Avgas

Hi all
I would just like to add that the cost or time it takes for getting avgas is alot less when you compare it to the time spent at the track or in the garage spending time and money on fixing your engine due to seizures what are alot more likey from running normal pump fuel!!! We can all go on about how it was done in the pass but if the hole world was like that we would still be there. If the fuel is out there and is easily accessible why not use it. i spent a hole season seizing and was on the way to giving up so why make matters worse from using pump fuel. to anyone who seriously cannot get hold off avgas then im sure if there asked one off the 18 ish racers that they would be happy enough to collect some for you and take payment at the meeting as mentioned above^^^^
regards michael

Right Michael we should not dwell on the past ...

And you are right about using the best fuel you can ....

... Always!

... we should not dwell on the past -- but we ought to learn from it....

Running on pump petrol would be as bad as going naked Bantam again but if there was a formula that specified both within a formula that limited the cost of that class of Bantam racer to something reasonable --- ??...

... Uh oh! I have said all that before and no one cares for the idea so I´ll crawl away and keep quiet.

So as I read it, there are 18 Bantams actually being raced this year -- or are there more, out there, preparing to get started?

-- And of course, its not just the cost of the bike -- the weekend´s racing costs more than a fortnight holidaying in Spain.

Cheers!

Hi Nigel
I would recommend that you start with a lot lower ignition timing than that.
I set up both our 175cc at 1.5mm btdc 60" we have run THE bantams at 7" Thou and they did run but would not pull a skin off a rice pudding but that was a big cock up on my part but that a another Story   
Start low and work up sure will find it will start holding back about 70"
I have found The best CR for my engines run happy at 60" 8.75to1 with good results
Still more power to come but at what cost?????
Start low and rich and save your engine good luck
and if you need any avgas sure we could help. your not alone with bantam racing theres help you just need to Ask
Robbie

Thanks all for advice Michael,Robbie,John, hoped to go to mallory this afternoon but that window of opportunity has closed. Ill have to curb my excitement for another day  

mike redhead wrote:

Hi I am looking for a bit of help, does anyone know where I can get a regular supply of avgas, unfortunatley my local aerodrome have become a little tetchy about putting avgas in anything other than aircraft, a little pedantic I feel but "rules is rules,"(his words not mine). Dont mind a bit of travelling to collect.

Regards,
Mike.

have you tried glueing wings on it??   

Got 20 litres coming.. Not for bike but for my Micro light..
lol����

that's the way to do it  . would be interesting to know how many current bantam are running avgas ????? I would guess 90% of riders

It might initially appear that including some data about the Todd-Amos 186 might be getting a touch off topic however there is some relevance. The actual capacity is taken from the cylinder geometry of 62mmx62mm which gives 187.2cc; it was George himself that quoted 186 and the title just stuck.

The combustion chamber volume at tdc was measured as 16cc, using the 187.7cc together with 16cc the compression ratio calculates to 12.7:1. For a fast circuit like the old Snetterton the ignition timing was set to 20*(2.36mm) btdc, and on the shorter tracks, that could go to 22*(2.84mm) btdc.
We always tried to gear for 9,500rpm about 3/4 the way down the longest straight, providing that the winds were favourable. The engine was good for 10,000rpm but we always played safe, and power was beginning to fade anyway!

So the puzzle is, if the 187 of 1969 can run with these numbers, on pump gas and Castrol R40, why can`t todays big Bantams do the same?

Trevor

Ethanol I guess is the reason , so called progess has added detergents etc too, bantams now are also 58 stroke and larger 64 piston,I was taking mine at lydden to 11500 rpm just to play it safe!

If you haven´t seen it, you should:-

"The World´s Fastest Indian" is a video about racer Bert Munro who scrounged his way from New Zealand to the Bonneville Salt Flats with his 1915 Indian with which he broke a long-standing record (or recods?)

During scrutineering several oddities came to light including a champagne cork as oil-tank-cap*** and just before setting off on his record breaking runs he popped a pill into his fuel tank. A volunteer helper asked what it was for and Bert laughingly said, "Luck. It is one of my heart trouble pills." I wonder if Nitro-glycerine works in the same way TEL does?

