Liquid or gas ?

Of all of the heat produced during combustion in a race Bantam engine , only a small percentage is converted to mechanical energy to propel you around the circuit. The remainder is dissipated through the body of the engine or straight out of the exhaust port, thence to the pipe and atmosphere. That which is shifted by the barrel and head finning is, by definition,
 a challenge to be adequately got rid of with the typical Bantam set up. With fin area remaining a constant, within the confines of individual set ups, the only way to improve cooling is first, by using fuel, and its latent heat of evaporation, adjusting ignition settings or by increasing bulk air flow by judicious directional ducting of cool air, or simply of going faster!
With air being a gas, it is limited in its capacity to conduct heat, and in a lot of applications air makes a very effective insulator, so in order to radiate a lot of heat into the air, race engines require a lot of exposed and uninterrupted fin area, and a high volume of free flowing air passing directly through the fins in order to keep the engine safe.
The, heat is power is heat, mantra has been quoted often enough but it is none the less relevant for that, but being unable to control the one, will compromise the other, but there is a better way! 
What we need is a system containing medium that possesses a higher thermal conductivity, high thermal absorption rate, and higher density . In simple terms, water can absorb more heat and do it faster than air can ever do, and the implications for a higher state of tune , and subsequent heat control are pretty obvious. Add to this that the circulating water will be cooler going in than coming out, the case becomes all the more compelling.
The construction of a water cooled barrel, and I don`t mean smash the fins off and braze a sheet of tin around , is not easy and is time consuming and needs access to some engineering kit but if you want that step change in power with reliability it has to be the way to go !
If you fancy a go the first thing you will require is a basic drawing board and some draughtsman kit , getting it all down on paper, where you can make all the mistakes and then correct with an eraser, will save you knackering things up!

More later ? Trevor

Courtesy & Property Of Trevor Amos.

Many thanks for posting Ed !
                                         This is the George Harris w/c barrel and head that has featured recently on the Forum, it depicts the popular method of constructing a water jacket that of wrapping around a steel sheet and brazing where appropriate . All is pretty well self explanatory and the end result was a very good, reliable engine and could be a model for others to replicate.
An alternative method will come later, just got to dig out all of the note books, sketches and drawings, to say nothing of motivation!

Cheers for now,  Trevor

Courtesy & Property Of Trevor Amos.

Fascinating!
Wish I could start again...

Hello Ed,
Many thanks for posting the drawing and photo, I`ve been out all day so have had no chance to write some explanatory notes,
will do so in due course.

Trevor

The part section drawing is almost self explanatory, and the pic shows the top surfaces of the barrel and in particular the small amount of braze needed to secure the water jacket to the original fins , the bottom fin is similar. The water jacket is a rolled tube, seam welded and produced from 4mm black sheet. The weld was dressed down, the tube was stress relieved and a dolly was slipped inside, upon cooling the tube remained round and in a neutral stress state. With the lower fin sliding inside the tube and the upper locating in the recess at the top
access is available at all times to very precisely match the ports to the jacket outlets for inlet and exhaust. Running braze around small joints when finishing completes water tight joints .
Vertical clamping forces for the actual cylinder head are taken by the original cylinder wall and liner and the water jacket takes the force of the head, water jacket clamping , and any distortion that could occur is almost eliminated. And with the studs remaining close to the cylinder wall twisting and bending brought about by piston/rod action, in rotation direction, is well resisted.
If these views are looked at in conjunction with the pics from " quiet flows " , then a general picture of the construction and general thinking can be built up .
The exhaust duct and reed block passages were both fabricated , with ex duct requiring three dimensional radii and two dimensional tapers,
it was time consuming and damned frustrating, but, if you`re going to these lengths then short cuts only serve negate the whole exercise.
At each stage of machining and welding the whole thing was popped into the oven at 220*c for a couple of hours and cooled overnight .
What you don`t want is to de-stress the barrel at the race circuit, only disaster can come from that !

