Amos Todd 186

Not wishing to stir it up again -- but that exhaust pipe IS different from the normal run of Kaadan pipes and that, combined with a smooth, central straight port exit .... --- who knows!

George does --I´ll bet!?

STOP PRESS! I just got the message that Derek had sent me a message and I think the above could say it all -- BUT WE`D NEVER BE SURE UNLESS a dyno test was run or `someone´ confirmed that it is not THE PORT ALONE that give a power-advantage it is THE COMBINATION OF PORT-AND-PIPE ....

Ahhhhh--- men!!

Very STRANGE! I suddenly had a glut of PMs -- like they´ve been held up for 2 MONTHS!
Thanks to all who sent them -- I have replied but my PM sending seemed to go to Pot.

Also very WEIRD was that I saw Alan´s reply to Phil Betty about Cadwell results -- which was a page of results showing Cadwell and Mallory. Then -- a couple of days later -- when I went to add something I found the page had vanished. This has happened before and what I think it is -- is this:

If you do not reply to a posting at the time it appears -- or is still there for a while -- when you look it up later it won´t be there. That seems to be because you haven´t involved yourself in that topic.

MAYBE I AM WRONG BUT IT SEEMS TO BE HAPPENING TO ME....

What I wanted to reply to, was the 2012 Results -- was that Nick has got over his 2011 woe of not being on the Pace with Powell & Scutt etc.. etc... So I shall say Good Luck at Snetterton young man and show them it was no fluke at Cadwell...

Go well and keep well,

JayBee -- for John-Boy, never -- ever -- growing up!



Cheers!

Hi John

your not.

These Engines /Barrels are about, although may be better to get them from Ireland as thats were most of a large batch of casting went to a motor cycle dealer in Dublin or may be a dealer by the name of Dublin.

They are 1/4" longer than the trials Barrels and have one more fin, Im not sure why, but Im guessing this was to accomodate the longer stroke of 62mm than a std Bantam, at that time.

other things I have found out about this, other than what Trevor has contributed, where he clearly shows a single exhaust and central, if thats what your talking about, although Im sure like the BTW there is enough scope to do as you please on porting especially if its converted to a 125 cylinder, however I think taking it out and using it for a 186 with a 58 stroke would limit the ports compared to a BTW cylinder that has a lot more metal around both transfers and inlet ports. My research found out the castings were born in the foundry at Redditch factory, I think this was the location of RD and GT was to or did rent a property in Solihull a little north of this, Im sure GT could confirm this. Apparently the site was eventually bulldozed and sold to a house building company, when they built some houses the storey goes the builder found/sold 90 tons yes "90" of scrap metal to a local scrap metal merchant, that he had to dig out the ground to do the foundations, put the program back a bit and in news papers at the time, what a nice find that would be today, especially with the price of metal !.

regards Derek

Right Derek!

...we are not comparing ducks with ducks when we look at the GT barrel installed on a 125 Bantam case...

Is that correct??

The fact remains that it was said a, "... central, straight exhaust port exit gives a `Power Advantage´..." maybe not in those words but so implied that the readers have no other attitude to adopt than that such a barrel is unfair as well as not being ORIGINAL Bantam.

Isn´t there a committee -- or organised group of some sort -- in VMCC & Classic Racing that makes decisions on these situations and who DECIDE ON FACT (pukkha testing) and not on heresay & HOW something appears to be -- `unfaior´....?

In my memory bank is, that only a few years back, objections were made over a deep sump being fitted on a G50 engine. This innovation (to my mind) was not in any way an unfair advantage over others ... and more the safety feature the inventor suggested.

Unless the GT ports and pipe are included I cannot see how this straight, central exhaust port is unfair when attached to a Bantam 125 crankcase with its limited (permitted) ports etc ... etc...

So, like the G50 deep sump isn´t the GT barrel just another "impossible to prove assumption..."? A small weight advantage -- perhaps!?


If you painted it matt-black -- who would know? Get rid of the heat quicker....!!



Cheers!

