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john bass

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PostSubject: Depends Les...   Wed May 16, 2012 6:46 am

It depends Les on whether your system has a pressure cap or has a normal-ambient-pressure rad cap. If I remember aright the WC 250 I rode had a 2.5psi pressure cap which meant the temperature could go up to 105°c without the water boiling and it ran at 95°c during racing -- but I have no idea what the Water Cooled Bantam lads are running at or whether they use pressurised rad caps.

Be interesting to find out.

Many air-cooled industrial engines have thermostatically controlled electric fans thus with heftier air-flow the fin surface area can be less than when using fans with no thermostatic control. As stated before this improves combustion efficiency and reduces exhaust pollution as well as improvement to fuel consumption.

Cheers!.
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PostSubject: Re: Ned Head   Wed May 16, 2012 8:33 am

Hi Les

1.5 litres of water so 1.5kg, Temp don't know? When i had a gauge 70/75*C Radiator mounted.
Pump speed approx 4lts a minute. Thermo syphon? bit old hat but if it works for you - Great.
Like your point - how much does JS2 weight?

Regards Mike
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Derek

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PostSubject: Re: Ned Head   Wed May 16, 2012 9:23 am

blimey john (bass) - allow me to Educate you !!! " tut tut have you ever heared of a centrifuge pump a lot less losses than a mechanical pump and far more effective than a electric pump, but the secret is nowing how to set up a cetrifuge - "you Rodney".

les2012 talks a lot of sence

john sendle - dont all them racers use methanol so dont need any finning another Rodney and Betts senior, ?? if i sold a second hand car it would always have one careful owner , where do you think i get it from ??? selling is easy especially, when your selling something you no longer want to some one who has "sucker" on his forrid !!!!!!!!!!!!!!!!. lol

Mike 4ltrs min ? my pump connected to a pipe from a bucket can hit the end on my drive from an accordingly pointed hose from the pump while blipping the throttle i dont believe its only 4 ltres a minute you mean with a flat battery..

best and kind regards to all

Derek


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john bass

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PostSubject: Ooooh Derek!   Wed May 16, 2012 7:37 pm

Ooooh Derek! -- of course I will allow you to educate me.***

How wonderful to have someone so knowledgeable as you volunteering to teach poor Rodney DumbCluck me -- free and bucksheesh!

And I do like that method of measuring the flow of a water pump. Very simple and low cost. A bucket, stop watch and a back yard...!!

Yes, I did hear of the concentric water pump ---

--- it all comes back now you have jogged my memory (actually the missus said the other day I was definitely in need of a brain transplant. Now we await a donor...). It was at Dunton on the Ford York development engine programme that I heard that the (new in 1967) concentric water pump would not lift its cooling water on the dyno test beds and I had to rapidly get back-up Worthington Simpson water pumps for every York engine on our Dunto dyno test.

.... I just wonder how I managed to get thro´ 50 years of Auto & Mechanical Engineering developments and problems (similar to the concentic pump problem) WITHOUT YOU?

***perhaps you´d begin by explaining why the NED Head fins are NOT long enough -- or was it, tall enough -- see! I do really need that transplant!

Cluck Cluck Cheers!

RD -- Rodney DumbCluck the First.
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les2012



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PostSubject: ned head   Thu May 17, 2012 12:41 am

Hi Mike,
Many thanks for the info, having no experience with pump systems it's all new to me but I think I'll leave well alone until I learn
more,thanks again.

Now with regards the weight of JS2 I still have to get another set of bathroom scales one for each wheel ect, all I can say is it's
ruddy heavy or seems so when loading and I've already shed one and a half stone of it so what it's weight was before I'll never
know or maybe it's since I had my hair cut.

Thanks JB for your interest, I don't know what cap it is, now that you have bought it to my attention I will have a looksee.

Regards,

Les.
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Derek

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PostSubject: Re: Ned Head   Thu May 17, 2012 1:17 am

john bass wrote:
FACT: In a fairly well tuned IC engine *** roughly a third of Heat Energy available from the fuel goes into making power at the crankshaft, roughly a third goes to friction and mechanical losses and a third is "wasted" on necessary cooling.
...!