More again , later ? Trevor

Hi Trevor
just like to say thank you for this and all your contributions, Trevor a splendid job mate, I remember bugging the hell out of you some time ago to contribute, I'm so please I never gave up.

Now just a few quick questions.

I note the shape of the burn on the piston outer edge, and the toncil shape of ? "the third transfer" perhaps?

anyway one main question is you say welding but then detail braze ! just to clarify I assume you are welding all bar the water jacket, what about round the exhaust stub and inlet/reed stubs, ? are these brazed or welded, ? and what type of welding tig/argon/stick and (if stick chrome molly or what ?)

more detail on that radii on the exhaust duct would be just great please, its just a wish list of question of mine

please answer how you feel comfortable "no pressure".

have more good news on that revised pipe design/drawing you sent me thanks, its certainly doing what you said, I can not wait to get this think back on track certainly going in the right direction. P.M you the dyno figures, still not sorted the bits for the new ignition though " no time"!.

don't forget the "more later" bit!

best regards Derek

hi Trevor
another observation i recon the piston is showing signs its just about touching ? talk about running it tight !!!

regards Derek

Evening Derek,
Sorry about the braze /weld confusion, the inlet and exhaust ducts and reed block were made from steel and were of welded construction. These in turn were brazed, using a generous fillet, to the cast iron cylinder and then when I was satisfied with the inside profile these stubs were skimmed to the same diameter as the lower fin . The barrel could then be slipped into the sleeve and the joint between sleeve and stub ports could be brazed. A similar pre-braze prep was made to these joints as with the top and bottom fins, the reed block and exhaust flange were then brazed to the sleeve .
The ex stub duct had to curve down from the port to outlet, it also needs to have curved sides with blending corner radii, easy with a casting but my only option was to hand grind, re-weld, grind again, build up, and continue this process until I had a profile that blended to the port and the oval outlet all the time trying to maintain a constant wall thickness !
I didn`t intend the piston to become a topic, just a focal point for referencing diameters. After saying that, the contrast between clean aluminium and black carbon illustrates the respective transfer port flows, and the high heat point in the piston centre at the combustion chamber proper . With the front of the crown there is only staining, indicating very little short circuiting of transfer charge carbonising at this high heat position.
Whilst I don`t run high comp ratios, I do try and achieve as much turbulence in the combustion chamber, by using as a high squish velocity,
as I can achieve . This will ensure rapid and complete combustion , max output for the modest squeeze ! One way of achieving this is to close the clearance to the least achievable , just occasionally touching occurs!

More later, again ? Trevor

Hi Trevor
Thanks for clarifying the welding process, interestingly you added another snip'it "the maintaining the exhaust stub ? "wall thickness" ! I never new this was so critical, out of interest what steel did you use for this Mild/black plate ? not sure you said this already ! if so I apologize for my lacking to take it all in, I think I may need to re read your posts again,

Trevor yet again some really great information added to Picture and drawings, so much better with content added in this way, these topics allow the inspired/enthusiast to digest what is shown in a picture, ! what a pity we don't have more of this type of meaningful information on similar subjects.

a wonderful Topic with some history too, thank you again.

regards Derek

Excellent post Trevor.. Interesting reading your cylinder has been made simular to the 3
I have, all made by Tom Miller dating from 70s 80s and 00s.. Regards Mike

Derek ,
I used plain mild steel for the ex duct, there is complication enough with cast iron, steel and braze construction and their differing expansion rates, using some exotic material here is just unnecessary . I may use S99 for cranks and EN24t for clutch baskets, but barrels don`t warrant that sophistication .
Maintaining constant wall thickness makes sense, for unequal wall size creates differential expansion rates, and this can lead to fracture through flexure, those insidious cracks that lead to mysterious leaks ! Compounding this is vibration, thin walls vibrate at a high frequency and in turn produce bubbles in the coolant . Heat will not transfer to the water so efficiently and could even locally boil, in an extreme case, and reduce overall heat extraction , which defeats the point of water cooling in the first place.
Thinking about these things and trying to anticipate shortcomings, and at least for me , making drawings and notes helps to get things correct in the first place. In the long run, attention to small but important details always helps to make the power, superficial similarities only run skin deep ?

