midlands Centre

Great picture Nigel, blown up to a size so that we can see all of the details. That cylinder can flow enough mixture to produce almost 60 crank hp and 16bar bmep. Lovely smooth free flowing radii every where. Perfectly illustrates the point I was trying to make! Area ratio takes a back seat to flow ratio.

However, the precise theory behind the effects of det-buttons escapes me, perhaps significantly they had their place in time, but are not used now? Even more puzzling was that they didn`t feature on all of the pipes on a four cylinder engine.
Seem counter-intuitive to stick a protuberance of that size into a sonic speed, exhaust flow situation? Does it affect the outflow or the return pulse, anyone out there have the answers, I`d love to know?

Trevor

Interesting indeed!

Large pressure probe ... Were they looking at only  exhaust pressure waves or combustion-chamber pressure diagrams as well --  both simultaneously like with a pressure sensor in the combustion chamber? And was the detonation shown on a combustion-pressure versus time diagram because -- as we all know -- inaudible detonation*** is as destructive as audible....

What era was that? I ask because the piezo-electric or piezo-ceramic sensors we used (in early Eighties) could be fitted virtually flat-flush with the inner surface of head & exhaust pipe and not protrude in such a manner. The sensor shown seems large and cumbersome and at a guess I´d say was typical of the Japanese attitude towards auto engineering of the earlier times. More like that   of the Sixties-Seventies when we were all grabbing at new technology. I can recall some `hairy´ contraptions to prove a point for a graduate to produce a highly academic paper rather than some highly skilled. pragmatic technician endeavouring to make a pipe work properly. If that is a pressure sensor then it really is early. It would have been the `Direct pressure-sensitive resistor´ OR `Diaphragm distortion resistance´  type where the stretching or compression of a resistor gives an output signal.    .

***For at least a couple of decades there has been available a `Knock Sensor` which detects -- on the outer surface of cylinder block or head -- `Inaudible Detonation´ going on inside the combustion chamber and coupled with an actuator retards ignition or corrects Air-fuel ratio (if either or both are outside limits). I have since been out of touch with this development so maybe someone out there has experience of this work?  Mercedes did wonders with their Engine Management system which shows clearly in F1 car racing this year.

Or...

...am I missing something in the header pic...?

Cheers!
JayBee.

Derek's Notes from the meeting.

Topics covered with Midlands Bantam Racers Meeting In November.

1) Area of the crown
2) why a 58mm stroke with 116mm rod
3)Blown down
4) Total port area/ effects/ Balanced.
5) %of exh port/ports ? -velocity of charge increases/reductions

Transfers
Angles/Direction into the barrel
two ports against four and five
inner angles-= parallel ! important, for best velocity
choreographed tansfer ports vital
DO WE REALLY NEED BIG TRANSFER PORTS ?

Flat slide carbs
flat slides with reed valves ? need weaker primary jetting
shape of top exhaust port-best time area for a given shape/timing/area.

Water Pumps
water flow round the cylinder/volume of water/flow rate of water
where to water pump readings from.
water Temp 60 deg.

Exhaust port stub - inner outter, and areas,s tapers,the effects on the first defuser taper and length %percentages in the exhaust design, and the common themes from old school designing of pipes to the current day theories.

scavenging
velocity/pressure/temp/time - all related
Reed Volume - changes with time and pressure
reverse flow - inner transfer profile , Coander effect.
length of transfer ports, from spigot to btm of port window, lengths

bore snd stroke configurations and there effects with the above topics on
56x50 - 52x58 - 54x54, 56x58 -64x58
analysis of Gas flow in the transfer ports
Long stroke advantages and disadvantages , torque v piston speed / reliability.
Angle of AIR ferrel colum important
Two Ports should be better than one, but why, because its better to have two different entry angles.

all in that order and as I wrote it down, i have obviously a lot more detail but these are the main topics we all spoke and asked questions about.

let me know if I missed any.

regards Derek

I hope that all of you Midlands Centre guys can enjoy a great Christmas Time and that the New Year can be a good one for you and your families.

Love and peace to you all, Trevor

christmas greetings to all ..... whats the barrel detail all about?

Hi Nigel,
Looks rather like the thinking out loud performed by the BSA race department that Derek was relating to at the meeting and on FB. Intriguing stuff, pity they didn't go further with it!
On the other hand, did Bantams ever even get to qualify for a, serious, race department "look in", have my doubts?
Pity about the illegibility of some dimensions, produces some odd numbers on the calculator so I guess I`m reading it all wrong. Eleanor recons that judging by the quantity of empty wine bottles that are in the re-cycling box the problem lies else where?

Trevor

Yes Trevor, pity about the quality of the drawings... wonder if such a barrel is alive and kicking today. Mmm facebook, dip me toe in now and again

Nigel.
Would be a worthwhile pursuit to track down the barrel, if one was ever made that is, but who could you ask where would you start, I expect Derek might have an idea but he is still "persona non grata" as far as our great leaders are concerned? A forum based and informed quest would therefore be a non starter, pity.

Mmm facebook, I know how you feel, just the occasional nugget amongst the dross!

