Ned Head

I have a NED head casting I acquired many years ago, I am thinking of fitting to my longstroke aircooled 175. In order to answer eligibility questions I was wondering if anyone (was it Ned Q ?) could enlighten me when they were first used, CR, advantages etc ? cheers John

Hi John
Nosing around in Toms Millers workshop I found a triangular piece of plastic with the corners rounded and a dome fitted in the center. When I asked Tom what it was he explained. Mick Scutt and him had come up with the concept a few years earlier that air cooled heads could be more efficient than the only option of the time, Tod heads.
The thinking was that the fins should direct air to the hottest part of the head and spark plug. Mick had done some research and decided that for better radiation fins could be shallower but with a better radius.
They had however abandoned the idea because they couldn't think of a way to form fins on what was to become the pattern for the moulds.
I told Tom I thought I could do it and the project was handed over to me.

I had a split mould made up in work to fabricate a fin in 'Devcon'
For every two that came out OK one would be floored or break and because only one a day could be cast was a real bummer.
The fins were individually glued in place before the arduous task with needle files and emery cloth of cleaning up the contours.
We have a photo that she who must be obeyed took of me filing the pattern on my lap while the kids played with their toys Christmas morning.
As a final gesture, feeling like Michal Angelo of the bike world I put my name to the bottom. Not even sure it would come out in the casts, but it did and and the name NedHead stuck.

Tom financed the project without making a profit for the benefit of BRC members. Small batches were made at a time and because they were cast as blanks, Tom could machine them to members requirements, stud spacing, compression, squish etc.

The first one obviously was used on my bike but the old grey cells cant recall what year. If I dig out that Christmas photo the guvnor no doubt will tell me when it was. I was water cooled in the 80s so it was probably mid to late 70s

Dear Ned, great thanks for that info. It still looks a great piece of kit. I shall try it on the 175, it looks oldish. As long as I don't win a race or championship, then its unlikely any r..... orifice will challenge it. Any thoughts on maximum compression ratio, given I can run on any fuel (avgas or 110 most likely) in modified class ?

Great! The club had engineering talent... No! it still has engineering talent -- a lot of which was never revealed.
...
Someone ought to have recorded it all -- Ned?

johnSbantam wrote:

Any thoughts on maximum compression ratio, given I can run on any fuel (avgas or 110 most likely)

Cant help you there mate you need to ask one of the current riders.
Avgas wasn't permitted when I was riding. Even though we new some of the opposition were using it, Tom wouldn't.

Hi Ned,

Found this an interesting read, did you ever find the photo?

Kind Regards


Eddie

Somehow I missed the NedHead bit. Brilliant Ned!!

JohnS´s query over how high can one go with Compression Ratio when using a doped fuel? was also missed...

I should say there´s not a lot of point going over 18:1 because you´ll most likely be dieseling at that and at 20:1 ... besides which the Thermal Efficiency curve begins to flatten out above 16:1.



Only when it is legal, of course, and on Grass Track it was:-

I ran my 500cc JAP at 16.5:1 on Victor Martin Track fuel which was normal Methanol with 2% Puridin (obviously a trade name for TEL) added. It meant an advantage over normal methanol of being able to weakon off on the main jet to get a bit more grunt without holing the piston... I used an 850 main jet whereas those on Methanol were using 1100-1200 main jet in Amal Track Carb....

Interesting aspect of the C.R. versus Thermal Efficiency curve is that raising the compression-ratio from 6:1 to 10:1 brings 9% thermal efficiency improvement; whereas from 10:1 to 14:1 its only 5% improvement, 14:1 to 18:1 brings <3.5% benefit -- with the TEL additive to several different fuels ....

As I said -- I think -- I said before, addition of Tetra Etyhl Lead raises the octane level enormously (>160) and if there´s no law against its use in vintage machines where you are, JohnS -- why not take the advantage?

It burns so clean...!

Cheers!

The problem with high compression ratio's is they work brilliantly to
a point - then it works aganist you and stunts your rpm! Unless of
course you have a 'High Interia' crankshaft which will overide the
'brickwalling' of the high c/r.

nedquirey wrote:

The first one obviously was used on my bike but the old grey cells cant recall what year. If I dig out that Christmas photo the guvnor no doubt will tell me when it was. I was water cooled in the 80s so it was probably mid to late 70s

1978/79 season I Think. I remeber Ned had a long piece to his fairing Top, as I watched him remove it "this went under the tank quite a long way, I remeber him pulling the top part of the fairing only forwards"? to a point well in front of the front wheel to remove it for access.

