Heavy Crankshaft....

mm tribsa I would suspect all of them- I like your questions SOME GREAT QUESTIONS IN THERE.

you can always make time / resources and I am sure no one in the paddock around Bantam racing would refuse a request for help especially with this or any other issues.

besides:- Money you seriously can not buy these cranks, finding a company with the knowlegde would be difficult enough, but blimey you don't need to, the resources/ knowledge/ expertise and help is in the paddock or on this forum we only have the best "you Know" with any of the bantam racers,

just got to be brave enough to be able to ask for help

Tom made from scratch a crank for me, when it arrived I checked it in an engineering shop, of some what great presence? anyway the run out -was ZERO ZERO YES i SAID ZERO ZERO" i HAD TO CHECK IT SEVERAL TIMES, to believe it not even half a tenth OR A SMUTTERING ON A TENTH CLOCK NEEDLE , out of a shed thats amazing - and turbine smooth killed all the vibration well most of it, not never had a frame break or crack after that, mind you when Micky Nash helps you never really have issues in this area, "so" this is all about what we are trying to say, engine's barrel's / liners / ignitions / frames wheels / even gearboxes, well anything you need, just got to show you are a seriouse guy /team about racing "not in 20 years time" and all the help will be forth-coming - does any racer disagree with this - come on lads back me up please:-

who has helpped me
TOM / ALAN BROWN / TREVOR / BRIAN WHITE / MIKE POWELL - IN FACT AT SOME POINT ALL OF THEM,

BLIMEY EVEN IF YOUR BIKE BREAK'S DOWN, THERE IS NEARLY ALWAYS A SPARE BIKE TO RIDE, IF YOUR'S CAN NOT BE FIXED.


I remember working on my engine till 2.0 in the morning in paddock at Pembrey Mike helped till his dad came back into the paddock for him. you just can not fault that type of support. in any arena .

I am just loving every minute of it its such a stress relief from work too. just great to be back where I finish who knows who cares, but slowly and surely I'm getting quicker, its actually exciting.

is Bantam racing about who has the bigges wallet, No - and it never will be.

Are the formula Bantam Racers a collective group of enthusiasts, YES.

PS THE CRANK FROM TOM MADE TO MY DIMENSIONS INCLUDING SUPPLYING THE CONROD cost me £120.0 now that aint expensive, OR UNREALISTIC TO FIND .

WHAT DO THINK? YOU COMMING OUT TO PLAY?

LETS SEE A PIC OF YOUR BIKE.

KIND REGARDS DEREK BETTS

After seeing the comment of con-rod and crank costing 120 quid I reckon I raced Bantam and 250 ABS when it was really Racing On The Cheap as Roy Bacon titled the BRC... I built both my two Bantams for that amount -- first at around 80 (the engine was found in a field) and second at around 40 -- hoever, I did have lots of bits lying around and of course, nothing exotic, both standard long-stroke, CB points ignition, Sports Continental tyres (to begin with) and that sort of thing in the good old days of NO streamlining.
...
Much more of a challenge when you know the other Bantams are that much quicker...
...
Great club and pity I had to leave to go to Canada for more money and better status -- very selfish of me -- Ned was probably a better chairman anyway and the Newsletter he produced was certainly a neater job than ours.
Yet Dick & Dave Hunter & Poddy Phillips regularly produced a very newsy 28 -- 32 pages regularly, during the season and not many clubs have matched that...

john this was done about 1996 a bit different to the 1940;s mate ?

but in monetary similar to about £6, ten shillings and sixpence. about 3 days wages for the era?


Derek

I was talking mid - end60´s, Derek -- earning about 1100pa... House at 5000 quid sort of thing.

Getting back to heavy crankshaft and effect of the response during acceleration of engine speed from idle to max speed. This is also greatly influenced by piston-& piston-ring friction losses which are usually over 50% of all mechanical losses.
So if anyone is looking to find the `feel´ of an engine´s response to heavy or light flywheels he must first establish that the piston-& piston-ring configuration is the same as before otherwise the comparison is invalid.