So, the amount of power that gets to your rear wheel on full elbow !!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!- -

Please every one dont read this while I educate John.
1) i - every one knows you use your wrist not your elbow - to open the throttle !!!!!!
2) stop watches are good for clocking the grand children at the local fate.
3) light-load on road vehicles - you mean average ! Or have you forgotten I will give you a chance as it must have been a long time.
4) you should know better - asit was you who said "The old saying clangs so very true: "...she was going really well --- just before she seized."
5) I bet you dont even know how many apples in pound, do you !
6) most family saloon cars are at about 16% !!! - myu God john - how long have you been in the automotive industry, things have really progresse in the last 98 years havent they. !!


kind regards Derek


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john bass

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PostSubject: Thank you Derek...   Thu May 17, 2012 4:39 am

Thank you Derek for the first lesson... In reply I can only say this:-

1. "Full Elbow" I must admit is an Old Hat expression that the grass track and Speedway racers used. With quick-action twist grip the elbow did not move far -- there being "Zero & Full Elbow!" Full Elbow did mean Full Throttle.

2. I don´t know much about grandkids... My two children are business orientated.

3. No I do not mean "average" when I say "light load" or "no load". I mean the engine at any speed between its max and idling speed is pulling a small amount of torque or no torque. It is a matter of semantics belonging to one of my many expertises -- that of Automobile Engineering.

4. Point being made here is that to get the optimum performance from an engine the combustion chamber has to be at the optimum temperature for complete combustion. Too much cooling and the combustion is incomplete. Many engine companys .. the ones I worked for included -- tried ceramic coated piston crown and combustion chamber (in the piston) but that innovation lacked reliability. Possibly would last long enough for a weekend Bantam racing.

5. 4 apples. That ´s if they are of Eu/Ec regulated size. But you must NOT say pound Derek, when buying apples. That is illegal -- they are sold in kilograms.

6. Why do you think there has been so much fuss over fuel consumption since the late 60s??

Just try doing the arithmetic. Thermal efficiency of a modern IC engine with 8.0 to 8.5 compression ratio is around 55% (refer to a graph I showed earlier), volumetric efficiency is about 70% and mechanical eficiency is also about 70%.

So we have 55% X 70% X 70% = 27% before the vehicle gets on the road. The cyclic Load Factor (wind, air-drag & hills etc...) and trip Duty Cycle (city traffic or motorways) are both varying during any trip which means the amount of time the engine is running at its best fuel consumption speed is only a fraction of its total trip running time. Which means 16% for many a family saloon is NOT an exaggerated figure. I obtained this fact (16%) from TÜV (German MoT here) about 15 years ago when being involved in an Automotive Engineering semina.

Why don´t you try some of the arithmetic and see for yourself? Or rather use one of your simulation programmes which will do the calculating for you. Say, using an iso-ctane which has a calorrific value of 10,620 kilocalories/kg...

Added on 21st May: -- IF the conversion from heat energy to mechanical energy was PERFECT then 1 kg of the above fuel would give 1,890horsepower. A well tuned Bantam is consuming about 39 to 43 grammes of fuel to produce 25horsepower at the rear wheel because its conversion is NOT perfect.

Hey Derek! I saw you finished in 4 races -- in good postions too. Well done! Whatever happened to the dreadful adversary??

Cheers!
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Edward Pickering

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PostSubject: Re: Ned Head   Sun May 19, 2013 3:05 am

Good Afternoon Trevor/Ned,

Is this what you were looking for?

Kind Regards


Eddie
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Trevor Amos



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PostSubject: Re: Ned Head   Sun May 19, 2013 8:44 am

Grateful thanks for your investigative efforts Ed !.
I have passed on pics of the head to a couple of contacts of mine for their opinions . One has a masters degree in mech engineering and is employed in the aero space world and the other is a free lance aerodynamicist , have done work for McLaren in their wind tunnel . Any opinions they may have could be enlightening and mutually beneficial .

Cheers for now , trevor
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PostSubject: Re: Ned Head   Sun May 19, 2013 11:20 pm

Hi trevor

im very interested to hear/see their opinion on this, as I have been doing some work in this area, recently as trying to avoid having to go the water cooled route, I have some experience/knowledge in this field, and I used a Ned head for many years "they work", however the fin area & thickness is based on what!. George Todd used a tech paper when he designed and made the GT heads,

But why are they so different to each other, both are based on the same formula, and perhaps more details of the radii detail on the technical paper, or just sound technical assuptions/thinking, this paper was forwarded to me recently it covers fins/ribs in alloy castings and fillet radi. I'm sure I loaded them on here somewhere, anyway heat traverses a path different along the base fine than is does the outter fins that are in reality ineffective compared to the base fin for cooling (air cooled), Radial fin heads are said to work far more effectivly, and perhaps why so many of the 70's MX single's had radial fin heads, yam/MZ/MACO/ and a lot of Go kart race engines -BM/Parilla/Hewland. I feel its better to evaquate heat from that all important area, the central section, and how it feeds the other fins than air flow the important but its always the fin area
that will better affect the ability of the head to take heat, Interestingly looking at a GT head its fins are taller than the Ned type, so it has greater surface area than a Ned head but why ? .