Cheers, Trevor

evening trevor, are there any pictures looking down inside the barrel with the piston removed?

Hi , Nigel ,
As of this moment there are none , but that could be arranged , do you want the current state, or, as it will be when we go out
again ? But anyway it`s just a load of holes, where`s the attraction in that, bearing in mind that it is unchanged since 2007, it may
take a little time !

Take care , Trevor

trevor, as with most things in life, we gain inspiration from things we see. can you remember what you had seen or were looking at which gave you inspiration  to sit down and decide you needed to design and build your own water cooled barrel? bearing in mind the constraints/problems of producing it in mild steel and not aluminium.Or maybe the reason was purely just to keep the barrel cooler to avoid constant cast iron barrel piston siezures?something which has caused me problems once again.

Evening Nigel,
Influences, experiences and the accumulation of knowledge certain do shape thinking and actions, that is the upside. The downside is that the same can also be a negative if we are confronted by poor or downright incorrect information. The Bantam world is full of the latter, but my long layoff from any contact with racing Bantams, personalities and factions was a great bonus, it enabled fresh, independent thinking !
From starting in the mid 60s I had built the standard, traditional long stoke , the same but with a short 116mm con rod , 54x54 long rod again, 116mm centres, a 56x50 , ditto with water cooling, and, had a hand in other motors including the engines powering Mark to 3 championships. All of these engines won races but all had a breathing limitation, and that I concluded was the fault of the transfer cycle, and the subsequent scavenging and combustion events. So , how to improve the transfer flow, and at the same time cram in adequate time/area with a low port timing that in turn allows sufficient exhaust blowdown to get the job done. The easiest way would be to have a 5th port, and that meant a reed valve inlet . By now a picture was beginning to form , so in 93 , out came the drawing board, I flirted with built up sheet metal trans ducts , but these produced awful shapes so the one piece fully machined jobs were developed and these are to be seen on the forum. Water cooling is the only option the incorporate the large reed duct, complex ex duct and the transfer ducts .
I collected all of the necessary hardware together, rod, piston, reed valve, ignition, carb, gearbox needle rollers, and other bits and pieces and started the drawings and then the machining, welding, milling, grinding, turning, scrapping and starting afresh ! Three years later we hit the track with a winning, record breaking, debut !
I suppose the answer to your question is that what I wanted could not be created in an air cooled barrel, so having the great advantage of water cooling was a bonus that could be factored in. The advantages of reed valve induction made it an obvious inclusion, and is especially suited to Bantams . Additionally, a 54x54 reed valve, water cooled engine was just about the only configuration I hadn`t tackled, and , along the way I drew up details for an exhaust power valve, but as I already had enough on my plate and some sort of deadline , this was deferred for another time !

Bit long winded but gets the reasoning over, I think ? Cheers Trevor

Hi Trevor/Nigel/Mike

this is indeed a great Topic, Mike makes an interesting comment, on all three of his barrels being made in the same way, so was mine and just as powerful  as most, but it self destructed, because of inbuilt problems during this process causing a catastrophe of heat/expansion too much braze/too thin walls, caused by me trying reduce the distortion, my efforts of making new liners and out of thicker only made the problems worse, as it weakend the main/most important part, all down to my lack of knowledge/experience/abilities.

if this topic drawings/comments/ help /support/ with the openness in these postings had been available at that time then I'm sure things may have been different for me, to succeed with my water cooled barrel, I still feel new starters should start with air cooling and we should have banned water cooling !, but hey this does not mean I'm correct, its just my opinion.