There used to be pills available (at a price) for, "...upping the octane number" that a chap I knew in Devon used in his Spanish bike that had a high CR ....
Probably those pills contained TEL (tetra-ethyl-lead)? Anybody know?

Cheers!

*** reminded of scrutineering (twice) for the Bantam Club when some amazing re-arrangements of kitchen-ware
were seen on the 1000cc Allcomers as well as bantams....

Hi all well in 1969 I was a small ten year old and was taken to my first motorcycle road race meeting at Brands hatch. it was not and till about 1973 I went to the petrol station to buy my first gallon of petrol to put in a C90 to ride over the chalk pits. and then there was the pumps 2star 4star and 5star which were all leaded fuels. Could this be the problem we stopped selling leaded fuel in the uk 1998 so why don't we use unleaded fuel and put a additive in it great Idea. till you read the ACU rules additives in fuel are banned If anyone wants to run unleaded fuel they can. good luck

Hi Dan and Co,
            I hope you don`t rev your big un to 11,500 too many times or you may experience an expensive bang when the rod or gudgeon pin gives way! You will also put the engine into the piston speed realm of GP engines, that rpm corresponds to 22.5 mtrs/sec, the Aprila only goes to 24mtrs/sec at 13,250rpm and that engine enjoyed the finest technology available to stay mechanically safe. Factor in your heavy rod/piston assembly and the forces involved in stopping that lot twice per rev become enormous, and fatigue inducing!
By comparison the 54 stroke engines at 11,500 are only zipping along at 20.7mtrs/sec and the piston/rod combination is far lighter. The piston, ring, pin, clips and small end bearing used in my w/cooled engine weigh 161grams, far less than a 64mm dia; Any chance someone could weigh theirs and let me know, could make for some startling calculations?

Getting back to the fuel business for a moment. Ethanol wasn`t in fuel in 69 and is not in Avgas today,( but it will be eventually), so that is a non-starter. The old 5star we used had lead and reasonably high octane , so not very different from Avgas. Does the puzzle remain?

The curved surface area of my 54mm piston crown is 2309sq/mm, I can`t do the same calc. for a 64mm for don`t have the crown height or radius. Would any one like to offer that data? So for the sake of continuity the flat top option will suffice.
64mm......3217sq/mm
62mm......3019sq/mm    The difference between top and bottom is 927sq/mm.
54mm......2290sq/mm

Interesting is the fact that a full hemisphere from the bore dia has double the surface area of the flat piston. So it become plain that the interplay between surface area and then volume plays a significant part in determining the heat absorption potential of the cylinder head and piston. And that will ultimately determine the safe compression ratio the engine will tolerate before overheating!
In the case of the 186 the longer stroke and shorter rod ensures that the stay of the piston at tdc will be a far shorter TIME period, and that piston will accelerate away far more quickly than the more conventional 58/125 arrangement can ever do. That longer stay incurs extended power robbing, heat absorption time!
Include also that the smaller, more compact combustion chamber of the 186 will have a far more favourable squish area to volume ratio and shorter flame path. All of which adds up to turbulent, efficient and rapid combustion, where heat energy is used for power. The deficit from the one to other is very stark.

Old George knows a thing or two about 2t engines, and he got it right.      

Trevor

Just to close the loop so to speak, I managed to get a decent supply of Avgas,and have continued to source from the same place for the last six years without recourse to letters, or bolting wings on to the bantam, thanks for the suggestion Dan! I have enjoyed reading the balance of the thread and once again Trevor has interjected some thought provoking observations,which keep the forum an interesting place to visit good luck to all Bantomites travelling oop north to race on the cobblestones of Wigan this weekend.

Regards,

Mike

The additives are available -- hundreds of them. "Magic Bullet" as one of them:  With such a name has me doubting its integrity. As Robbie says, ACU banned them -- as they should -- and as the government should have banned their sale on the open market and internet --  and do not -- for some undisclosed reason which we can all guess at... They are mostly in liquid  form and it seems about 2% doping rate -- which is a bit more than the TEL amaount....

BUT MY ADVICE IS TO LEAVE WELL ALONE BECAUSE ALTHOUGH SOME MAY BE GENUINE,  OTHERS MIGHT BE LIKENED TO TAKING ARSENIC TO CURE YOUR Flu.... (Arsenic definitely gets rid of the flu...).