dont forget the front pipe information and help Trevor.

regards Derek
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PostSubject: Re: Ned Head   Thu May 23, 2013 8:19 pm

Courtesy & Property Of Trevor Amos

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PostSubject: Re: Ned Head   Fri May 24, 2013 12:52 am

The Trev Head !

With water cooling so much more efficient than air , it would seem obvious to incorporate the benefits where ever possible . As messing with the BTW barrel is limited , at least the head can be seen as a blank canvass and this head is perfect for the job . Indeed , the head is away at the moment having the actual inlet/outlets made and shrunk in , the picture reveals just a mock up , a bit of thinking out loud if you will ! An automotive oil cooler will do service as a small radiator, and an electric pump provides circulation . The internal water passage has a cast in baffle that forces water to do a complete circuit of the head in order to escape at the rear , so there are no stagnant areas where cooling can be compromised . Extra top fin and cylinder cooling is catered for by extending the gasket face to seal the open water chambers , from the original engine . The boss on the side of the head is for a temperature gauge , and the electronic gizmo , with it`s jumble of wires is a multi speed switch for the water pump so if things get bit warm the pump can push water around a bit more . The heat sink is interesting with its deep finning and 8mm pitches , maximising area whilst allowing minimum interruption of cooling air flow to get rid of excess heat .
Finally , for those that like abstract numbers , the original head is 1.5lbs heavier than this alternative , so the total package will incur little weight penalty !
Aesthetically it won`t win any prizes , but that for me is unimportant , functionality is !

Thanks , once more to Ed for all of his help . Trevor
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PostSubject: Re: Ned Head   Fri May 24, 2013 1:57 am

interesting, any reason not to water cool the barrel too? or just too much work for little gain?

i'd like a brian barrel, hoping to be testing soon, i have fuel now and need to sort and find a carb that works for me , will be off to the isle of man this saturday for 14 days, once back i'll be getting on with it , lydden is fast looming .
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PostSubject: The comments on this subject were interesting...   Sat May 25, 2013 7:04 am

Hi Dansofield550! I reckon the barrel is more imoportant than the head to water cool because óf barrel distortion. I think if the hot water gets directed in the right directions it could be of more advantage than providing adequate cooling to the head...

Hopefully this will bring explantaions of WC-Head and AC-Barrel...

Cheers!
JayBee


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john bass

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PostSubject: The comments on this subject were interesting...   Sat May 25, 2013 7:05 am

The comments on this subject are interesting because the ´Ned Head´ and Trevor´s Head are wonderful imnnovations -- among thousands -- to the Bantam scene and I look forward to reading more from Trevor´s academic-aero buddies.

Derek sounded a bit as if he were wandering in the deserted wilderness of conflicting theories on which is better -- (More Efficient, I think the term was) -- AC or WC ? which starts with the fundamental question of HOW MUCH cooling do you need in a hard working engine? The more power an engine the hotter it will become and to avoid catastophe the need is there for more cooling--- The "Air Standard Efficiency" -- or `Thermal Efficiency´ -- curve, based on the compression ratio tells us that increase of CR means increased thermal efficiency but this is theoretically assuming complet combustion of air (with fuel, of course, at the stoichimetric correctness) with the combustion pressure characteristic over its period being conducive to con-rod angle. i.e. Ideal would be an increasing pressure at the end of combustion where the big-end will get more torque-push from the piston. Dope fuels tend to give a lower max-pressure with a longer time period of being at a relative high pressure during teh whole of combustion. Wheras with low-octane petrols the combustion-pressure curve is completely opposite, with the max pressure being a virtual spike....

Whoops! I got carried away there ...

Back to cooling:-

You are not alone, Derek. An engine can run too hot for other reasons than incorrect cooling and we all know that wrong ignition timing and carburration go a long way in this factor but ---

--- but if an engine is overrcooled its thermal efficiency drops...

So how much we need in cooling must surely be the crux of this matter. I spent ten years with an aircooled-díesel engine´s R&D telling people that
Air-Cooling is more efficíent than Water-Cooling because it is DIRECT cooling -- and water-cooling is INDIRECT cooling. AC is heat transfer through metal to air and WC is heat transfer from engine metal to water and water to air.