I wonder why this was !

Mike! you just raised the point of having a flywheel at all -- you knew ALL THE TIME! of course, the necessity of a flywheel -- compressing air slows the piston down which slows-down the crankshaft rotation which then speeds up with combustion-expansion -- Trevor called it, `Cyclic Speed Variation´ ....

-- the massive question was, HOW BIG should the necessity be...????

Nick should ignore this:-

2012 racers should remember `g´, the force of gravity. When g = 1 it is the whole of your body weight that acts as a force when you hit the tarmac -- so go on a diet IMMEDIATELY after Boxing Day.

Several people have asked me what a NED looks like; this:





This may have been partially machined for a 55mm stud pattern 125 with a 5/8" plug, so will be welded up before machining for 185

Wow!

A work of art and obviously of great skill -- Wünderbar!!

Answering Mike over his comment re the need for bigger flywheels when going to increased compression ratio because of the increased resistance to rotation caused by the higher compression pressure.

Not necessarilly true -- unless you are daft enough to use a low octane fuel (<100) with CRs above 9:1....

You all know this already but it is probably worth repeating:-

If on 15:1 compression ratio a fuel with octane rating well above 101 is absolutely necessary -- otherwise detonation and frequently non-audible detonation is inevitable. With a mere 9.5:1 comp-ratio running on a mixture of Benzine & pump petrol -- the octane rating at about 95 -- I have personally proved that to be true.

Any lower octane rating than 101, when on higher CRs above 9:1, and the heat release occurring BEFORE TDC is going to produce a force that opposes the piston such that a heavier flywheel is probably necessary (to overcome that extra resistance to motion) as Mike mentioned.

But there is a more positive side to using such as methanol with TEL additive where the slower, lower-pressure heat release before TDC and during expansion of combustion DOES NOT PRESENT MORE RESISTANCE TO ROTATION.

Refute this if you will -- at your will -- a methanol fuel with the additive gives a slower and longer heat release -- and hence lower peak pressure -- burns slower and longer than petrols of <100 octane rating.

What I am saying is that with a <100 octane petrol there is a huge waste of heat energy in the combustion occurring before TDC -- which DOES oppose the rise of the piston to TDC -- as Mike said ...

... but that is not attributable to high compression ratio but more to early heat relaese (& pressure) before TDC.

A diagram might help here -- but I just made a resolution to stop being a BOF with all this calculation and diagram bullshine!!

So have a good time over the festivities period, youall!!

Cheers!

P.S. Just about to leave for the volcanic lake area in Süd Eifel. Well they were volcanic 10k years ago .. here´s hoping they stay so!!

hi all, am i right in thinking that all ned heads are for 125's or are they for both 125's and 175's ?
best regards adam

Good Evening Adam,

I have a Ned Head fitted to my 175 so they certainly fit on the 175, I shall let one of the 125 riders to comment on their suitability for the 125.


Regards, Mike

I used a ned head for many years, only now do I know they are limited, joking aparat, they look so ugley, and apparently designed for Bantams, I think if they had been designed properly or my an engineer the fins would have been longer/ taller.

anyway to answer your question, they came un-drilled and drilled with 55mm and 60mm stud centres, so they can be used on a 175, but I think they look ugley just like the guy who designed and made them. !! LOL, "no style"

regards Derek

Can´t agree with your comments Derek...

Fin dimensions as objective re the heat-balance requirement and the "ugly" statement as subjective. Regarding the latter a frog looks on another frog -- or a duck on another duck -- as beautiful....

I have already complimented Ned on his effort, several postings back, much as I would when discovering any well made piece of auto history.

Glop-glop! & quack-quack!

I've just bought 2x Ned heads for my next air-cooled light- weight bantam project
(no water -1.5kg rad -1.5kg pump- 400g battery -750g) hoping to get to 61kg.
Went for Ned Heads because of there design short fin, large fin radii and of course
there beauty!

hi mike

I would like to respond! but in light of your clearly superiority in taste, I bow to your view ! on the Head! adding its not just about the radii its also about area of fin's, short fins not as efficient as the samebut longer, also the surface finish is very important, all facts, they work but dont look as nice or authentic as a real Bantam Head, just similar to my point on fairings. tomeauthentic is beauty, new is "ugluy".

many thanks for your comments gents, when i first saw a ned head i didn't like them but after learning about the history,design,reasoning i get why they are like they are, like john said a piece of engineering/automotive history and not just to keep on your mantel piece.cheers adam

Last comment on this -- REALLY! Too much fin -- too much area and you get rid of too much heat -- that´s what heat-balance is all about. An obvious, very important, aspect for efficient cooling is airflow BETWEEN the fins and the Ned Haed has this right in having a flat surface between each fin root.