Be an interesting add-on to this flywheel debate to argue what piston-ring -- or rings? --is the best set up for a racing Bantam?

The Bantam Maurice Quincy*** was racing, and beating 250s with, when Bill Lomas was over in Australia had a single 16thou thin ring and although sporting no rev counter was said to rev-on-and-on ... He changed the ring between practice and race and between races -- it wore so quickly....
Andy Boyle´s 250 had a single Dykes ring....

PS -- *** I forget who made the bike ...
Cheers!
JayBee.

Can anyone weight a std175 bantam crank I know a lot of 175 runners use the
std wheels just to give trevor a number to play with...

Robbie I assume you don't know how heavy your crank is

At Last a subject I can contribute to - very intersting John, 0.016"thou never heard of one this thin on a bantam.

I was involved with manufacturing rings down as low as 0.004/6" thou in the car world, but never heared of once's 0.016 thou on a bantam - I am aware Brian white EITHER MADE HIS OWN OR CONVERTED and used i think two rings in the same groove.

no doubt thiner rings work better at higher speeds because of the reduced mass (above 9,500 rpm) but below this ? -

Now lets consider the frictional losses on a ring, but we must also consider drag piston rings produce pushing the oil down the bore, the presures in this oil/wave can be very high, and work against the movment, some of this presure kepts the piston and ring off the bore.

its my opinion this topic is of no consequence for a 175cc bantam "well thats unless some one is going to run it at very high RPM !

I was involved with a special products division both manufacturing and researching high speed pistons and ring product's, from about 1982 to 93 - rings from 1.0mm down to 0.1mm on very high reving engines, frictional losses- heat- lubrication- and oil wave forrmations, these were all found to be exponential as the rpm rises.? (i think thats the correct word), friction is not halfed as the contact area is by the same amount, its the mass that has the most effect, heat is also a consideration, a secondary function of the ring, infact most of the heat well approx 70% is past to the bore via the rings.

The lubrication wave comes into play,as does the profile on the lower edge, it can reduce the ability of the engine to disipate heat thru the ring as its contact area is reduced, this causes issues especially in high reving two stroke engines, often the edge profile of the ring has a bigger effect on oil wave and hence drag, as the ring travels down the bore, rather than the other way, thus increasing drag as it moves.

It was found that the thinner the ring, the lower the mass and the less likly it is to flutter - (notwork) this is were the ring moves off the lower face and allowing presure by pass - making the ring thiner reduces this, the down side was the temperature increase in the crown as the ring does not pass heat to the bore at the same level, this can be seen on FEA, the type of oil and the profile on the ring affect this.

Anyway there are so many variables, its difficult to say which one is best, each type has advantages and disadvantages.
but for higher engine speeds there is no doubt, low mass rings work better, but with very special materials, these are not nesecarily the thinest rings.!

My advice is unless you have a very sophisticated lab, a zillion pounds worth of electronic measuring sensors built into your dyno, and a computer capable or corellating the data, then just don't bother with this subject, just bear it in mind when selecting oil and the amout of oil content in the fuel, my theory is the more your engine can stand the better it is for to reduce friction and flutter!, and it increase the ability to transfer heat to the cylinder from the piston.

Better to concentrate on the more important aspects, like barrel, pipe, ign, head, and the rest of the package.

besides its only when you go above 15,000 and 17,000 that this subject is worth looking into.

ther have been many papers released by yamaha engineeres in the 60's on this subject, Some people would argue aganst some of this, but reseach result are available to check out all except data on oil wave formations, I dont believe any has been published yet, "still top secret" amongst a the few that know.

I'm currently using a piston with a dykes ring that resists flutter, better than most, it has a large cross section area, and a lot of mass, i have re-profiled the lower edge to my own design, that should produce a smaller wave front, the ring width is 3.4mm making a large contact area with the bore, to disipate heat through the ring. Also the ring has a chrome finish, to help reduce wear. I 'm using this as my theory is to try to increase the ability of my cast iron cylinder to dispass heat from the piston to the bore at a higher rate, well that's the theory.

