Phenomena-Plus

Easter Greetings John ,
You are absolutely spot on to suggest that the success of simulation and cad design depends on accurate , realistic
data being used , and to anyone who embraces this technology , i urge them to check and measure by every means
possible their engine`s vital statistics , and to return , subsequently , to reaffirm the original data .
It`s been said before , garbage in --- garbage squared out !

Just prior to making this post i had a chat with a very accomplished tuner who earns his living preparing
race engines, and doing developement work for customers . He uses sim software for initial research , mods
the engine and /or pipe , ignition and carburation , and then gets on his dyno to confirm his work has been
successfull , or a waste of time ! In short , he knows what he is doing . He consistently finds that from a sim
crankshaft power output figure to dyno rear wheel a reduction of between 12%-15% can be expected , and
it`s his opinion that for a simple Bantam engine , that has been well engineered , that figure is 10%-12% .
So your professor of 1939 was spot on ! !

As to losses of power , QUB may offer an explanation for at least some of it , the original design brief for the
big 500 single engine utilised a separate Seeley gearbox with a chain primary drive . During racing , that chain
was good only for about 100 miles after which it was worn out and stretched . The oil it ran in became so hot
that smoke poured from the breather , after checking the oil temp prof Blair calculated that to do all of this
used up about 6bhp . With the conversion to gear primary drive came an immediate increase of 5bhp and much
reduced power fade , through heat build up during a race !
So it may be not unreasonable to assume similar , potential , losses for a Bantam from it`s chain primary drive ?

Modern software packages , and that means those that benefit from periodic updating , are now , very efficient
tools to assist in engine developement . They have a host of alterable values for ambient air temp , pressure as well
fuel type , octane rating , crankcase temp, barrel temp , air cooling ,water cooling or both , reed material ,and
so it goes on , you can input your own , known , values or rely on the defaults offered
One thing that is not on offer , is the accurate interpretation of the statistics and traces produced , if you don`t understand
what is shown , you`ll have little chance to develope your engine sensibly .

Hope all of that is of some use , off now to pull the cap from another bottle of fine German bier .

Trevor

6bhp !

are you saying if we convert to gear primary drive our engines will delivere 6 hpmore to the rear wheel from the same set up. ?

Derek ,
If a Bantam was pushing out 65 bhp , had massive amounts of torque , had marginal cooling , then yes,
but as it has a small 25 bhp , no you won`t get 6bhp more , but i think you know that anyway ?
However , don`t let that prevent you from doing the convertion , could be quite interesting , or alternatively ,
a belt drive with an air cooled clutch . Ah , too many ideas and not enough time !

Trevor

Hi Trevor

really busy currently trying to get ready for Mallory on the 6bhp "yes I new, but I feel it was important to actually say this. It's a lot of work to convert to gear drive, not sure its worth the effort, especially with the current chains, reliability, and besides like you said the losses are possibly 5 to 8% less losses with a gear than chain-

for your reference its already been done on a bantam, from memory he was the first UK racer to convert to a gear drive, "Mick Nash d'villia", did you ever meet him, ! his bike is still racing or the owner is selling it or about to, "its a cracker".

anyway an air cooled clutch would be interesting, do you think there is material available (carbon perhaps) or somthing more affordable,
that would cope with a typical three speed bantam slipping the clutch.

but it certainly has been done in Australia, but with more gears 5 or 6 on some circuits, my dad has photo's

regards Derek

Mick Nash and primary drive by gears?? Fascinating! but my mind can´t visualise it Derek!

Have a solid back end and make the Final Drive gears big enough and they act like fliywheels?? Have the clutch in the rearwheel hub and then you build up a lot KERs energy in the Flywheel Gears....!!???

Re Trevor´s last suspicious²² ... graph: 6 hp(plus a little bit!) at 5,000 rpm... Interesting aspect from the clutch slipping at the start is that more than 6 horsepower (I know it is...) is transmitted. Makes you think -- don´t it??

If the clutch was not slipped -- say for 4 or 5 seconds -- you´d never get off the line so has there been any SIMULATION Calculations on this relative to 6 (plus a bit) horsepower at 5000rpm??

It´s a long time ago yet I can remember giving the Icarus-1´s twist-grip full elbow -- whilst seeing 8400 rpm³³... on the the rev-counter -- and feeding the clutch in slow.

²² --- only joking young Trevor! I believe everything you say!!