Trevor

Derek said, George Todd received some bits from Herman who did these barrels for moto cross racers teams, several went around the world, in all 20 castings were produced where they are? Who knows! Anyway they were done only for motocross in mid 50,a.
They were cast at woodland Erdington plant in October 1954, this is the old AEPP or AMAC aeroplane andmotor aluminum casting company. I worked at the same plant, from 1982 to 1994 as a piston engineer, iout of interest I also found the core boxes for the spitfire merlin engine, I often spent hours in my spare" time, as I worked shifts, researching what a pile of wood cores, that would easily have filed a few a train stations wad from from, I even found both steel dies and sand cast cores for the drive side bantam cases also cast at woodlane, it's all been scrapped no there's another long story on what happened to the merlin core boxes. I attempted to save them from the then idiot plant director, former accountant.!!! Anyway back to bantams, the barrels where both cast and machined I got mine from the sample pile always referred to for checks after proof machining and gas/porosity checks. But there is more much more that Bsa redditch where upto that never got out, the is a story told, I'm sure George Todd who new Herman well, could shed more light on.these motocross race bantams and all sorts of.special developments that went on with bantams like a twin cylinder 5 speed 250, and 350, that I know where made by Bsa redditch, because we did the castings as early as 1956?

Eddie, many thanks for the recent posts on behalf of Derek.

Do you know if your last post, concerning the castings, etc, was meant to refer to the earlier, sketchy drawings? If this is the case then the time line seems a long way out of sync. The sketches are for a 62mm bore barrel on 60mm stud centres and is I suspect for the experimental 4 speed scrambler engine of the early 70s. I just can`t see multi transfer ports/ducts being conceived in the mid 50s and not reappearing again for a further 10 years on the Meier designed Enfield GP5 engine.
I have scratched around on the net and in my own books and articles that have references to Meier at BSA but I found no reference to experimental barrels such as these during the period in question? Could have happened, but seems highly improbable!

Trevor

Eddie,
Derek sent me a long e-mail today that covered a lot of the, at times confusing, BSA 50s/60s Bantam related topics. He is also of the opinion that the sketchy drawings are as I surmised, much later. The problem is in so many cases of detective work where there are no contemporaneous notes in existence, solving one mystery throws up half a dozen others?
Fascinating and intriguing doing the research though, at least I find it so!

The great and good of the board rooms of the 60s bike manufactures never saw that the decline in Britain`s motorcycle fortunes was theirs to correct or ignore, guess which they chose?

Trevor

Trevor Amos wrote:

The great and good of the board rooms of the 60s bike manufactures never saw that the decline in Britain`s motorcycle  fortunes was theirs to correct or ignore, guess which they chose?  
 
Trevor

So true Trevor. A 250cc max capacity for learners law was introduced, making a captive small bike market for beginners. What did all our leading manufacturers do ? They chose to stop making small bikes and open the flood gates for the Japanese.

Good Evening All,

As it is the end of the season I have been asked to suggest a Midlands meeting again, its intended to have it at the same pub venue as before. The opinion is for November and currently the venue is available on all the Sundays. Please can people let me know who wants to attend and what dates suit.

Kind Regards

Eddie

Morning Eddie,
That is great news, historically, a terrific day out disseminating Bantam matters amongst like-minded enthusiasts, lots of new stuff to discuss!
I have one possible weekend spoken for during November but that may be negotiable, so I can wait to see what the majority opt for.

Grateful thanks to you and dad for organizing another get-together!

Regards, Trevor

Hey, well done Nigel, with your new found `association` with Frits perhaps you could persuade him to pop into the upcoming Midlands meeting and get him to spill the beans on the Ryger concept? I guess we could keep him in beer and nibbles for the afternoon!

Cheers, Trevor

Trevor.... im gearing up for water cooled "smoker".... but anyone is welcome to my "rotary rodent " Idea.

Hi Ed

whatever the day I will be there.

Mick.

Good Evening All,

We are currently looking at Sunday 29th November, I hope that is acceptable to all so we can get the venue booked.


Kind Regards


Eddie

Sunday the 29th is good for me.

Good Evening All,

Just to confirm that the meeting will be held on Sunday 29th November at The Avenue Pub, Gloucester from noon. If you require any more information please dont hesitate to contact me.

Kind Regards


Eddie

Thank you Ed, relieved the delicate negotiations went favourably. See you all there!

Trevor

Good afternoon,

Just to confirm that the meeting is this Sunday from noon at the avenue pub, Bristol road, Gloucester, Gloucestershire.

Kind Regards


Eddie

What a pleasure it was to meet such an enthusiastic group of "bantamistas" and "50" fans I don't know about you but I really enjoyed the camaraderie and technical talks really learned a lot thank you to Derek for organizing it and Trevor for inviting me as a complete novice.Merry xmas and a successful season to all. Mike

Many thanks to Malcolm and Eddie or setting up another thoroughly enjoyable meeting. Another excellent talk on suspension set ups from Mick Potter and Trevor Amos or his Tech talk regarding the exhaust and its various elements and there use and effect through the engine cycle. Thanks to Derek for inviting more new faces swelling the ranks, good work.