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 midlands Centre

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Trevor Amos



Number of posts : 860
Registration date : 2010-08-13

PostSubject: Re: midlands Centre   Tue Dec 01, 2015 1:45 am

Best ever Midlands Meeting, best ever crowd of guys!

Special thanks should of course be paid to Malcolm, Eddie and Derek for enabling the whole event to take place, their hard work allowed the rest of us to indulge ourselves. Lots of new faces and every one offered help, advice and anecdotes, and Rob offered to sort my cracked crankcases for me, a kind gesture that will be accepted in due course.

The very welcome addition of the visiting `50` experts gave an added dimension to the normal Bantam topics and considering the distance they all travelled to be at the Avenue we are all doubly grateful. I personally hope those guys will come again to the next meeting, and maybe bring along some of their racing hardware? Getting 13+hp from those tiny engines shows considerable skill and tuning abilities, and earned our respect for their achievements, and we can all learn a lot from them.

Thanks again to Mick Potter who gave the most detailed and enjoyable talk about cutting edge suspension set ups that you are likely to hear anywhere. Accompanying his talk were before and after fork legs demonstrating the message he was conveying, together with detailed hand-around photos of the sequential stages of internal modifications. I recon I learned more in an hour or so from Mick than during the last 20 years, definitely the man to sort out machine handling for you.

Our newcomer Mike was warmly received and then persuaded to dismantle the engine of his delightfully compact Bantam racer for us to have a look at. He seemed to enjoy the whole thing and was offered help and advice from just about everyone there, went home fully enthused and I hope not too bewildered!

To those who, for whatever reason, were unable to make it, there is always next time!

Trevor
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Mick Potter

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Number of posts : 125
Age : 60
Localisation : Cheltenham
Registration date : 2007-06-09

PostSubject: Re: midlands Centre   Wed Dec 02, 2015 6:10 am

Thank you Trevor for your appreciated comments about my talk on suspension set up on Sunday. I do not consider myself to be an expert in suspension theory (that is for those who get paid for it) it’s just information that I have accumulated over 35 years in the motorcycle trade. Most people think suspension is a black art, it is not. You just have to look at it with a logical eye as you do with engines.

Mick.
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Jimmie



Number of posts : 125
Registration date : 2011-07-25

PostSubject: Re: midlands Centre   Thu Dec 03, 2015 6:40 am

Mick's modest comments that he just looks at a problem with a logical eye' reminds me of the late Rex McCandless - he of the featherbed frame design. When asked how he approached problems he said " I always seemed to have an instinctive ability to know what was wrong, and to find a very simple way out of what appeared to be an obscure problem. I can't account for it. I'm just very lucky. I even know when I'm thirsty."

Jim
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john bass

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Number of posts : 1712
Age : 88
Localisation : Bensberg, Germany
Registration date : 2006-12-06

PostSubject: Wünderbar!   Thu Dec 03, 2015 7:30 am

Wonderbar Jimmie!

Rex proved he was instictively a real engineer and not just a title on paper  by making some fanatastic machines which worked excellently on the road and in the air.

He made his own Autogyros which flew well  and knew why they fell out of the sky but the aviation  powers-that-were put a ban on procduction and use  of them until a few years back when the auxilliary drive to the rotor blades was introduced.

If you´ve never flown in an Autogyro you should -- I´d always been convinced that gliding was the real way to fly but the Autogyro has more now. It can just hover and do aerobatics that make you wish you´d never had that big British breakfast or pint of cider....

Cheers

John-Boy
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Jimmie



Number of posts : 125
Registration date : 2011-07-25

PostSubject: Re: midlands Centre   Thu Dec 03, 2015 7:59 am

John you are correct, Rex was a gifted engineer who had a habit of speaking his mind without caring who he annoyed. He told the story of when Harry Ferguson offered him the technical directorship of Harry Ferguson Ltd, he refused as he realised he would have to be a yes-man adding that "we had no problems at all in falling out." He had little interest in business as his mind wanted to be attending to the next problem.

He perfected a design for a brick making kiln in your part of the world (Germany).

file:///C:/Users/Jim/Downloads/US3352605.pdf

If anyone is ever over in Northern Ireland, forget about the Giant's Causeway, instead visit the Ulster Folk and Transport Museum (just outside Belfast) where some of the his work is on display.

Jim
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Trevor Amos



Number of posts : 860
Registration date : 2010-08-13

PostSubject: Re: midlands Centre   Thu Dec 03, 2015 10:36 am



The combination that created a legend! Joe Craig the Norton engine maestro, and Rex MaCandless, creator of the revolutionary and most copied frame of all time, both pose here with the prototype featherbed Manx in the yard of the Norton factory.
It may also be worth considering that the Manx and the Bantam are two of the most most continuously raced British motorcycles of the post war years?

Trevor
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Edward Pickering

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Number of posts : 734
Age : 40
Localisation : Gloucester
Registration date : 2007-02-19

PostSubject: Midland Meeting   Wed Sep 14, 2016 5:47 am

Good Evening all,

Well it's that time of year, we were thinking of having our meeting again at our normal venue. The date we were looking at was Sunday 2nd October.