I´d imagine anyone running on unleaded petrol -- even if said to be Premium,  98RON (research octane number) -- would not be entering a Bantam race to win these days . I´d offer that it would be `Just for the ride´ ....

What´s that about cobblestones oop north Mike? I had heard there is a circuit in existence where riders have to avoid the cobblestones but I thought it was in Australia ...

Cheers!

Hi everybody ,sadly avgas not available to every one,local airfield will only sell to registered pilots,of which I am not!
Good luck to those who can get it.
So I have to run on shell v power, it is true I will never win a race ,the boys are far to good ,
So run on what I can get or stay at home,which won't help with grid numbers.
Pump fuel works,maybe not as good as avgas ,but so far no holed pistons no seizures only issue is it wrecks fibreglass ,I guess the answer for me is to get aluminium tank.
Cheers for threads very interesting .Graham

One thing is absolutely for sure Graham , if you want Avgas someone will get it for you! Just ask and arrange it on the forum and it will be provided, then pay on the day. ANY OFFERS FELLAS !
Glad you enjoy the threads, but why don`t you give us some of your experiences or perhaps just ask some questions?

Trevor

Hi all,

I am apparently in an enviable situation, as I can get Avgas from my local airfield which is less than 5 miles away with no questions asked. If any one wishes to supply me with a fuel can then I can fill it when I next fill my cans. But if my understanding is correct a powered Parasail needs to run on Avgas but has no registration number and therefore they have to supply you with fuel, please correct me if I’m incorrect but it must be worth a try.

On the other side of this post on fuels. Pump petrol from the 60’s/70’s/80’s is NOT and I say again NOT the same as what we get out of the pumps today. Way back when, the stuff that came out of pumps was petrol the best I can say of what we get now is that it is fuel.
At work we see quite a few bikes from these times and in there day they ran just fine. In order to get them running cleanly on modern fuel we sometimes have to increase the jet size by up to 50%. This doesn’t account for the ethanol in modern fuel or the differences between winter and summer fuel that also needs a jetting change.

I don’t know what goes on behind closed doors in the EU/UK, GOVERMENT but what I do know from my experience with modern and older bikes is that the quality of pump fuel is vary variable.

My last fact about pump fuel is that when you fill your car/bike/can at a pump, the only thing that is subject to legislation is the amount that is dispensed. There is NO legislation about the quality about what comes out of the pump.

I am not even going to go into the problem of ethanol in fuel on this forum.

Keep it rubber side down.
Mick.

This is probably something you could help with here John, Now that the old grey cells have been prompted to function, I seem to remember way back garages selling Cleveland Discol petrol which as the name implied contained alcohol of some kind. Any ideas on that, could I have used it in the Bantam, and does the time line even fit?

Trevor

To Mick Potter
As Alan Brown keeps telling me you need Avgas,so your kind offer is right up my street. And you have seen the state of my fuel yourself,when we checked it at Lydden .
As I probably live miles away from you ,how about I send you the required amount of cash to buy container and Avgas..
If this is acceptable please E.Mail me at gjn1947se5a@gmail.com
Thanks Mick,

Hi Trevor
Your right about Cleveland discol I ran my Bantams Bultacos and my Maico on said fuel I found by using the same garage all the time and fresh fuel every meeting it was easier to get the carburation right [any fuel left at the end of a meeting went straight in the van]. With regard too modern pump fuel recently I have ridden a ex factory Tr500 Seeley Suzuki as I was only paradeing it I tried pump fuel it detonated every were was told by a ex Suzuki mechanic that they ran them on blue gas which I am told is a military version of avgas meant for Spitfires etc I wound up buying 118octane leaded from Sunoco a bit expensive but couriered too your front door in 25ltrs, it transformed the bike. Another problem with pump fuel some of it doesn't mix well with two stroke Ron Phillips [Fahron] tells me he uses a teaspoon of acetone too stop the oil separating.
Bill.

Graham! it was the case when I was riding Icarus-1, Bantam  --  that with best pump fuel -- at about 95octane -- it was not competitive in the Senior Class events (at an estimated 12hp at 8,400rpm) of that late 60s´ early `70´s era but was reliable enough to earn itelf a few trophies as an Intermediate....