³³ --- that´s known as Ned´s, "Will to win" ... Icarus-1´s motor was quite reliable!!

Cheers!

Derek , or indeed any one else !

Check out " Rave Motorsport Engineering " they advertise BSA Bantam Aramid Friction Plates for the " Allen Performance "
dry clutch conversion ?
Bit of a mystery but i expect the bloodhounds will soon sniff out just what is going on . Could be what you need ?

regards Trevor

for John and Trevor.

Actually my dad did the dry clutch thing, many years back, he did all the casting and machining, I think he still has them, made around 88/89 I'm sure it was a chain drive, anyway like many things he made, never got to the track, but I know he still has the machined castings, cast at home in the back garden, along with a load of other stuff, using some simple tools like a 5 gallons drum, ends cut off, a bag of coke, a vacume cleaner, normal builders sand - pre heated, and some fluxing tablets, I remember one day we had to run as it rained molted aluminum balls, we hid under the bike covers next to the shed, I recon one of the alloy head castings he was melting was porus and had been sitting outside for some time so moisture had got in, when the temp got how enough it litrally exploded. This oftem happened at work at AEPP, the melting/mixing furneses, would often explode with some poor bloke covered in molted aluminium, a frightening experience with 15 to 20 tons of molten aluminimum exploding out of a door 3ft by 3ft this only ever happened on the afternon shift, the ground shook, we always new after a short time if it was a bad one, the calls would come out for first aiders, i was one, but stood down after my first experience of this, so believe me, its not something Im going to remeniss about as a fond memory.

anyway John on the 6bhp not sure I'm following what your suggesting please explore this one!.

Trevor been trying different profiles on the transfer ducts, I just can not believe what differences this makes, what I have noticed is the top edge or direction of the top of the port seems to have a lot of effect on the power and place in the rev range, top end but also it tends to kill the btm end if angled upwards too much, what am I doing wrong here I would like to gain both some juggling /compromise here, and its difficult to reproduce the same results once changed, minor changes here make as big a difference as having no packing and then packing on the inner walls.

So I have 2 questions, i need MORE help here.

1) where should I be concentrating - I am limited to get a really good radius into the std D1 barrel, and if I try to get it too much of nice radii "it tends to narrows the ducts, this really brings the top end power down, I have now tried many different shapes and sizes here, using putty molded on the inner and top edges, so I'm starting to understand the effects it has on the power and sspread, but there is no doubt Volume seems to have a big effect on the top end, and torque, but by working the inner transfer port walls it adversly affects the total power output, so im beginning to think I may have another restriction in the engine or pipe that is stopping us moving forwards and incresing both.

I have generated a great inner profile and whileit does give great torque it also limits the revs, and it just will not rev above 9,200 !!

2) we are begining to thing we should put it back to how it was, with a small mold on the inner walls, and take out the angles on the top edge currently these enter the cylinder square to the bore axis (straight across the top of the piston, so the top edges of the transfers are flat,
my question to you is should we be messing with this, In the aid of increased power with the same level of torque, or it be better to leave it at 9,200 and look to the pipe to make it rev, ?

regards Derek

Hi Derek ,
Just a quickie and i`ll get back to you later , but hey, look at what you`ve learned in a small time frame !
I think it illustrates what we are up against with our home tuning in that the RSA Aprillia in one transfer duct
uses 5 separate radii for the outer wall , ranging from 65--28 , and the inner wall uses 3 , ranging from 30-- 15 ,
the cylinder outlet is quite flat and appears to track the piston crown inclination . So , looking at that we just have
to do the best we can and compromise . It is also worth realising that the outlet port to the cylinder is constantly
altering in area , but the inlet , at the crankcase , remains constant !

Catch you again , Trevor

Courtesy & Property Of Trevor Amos.

Hi All ,
Again , many thanks to Ed for posting the QUB info .

In many ways it`s a pity i wasn`t able to show this earlier , with the annotations explaining what goes where , understanding it
all is a lot easier , but as i have , only this week , discovered it , that would have been difficult !
After saying that , the images must by now have a certain familiarity about them, and bear a striking resemblance to the graphs
both Mick and myself have posted previously .
Back in 1974 the means by which to aquire such information was cutting edge stuff and here we are today , with computer assistance ,
able to exceed what was achieveable then ! The 500 in so many ways is just a big Bantam , so the traces shown should have a certain
resonance when analysing them . Anyway , have a look and see what you come up with .