I believe most rings made now for high rpm engines, are steel and plated, some cast rings are still made of iron, but these are a lot more prone to breakage, and in my opinion to be avoided.

regards Derek Betts

I did a lot of development work on Diesel engine piston rings with Carl Schmidt and another German Piston company but we were aiming at compatability of performance with optimum oil-consumption not developing for racing´s high performance with very high revs....
...
Seems this Australian Bantam builder used one 16thou thin ring for sealing by wearing-in because as I said the ring was changed frequently. I have the article somewhere -- I´ll try to find it although I don´t think the idea of much use here.
---
Engine designer Mackerle reckons the (piston & ring)friction-loss curve in most engines is a square law of the engine speed -- so a high revving engine will be wasting energy to this factor if its not optimised.
...
I think most Bantams are using two compression rings...

Hi John yes spent eight years making Karl Schmitt's amongst others for T&N re AEPP, I know most if not all the German companies well, I us to make scmitts high speed and medium speed deisel pistons, and sort out their design faults, two piece / steel crown / solid sg iron cast lron types. drawings ? especially on the skirt profiles, problems with polar co-ords, both secondary and tersary clearance, the drops dimensions were always wrong, never fitted the profle graph's, I think thier engineers had problems understanding secondry axial clerance facit effects to the drops not taking into acount the barrel shape on the drop, especially on the negative sign's!, anyway good times.

The other one - current technnology moved on quite a bit, using d2 Ring material in diamond hard pure silicon bore's well 40/60/76% silicon varing top / middle and btm of the bore, then all - iron nitrided, (ELECTRICAL PROCESS) looks the dogs tagums - bright shiny gold in colour, the hardnes is incredible, virtually no wear ? well not measurable after a full GP - has a very low co-efficient of friction. The rind edge is also plated too but, not able to say what with.

so lets stick to Bantam's i did have the inside of an exhaust port coated with particulate, it reduces the heat drawn into the barrel oto the cylinder especiaslly under full throttle/ on the pipe where most of the heat is

Derek

Carl Schmidt had the wife & I to dinner in Chicago ...
Yes Derek, let´s stick to Bantams -- It was The Eric Walsh Bantam and I still cannot find the article where Bill Lomas and Dickie Dale were in Australia racing works Gileras and Bill was persuaded to try the Walsh Bantam. He really enthused over it having beaten 250s, at several race meetings, with Maurice Quincey aboard...
Dreadful looking thing! Really scruffy. Could do with a good clean and lick of paint! No fairing, of course -- people didn´t bother wearing skirts in those days. Had plunger rear springing and -- of all things -- an open megaphone exhaust.
Must find the article because Bill mentioned the flywheel assembly, including a picture.
Cheers!

Trevor a number for you - 175 crank assy 3.8kg.

Humble apologies: I was going to say I had made some "deliberate mistakes" in my comments earlier but that would be a deliberate lie (to let myself off the hook): Bill Lomas & Dickie Dale in Australia were riding Factory, "Works Guzzis" not Gileras... And the ring thickness of the Walsh Bantam was 60thou -- not 16...!
I have a picture of the Eric Walsh Bantam with rear end plunger suspension and megaphone exhaust showing... Another of Bill on the Walsh Bantam with full "Dustbin" fairing (replica Guzzi) and also Bill´s article speaking about the engine details. In the latter it states that this exceptionally quick Bantam had standard stroke & bore, 15:1 compression-ratio and that Eric Walsh reckoned it would rev to 12,000rpm although no rev counter was fitted; the cylinder head was a home-made Walsh, with a squish internal shape and central 14mm plug ....
...
Sort of reads as if a tall story -- standard long stroke revving to 12,000 -- but I had read the same in `Motor Cycling´ & `Motorcycle´ of that era when Bill Lomas was one of my heroes and road-racing was only for the very very brave...
...
Sounds like an exciting weekend just gone -- very envious.
Cheers! .

PS... I meant to add I am trying to sort out my German PC to send those Pics but so far I can´t even find the window that says -- "Send Pics..." or anything to do with pictures....

