more give in them to accommodate impact, however it is still risky. That crack through the bearing housings doesn't appear for no reason, and it is a common failure. If the rods don't give up or the valves tangle, a commando engine should cop 8,000 RPM easily - the fact is that they will not cop it with the standard balance factor.
If I had a standard commando, I'd balance the crank to 72% and live with the torment of riding it in traffic while it shakes. It depends on how often you need to do that, and whether you care about getting booked for speeding. That is why I don't ride on public roads.

I've ridden an '71 that did not isolate till like 55 mph/3500+rpm so was nerve injuring annoying to follow traffic at 50 mph with constant dangerous temptation to exceed 50 to get some relief. A balance device that is not pretty close to or in line with the main oscillators might not work very well. Alan the Seeley was made for rigid vibration tolerance but the Cdo frame is not, yet there are examples of both frames breaking with not enough rubber isolation freedom. Frames and engines and pilots are weakest to vertical vibrations so upping the BF for high rpm helps survival of those external things while increasing internal stresses. The two part isolatic frame/power unit was ingenious idea for road bikes and Harley incorporated it from Mr. Hopper after Norton failed. Un-tamed w/o swash plates or radius rods the floppy eared isolastic Cdo can become a like a fish flinging its self off the deck. Best I can glean from racer MacBride on Herb Beckers robust triangulated swash plates is that it equals the rigid Seeleys in handling while retaining lower BF on internal stresses but then runs into the same problems the elite modern frames do, too dam rigid to take up the conflicts of tire directions induced by counter steering so engine vibes can suddenly match tire harmonics and road texture-> ZIP>SPLAT. Freddy Spenser and others state that when they try to weaken forks or swingarm to get some frame-fork twist out of line compliance the parts either were too weak to control the race forces aiming or just broke. No one but me has experienced the Flabbergassting Fabluous secure smooth sensations of tri-links via very robust rump link with two rather compliant helper links that lets the frame twist distinctly under ya and hold it twisted till releasing the energy w/o any rebound but to perfectly neutral for the next instant of breath taking loads. This frame compliance allows incredible increase in side load traction and power planting on skinny tires, to point i had to exceed speed and power and lean and fork angle loads of moderns before I could get Peel to break free to make pavement act as like THE Gravel travel and only allowed tire patch grip sense on road texture though to point I could play tunes of howl, squeal and chirp to sharpen up turns for adrenalin highs. My factory Combat is very dangerous to keep up with hot shots just on tour and no way can handle the Mt. Road turns like they do, so am limited as anyone else by the isolastic let downs. i discovered un-tamed isolastic crazies on pre-Peel so thought I'd made bad error getting a Commando and built Peel into a type of foot forward bagger till I could be rid of such dangerous old cute clunker.



Something else revealed by Ms Peel that all your under powered too rigid or too floppy frame riders have never mentioned but the GP elites do all the time is the engine drive train harmonics on power pulse tire hook up, aka Big Bang Firing Order. Ms Peel has 4 dampening suspension systems, forks and rear shocks, frame twist and return, isoloastic engine up/dn support and rear tire thrusts inline of travel through frame taken up by the isolastics for type of traction control that still leaves me quivering to think about. Peel passes through the counter steering handling with a fork flip into straight steering just as rear traction giving up but then twists frame in a way that levers whole bike/pilot mass on rear patch so traction spikes and can put down more power to point Peel would hook up a side way wheelie impossible to skip tire so can add even more power as front unloads completely while hooking a decreasing radii turn and coming out rather faster than entered. Poor ole elites don't stand a chance keeping up with that and really are no longer on my mind as worthy competition so off road antics is my main interest to tackle.

Al-otment said:

Rohan said:

Indeed Aco - balance shafts and rubber donuts do NOTHING towards giving the mechanical parts an easier life.
The main bearings and cases still have to be strong enough to hang together, no matter what...

Click to expand...

I agree isolating the rider from vibration using rubber means the out of balance forces still exist and therefore components need to strong enough to cope with the stresses, but balance shafts cancel out the vibrations and therefore reduce stress.