Hi John

yes you are absolutly correct, there is indeed NO power advantage, until such time there is!!! not sure that makes sence, anyway

Its actuially now finished and been on the dyno, same engine with exactly the same porting as best Ican match, the pipe port timings the only real difference is "its piston ported" currently, my current bike is a reed valver, so much easier to set up than a piston port, so my Iron barrel back on. I have tried as best I can to copy the transfers inner shape always difficult an area that really does give you seat of pants action, anyway after all this hassel with my straigt out and kinked pipe its generating 7hp and 5 ft lbs! for those that suggested it has a power advantage, I wish! - I will load the graphs to prove this, actually I would have thought the same pipe, port timings, comp ratio, acrually slightly higher, etc all exactly the same you would think it would at least be matching what I currently have, rather then delivering 30% of the power, so its back to the Iron Barrel for snetteron with some minor mods, and dad is going to cast a reed block in the back garden with an old 5 gallon drum/coke and a valume cleaner blowing, there is just enough room to get a reed on the back of cylinder by milling away some of the inlet port, as I would at least try and prove /disprove this theory, by making it all the same, time will tell.

John and its not a 125, but was actally an original 186 casting, I' know someone sid this so not sure where this came from, I have actually two cylinders, both were damaged one is scrap the other, I have repaird by welding and dressing I have to say a brilliant job ! "thanks colin" if your looking in, I actually feel this is a similar issue to the, "none exsistent" 4 speed close ratio boxes that are actually still being manufacturered to this day, and being sold.

if anyone wishes to have an Iron cylinder from what I consider an Original "original" Bantam that has a far better exhaust port transfer arrangement, that should be quite legal, should go on German Ebay amazing what you can find for a very resonable price if you just think outside the box.!


Thanks for the comments John, hope I answered yours, I think everyone has switched to face book, or hibernating for christmas.!!!

regards Derek

Right Derek

In engine tuning, I know you know this but I´ll say it for general consumption any road up: What must be remembered is that a small difference can make a big increase or decrease in engine output and two changes, made at the same time, totally confuse the results. I know of a situation where a square corner in an intake port worked better than a smooth radius and it could not be proved why? Other aspects took priority and the testing went elsewhere in that particular engine....

I´ve already stated somewhere here that increased bore-size means increased friction loss. i.e. Pi as 3.142 x the diameter means that an increase in d means an increase in friction attributed to the extra length of piston ring and piston wall area contacting the barrel.

General remark: I know it is boring hearing the same thing over and over again but I have already mentioned somewhere here that the difference of 175 from 125 friction losses attributable to piston ring (of the same tangential and radial stress) perimeter length is 18.4% at only 4,500 rpm so any attempt at comparing output of a 175 with 125 has to take this difference into account -- plus, that for a true comparison the piston area difference also -- otherwise it is comparing a duck-egg with a bantam pullet´s egg....

I´d say your dyno results are worthy of a look Derek and I look forward to seeing them.

I like this method of casting in the back garden -- sort of thing I´d love to be doing, if we had a back garden. As it is I had a (gas-canister) blow lamp leak on me a couple of years back -- on the balcony, melting lead I was... -- and momentarilly I thought of this whole apartment block being ablaze as flames sprang up everyhere the gas leak went. In desperation -- looking this way -- had flames springing up all over the place... Fortunately I had a bucket of water and an old blanket standing there. Holding the blowlamp under water there were still flames leaping about everywhere the gas escaped. So, with one hand holding the blowlamp under I threw the old blanket over the lot with the other hand and solved the problem. Only thing was I had a badly burnt hand (and half of my nose -- which says something??) -- which was agony for a fortnight.

Derek, I hope your Dad has fun with his casting and none of the above....

Cheers!

Hi John
The barrel has been linered to a 54.0mm bore and has approx an 8mm wall thickness actually 53.6mm to be exact, there is a reson for this.