Whilst on, there is a bit of technical info... you might sneer at, but could -- PERHAPS? -- be tried on a Sprint Bantam. It is the `Exhaust Ejector-Jet´... which I briefly mentioned once before. Its a very simple theory: a duct surrounds the exhaust pipe such that where the pipe has its diffuser the duct diverges (opens out) and then after being parallel for a short distance... converges to a straight portion (much like a magnified shape of the resonant pipe!) which means that when the machine is moving the ram-air rushes into the duct, loses pressure at the divergence to increase its volume which then picks up exhaust-pipe heat to expand and build up pressure as it hits the converging section to then act as a pressure jet at the outlet. Sort of jet engine with no moving parts!!
The theory still works OK for a Stationary engine in that it can be used to draw air accross the cooling fins of air-cooled barrel or water-cooledradiator thus eliminating the need of a fan.
...
I say in Sprint because there´d probably be no place for one of the rider´s legs on a racing Bantam and maybe on a Sprint job the duct could be inveigled in....

...
Someone sniggered!!
Come out whomever you are....

Hi Mike,
Thankyou for that, but by christ that is heavy ! the 186 crank was 2.8 kg and spun like a dream .

regards Trevor

Trevor that 3.8kg crank was D7

D14 is 4.5kg.....

Trevor any numbers ref crank weights??

If you were making a 125bantam motor now how heavy would you make it?

Same as a 6speed honda or heavier?

And if you were making a 175 bantam ??

Getting back to Rossi and his feeling that the Ducati´s Urge comes in too quickly for his liking: and he has been falling off a lot too much for the good of his health lately -- the mechanics ought to secretly make his twist grip slower acting.

With a 4-stroke motor the pistons are lighter than two-stroker´s pistons by virtue of the necessity of the skirt being longer and this extra reciprocating-unbalanced-mass MUST be balanced by the flywheels/crankshaft -- or are geared, external balance shafts being used??

Looking back over this discussion I realize I had caused much deviation from the original topic -- for which I now beg forgiveness...

I didn´t read the article but I take it Rossi was uptight about his Ducati being too snappy, power nil, tweak the throttle still power nill -- then another tweak and suddenly all power rushing in at teh rear wheel....

It was a similar rider complaint Slick expereinced with a Superbike star (not Fogarty as I said before). Slick was only with Mr X for one season and experienced unexpected temperamental outbursts from the normally calm man when Mr X fell off during practice at Brands whilst exitting a bend he normally felt fully confident with . He was using an engine that had been tuned recently by a renowned London tuner . Slick then installed the engine he had tuned and Mr X was most happy after another practice session because he had inproved his lap times --and felt more confident in winding open the throttle in the bends....

On this occasion I happened to be in England and had the great privilege of a few hours with my Son (when I had to treat him to lunch because Mr X´s sponsor had not yet paid Slick, his salary), and the greater privilege still of seeing the power curves of these two engines. Both had almost the same top end power with Slick´s engine being 2bhp down at max... (which was about 1,5% down ...) but with Slick´s tuned moter the torque curve had a hump at 5,500 rpm which `tailored´ neatly into the torque curve up to the 14,000rpm max full-load speed.
Whilst talking about Mr X´s reaction to the `Feel´ of this engine compared with the other engine Slick mentioned that "his engine" had a heavier crank ...

Slick had purposely worked on the intake ports airflow, at mid-speed range, to get the Hump which cost about 2 horspower at the top end ...

I´d not thought of the latter until it popped into my memory just recently with the mention of Rossi and his bother of too lighter crank...

I can certainly understand that when a rider has say, 136horspower -- and MORE -- available and has the feel of PUSH at part throttle in a bend -- which he can increase with a good feeling of total control -- the rider must feel aprehensive when he only gets the same push at an increased throttle opening with the feel and chance of wheelspin flipping him off.

However this garbage I spouted above becomes inconclusive because the bumped-up-torque might have been the reason for improved confidence feel than that of the heavier crank.

And speaking of that, as I see it, I must ask -- would a lighter or heavier crank make much difference on a Bantam...?

And calculations relative this ... ?

Calculation of stored energy from flywheel/crank assy, from say 2,000 to 12,000(?) rpm could tell time taken to go from low to high speed but that leaves out weight of rider plus bike which must come into the calculations -- SURELY??