Click to expand...

Are you talking about stress on the rider or on the engine internals ? If the crank shaft is spinning at high revs and out of balance the damping from balancing shafts would be applied to the end of the crank, you might save the bearings , however perhaps you would be more likely to fatigue it ? My feeling is that if you want to ride a big vertical twin, you set it up to be smooth at the top end of it's normal operating rev range, and tolerate the vibration at revs where the motor is not in the most use. There was an easy answer back in 1970, if you wanted a smooth motor - just buy a CB750. This is what this is all about, and the reason Norton used isolastics and a big hole bored into the crank counterweight. Norton wanted their bike to be something it could never be, and would any real motorcyclist really want it ?
I'd love to see what a standard commando crank looks like spinning at 7000 RPM with a strobe light shining on it. I think you would see it grow in the middle.

If you belt something with a hammer , if its on an imoveable surface you get a impact . If its cushioned the shock loading is less .

The Commando engine , thus the BEARINGS , are cushioned .

If this was the case for the commando engine..why the common crank case and Crank failures?

Consider the forces....the crank as considerably force to shake the whole bike, including the rider back and forth/up and down many times a second. i would consider that excessive ...Concord was scrapped after tests showed the aluminum was getting brittle...due to vibration. I have no idea how super-sonic speed effect's thin section alloy...but it cannot be good...but thats getting of the track...or is it?

Back to the commando...did Combat owners with this "super sports" bike rev the engine above the safety margins,,,with increasing vibes and flexing cranks ..then BANG!

Matt Spencer said:

If you belt something with a hammer , if its on an imoveable surface you get a impact . If its cushioned the shock loading is less .

The Commando engine , thus the BEARINGS , are cushioned .

Click to expand...

A / . Norton gave 5900 as max continuous operateing speed .

B / . Tho od bod bought a Norton for Stop Light ' grandprix 's . typically 18 yr olds .

C / . if there are excessive clearances / maladjusted componentry , strain is severly increased at max operating rpm's

D / . DUNSTALL , around 68 / 70 were running 7500 & claiming 70 Horsepower . Their maintanance & parts replacement regime would be continuous .

E / . operated in a comparable manner without a skilled / experianced mechanics attention , leads to . . .

F / . Pre Unit Construction gives smoother running precisely because there is more ' give ' in the contraption . This allows a few thou's absobtion of motion . ( Isolastics or No . )

G / . If youve ever riden a 60 Hp Pre Unit Triumph in its ' bedding in ' phase , you'd discern wayward tendancies . TIGHTENING all the through bolts everwhere severly , AND
adjusting / maintaining / serviceing to specs or preferances , sees a completely transformed machine . Unless its a Pre 60 on Tarmac , where directional waywardness
will lead to tears or a new chassis .



F / . The COMMANDO with its Three Point / Single Plane restraint , if operated entusiastically on undulateing or irregular surfaces , is wracking & wrenching through the Powertrain .
It needs to have the fasteners secured firmly .

Thus. besides all the other issues , you can see theres room for error to creep in . Likely 72 there was a Brrp , Brrr , BRRRRH across the Valley . Some young shonk had traded in his overly harrased
( some would say the most well used , though well might not be the most accurate definition, H1 on the shore ) on a 72 Combat Roadster from the Honda Shop in town , who had a buyer for the H1 .
The Commado had been dropped twice in town by the straight , in winter ( wet ) so needed odds & ends for a upmarket shop , includeing a tank . Thus were glad to loose it at a discount . $ 1500 I
believe with $ 100 against the Kawa .
ANYWAY . The Former Techer with the Fastback was the Mentor , From which the Combat was Exiting after maintanance , on its back wheel , a mild wheelie , dropped for the tight twisted left . then
up & vertical . And of home to pack & head for the hills . Away from all the nancy hysterics and gossip of the wayward suberbs .

Therefore & Insofar , one or Two Commandos Got a fair bit of stick . And were expected to take it . Some got the requisete maintanace , unlikely there was a shop up fully on all the whiles of the machines ,
or economics would intervene . Nearly any hard riden machine in N.Z. was owner built and maintained . The faster lasting ones anyway . if im ever back I will endevour to interview the culprits .