Cheers for now , Trevor

I said the writer of the example quoted 88%efficiency for "THE TRANSMISSION EFFICIENCY " of his ancient example´s motorcycle and you both jump on the chains as being the horror-story-of-the-month. Many years ago, when BMW were calling on all motorcyclists to heed the wonder of their shaft drive a Hero of the British Empire²²² produced test-work evidence of the chain efficiency being at 98% and the shaft-drive only at 95% -- so let´s not go crazy about gear drive when you look at the arithmetic associated with Primary-and-Rear-Chain´s combined efficiency. It is 98% X 98% = 96.04% which means if the total Transmission Efficiency was at 88% then approx 8% is lost to the gearbox. And by common-sense thinking we can imagine that the gears churning up the oil MUST present more Drag than do both chains.

That latter point applies to Bantam (and Enfield -- & others?) primary chains running in oil also. Must have the oil there, of course, for the slipping clutch ... and Derek has a good point about a dry clutch but how long would it last? Even well-oiled my clutch plates were constantly needing changing.

And, of course, common sense tells us that Total Transmission efficiency in these 73 years since ... must be above 90% ... JayBee was only quoting an example from a book written in 1939!

Elliptical gear teeth ROLL on each other´s flanks so there should be little drag from the gears -- it must be the wild threshing about of the oil that causes the drag. What about a dry gearbox? graphite coated gears -- a really daft idea?????

With your simulation programmes can you get a fix on what the Modern Total Transmission Efficiency should be??

OK OK! So I´ll curl up in the corner again -- yawn!!

Re dry clutches -- they always were on grass-track and road racing in the Godd Old Days -- except when it rained, of course.

²²²-- he was probably a Renolds employee!!

Many yawns & Cheers!

eliptical gears, on aircraft, or in high power trasmissions, as the casing distort underload they come into lline, but sadly not found on a humble bantam no need john.

Just Checking if you were still there and awake Derek.

Deliberate mistake!!!?? "Involute" gear teeth roll on each other -- there should be no sliding friction... OK?

What form are Bantam gear teeth?

Cheers!

For John yes its is early, had to drop wife at the airport this mornning she's off on business to Rome, at ist corporate we have a meal and opeara saturday evening, I will join her later this evening, sadly we do not return till sunday at 1pm, I had to drop her at 4.30am so just came into catch up on paperwork,
and what are you doing up at this time!! you should be in bed man enjoying that retirement.

anyway I think a Bantam is tooth is a 16dp or is it 20dp with a 20 deg pressure angle.

on involute just checking your awake John" lol. some people believed BSA worked in a tolerance to to teeth when the box came under load, it would align inself, this is farsical, and not true, this was the general errors produced from the transfer machine that machined the crank/geabox and housings all in one hit. it suffered with the bronze bushes that located the spindles on the transfer m/c thesen were not properly maintained or eioither of a suitable design, to give consistant capability/repeatability or a kpi or sigma number anywhere near what would be expected in todays world.
the wear in these bushes caused the spindles to move apart and out od square to the faces, causing both alignment errors between the two spindles that drove the cutters for the layshaft and mainshaft bearing holes, they would go in any direction as they wore as a belmouth looks.


Derek

Senility struck at last -- like Geoprge Washington said, I cannot tell a lie -- when I wrote "epicyclic" I thought I was writing "Involute". Thing with the latter is it is SUPPOSED to roll flank upon flank so that there is no tendency for gears to push apart from each other -- a BMW engineer wrote a bit about that not being totally true but I cannot find the article -- was relatively Old Hat anyway in being published about ten years ago.

I realise now in not getting involved with tuning in my `racing days´ I missed an awful lot because as you have said, Derek theré´s a wonderful hive on info... on here but then -- correct me, Sticky Mick if you will -- we didn´t share too much info... in those dark days of `68 to `74 did we?? I remember Colin Alridge wandering the pIts with a vernier guage inside his voluminous Barbour coat (which looked quite hideous with its crotch-piece hanging low...) and chortling to me that he had just measured the Scutt ports `cos Mick had had a scuff and the barrel was off ....

Have a good ride at Mallory -- or wherever it is -- all the best,

Cheers!

