The real state of play?

I have always enjoyed history , both as a subject and as a source of perspective. Today is always better viewed with regard to the past.
Today, 2011,is exemplified by the recent release of perfmance figures for a couple of " state of the art " Bantam engines. These values
being 18.6 and 14.9 bhp. Yesterday is represented by the EMC race engine of 1960 with similar capacity and bore and stroke as the two
Bantams. The article , from my archive , shows dyno graphs for bhp, bmep and torque and power output was recorded as 21.3 bhp !
How is it possible , given a time span of 51 years , that this disparity can exist for so long ? The difference in power output may be small
but the available technology of today is collosal , seems we havent progressed at all.
Makes you think , does'nt it .

To be really fair... the EMC was graced with a six speed box!

http://www.motorcyclespecs.co.za/model/Classic%20Racers/emc_125_1960.htm

Alan

Power is produced in the cylinder , not in the gearbox

Very True Trevor,
But the use of a tighter powerband and six gears does have some advantages.
For instance... The james cook bantam the first season he raced was 22 Bhp and had a powerband more suited to six speeds (very peaky), and it came in at the back of the bantam field. After a good "tuning" session then had only 18 Bhp and an enhanced power spread.... It then was good for 5th and 6th placings.
3 speeds requires slightly more thinking when it comes to power delivery.
What would be the state be if the bike had 6 speeds?

Cheers,
Alan

I to like history as well and dose it not tell me the EMC also had disc valve. I do agree with Trevor we should be making more power but as well as three speeds the gear box is fragile and very old (not many good ones about) I think without the restriction of using a BSA Bantam cluster we could build 30 BHP motors. I believe I am right in saying one of the main reasons Gerry Pell stopped racing his Bantam was that he kept having broken gearboxes, and I would guess his made a little over 20-22(I apologise to Gerry If any of this is wrong). The formula was written to make Bantam racing close, cheap, and able to be done without a workshop full of machines. I will also add what a great job was made by those how wrote the formula.

Trevor/Alan/Ted all, I know what you all mean...

Trevor i've raced my current bike for 2 seasons thinking I had 22bhp and was shocked to find last October I only had 18! I'm working on it to get it back to its user un-friendly 22+ !!

I have had 24.5 Reed valver and 23.8 Piston ported in the past.

What power figures did you have on the Mark Carkeek motor? Was it a fast motor or 18ish and a good rider?

I believe Peter T has had 25bhp in the past, and I think he has that now too..... Ian's motor is suppose to have 27bhp...

Look forward to your comments....

Hi all my a/c bike of 2008 was made to produce just over 26 bhp and the new w/c closer to 28. I have not had the chance to find out exact figures on rr as posted previousley figures vary repentant on road and user but I have to agree with ted too much power and the poor old gearbox won't take it

I know the dangers of this at my advanced years but I’ve been thinking again. Am I right in thinking that the EMC figure would have been measured at the crank shaft and ours at the rear wheel on a rolling road?

Hi ted think your missing Alan's point -the EMC had seven then six speeds, in this era?

hope your treatment going not too painful.

kind regards

Derek.

Hi Ted,
I think it is fair to say that one would normally assume that dyno testing in the 50/60s was conducted at the crankshft.
In the case of my , as it turned out, contentious use of the EMC i can again confirm use of the back wheel!
Let me present a little back ground. The event was a press day to illustrate a rare British success, and, the venue
was the de Havilland small engine factory. The author of the article was Phill Irving and it was published in November
1960 in the Motor Cycling magazine.Let me quote from the text, "It must be remembered also that the overall efficiency
of the drive, including as it did two gear reductions, one chain reduction and friction losses etc, could not have been more
than 92% so that power at the crankshaft must have been at least 22.8 bhp with a bmep of 114 psi throughout most of
the power-band". There was however , no mention of a seven speed gear box !
Hope this clarifies things a little.

Trevor i remember a few of your motors:-

1 As raced by Stevie Hall early 80's 50.7x56 piston ported, based closely on an MT125 with a transfer over exhaust and water cooled of course.Mike McDonald86? Mark went on to win the championship on it in 95.
2 Air cooled short stroke Mark used 1996/97 piston ported (not fast)
3 A new 50x56 water-cooled reed valver which Mark used 97/98/99 (no faster than my 24bhp reed valver)


So what sort of Power did you get out of them or did you never put one on a rolling road??

HI Trevor

The officail word is its really great to see you posting regularly, sincerely we need guys like you contributing there are many people looking in who chose not to this is a shame, it takes a while but the efforts Mike and allan and one or two other are starting to creat some interesting subjects I wished others would contribute as you have, I would like to thank you personally for your contribution and please keep them comming.

Now on EMC I was not born until the following spring and as you can tell from my typing and spelling ability, from my posts, I may well have got this wrong, I'm prity sure Iread this but could be wrong, however as my wife continually reminds me Like all men I have a tendency to make the wrong decision, exzaggerate, and talk Ballocks now and then, appart from ted he does it all the time !I'm prity sure we have all been guilty of this at some point or another, I mean have you seen some of the BHP figures been banded around this forum.

I remeber you have such a wealth of knowledge in Bantam racing, and helped me with both encouragement and technical info, you were always so open, and never secretive, it would make things much more interesting if other have done as you have, I'm hoping they will take the plunge, as you have.

Now you have started this so expect questions I have one or two. The more imortant question : -can not wait so dont let me down answer these gems.