My Std L R was bought at 7000 miles with shot ball races , was non combat spec . The Villiers built motors useually lacked attention to detail and full care and consideration in manufacture .
There were good ones and somewhat less good ones . The Early Fastback of the Teacher ran 43.000 miles trouble free when parked , looking weathered & dog eared but sound and operateing .

If the owner wasnt a speed demon , chances are it gave long service if not neglected . Some agronaughts maintained them as required per use . Any neglected machine the laxness eventually
catches up somewhere down the line . Remembering some were well removed from skilled maintanance & tuneing . Many in the states were parked when they proved to be not a Honda in that
respect .

Any that havnt had the head off at 100.000 miles were likely not taken past 6.000 and had a mature owner , remembering a good Combat might well run 8.000 rpm & a well adjusted std. 750
straight past 7.000 . If there was bearing wear or missalignment the out of shape tendancy might shortly become exagerated .

check out this , ive stuck the bores & strokes on .

In the Local Honda shop , evesdropping :mrgreen: the two AJ / Matchie singles were no trouble to loose , all the Brits ( 4 ) had oil trays . the 650SS wasnt going to be let go for a song .
Thinking its maybe Marks one now . The Salesmen were in their 30s and wernt concerned if it sat there forever , the other Dommie mayve been a single and wasnt there much over a month ,
despite the price . Neither were waxed & shone .
The Black AMC things had the most pressence in that repect , but a $ 2.000 + Honda Four was the salesmans delight , when they could find one . Though the 350 4 caused hudled conferances ,
and steering uneducated mugs with stars in their eyes thataway for a time before one that couldnt afford a 750 rode off on it unknowing . But he wouldntve been the H1 contender , the Bank
Clears one was observeved by the Village for discussion , early days there were indicative it couldnt be ridden like a Matchey . :lol: The H1s'd tear the bores out in 20 & the bottom ends in 40
thousand imperial miles .
None of this kilometer nonsence back then .


http://www.youtube.com/watch?v=iOFFSRIBTeg not pedal to the metal , unfortunately . But a tooned Pre unit requires similar finesse of operation for longevity and to give its best . :twisted: :mrgreen:
Id thought it was a Rampent TIGER ( badge )

One of these at 70 + with a skilled experianced operator can exceed the anticipated expectations .
though inevitable comparisons with modern ones where the drivers not required to leap around like a madman
with all the power assistance , havnt revealed as compatant a chassis . Or a matching ruump ruump ruump at
idle after exercise . :lol:

Supermarine Spitfire or Airmacchi ningnong , the ningnong would be current or more nearly But it wouldnt be the SAME .
Useually took the dropout hippies to run the coach into worthlessness . At 9.000 rpm a Commando might not last long .

The Tachomete was not renouned for its instantaeneos recording of exact rpms . Lag & swing being more ascribed characteristics . Teanagers could be apt to change gear when it went flat , particularly on Jap
stuff . Some couldnt read - typically ones out working - manual work + $ $ $ . Others studied , possably more intilectual ones . What did Croxford ride pre Circuit Raceing . :lol: :lol: :lol:

Cracking Up , http://news.bbc.co.uk/2/hi/uk_news/849073.stm Thermal expansion on the Airframe was substantial too , at speed . Wonder if the Commandos a foot longer at Mach 2 .

Al-otment said:

Rohan said:

Indeed Aco - balance shafts and rubber donuts do NOTHING towards giving the mechanical parts an easier life.
The main bearings and cases still have to be strong enough to hang together, no matter what...

Click to expand...

I agree isolating the rider from vibration using rubber means the out of balance forces still exist and therefore components need to strong enough to cope with the stresses, but balance shafts cancel out the vibrations and therefore reduce stress.

Click to expand...

Re-thinking the above I've now decided the same stresses still exist due to the reciprocating parts, it's just that the balance shafts reduce engine vibration by applying an opposite force. Con-rod, small end, big-end, mains, crankcases and shaft are still subjected to whatever the reciprocating force is. There fore it makes perfect sense in any engine to reduce reciprocating mass to a minimum. I'll have to start saving for the JS rods and pistons.