I´ve tried avoiding this one but it won´t go away. With respect Trevor --shoot me down as you will ... or want... you have just looked at the engine accelerating against some load -- not connected as it were.... What I said earlier I shall try to explain now:-

Firstly, it must be consideresd a system of several, connected (unless the clutch is being slipped) rotating masses: -- crankshaft assy, clutch assy, gears probably negligible and rear wheel definitely acting as a flywheel (see note below about a bicycle wheel).

Secondly, as the question IS of (Rossi´s) handling*** being compared with a Bantam rider -- it is assumed the feel is of a sudden surge of high-speed-power (coming in at too large a throttle opening) rather than that of the "push" feel of high-torque at a lower speed (coming in at a small throttle opening) -- Rider & Bike weight are involved in the comparison of sharp or gradual acceleration....

e.g. A bicycle wheel weighing 2 kg (4.4lbs), with diameter 700mm (27.6") rotating at 150rpm (37mph on the road!) has a stored energy of 30Joules (22.7ftlbs -- I think?)

***there´s a big difference in power, forces and inertias which to my mind almost
makes this thing of handling -- relative power response attributable to crankshaft weight, hardly worthy of comparison -- but that is based on my first Bantam which had about 12hp at 8,400rpm that seems about half of what Mike -- and Mike´s competitors have nowadays so I expect the argument has to go on -- and on -- and on......

So!?
What would the weight of a Bantam rear wheel be?
And Mike and Mike´s bike? -complete with leathesr and crash hat, of course.

At the moment I feel as if I might make an arse of myself but I got this urge to calculate Motion & Inertia of a TYPICAL Racing Bantam being accelerated from low to high speed (clutch engaged) with (a) 96mm dia flywheels and crankshaft assy weighing 2.3kg...
(b) (D7?) ... same dia or 98mmm -- weight 3.8kg and (c) (D14?) ... 98 or 100mmdia and weight 4.5kg....

What is needed to do this job properly are the following:-
1. Typical total bike weight. 2. Rider (helmet, boots & leathers) weight. 3. Clutch weight ... 4. Rear wheel weight... 5. Gear ratios Ist, 2nd & 3rd... typical for any regularly used circuit ....

Could one (or more) of you (keen types) supply the above information -- otherwise I´ll guess at it ....
... like bike 160kg (350lbs) -- Rider 70kg(11stone) C/W race gear (154lbs)

If you´d like me to have a go at this -- last time was for an HGV about 40 years back -- say the words and I´ll give it a whirl ...

But don´t expect too much in a hurry -- if at all (will mean I have made a pigs-arse of the calcs...).

and NB! If I DO cock up the calcs I probably won´t be heard of again on here.

Cheers!

I´d forgotten the rear wheel dia -- I think about 760mm (30")...? Anyone tell me please.

Also if someone who had his engine on a dyno could/would be so kind as to tell what the torque value was at 4 points on the curve: the lowest engine speed and the max full-load speed (at max power) with two more... spaced between -- otherwise I´ll just guess them.

Derek mentioned the clutch at some time, earlier, with his having loaded it somehow -- the clutch does also act as a flywheel: energy storer, so it might
be worthy of consideration in the whole-system assessment of acceleration & inertia -- but it looks to me as if the clutch runs at about a third of the engine speed. What are number of engine & clutch sprocket teeth??

Just got an e-Mail that had this WARNING:

For the Gents:-
The consumption of alcohol may may you think you are whispering when you are not.

For the Ladies:-
The consumption of alcohol may leave you wondering what the hell happened to you bra & panties.
And it may be the drinking of alcohol made you pregnant.
If so read a good book --- in future
Cheers!

PS. If any reader is offended I call back and delete the technical garbage.
JayBee!