The big thing about water-cooling is that if properly designed it can be more efficient in getting the cool water to the hotest places fírst so that the then warm water is directed to the lower temperature areas and the temperature of the engine components becomes as near to constant as possible.

A similar thing with cowlings (around the outside of the fins) and fin-shaping can be achieved with water-cooling and Mackerle in "Air Cooled Automobile Engines" gives a lot of emprical ( based on observation of tests) tables showing that high performance AC petrol or diesel engines still need a fan but the AC fan horsepower is a 1/3 to a 1/4 of the WC needs (which is the big argument of air-cooling being direct cooling.)

Acceleration versus acceleraion is what racing is about. As the Bantam engine is getting to its max power in the lower gears its cooling air speed will be relatively slow compared with say when its speed is at 90-95mph. This tells us that the finning surface area of an AC engine at the slower speeds is either too much at the slower road speeds and right for max speed or maybe not enough for top speed but adequate for the slower times.

How do we measure these aspects? And are those periods of acceleration too short to give much thought to....??

In modern WC car engines the cooling fan comes on when the engine gets above a given temperature so that the cooling is adequate at all road going conditions.

The AC Bantams don´t have that -- and neither do the WC Bantams -- ? How could that be coped with -- without using power to drive a fan?

There are a lot wonderful formulae in Mackerle as in many books on the theory and I am sure I would spend a lot of time producing something that would be quite useless to would-be Bantam tuners if I got stuck into this but I´d rather wait and see what the aero engineers say....

Well, take for instance the first consideration in dessigning the AC fins cooling area needed -- you need to know the power being produced along with the AIR-SPEED (when this power is made) thro´the fins , their shape with pressure-drop (Bernoulli effect...) the fin material (staggered & intermittent copper-fins on a steel barrel arrangement has a 3 times better heat transfer efficiency than machined-steel fins on its parent barrel ...) the total fin-area and some other things I seem to have forgot....

Before I close -- Just one thing Mackerle states in a table for "Minimum Cooling Input for a 100bhp Engine" in which he compares AC, Air-cooling with WC Water Cooling:-
He states `Heat required by cooling 0.6hp kcal/hour as 38,000 for both with with "q" as heat transfer at 80mph of 100kcal/m²hC°... which shówed a temperature gradient of 60c° for AC and 160 c° for WC....
Which meant the surface fin surface area reqired was 2.38m² for AC and 6.33m² for WC....

Now that does not tell us why water-cooled Bantams appear to be more successful than their air-cooled brothers but are we comparing Duck eggs with Bantam eggs? Has the WC engine ´got less barrel distortion than teh air-cooled and getting down to really basic were the WC machines better tyre-shod, better handlers and a thousand other things not included here?
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PostSubject: Re: Ned Head   Sat May 25, 2013 7:43 am


Not sure wc is better, after all nick was the champion last year on his air cooled 125. I like the idea of air cooled with the weight savings and simpler build and repair, the Ned head looks a little like an ajs type but bigger

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PostSubject: Re: Ned Head   Sat May 25, 2013 12:04 pm

john bass wrote:
I spent ten years with an aircooled-díesel engine´s R&D telling people that
Air-Cooling is more efficíent than Water-Cooling because it is DIRECT cooling -- and water-cooling is INDIRECT cooling. AC is heat transfer through metal to air and WC is heat transfer from engine metal to water and water to air.

Being pedantic John if the rad is metal W/C is - metal to water, water to metal, metal to air Laughing

This talk of thermal effects reminds me of some of the crazy topics we discussed while tinkering with our mounts. We never talked about the things the average guys did like football and girls. On one occasion after noting how quick our coffee had gone cold that Mary had supplied, Mick ,Tom and myself decided cups were designed AAF with the widest part and surface area exposed to the ambient air. We concluded that cups should be wider at the base with a small aperture at the top. Pete would rarely join in with the conversation preferring to raise his welding mask and give the odd wry smile indicating he thought we needed a nut nurse.
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PostSubject: Re: Ned Head   Sat May 25, 2013 6:11 pm

John Bass :- I found your last delivery absolutely fascinating, I actually enjoyed reading it, found once I started, I could not stop reading it, quite a book of information you are, lets have more of that type posts please.