The other point is its not a 175 but a 125cc with a long rod and a 54mm stroke also a reason for this as I intend to check out trevors theory on the long rod verse small rod and blow down, I would really like to know what happens here, so its curently only about 123cc at the moment the only real difference to my current bore at 54.43mm. actually using the same head, crank volume is slightly less to as the transfers are not same, I'm running two as opposed to three transfers on my current cast Iron D1 barrel.

so as I write more you can see there are quite a few differences, other than the cetral port.

Now from the PM i have had "Im prety sure" that the overall consensus is we are ok to use it,

for what its worth I'm prety sure its ok to use any Barrel on a 125 short stroke bantam, no matter what, other than perhaps an aluminium water cooled barrel is certainly not allowed - aprillia or rotax 125 cylinder, I feel this would be pushing the boundaries, but if some one wishes to do it, I would never complain against it as I think the 125cc class should be a bit more open than perhaps the 175 cc class I feel is imperative that we keep this very strickt, for the single purpose of allowing new starters a way of getting into the spirit of racing a Bantam without the need of an engineering degree, or aircraft/ or development background in atomic science, this was the single and only reason I scoffed at the Tom Snow special that in my opinion is one for the specials class, I just made a simple mistake by doing it inappropriatly, "but hey" we are all human, but lets not get into this on again, as its simply an opinion, Im absolutly sure not shared by others.

While we are on the subject of 125cc barrels, whats allowed etc. I have a crankcase reed engine, that Im dying to get some time to take another look at I was hoping to pursuade Trevor Amos to do a barrel for it, but he said no So with a little bit of work could easily take any of the "yam/hond/rotax/aprilia" Barrels and I could certainly race it in the specials class, I will one day possibly graft one of these on, but by doing this to my mind without the nessasary development/tuning as you quite rightly point out would also have lots of potential but that it.

Sadly the days of the cast iron barrel is numbered, because of the direction with fules/bio contents the writing is on the wall I,m affraid, but perhapps we have 15 to 20 years left certainly see me out, I was thinking I could make a comback at 75, certainly trying to get my dad to perade my bantam Ithink it would be a real treat for him especially how its currently performing, John at 86 is my mind still young, you should really consider parading a bike again but this time not in wellingtons or was that someone else, before you know it we are gone, only her for such a small period really, so make the most of it.

Best regards Derek

PS... I took a look at the 175 formula -- 190cc?? and stroke at 58mm??

Must be confusing to the first-time onlooker ... how did that come about?


Cheers!

PPPS -- just got the other message --- Yeah! I thought you were making it a 125...

The Terry Betts fellow --- 86 -- really!!

It was Roy Bacon doing the `81 parade in his short wellies. If I remember aright he was wearing what looked like a poacher´s jacket and I expected him produce a dead rabbit or dead rat from one of the pockets. He headed the `81 Parade and looked really regal....

It was a lovely parade -- marred by only one thing that Ned remembers well.... but Dick Hunter & Bill Lawrence were to blame for my ending up in Norwich hospital....

But back to the 175 that could be 190ccs -- keeping its stroke to 58mm makes it "oversquare" with bore at 62mm (ennitt??) and surely it ought to rev higher than I have been reading of `175´s on here.

Go well & keep well ....

JayBee.

Hi John

yes 86 Terry betts I think he would cough at this he is actually 78 or ios it 79, I would really like to get him out parading my bike, well its about time he done somthing. as Tom sprints, I thought you were 86 may be Im getting you mixed up with GT, anyway spot on John yes a 58mm stroke and a 64mm bore not 62 is allowed in the 175 class, and yes 190cc allowed, the poor gearbox! and primary chain /clutch, mind you its the better availability of pistons good quality that makes all the difference, and REX GAUNT has had his own made Im going to try one they look the buisness being a single ring job, mind you I recon you could be better in the use of the RM pistons at 66mm, still make it under 200 and good for tha 200cc class a number of clubs cater for this now aintree what a circuit, not spoilt yet I went along a few years back now.!

ANYWAY THE SAUSAGES ARE BURNING, and Monty is looking too keen, so Ihave to go attend the Barbie otherwise she will moan when I return to my prep, that I need to finish this afternoon. for next week end.

and John lets not get hung up on anything,! especially age, its like most things a mathematical number, !