1)Who are you helping ? at the moment, ?
2) Are you going to build any more engines ?
3) if you were ? what setup would you go for 125 ? 175? (125 short stroke 54x54 or 50 x 56) 175 cast or alum barrel.
4) I'm currently trying to design a new Exhaust, I have started can you help with this by answering the iitems blow with some guides please see below.
5) also ! I remeber you telling me about your rules for ports openings and sizes, they are such simple rules ports 50/50% exhaust Transfer etc etc etc etc : please elaberate on this for others.
6) can you tell us on the criteria for your exhaust designs, you would chose for your choice of theoretical engine
type as above.
ie
a) large volume or small volume chamber
b) front pipe diameter at exhaust port - 30 / 32 / 34 / 36 / 38 or bigger
c) center section diameter,90/100/110/120 ?
d) carburetor size 30, 32, 34,36/38 or bigger

Thank you again for contributing and posting pleae, keep them comming.

O" and one for Mike - yes I ask a lot of questions, but not always able to answer as Idont know, but I always ask the right questions and the right people, - "don't you think"


best regards Derek

Hi, Mike.
Sorry to have to correct you on your "memories" of my motors.
My involvement in all things Bantam ended in the late 70s with my late wife contracting a fatal illness.
I gave work up to nurse her and care for my young family.
In the mid 80s i re-married and relocated here to Somerset, putting 200 miles between my self and
Steve and Mark. Bantams re - emerged in my life in 93/94 when Steve pursuaded me to do a new motor,
this i, hesitatingly, agreed to , it took me three years to complete.

Any engine puporting to be "mine" in that sixteen year period cannot possibly be attributable to me
i was too engrossed in rebuilding my life !
Transfer over exhaust , that seems a little jumbled , i assume a typographical error ?
Mark did'nt race the old air cooled engine in 97 , it was the new water cooled one and in June of that year
he established a new lap record at Lydden of 48s and where you came in 23s behind, remember!
I have never built a 56/ 50 reed valved, water cooled engine.
What sort of power did i , do i get? Enough to beat the opposition, and, do it consistently.
Had a chat to Mark last night , he sends his regards to you all and to remind you that, when the flag
drops, the bullshit stops !
Hope all that clarifies things a little.

Hi Trevore

" a man as respected as you are, always get people to listen, your views very well recieved, in the light I'm sure they are intended and "most welcome".

Me on the other hand I have many opinion, but can not always share them, I was aware of your expalanation on your past life thanks for sharing that with us, and credit to you, there are people on here posting with similar circumstance, so lets move on. positively it would be great if you answer my question in the previouse post, or just give us your technical thoughts on each item, even if you do it hesitatingly.

now "on my questions" - not just the "exhaust over transfer" your quite correct, a typographical error on my part, well spotted!
but I was 18 at the time and 49 now, i was a very impressionable 18 years old, have i got this completely wrong ? did you not say exhaust should be 50% of stroke transfers 50% exhaust - its this I was refering to.

But Im not affraid of making the odd (well may be a lot of) mistake on here, all your commenet liked disliked, good, bad or indifferent are most welcome, "that official" and this is what htis forum is all about its our voice, to spread the word, now come on answer the rest of my questions, for the new and old people looking in, you woud be surprised at how many there are, and how many are just starting ! most talk off line, in my opinion affraid to comment, just in case some numpty corrects their spelling mistakes, anyway take a look at the post and comment we are all waiting, i'm even holding my breath in antisipation of you sharing the knowldge you have.

kind regards

Derek Betts

Hi, Derek,
Thankyou for your kind words, be assured i'm only too pleased to help in any way i can.
The questions you ask could ammount to a huge post , so be patient it may take some time.
Working now ,as i do ,with RS engines of Steve which show around 44 bhp on the dyno it promps the following question.
Why is it that, as a conseqence of the open cycle dynamic gas flow which opperates with the same sequencing for
Bantams and Hondas, does the RS cram around 130% more fuel/air mixture into it's combustion chamber than ,say ,
Mike's 18 bhp motor does ?
A nice conundrum for you all to ponder on !

Hi Trevor

Really looking forwards to hearing your answers and explanations, now try to make it a little simple remeber we are lay-people.

Great to have you on board. "thank you"

Kind regards Derek

trevor, to produce those figures, sounds like youve managed to intergrate an old girlfriend into the exhaust system. blimey that brings back memories, shiela blewitt!, with lungs like hers she could out perform any expansion chamber.....

Hi Trevor great little Gem please educate us, just had time to think on your conundrum question.,

making a stab at this, could I suggest, its to do with the breathing efficiency / effectivness of the cylinder filling / evacuation and recharging, all I believe influenced by port area / shape of port / direction / transfer flow / and the ability of the exhaust to work effectively to recharge the cylinder after evacuation.


now what did I miss, with my lay persons interpretation, of the evacuation and re-presurisation of the cylinder. ?

notice I never said ignition timing or advance not sure why I never said this. !

regards Derek

Hi Trevor

Thanks for the info , didn't realise the Stevie Hall wc 56x50 and the air-cooled were nothing to do with you. I thought yours connections went back further than they did, assumtion eh - well there you go!

Sorry yes typo should of been - transfer over inlet.

Remember the wc rv and i guess 54x54? very well, was that the debut of that engine at Lydden? In which case quite amazing. Did Mark have lots of gearbox trouble with it or something -assuming again... not at Lydden just generally?

Tell Mark to get on here... and keep in touch... tell him there's race bike parades at Mallory Park Festival of a 1000 bikes 10th July. Quite a few of us bantam racers are going.. Great to see Mark at Cadwell and Lydden last year.

Mike