X750h!

[750ynot]

Can I ask about the fins you are going to afix to the cylinders, where are you intending to fit them exactly ?

[750ynot]

Tony / Teazer - you are correct - thanks!
Had a chat with an engineering company who specialise in re bores and they confirmed what you have said - it needs boring to the T500 clearance.
Although their first question, after I mentioned that I was air-cooling a water-cooled motor was................ WHY?
Live and learn!

I remember Baz telling me that tolerances are less on a liquid cooled engine as
the temperature control is more consistent.

And LC is also cooler running.

[garry55]

Tony / Teazer - you are correct - thanks!
Had a chat with an engineering company who specialise in re bores and they confirmed what you have said - it needs boring to the T500 clearance.
Although their first question, after I mentioned that I was air-cooling a water-cooled motor was................ WHY?
Live and learn!

I remember Baz telling me that tolerances are less on a liquid cooled engine as
the temperature control is more consistent.

Correct Sir!

[garry55]

Can I ask about the fins you are going to afix to the cylinders, where are you intending to fit them exactly ?

They will be welded to the barrel to help dissipate heat.
There will be 6 fins on the barrel and 6 on the cylinder head.
Probably.
The X75 has 8 on each but I don't have the room for them if I copy the T500's barrel spacing.

[750ynot]

Can I ask about the fins you are going to afix to the cylinders, where are you intending to fit them exactly ?

They will be welded to the barrel to help dissipate heat.
There will be 6 fins on the barrel and 6 on the cylinder head.
Probably.
The X75 has 8 on each but I don't have the room for them if I copy the T500's barrel spacing.

I don't suppose you can draw a pic on some paper and post a pic so we can see your intension

You can tell me to uck off any time you want Garry, but I am very interested in this and how you are going to overcome the heat transfer to the cylinder wall

I don't even know if its an issue, does the extra piston bore clearance take care of the extra heat, meaning it doesn't matter ? I ran many a 2T with lots of broken off fins, with no issues.

I know that RDLC runs around 50 to 90 degrees, but ideally 55 degrees is best for fuel air mix / density of air, as heat rises further performance starts to suffer, the later YPVS had thermostat that opened at 55 degrees, this seams to be a ball park figure for LC 2T bikes that I have had.

I had an RD200 that I did a lot of mods to, aircooled 2T, that used to run around 110 120 degrees, a number of people also checked their rd250 aircooled bikes and found the same, heat measured at the exhaust front pipe very close to cylinders, now that's a big difference in heat range between LC and aircooled, and there is also a big difference in the piston bore clearance.

People say O you can't do that, it won't work all the time, but don't really know why when you go into it, trial and error is the best teacher there is, unless someone can say I did this and this happened, then its give it a go and find out.

Just my rambling thoughts for you to consider, and anyone else.

[garry55]

Simple answer is that I don't really know.
The cylinder sleeves will have plenty of cool air circulating around them (more than a T500 would have) when the bike is on the move.
The cylinder block, as a whole, will get warm as heat will dissipate through the solid casting at the bottom (where there aren't any cooling channels) and also via the internally cast strengthening webs that connect the inner casting to the outer jacket wall where there are cooling channels. The fins will (I hope) help dissipate this heat as per a normal air cooled engine. But the fins most important task is to hide the "core" of the engine - the ugly barrel and head that I have butchered - and give the impression of it being a traditional air cooled 4 stroke engine.
It would have been much easier to just mount a GT750 engine in the Triumph T150 frame, but that's all it would have looked like - a Triumph X75 replica powered by a GT750 2 stroke engine, with a big radiator hanging off the front. Not what I had in mind when I set out to create this project.
Other ideas I have thought of to keep the project "true" to the X75 mantra is a false oil cooler (mounted above the engine as per the X75 / Trident) that will actually be the 2T oil tank and a pump assisted fuel transfer system to move fuel from the standard oil tank to the main fuel cell. That's an extra 5 pints of emergency petrol !
All these ideas are works in progress.

[750ynot]

I suppose not having the radiator in front of the engine will give plenty more air rammed at the front, looking forward to seeing it progress

[750ynot]

I can't stop thinking about this!


I think I get what your trying to do now ?

the reason for the GT750 engine is because of the head ? and the fact it sort of looks like a cam cover.

I wonder if you can cut the head in half lengthwise, you could weld some fins inside and weld back together, cut some slots for air to go through front to back, sort of like the ram air idea Suzuki used on some GT models.


Could cut some bits out the cylinder and do same, then cover with some fins as you said to hide everything.

[garry55]

That's what I have already done (minus the welding of the fins).
Slots cut into the front of the cylinder block allow air to circulate around the water passages, cooling the 3 cylinder sleeves, before exiting through similar slots cut into the back of the barrel.
Matching slots have been cut into the front of the cylinder head, again with "exhaust" slots to the rear. On the move, air will be forced into these cavities to promote internal cooling of the cylinder bores.
The welded-on fins are, as previously mentioned, mostly decorative but will offer some aid to the cooling of the cylinder block and head.

[garry55]

A bit more butchery on the GT750 barrel - I have opened up the water transfer passages to get more air to the bases of the cylinders.







I have also purchased a "profile gauge" - 10" version on which, sadly, the profilers aren't long enough to accurately "map" the barrel end contours
I'll have another look at that tomorrow.