Best regards Derek

Humble apologies to Terry -- and it ain´t me what´s 86 -- long way to go yet...!

Never get hung up on age except when it happens as happened recently. An old chap came up to Irmy and I, asking what my age was ... Complete stranger who´d seen Irmgard and I wandering in the woods etc... etc... Sort of felt like saying pee-off mate -- none of your business -- so I said, "Ein-und-swanzig -- twenty-one -- I have had a bluddy hard life."

He didn´t answer and went off in what appeared to be a right-huff.

What I found alarming (at first) was the remark just recently, "Well, what is Bantam in a Racing Bantam these days, then?" and my thought went to 190cc as the capacity of the 175 Bantam. But then I remembered that without that allowance -- allowing other modern bike parts to be used, there´d probably be no 175 Bantams -- so there has to be the questions regarding 125 Formula being exploited and taken well care of ... I see no infringement in your barrel as you´ve explained it -- but horrors upon horrors, 4,500quid ....??

This has reminded of your long rod query... I must look it up -- its a hell of an equation and will help towards keeping the grey-matter from slopping off it gimbals and dribbling into the sump. Just thinking -- sort of romantically about it -- I get the feel that a longer rod gives a a slightly less piston-acceleration and more time for the piston to remain at TDC ... But that is only "FEEL" as it was with a central, straight exhaust port exit -- unless the rest of the system is known then the feel cannot be verified as fact. But along with that is the feel that the rod would have to be a LOT longer for there to be any marked effect.

Something like that. Calcs seem necessary....

Cheers and regards to Young Terry!

4,500 was simply a wind up for those against its use, anyway! I'm sure they new this,

actually it cost me a tenner ? and the other came Free.! but my goodness they never new what it was and, its certainly worth more, putting my finance cap on, I recon £4500.0 is cheap for a fully developed current racing Bantam, no matter what the history,
one reason I keep mine and original.

John really just trying to get my son back ineterested, I was thinking of trying to pursuade him to build one of those "none fairied naked Bantams, a steel wheels, ! number plates, etc, like one of those little items with a fly screen, all in all would look very period.

Call it "ORB" the original racing-on-the-cheap Bantam as dreamed up by Bacon & Benn etc... etc...

We´ve gone thro´its formula before -- long-stroke whilst naked -- uh oh! sounds like another programme -- dunnitt??

Yaaawwwnnn!

Forgot to ask about the length of a Racing Bantam con-rod. 114mm sticks in my mind --

-- but what is the MINIMUM length used? and what is POPULAR length? and what is the POSSIBLE Maximum length?

Thanks!

Cheers!

just revisiting some past posts, was the bsa 186cc engine based on the montesa 175 impala engine which was a square engine, which apparently got montesa out of a sticky patch during the 60s and did really well...

Oh! J... Murphy!

I asked that Q 13 months ago................

I was trying to work out the pause-time at TDC and BDC to come up with a clever question for Trevor -- but somehow the time slipped away with the memory -- I suppose it might have been:  Which is better -- longer pause at TDC, or BDC?

Short pause at tdc gets the crank spinning sooner , rod angularity giving a good push and the piston gets an easier time avoiding excessive heat absorption . longer pause at bdc gives longer transfer port opening to pull gas from the crankcase . Stroke and rod lengths, and their combinations, all play an important part on a Bantam !

Trevor

Good Evening Trevor,

Do you know what the fairing, tank and seat were from?


Kind Regards


Eddie

Evening Ed ,
The tank and front forks came from a Mach 1 Ducati , the front brake is from a more potent Ducati, not certain which, the saddle is a proprietary item from one of the suppliers of the day . The full faring came from the Fi-Glass company, the half faring is a Fred/George job . The steel Ducati tank was later replaced by a lighter one from Fi-Glass .

Hope that helps, Trevor

Good Morning Trevor,

Thank you for that.

Kind Regards


Eddie

Bringing this thread to the top of the pile for George Todd to look at ...

oops...