If the force's are still there,then the engine would vibrate just the same? If the crank at 3 o clock forces the engine back..say 10 kg,,the balance shaft should exert a force in the oppisite direction to oppose the 10 kg..in effect the balance shaft "pulls" back the crank..thats what i thought?

Al-otment said:

Al-otment said:

Rohan said:

Indeed Aco - balance shafts and rubber donuts do NOTHING towards giving the mechanical parts an easier life.
The main bearings and cases still have to be strong enough to hang together, no matter what...

Click to expand...

I agree isolating the rider from vibration using rubber means the out of balance forces still exist and therefore components need to strong enough to cope with the stresses, but balance shafts cancel out the vibrations and therefore reduce stress.

Click to expand...

Re-thinking the above I've now decided the same stresses still exist due to the reciprocating parts, it's just that the balance shafts reduce engine vibration by applying an opposite force. Con-rod, small end, big-end, mains, crankcases and shaft are still subjected to whatever the reciprocating force is. There fore it makes perfect sense in any engine to reduce reciprocating mass to a minimum. I'll have to start saving for the JS rods and pistons.

Click to expand...

john robert bould said:

.Concord was scrapped after tests showed the aluminum was getting brittle..

Click to expand...

Concord was 'scrapped' because Continental left bits of metal lying on runways,
that wheels could be punctured by - and then puncture the fuel tanks. !!
Reinforcing the tanks enough to prevent this made it too heavy to fly....

Al-otment said:

Re-thinking the above I've now decided the same stresses still exist due to the reciprocating parts,
it's just that the balance shafts reduce engine vibration by applying an opposite force..

Click to expand...

A much better line of thinking. !

Balance shafts do nothing to reduce the loads on bearings from out-of-balance-forces,
or the stresses on the cases from same.
Just make it more comfortable for the pilot....

As far as light pistons are concerned, they stop completely and reverse direction at both the top and bottom of the bores. Ant reduction in weight on the little end of the conrod must help performance. When I fitted lighter BSA 350 Goldie pistons to a Triumph 650, I was amazed that I could feel the difference - I didn't believe it would be that significant. The way the motor would spin up was quite different. There was however one thing different also - I'd machined the shoulder of the crowns to make squish bands.

I am thinking the same.
But doesn't the balance shaft "pull" the crank in the opposite un-balanced directions, which suggests lots of power loss?

,

Rohan said:

Al-otment said:

Re-thinking the above I've now decided the same stresses still exist due to the reciprocating parts,
it's just that the balance shafts reduce engine vibration by applying an opposite force..

Click to expand...

A much better line of thinking. !

Balance shafts do nothing to reduce the loads on bearings from out-of-balance-forces,
or the stresses on the cases from same.
Just make it more comfortable for the pilot....

Click to expand...

Power is lost because the engine has to drive the balancer shaft - but I don't know what percentage this might be of total output. So isolating the rider and as much of the chassis as possible by the use of rubber is not such a bad idea after all - and much cheaper than redesigning engine cases etc. to accommodate the balancing mechanism. Losing weight from the reciprocating mass is definitely the way to go.

Best stupid V4 2litre Ford I had Id done exactly that . turned the bearing shells to block the pilways & tossed the shaft . With the 8 in clutch it got the flywheel mass pretty much right , with a nice ' cantering ' vibration .
NOTE a nice PRIMARY Vibration . Not one of those tingley secondary vibes , which can still be present with balance shafts though reduced in period or amplitude . Still set your teeth on edge .

This is some V6 one , but you can see thered by a bit of side thrust with those counterweights ripping around .


http://www.paralleltwins.com/pages/cont ... twins.html
Dreaded Norton P86 Cosworth Challenge infernal componentry . The shafts are fore & aft of the crank .



Then theres the Quill Shaft . Inside the Front Balance Shaft . More wind up than a honda , initially , were told . Be intresting to interogate Lewis or other pilot of the Daytona jobs .