Ned makes an interesting point, but my prognosis is a cup should have removable tops that screwed on, and a sliding slot opener in the top to allow you to drink out of, this would hold the heat longer, and save on the environment as my tea always goes cold before I remember to drink it,


Derek

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PostSubject: Be pedantic Ned, it is appealing...   Mon May 27, 2013 6:25 am

Thank-you Derek but you should not encourage me...
Ned!
You can get cups made of a material that transfer heat more slowly than porcelain... They are black....

Whoops! I just used an illegal word.... White is good but Black absorbs heat and transfer it more slowly than white...

If you have a water-pump, a pressurised rad-cap and a Fan you can do wonders with water-cooling. It must be remembered that the pump and the fan subtract a bit of your hard-won power....--- I´d say that if in my old (air-cooled-diesel engine) company days I was heard to make such a statement I would have to present the Elitists with a development program: manpower required, the timing, a critical-path-analysis and a costing. Off the top of my head -- as things were in R&D in the Eighties -- it would have been a minimum of ten qualified enegineers, 3 to 4 years and 3/4million Euro... with the critical path dependant on suppliers and skilled people in the back ground ... It is really amazing what some of you Bantam racers do -- and have achieved engineering-wise ...
First would be the gathering of information. Such, needs a lot of costly instrumentation and testing to establish where the Cooling Needs are and then the correlated dyno testing can begin. As I said before `over-cooling´ wastes power. The operating speed range of any road vehicle is very wide and although the Bantam `on-the-pipe´ might only have a 2,000 -- 3000rpm useable power-band it still means a lot of different loadings on the engine and a fantastic variation to the range of engine temperatures during this time. The `ideal´is to keep the engine temperature constant...

Nick´s ex Peter Tibbitts Bantam is fantastic. You (I mean all you Bantam racers) keep talking about Max Power and what you ought to be thinking about is "Max Power with a good torque curve". I think Peter went for that. This has been said before: Sometimes it is worthwhile to have slightly less max-power in favour of having a good torque courve. Like I said Racing is about acceleration but it is also about "Keeping the speed on through the bends" and if the tractive-effort is not there the speed will surely decrease... A little extra push at the back wheel when rounding and exitting a bend is also a morale-booster. I always thought it necessary to drive thro´the apex of a bend rather than `freewheel´ -- but then, I was nevera REAL road-racer.

CheerS!
JayBee.

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PostSubject: Re: Ned Head   Thu May 30, 2013 4:01 am

Hi john

I can not imagine how difficult a Bantam would be to ride, with only 2000 rpm rev range, or 3000 !!!! for some one in the order of 12 stone plus!!.

I struggle when the rev range was below 3600, my current bike is wonderful, we now have it pulling strong from about 5800 to jut over 10,000rpm, no real change to its deliver between theses values, due to a good torque value between these points, we have almost a flat curve, but vertical lines either side of these values, I would like a slightly more angled torque line onto the power curve, as I think this hinders my ability to get off the line at the start of a race, but being 3 or 4 stone heavier than most is not helping.!

its been said its almost entirely to do with the Pipe an or reeds, plans are to try a few things to improve these particular areas.

Derek
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PostSubject: Derek ?   Thu May 30, 2013 5:14 am

Those figures sound like a 250 of the mid sixties Derek. Twice the usseable power range of Icarus-I!

Uh Oh! I´m editting this because I just realised I´d ignored your comment on being a bit heavier than the "faster Bantam riders off the line"
3 o 4 stone heavier... excludes any rider taht much heavier from getting off the line quickly with a Bantam. It is simple physics with the maths as have been stated many times before: accelerating Force F = ma, where `m´ is the total mass of motorcycle and rider and `a´ is the acceleration. Thus with `a´ equalling `F´ divided by `m´ (a = F/m) the heavier m becomes so the lower the pushing F becomes.
A real F-up as you might say, when nature bore you as a rugger forward. Even a Rugger 3/4 at 12st7lbs would be diadvantaged on a Bantam.

"2000 to 3000rpm USEFUL POWER RANGE "-- and struggling to make 12st7lbs entirely naked in the nud ....yes it was NOT competitive to ride Icarus-1 that had only 2,500 rpm USEFUL POWER RANGE, with a peak at 8.400rpm. Non-competetitive except when it rained: then the others slowed down and the weight helped to keep everything stable...

I often wondered why I tried to `race´ Bantam -- 3 gears, no guts and only accelerating when the clutch was slipped, before the 250 ABS, that is, something else -- which could be called racing ....