Mike
I think the difference, between Trevor's points are clear, "we can see the drawings, the pictures and have a commentary of the reason and thinking behind it, the why's the how's I'm sure we all want to know-why'why'why, not quite had the same about your motor/s, perhaps this topic is a good opportunity.

It takes an exceptional talent to build race and win on a Bantam, but to do it over many years, one can only be envious /respect this.

I'm inspired by all the views in this Topic, even at my age of 52, I look forwards to having more time to perhaps completing my own water cooled cylinder, that's all I want at the moment just a little more time.

Nigel hope your well mate" you still at new street, I'm at Snetterton ready for a glorious weekend of Racing / bit of me time.

Nigel mail me when you get a mo, we have to meet up again, have so much to show you, I've at last had time to finished those barrels showed you, and the mini Motos so been burning the midnight, I'm contemplating grafting my Race Bantam Engine into a MX frame for the years Hanbury Classic scramble pre 65 class, the track is not 200 meters from my home, plan is for me to ride it in September, along with a c15 already pledged ! Im in training and still losing weight Im now a super light weight ! not been this weight since I was 22.  


regards Derek

Courtesy & Property Of Trevor Amos.

Many thanks, once more, to you Ed for so cheerfully doing, what I can`t !

Similarities and differences ?

The w/c head is clearly George Harris`s, superimposed upon it, just on one side, is a reasonable representation of mine. Reference points are the plug thread height and the general diameter . They are similar in that are both cylinder heads for a w/c Bantam engine, but they differ in the rate at which heat can be removed and that is our primary objective . The heat path in the one is very short, and the hot plug sees coolant flowing around it, the implications for racking up the c/r, keeping detto and seizures at bay, with some confidence, are plain to see .
As ever the devil is in detail !

Cheers for now, Trevor

In answer to Derek's questions ref water cooled cylinders that Tom made I don't know if there are
any drawings or what the thinking was behind it? So I can't help there I'm afraid.. but you are right
about how successful they can been 20(17 Bantam) championships in the hands of myself and Pete Styles.

The cylinders all have 4 sheet steel pieces making up the water jacket, the reason they work is because a
really good welder put all the bits together..

A four piece water jacket , now , that seems a very complex method of keeping water in, small wonder a very good welder was needed . My one piece job had to make do with a bumbling amateur----me , to get the job done !
In the event of there being no extant drawings ,Mike, are you allowed to knock up a few sketches with margin notes to illustrate method and thinking? My curiosity is indeed aroused , so many new things to see, always a learning curve where Bantams are concerned .

Cheers, Trevor

Will do Trevor but it will be in a while as busy trying to promote BSA Bantam racing at
1000 Bikes this weekend , then prep for Lydden followed 6 days later with another promo
at the Classic Bike Burn-Up at Cadwell Park.. We need to get the bantam racing Message out there..

My fast barrel is Pete Styles' 3ex 4tr 1in cylinder so dates back to the late 70s so
will be a bit dated, unfortunated it blew up in 2001 and was cast-aside for 8yrs until
Pete Styles said to Tom I think you could liner it, which Tom did it now only features 1ex and isn't quite as fast as it was?

My reed barrel which has been used off and on was originally a 2ex 6tr 1in and piston ported but my dad and I modified it to 4tr and added the reed inlet, and this is the motor I'm using at 1000 bikes. This barrel is a 70s spec but reed valved in 85..

My 00s motor is a work in progress and was produced the year after Ian Scutts motor which fly's .. Mine needs more head scratching as of yet I haven't managed
to get it to really Go...

Courtesy & Property Of Trevor Amos.

Mmmmm, nice pictures trevor, got any that show details with the the head removed, sort of, "down the barrel angle"  ?surely it was a natural progression from barrel with head and then barrel without head scenario, bit like woman with bikini and then woman without bikini kind of thing!!  or as you love to do the drawings first, a port map for this barrel??