We were lucky in those days that there was an Intermeidiate Class and I did `RACE´ in those events ....

I must admit to a bit of `experimentation´ with fuel with Icarus-2 which could not be called cheating because Icarus-2 suffered terribly from unreliabilty to the extent that it never finished a Senior race.  
.

Yes Trevor, Timeline Fits,  Discol was one of the additives  as was RedeX*** with something that replaces TEL.  
As was (1.5%) Puridin in Track Methanol  for my JAP and 250 Ajay on Grass. I have no idea what these additives are except  Puridin -- I was told was TEL...

I am not sure that straight alcohol (hic hic!!) mixed in with pump petrol was the thing to do because in the fifties-sixties the word went round that it was dangerous to mix petrol with alcohol°°° -- you needed a catylist additive to get them to mix properly. One could imagine an unmixed  gush of alcohol giving a powerful push followed by a slosh of petrol causing a seizure.  Whether that comment°°°  was true or not we used to see a numbere of riders, in the pits, shaking their bikes -- who, if asked -- would immediately say, "Getting the petrol-oil to mix properly..."
Rather a misuse of words there:  hardly a "gush" & a "rush" when the amount in the combustion chamber is smaller than the smallest head of a pin -- probably less than  5m³ per combustion but I think you get the meaning....    


I´d reckon some Bantam riders,  and a lot of other bike racers,  WERE using a mix of alcohol & petrol in the early days of banned TEL (tetra-ethyl-lead) and additives...  

With Icarus-1  Bantam racing it never occurred to me to use a special fuel but sevearl saesons later, when I was on my own with Icarus-2,  I got its motor to rev higher (with unrelaibility) but by then I had Andy Boyle´s 250 to help develope and we only used Premuim petrol in that .... There´s a holed piston on my PC´s tower as evidence that although we got it nearly right, it was not right enough:  the ABS was the fastest 250, on the Norwich Straight  in practice that particular Sunday -- and that after a new needle and doing plug chops with Gardner´s man on the Wednesday at Brand´s....    

***Redex was famous as Upper cylinder-valve lubricant -- after WW2 --  with the added advantage of increased fuel consumption -- which is also a claim for its 21st century  "Òctane Booster" additive.

It´s unethically right -- the government turn a blind eye at the sale of these Octane Booster additives which might be as dodgy as Lead.

Cheers!

Trevor! -- I was looking for photos and came across the Bill Lomas story in Classic Motorcycling Legends where Bill whilst speaking of the Walsh and other Ozzy Racing Bantam he mentions in one sentence, "Some also had a Glow-Plug ..."

With our Canadian diesel we fitted a glow-plug for military test cold-starting at minus 40 and I know one American engine did use something similar in its diesel combustion chamber with very good results re fuel consumption...

I had the feeling that perhaps some of these fast Ozzy Bantams were doing the same whilst using doped alcohol fuels and very high compression ratios. A glow-plug as well as spark plug...?

I wonder if it were the case -- of running a Bantam engine much like the model aircraft engines do it -- which was a well kept secret all these years....?

I mean the Walsh (and a couple of other Aussies) had a megaphone exhaust and ran on methanol which was well before the time of resonant exhaust pipes and were said to rev on-and-on (without a suitable rev-counter, in those days to tell what those revs were...) and one I read about, said he used an ignition cut-out button as well a throttle control during racing because the Bantam revved so high....

When I read that again it sounded nonsense --

--- but is it??? and if a glow-plug did improve things wóuld it be breaking the formula rules?
Cheers!

Glow plugs in Bantam engines are a new one on me, standard of course for my r/c model aircraft engines, both 2 and 4 stroke, when running Methanol. Things get interesting with a 10% nitro-methane mix, that stuff is so potent that normal safe practice is to reduce the compression ratio.

The latent heat of evaporation of methanol is so great that a friend of mine could race his old Greeves for a dozen hard laps and could almost hold a bare hand on the fins afterwards. So cool was the running with methanol, but he had a nasty fire engulf the bike when the fuel was mysteriously ignited. The tragedy was that methanol burns without a visible flame and the fire took hold without him even being aware. It was the heat given off that alerted him, but alas too late.
Like so many chemicals Methanol is very dangerous to health and is very readily absorbed by the skin and can have terrible side effects, be warned!