Could raise some hagkles ---???
I realise NOW that like many of the happenings of my life Bantam Racing came about by accident .... A most unusual -- almost abnormnal -- experience. Like banging one´s head against a wall and wondering why others did it and enjoyed it so much and then one day having it all come together and discovering the wonder and fun of it... NOW -- only a couple of words on a little pot to bring it all flooding back.

Remembering 250 Racing is to be 3rd and 4th each lap with John Senior on his Greeves Silverstone. We were 2nd and 1st Brit Bikes home and he showed his wicked, low-cunning by doing me on the last corner... Half a wheel in it though.

Aaah! The wonder of that. Pity I left england for more money and status -- which was anothe boring accidental happening in my life.

Yaawwwwnnn! Snnnnoooorrrr!


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Trevor Amos



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PostSubject: Re: Ned Head   Thu May 30, 2013 7:46 am

One of the arguments against water cooling seems to be that of excessive weight , when compared to the alternative of air . The aluminium barrel and head depicted in the recent picture , together with the cast iron liner tipped our kitchen scales at ... 10lbs 14.5ozs . My water cooled iron/steel barrel with liner , aluminium cylinder head and outer water cover...... 7lbs 14ozs !

Interesting numbers ? Trevor
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PostSubject: Trevore! -- Something confusing...?    Thu May 30, 2013 9:14 pm

Trevor!
Why Watercool the head and NOT the barrel?? or was the pic meant to confuse?

I doubt that but could the watercooling of the head only be for experimental purposes -- alone??


I am confused --


... which is what my missus is often saying these days.



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PostSubject: Re: Ned Head   Thu May 30, 2013 11:24 pm

When comparing the difference in the weights shouldn't the pump,battery,rad and water be taken into consideration.
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PostSubject: Re: Ned Head   Fri May 31, 2013 4:56 am

John ,
As far as I am aware , the alloy barrels cannot be water cooled , but no mention of the head is made in the controlling rules , so in trying to make the most of what is possible I have elected to make the compromise of a w/c head . An additional benefit of the small w/c head is that 30mm of the top fin all around the outer edge of the barrel is exposed to cooling air flow . Bearing in mind that the top fin in any air cooled barrel runs the hottest , this feature will be of great benefit in shifting heat .

In my original post , I omitted to include the aluminium reed block housing in the weight figure , so the revised total becomes 11lbs 4.9ozs .

Yes Ned , the items you list do indeed have to be added to the total but as my w/c barrel is already in credit by a fair few pounds to the ally job , the eventual difference will be not unreasonable ?
Weight has been touched upon , but not power , and fundamental to competitive racing is the ratio of power to weight . It has been incontrovertibly established that air cooled engines of similar power and capacity to w/c engines will loose power as a race progresses , they are in the category of the thermally challenged ! Yamaha published a paper in which it was reported that comparison tests were conducted between both versions of the same engine . Both started with 30bhp , within 4minutes of running the air job lost 4.5 bhp , the water , 3bhp , after another equal time period the air lost additional 1.5bhp with the water staying constant . With a liquid system temp can be manipulated , hotter or cooler by masking the rad or perhaps by increasing water flow rate , hence my gizmo for pump speed , with air you are stuck with what you have , be it good or indifferent !
The overall rate of heat dissipation to the air is dependent on fin surface area and its location relative to the seat of heat source , the air speed actually traversing those fins . the fin pitching and their geometric relationship to the direction of air flow .Ambient air temp affects both types of cooling but the air cooled will always come off worse , and if you run an iron barrel the problem is compounded .
The following is a question posted on another 2t site by a guy who earns his living , in part , in the challenging world of thermodynamics .
" Do the maths , what is the mass of air that you will have to chase through the cylinder fins to get the same amount of cooling you get with water ? What is the volume of that mass ? What air flow velocity will this volume require , and don`t bother with mtrs/sec, Mach numbers will tell you enough ! " Calculating heat loss in a radiator system is a much more straight forward calculation however .
Radiators are usually at the front of the bike , taking advantage of the coolest air available and the highest relative velocity , any thing downstream starts to get compromised . Take the simple frame front down tube , air impacting this will divide and create wake flow , and the closer the head fins get to that wake of no- flow so the less will be the cooling , pretty obvious when you stop and think about it . And so it goes on , and , any feature that will deflect air from the fore and aft flow will slow it and detract from the overall cooling ability of that air flow . Eddies and vortices abound in the parasitic flow regime that exists inside a fairing , so it is by no means guaranteed that an air cooled cylinder is enjoying the most efficient cold air draught that it demands and needs .

Cheers for now , Trevor


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