Ende!

John Mike and who ever, - "Getting rid of "too much" Heat John tut tut.

My view" - with an alloy barrel that runs cooler at the root than a cast Barrel, "why" ! a lower temp " than an Iron barrel. ! look at a road going 150cc MZ this is what I would have designed somthing like, "In fact I used these for sprinting and racing with other classes, "for many years after I stopped racing with Bantams"!!!.

I surpose its all a lot of hot air really! anyway we did run a water cooled head for a few season's to iron out the normal issues, like having to keep a battery in tip tip condition, eventually when I went water cooled, we fitted a water pump (with a difference ) on the end of the crank a lot lighter, easier to look after and more reliable than a battery.

we found a head with deeper fins worked far better, more consistent - this is all i was saying, especially on "pump fuel"- that is much more variable than avgas, so yes I agree with you John a ned Head is not as efficient as it could be" at removing heat. - if it had been designed properly with deeper /longer fins with more area it would be!, this is my obesrvation, as I was asked to comment "I answered" its a free world, as far as I'm aware I have not isulted anyone. !

"So to clarify" a longer fin/bigger area on a head is more efficient at removing heat, than the Ned head is- I think we all agree on this,
what I said, is I feel they are not as authentic as a std Bantam head, and spoil the look of a Bantam top end, another simple comment, I dont see why you all need to Defend Ned's design, I have not insulted Ned either, "I like Ned" he helped me when I started many years ago, and Im sure many others, - but"its a free world John I was simply replying to the question others commented on it, I try not to jump on the band waggon and critisising others comments (well I could ) -

but I do agree, my comments are all based on my limited experience.

Actually I agree with Mike the complexity of water cooling, is a pain, comparing an alloy barrel to a cast item, its no contest. unless"?

you have greater scope with a water cooling, for bigger or should I say, the scop for more control over the port direction, than with an air cooled barrrel, also when you go down the route of welding on additional ports, water cooling is effective at then keeping the barrel cool after you have removed the fins. I dont think its a consideration of weight, when you swop to water cooling,

comments, what I see on your comments - both from you and Mike - sounds rather a silly statement, "to suggest swopping to water cooling because its heavy'er". is it /this surely depends it your alloy or cast top end, !!!!!!!!!

the forum seems to sprout roots when we get a difference of opinion, but can we leave the personal band waggon comments to one side, and all remain objective I think all comments have validity, but could be said more objectively (Mike John).
or it may be we are getting too sencitive in our old age.

regards Derek

Well I think Ned's original design is well proven and certainly looks good atop a Classic cast iron barrel.
I got mine from Mr Betts senior, he thought they were good !

I am over in Perth, Western Australia, visited Dave King and saw his well engineered rotary valve air-cooled 125 racer on Sunday.
Got me thinking. Disc valve (was done in NZ 1960) 175, NED head 16:1 compression, methanol and 4 speed CR box could make quite a weapon.

Interestingly the good Aussie cylinder heads like Walsh, Hagan and the Kiwi Ward heads all have big thick short fins like NED.

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-full load is about the same amount of power that´s lost to cooling. The reason for thermostatically controlled electric fans (switching OFF to keep the engine warm when running on no-load -- light-load on road vehicles) is first to improve fuel consumption and second to improve combustion efficiency over that of when the mechanical water pump keeps the engine too cool. Tutt Tutt ...!!

The old saying clangs so very true: "...she was going really well --- just before she seized."

***Street motors have less than 25% efficient conversion of fuel energy to mechanical energy -- most family saloon cars are at about 16% ....

Tut Tut to you too...!

Hi Everyone,

I have a question regarding water cooled Bantams, I see from present post M.P is thinking of air cooled " light weight Bantam"
can I ask (purley out of interest) the average running temperature of his water cooled engine, the amount of water in the system,
and the speed of the pump to circulate same. I ask because JS1 ran thermo syphon, JS2 I have retained thermo syphon but with
less water load, no pump,no battery,smaller rad and still self regulating and running at a reasonable temperature on a hot day.
The way I see it, a large fin modern alloy barrel fitted with a modern machined liner plus head will carry more weight than a machined original Bantam barrel converted to water cooled to run thermo syphon with all the added ports added.

Les 2012.




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