It would appear from reading several Australian accounts, that enlarging the main jet of a large carb with a 1/8th drill was standard practice!?

Trevor

I did that on my 1927 500cc  Triumph -- upped the compression ratio and drilled the main-jet with a´1/8" drill. It would have been competitive in Vintage races (on Victor Martin Track Fuel) if I had sorted the gear box and fitted foot-change (as allowed) but even then it finished in front of several other Brit bikes including an Inter Norton and a Rudge Ulster at Cadwell....

Fires with methanol...
Had it happen on grass Trevor! You are right and many a bike was incinerated because people didn´t ctach-on that the carb was on fire with methanol....

  My `Gofer´was a young lad whom I couldn´t refuse to help me at grass-track meetings and on one early occasion  he said he´d start and warm  up the 500 JAP before I could tell him...
It was fixed ignition timing and hence when running & bumping it would sometimes kick back and flames shoot   out of the carb... Normal air cleaner was a lady´s stocking stretching from the bell-mouth to a frame member beyong the saddle down-tube. There was a "Kkkraaack!" sound and I saw him spreadeagled over the bike with the piece of stocking rapidly  flaming to nothing. Poor boy was throughly shocked at what I did next. With him still lying across the bike I viciously rotated the rear wheel by hand. Amazingly the engine fired up and ran a few revs on its side. He had not realised the flames were still around the carb and the engine rotation had actually sucked the the fire out.

It was the old grass track & speedway bike, trick-start  -- that the `expert´ would show-off when he had  an audience -- to have the bike propped up and rotate  the back wheel  to start the engine. I saw Alan do it with a Bantam at Cadwell 2 or 3 years back (not showing-off, of course -- probably Alan´s normal way of starting a Bantam...) but a 500cc single cylinder is  a bit different and if it kicks back the shoulder could be pulled out of its socket!!!

I found a lovely bit by Julius Mackerle in, "Air Cooled Automotive Engines" which this Czechoslovakian Engineer wrote in 1961 which describes  a Single cylinder engine test*** he did defining decrease of power output with falling   Octane number....

Din-din´s calling --  for what´s its worth, I´ll write it up later....

***It was normal for all engine testing to start off with a single-cylinder motor to establish a base line for the multi-cylinder version.

Cheers!

Julius Mackerle said on page 237 of "Air-Cooled Automotive Engines":-

"Altering the ignition setting is another way of combating detonation. Not even with fuel of a low octane number  will detonation occurr if the ignition setting is retarded..."

We all know this of course but what we probably don´t know is how much of a difference the octane number makes to the performance ... Mackerle goes on to say:

"The results obtained by laboratory test on a single-cylinder engine with a compression ratio of  7.25:1 running at 1000rpom on full load... " are shown as:-  he shows in graph form which I have numbered here:--

With octane number 98 for 100% output to be reached  the ignition setting must be 23°advanced...
 "      "          "             96 "     99%  ...                                                                18°    "
 "      "          "             93  "     95%  ...                                                               11°    "
 "      "          "             90 "      90% ...                                                                 6.5°  "
 "      "          "             86 "      85 %...                                                                 2.5° "

From that simple test it can be seen that the power output suffers a 15% loss for the difference of what was called Premium petrol at 98octane to a petrol (of the sort, just after the war) of 86 Octane... and that the spread of needed retard from 98 to 86 octane is a massive 20°.  Any attempt to advance the ignition brings detonation (some silent and not `pinking´with the same effects) of destruction...

At that time Aviation fuel had a quoted (garanteed)  octane number of 101-130 which meant it was definitely over 100octane.  Nowadays,  I´d expect it to be closer on its limits.

Not much use to Bantam racers except perhaps to give a genuine FEEL for what octane rating means ...

...I hope!

Note the compression-ratio used for his test was normal for that time. Higher compression-ratios came into being with Premium petrol and no bann on lead which meant car production engines CR jumped to above 10:1 with well leaded petrol of 98octane and more...   and then the bann came and they dropped back to below 8:1

Cheers!