John - et al ,
Just dug out my old BSA service sheet 501A , group gear ratios , of May 1965 . Scrawled on it is 16DP / 20pa , giving
a shaft center spacing of 1.475 inches .
If anyone cares to Google " Ivolute Gearing " somewhere there is a very nice animation of the rolling contact between
engaged gear teeth . It`s not an easy concept to visualise but the little video explains all with great clarity !
Gearing is an astonishing , practical application of mathmatical theory , one of the truly masterfull creations we all take
for granted , but know little of !

Bye for now , Trevor

I´d already got the centres-distance from Alan´s Gearbox section which gave it the same -- near enough!! thanks anyway -- and that with what Sticky said about the clutch I assume and estimate the torque conversion generated by slipping the clutch from bike-standstill to fullly-engaged-clutch to be 2.3:1... From your previous graph gives over 60 horsepower -- forgetting all the losses and inefficiencies therein ... -- which must be divided by 2 to give the average horsepower when accelerating from zero as the average power during acceleration.***

Interesting dialogue from Derek just recently methinks he´s taken religion. Sort of puts me in mind of when I accompany my dear missus into her holy place -- just to keep her company I don´t understand a word of what´s going on (latin plus Deutsch) but the words and music really send me...

... I go out on another plane as it were ...

... Dreaming of Brands where I finished 4th in the race and was only 14th in practice or Llandow ... or thinking of the lovely people in my life long ago....

And me a Pagan -- Aaaahhh, just got struck by lightening.

***I full understand if you say you don´t understand me -- many have said it before....

Cheers!

Untouchable JayBee!!

Hi John & Trevore'y

I think i may just get to Mallory with my Bike if all goes well, as all finished here, and yes John the coluseum is something to see and its certainly phenominal.


On the gears, dad rebiult the phouter gear curring machines, that did the main shafts for all the ranges of Trent RB engines, aparently it was explained to me as "if you think a std pressure contact gear is a mastical of mathematical engineering theory "in practice" you should see these forms, they do not align correctly even when spinning at 50,0000 rpm they only align under loads as the shafts distort and bend on take off, aparently they bend so that the load on the gears becomes aligned to where is should be, and yes gears absolutly mysticaly of siimplicity, under normal conditions gears should never wear out, but like you say its a presure roling contact, reality is in aircraft they become fatiged not worn, but my good ness you should see what a gear box main central 3rd or 4th gears out of an F1 Box look like after one race, they are completley knackered. and made from the best materials, mear mortals have never heared of never mind BS specs, these are the same principal.

Gears what a great topic, ! just a moment, sory have to go, she's calling me again I need to go and look as something.

cheers Derek

Hi Trevor, I have taken the liberty of using your horsepower data in "Power Through The Gears" to transpose it into torque and then using gear ratios Sticky Mick showed on here, plus adding 14 x 48 (g/b & R/W sprockets) to show a map of Tractive Effort(and Tractive resistance) versus Road Speed.

I´d made several such graphs -- explaining my notion of TE-TR = force for acceleration plus toque magnification by clutch slip --and just a little while ago tried to send them to Eddie to publish.

Unfortunately -- I think -- only one map went, which I hope did get to Eddie and that he can post it ...

If it is Te-Tr V mph then -- maybe -- it shows something worthy of the telling.

Like Robert Bruce with his bluddy spider I must -- I will -- try again with the other graphs...

Only not today. I am weary....

Cheers!

John-Boy.

Hi JB,

Yes I have got one map graph, I'm on the way back from a job so will post it when I get home.

Eddie

Hi Eddie! Thank you young man -- it is I think, map 2 of "Tractive Effort minus Tractive Resistance" versus "Road Speed" which won´t suffer greatly from not having Map 1 first -- but it is important (I THINK??!!) to have Map 1 as well.

Big thing about these two graphs is that they show just how OPTIMISTIC young Trevor´s publications are -- particularly the "Power Thro´The Gears" of "Phenomena Plus" (or whatever it was) earlier.

Maybe NOT optimistic but REALITY??

Awful thought: to compare the performance of Icarus-1 Bantam with that?

My calcs (which may be arithmetically adrift in places!!??) show that one needs a power-band-spread from approximately 7,000rpm to 11,000 (4krpm???) and a run-on -- or overrun -- of more than a 1,000 rpm*** to get 107mph with an almost unrealistic Tractive Resistance (ie Rolling Resistance plus Air Drag)

NB. Important to remember is that Tractive Effort - Tractive Resistance = force to accelerate -- thus it can be seen that at 107mph the TE = TR and since TE - TR = 0 the bike will go no faster -- ON A FLAT STRAIGHT ROAD, that is!!