Let me know peoples thoughts on the date.


Kind Regards


Eddie
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Trevor Amos



Number of posts : 860
Registration date : 2010-08-13

PostSubject: Re: midlands Centre   Wed Sep 14, 2016 8:42 pm

Morning Eddie,
That date is fine for me, but am happy to go along with the majority if an alternative is more favourable. Thank you for using your negotiating skills on our behalf in arranging for us to use the Avenue once more. I`m very much looking forward to seeing old friends again and new faces, it will be a great day!

Regards, Trevor
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Trevor Amos



Number of posts : 860
Registration date : 2010-08-13

PostSubject: Re: midlands Centre   Wed Sep 28, 2016 9:18 am

Hello there,

(1)   Is it important to match exhaust pipe diffuser angles and lengths, thus diameters, to the transfer duct/port geometry?

(2)  Given that they have a whopping 50% capacity advantage over the 125cc engines, why don`t the current 186cc engines, by comparison, perform up to their potential?

(3)  Could the formation of boundary layers in the ducts of small capacity cylinders, eg, 50cc, be an impediment to achieving high output?

(4)  Raising the exhaust port duct floor/port window profile from bdc has produced promising results in other race engines, could this feature be of benefit to our Bantam engines?

(5)  A large case volume is a proven requirement for high bmep, full-house disc valve GP engines, but is this even close to being a positive element in reed valve/piston port engines of modest bmep with the seriously inefficient transfer ducts of the type so frequently found in Bantam cylinders?

(6)  Does the exhaust pipe header bend angle from the barrel relative to the cylinder axis, have any influence on the return pulse plugging action?

(7)  For a race engine running a lower compression ratio, should exhaust pipe wave speed be made higher?

(Cool Scavenge flow (gas exchange) is a three dimensional, unsteady, time limited process that involves the mixing of fresh fluids with impure gas of varying temperatures and density taking place in a constantly changing volume and pressure.
As such it is the most complex and least understood flow process in a two stroke race engine.
By establishing some control over these events can race engine performance improve?

(9)  When revving an engine too high and/or for too long will the piston have departed the scene well before combustion can be completed?

(10)  By their very high revving nature, 13,000rpm upwards, do small displacement reed-valve race engines need to carefully balance reed petal resonant frequency with the inlet duct tuned length and engine rpm?

(11)  As detonation begins at the outer edges of the squish band, should all practical efforts be made to encourage the cooling medium to closely access this area of the cylinder head and barrel?


The above list is a possible agenda for discussion this coming Sunday 2nd at the Avenue pub in Gloucester. Some are left over items from last year but we ran out of time, some are new queries set by others, I hope to expand on question 8 (scavenge flow) with a short chat. I hope that Mick will continue with his enjoyable and expert analysis of frame geometry and suspension and as there are a few of the 50cc guys coming and can bring along some engine stuff, or even a complete bike we can get a deeper appreciation of their speciality. Nigel might be there together with his latest innovative concept engine?

However, if the usual run of events happens we could end up talking about something else entirely! If any of the topics highlighted appeal and/or you can offer some insights I am sure we shall all be very appreciative. In any event it will be a most enjoyable and light hearted afternoon.

Hope you see you all at 12 noon on the 2nd.
Cheers Trevor
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Trevor Amos



Number of posts : 860
Registration date : 2010-08-13

PostSubject: Re: midlands Centre   Tue Oct 04, 2016 9:47 pm

Another Midlands Meeting has come and gone with again, too little time to chat about all the subject matters that are of common interest to us all. The one big regret is that Mick was unable to attend so we sadly missed another instalment of his suspension and frame talk that so impressed last time. However, this provided more opportunity to examine the fascinating world of the 50cc racers. The engine that was on display to examine was a case reed job converted to disc valve, and whilst it is still very much a work in progress, the highly accomplished engineering skills needed to create this little gem greatly impressed us all. To be able to extract 14hp at 13500rpm is very impressive and displays an in depth knowledge of the delicacy and precision needed to work at this relatively small scale, and succeed. I couldn`t help but contrast the lumpy piston from a 64mm bore Bantam in one hand to the delicate almost filigree dimensions of a 40mm race piston from the 50cc engine in the other. The intelligent and methodical way in which these guys approach their dyno development work is carried out is a rare example of best practice!
Eddie even regaled us with his exploits with the fire breathing car he runs and that keeps destroying the exhaust pipes, last year the shock waves pulsing out of the huge silencer pipe shook the delicate building we were in as he blasted out of the car park!?

As always our thanks and sincere gratitude go to Malcolm, Eddie and Derek for doing all of the hard work that enabled us all to have such a fine time, it is so often the case that those who do the most work in the background are not always acknowledged, and I do hope that the `Avenue` was not one of those occasions.

To those who were not there, next time beckons and invites you?

Trevor
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