Liquid or gas ?

The plan view pic very clearly shows the access passages allowing water to travel from the barrel, over the cylinder head and out at the rear, which is also the highest point on the engine , from there to the radiator. The head outer jacket has only .6mm clearance between the o/d of the head and its inner wall, so the pumped water is compelled to flow through the open holes and thence over the head, taking transferred heat with it . The surface of the skull is intentionally coarse and rough , the large radius was free-handed on the lathe, and this increased the surface area and helped a smidge more heat to be leached away. In similar vein, water is able to get within 6mm of the plug threads at their hottest point, again, an obvious benefit !
With the conductivity rate of water ( .6 for water and .025 for air ) W/(MxK) , it`s advantage over air is huge, additionally, water has a higher heat capacity, rate of thermal conductivity, density and is constantly moving and at a rate which the designer can predetermine and even adjust on the move . Air flow rate can only increase on a finned head by the machine going faster, if your tuning limits any increase you have a problem .
What I was trying to achieve was having all of the water being able to flow over the whole of the head, when developing this I made a false jacket from a scrap piece of tube and siliconed a clear lexan sheet on top with an outlet hole and let the water pump rip and watched it all happen. To my great surprise the water streams did the job well, I later repeated this experiment with the triple speed gizmo and the flow rate was stunning ! With the two, rear water outlets being the smallest and offset from the central outlet to the rad , short circuiting is minimised, ensuring all water moves , no stagnant areas , and is always taking heat away .
If anyone feels like having a go at w/c there is enough information in this topic to get you going , but I would encourage the construction of working drawings, they don`t have to be of professional standard but it is far easier to alter a line on a drawing than to remake a faulty component .
Any questions , just ask , open forum or pm .

Trevor

PS. Patience Nigel , the next Midland Meeting can`t be too away !!!!!!!! The girl is better in your bed than on page three ??????

Brilliant Trevor! -- I bow to your WC engineering
and wish you more power to thy elbow ...

... don´t let Nobby take that the wrong way!

nobby1 wrote:

Mmmmm, nice pictures trevor, got any that show more!!! details, sort of, "down the !!!(bra) angle"  ?surely it was a natural progression from?, (like all women), better more exciting before the event, anticipation!!, looking at a bikini's first!!, woman without bikini's are just too bare!!, best to allow the mind to imagine,!!!!

Hi Nigel just playing, its our big launch this weekend, for BSB teams and launch, been top secret been working on it all year, anyway could not help but chuckle at this one, seems Trevor is doing a typical (you need to buy me a ring first then Ill show you)!!! or little by little, just like your big night and the lady undressing herself, once she does it the anticipation and excitement has gone, so I say Trevor take your time, the slower the better, keep em guessing, I can not wait till our next midlands meeting, !! perhaps we could see it unclothed in the raw, (no pictures well" perhaps some but for a small fee'! and my 10% )I hope we don't have many females looking but I understand there are more than a few that post !!!.

Derek

mike's engine

So what exactly are we looking at here, is this the four piece barrel or another example of a water cooled engine, but those are very big water channels, I can see scope for sluggish water flow areas here ! Any chance of some explanatory notes Mike ?

Trevor

As can be seen from the pictures so far posted up, the popular position for water inlet is at the lower front. However, there is an alternative which offers a better, potential, return in overall efficiency. The cool water from the rad should enter the cylinder above the inlet, and then to the transfer ducts, on to the exhaust, to flow up through the only access in the head, over the combustion chamber towards the rad . The implications for an increase in volumetric efficiency are obvious, a hot inlet is a power sapper, there is no point to being handicapped before you even start! It still has to be said though, that if maximum heat extraction is what is required, then the current vogue is probably correct, but don`t ignore that old adage that, power is heat is power!
As heat builds in an engine during a race, local hot spots develop and coolant can approach boiling point, bubbles form and heat extraction drops ( have a look at a pan of water heating on the cooker, bubbles form way before boiling point.) ramping up coolant velocity helps to a degree but if the water jacket is too big local stagnation occurs . The answer is to " shrink wrap " the water jacket, have a smaller water volume, a rapid pump and large rad ! Or, two coolant streams, one to stabilise the cylinder and one to allow the head to only release enough heat for reliability ?

Stay cool ? Trevor

Hi Trevor pics of my piston ported 001 barrel from the 70s and very like George Harris', not sure if the big passage ways are anything to do with the fact when made it didn't have a pump but relied on thermo-syphon to get the
water round at what I assume a fairy slow rate. It just happens that the pump packed in at the weekend in the first race on Sunday and it spat a bit of water out the overflow on the sighting lap and first lap and then completed the next 7laps without a problem. I will do some sketches and will talk to Tom to see what else I can find out on the
subject of barrel manufacture..

Regards Mike

Courtesy & Property Of Trevor Amos.

250cc ossa?
Bill

Thanks are due once more to Ed for posting these pictures up .

Yes Bill, full marks , if I was awarding prizes you would be the winner, the Ossa 250, perhaps my favourite race bike of all time , however it is the cooling that is of interest !

The two cylinder heads here represent differing approaches to the same problem, adequate cooling, and to quote from a recent post by Jan Thiel on the Ossa , "Beautiful picture, that thing is a technical and artwork remains, and did not seem to suffer as much from heat " . The centre fins are the deepest and are rooted directly to the roof of the combustion chamber providing for maximum heat transfer and dissipation , their spacing is close enough to allow high speed air flow to scour away insulating boundary layers and maximise heat removal . The least effective fins, on the extreme outside are small by comparison and so do not interfere with their more efficient neighbours . Cunningly, the support brackets holding the engine to the frame double up as fins, again with an air gap between them . I guess one might characterise this engine and it`s design concept as a maximum impact for the least outlay ! The GT heads have these attributes, just one reason why they continue to work so well .

The radial finning on the other head still has fins emanating from the hottest area but the huge spaces between them is more suited to slower bikes, road or motocross and trials where a lot of the cooling is mere convection, good for waiting at traffic lights, and being choked with mud but the die cast, smooth, finish does no favours in the overall thermal battle .

As an aside from heads but still of interest, F1 designers employ splitters in the side pods where the radiators are located to disturb local air flow enough to discourage the formation of boundary layers and increase the overall efficiency of heat removal .

Don`t get too hot over all of this ? Trevor

Raced by Santi Argo herrero" not sure on his name spelling, what a rider. killed at the TT, what a great loss. OSSA seemed to loose interest after this.