*** from full-load speed to maximum run-out (run-on? or Overrun?) speed ....

Cheers!

John-Boy.

Courtesy & Property Of John Bass

There´s an arithmetical error on diagram 1 -- At 61 mph it states the engine speed wrongly -- on the TE (red) curve --as 10,891rpm... It should be 10,545rpm.

10.891rpm is the engine speed at 63mph where the TE (& power) curves turns over at their maximum.

I did ask for gear ratios relative the, "Power Thro´The Gears" diagram and since they weren´t forthcoming I used the ratios Michael Scutt provided and took the liberty of transposing Trevor´s Horsepower values into torque and thence into the TE by the final drive ratios as shown on these maps....

Clear from these diagrams is that the Tractive Effort increases from around 86lbs force at 40mph to 167lbs.f at 60mph -- in first gear (red) and that changing to 2nd gear at BHP peak at 63 mph would be a mistake because the TE would drop from 165 to about 110lb.f which would surely be noticeable in terms of reduced acceleration feel.

But here I would add that very few Bantam power curves -- I have seen -- have such a long overrun from peak power speed as Trevor has shown. Again I query if the "Power Thro´The Gears" is for real or a simulation exercise...

...i.e. On the red curve: 10,891rpm at 63mph to 11,842rpm at 68.5mph!!!

...that´s 861rpm overrun??

It can be seen that gear changes made at the point where the overrun cuts the next gear´s TE curve is advantageous in terms of maintaining the best acceleration possible. Early gear change from 1st to 2nd would mean a drop of nearly half the TE at 60mph and similarly at 77.5mph would mean a drop of a third of from the max TE-TR when in second gear... From around 87mph onward the Tractive Effort dimishes rapidly with speed ....

When TE = TR you cannot go any faster.

Which I know you know by experience.

I do hope these graphs are understandable. Just substituting torque values & gear ratios from other individual Bantam engines would show the level of acceleration possible when Total Weight (rider & bike) are used in conjunction with the TE -TR force.

e.g. From these optimistic graphs we could deduce that a total weight (rider plus bike) of 320 lbs when at 40mph with TE - TR at 86lbs.f would have an acceleration as follows: a = 86/320 X g = 0.269g = 8.654Ft/sec² ...

... and then at 60mph the acceleration would increase to 167/320g = 0.522g = 0.522 x 32.2 = 16.8ft/sec² ...

... WHICH DOES NOT TAKE INTO ACCOUNT THE EFFICIENCY OF THE TRANSMISSION which is probably around 88 - 90% which would knock both down to 7.6ft/sec² -- 7.8ft/sec² and 14.8ft/sec² -- 15.12ft/sec²... Still (in my opinion) very good acceleration.

Well, I think that is enough for now -- perhaps later someone could come up with less optimistic values and repeat this exercise for the rerst of the Bantamites.

Cheers!

Love those graphs JB !

Impressive that you could do all that by hand from a measured power curve graph.

Here's a similar one. The power curve is from a simulation and fed into another program where you can play with the gear change rpm, rider/machine mass, Flywheel and clutch mass and diameter, tyre pressures and a load of other parameters including transmission efficiency.

Some values are guesstimated like the frontal area at 0.4 m^2 and the drag factor of 0.6 which may be a bit high but the results are close to what the bike does in practice.

The vertical spikes on the TE trace are the 0.3 second delay for the gear changes and you can see that holding on to 2nd gear a bit too long increases TE after changing up. Run on is around 800 to 1000 rpm.
Colours a re a bit washed out - not as clear as your graphs !
Mick

Hi Mick 0.3 second delay !!!!!!!!!!!! Mick how fast can you change !!!!! so quickly,

sounds like you have either a sinko Box, or have you one of the new type F1 semi auto boxes with resolvers on the shaft, or as simple as a clutchless change "ouch" my poor gears,

I dont use the clutch at all between upward changes, only downwards, its quicker but somes times have to be gentle between 1st and 2nd.

I find this type of graph boring "sorry" the reason is possibly I dont know what Im surposed to be looking at !.

Mick do you look at the rev counter between changes, I had too much to do trying to avoid running into the back of one of those ducatis or avoiding that id Mike Mc donald who was fyling !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!along on his backside lol

so seriously why should one be looking at this information and what does it tell me.?

you certainly have my ear, so I'm paying attention.

kind regards Derek