Bluddy thing won´t go away --- I tried thinking of politics, religion and another thing I seem to have forgotten about ... but woke up knowing there was something wrong with my bicycle wheel´s (stored energy) quote -- I cribbed it out of a Sports paper...
Just to get the bicycle wheel off my back the 30Joules of stored energy in the 2kg wheel rotating at 150rpm is equivalent of 160Watts which when compared with Trevor´s two crankshafts´ Wattages sits somewhere in between. Point there, is that the engine revs are a lot faster (engine in 1000s and wheel just 150...) hence the higher kinetic energy is in the engine crankshaft -- at higher revs...

I really think the whole bit about the Rossi complaint is more that he had to think of something to say to a journalist and he´d probably had someone give him the idea that the Ducati crankshaft was too light sometime eralier...

Where in my opinion -- just guessing again, of course - ey Derek!? -- it is THe Difference in Torque, the instantaneous energy Push -- at the rear wheel for small to larger throttle openings which was what he was bothered with...

Imagine having a flat torque curve and going faster according to twist grip increased rotation? The electric motor drive is like that. There´d be none of that "Nothing at a `bit of throttle´and a jolting-lot" with more elbow action...

I looked up the Jimmy 175 curves and must ask -- what sort of dyno was that? Looks very much as if there was a heavy SURGE in a flywheel in the dyno during the test runs there!!!??? However, ignoring the torque curve entirely and taking torque values from the power curves the Max torque at 9000rpm of 13lbsft -- and 22horsepower at 9500 (meaning 12.2lbsft with over 11lbsft at 7500rpm) seems really good to me --I´d like to have seen more of the lower end torque readings though... which seems to smack of resonant pipe-efficiency and, for me, is the main thing to put a comparison of Bantam (2-stroke & small engine) with a large 4-stroke energy-pick-up as quite dubious, since the Bantam torque kicks in with the pipes resonant speed which must be larger than anything from the flywheel inertia ... ??? .

Repeat: I´d like to see torque reading at around 2000 to 7000rpm rage?
Particularly for the 125...

Since Rossi was on a big 4-stroke and was probably making excuses for having been so far back plus excusing himself for fetching Casey off and the Bantam is a little two-stroke its rather difficult to make comparisons of the two of them -- but then I am thinking of my time riding Icarus-1 -- my first Bantam racer -- which required a lot of clutch-slip to accelerate out of any bend. I have a permanent deformity*** in my left hand thro´ the method I used -- it´d be 8000 thousand on the clock and feeding in the clutch gently(although in great Road-Rage fever...)
Looking at what you Modern Bantam racers have -- 23horsepower & more... out of a 125 makes, me pewk with envy -- my tuner & mentor reckoned we had about 12 (no dyno testing for us...)hp .

I can imagine Valentino wondering how he might explain his taking out Casey Stoner the way he did -- it was pure animal -- and then remembering Luigi, the lavatory janitor in Milan telling him, "Dat Ducati she enn´ no good yew `ear, Hedgehog!
dee fleewhyles dey enn got no mass..." and Rossi remembering then, that he´d not said his prayers -- and knowing deep inside him, that that was probably the real reason everything went wrong -- knew he couldn´t tell such a thing to a newspaper reporter -- so yeah! its the flywheels fing....

*** --- only joking but the knuckles of my left hand do hurt when compared with the right... Oh! and when racing on the grass I frequently changed gear without the clutch and never -- never-- broke a layshaft.

Cheers,
JayBee -- John-Boy from the county of Essex not yet extinct!
Happy Whitsun all!

I mentioned electric drive earlier with flat torque curve and might have given the wrong impression of smooth drive uptake, which is not true with very high torque electric drives, these require some sort of slipping clutch type of connection -- otherwise driver/passengers get the same shock treatment as Rossi.

Good!
No longer interested...!
And just when I´d made headway wivv der maffs...

Cheers!
JayBee.

Watch out for Big G at Cadwell -- I felt the Force there -- long ago, of course when Bantams went naked. JB.

Hi, John,
Now this could really sensorsed you off !
The example you provide with the bike wheel, i checked the data and ,yes ,you can arrive at a figure of 30j
but only if you model it as a ring. If you assume the wheel to be a thin disc , having a hub and spokes not at the
rim , as clearly they are not, then the calcs come out quite differently. Funny that , any ideas ?

Keep cranking , regards Trevor.