Water cooling.

[saxet]

Can anyone tell me whats involved in water cooling a 2-stroke head.Are there calculations involved or is it a suck'n'see thing.
S'pose it should be calculated out to prevent over cooling.

Thoughts please.

[Buckets4Me]

Can anyone tell me whats involved in water cooling a 2-stroke head.Are there calculations involved or is it a suck'n'see thing.
S'pose it should be calculated out to prevent over cooling.

Thoughts please.

I thought that was what a thermostat was for
or tape over the radiater

I believe that you run the rs125's at about 70 degs

50 deg+ (water temp)

[SS90]

Can anyone tell me whats involved in water cooling a 2-stroke head.Are there calculations involved or is it a suck'n'see thing.
S'pose it should be calculated out to prevent over cooling.

Thoughts please.

Well, it depends on what you want to do.

I can offer some advise (if you would like it) on how to achieve it,but it may well be prudent to see if you actually NEED it!

Are you making an engine that REQUIRES a water cooled head (i.e what cylinder compression ratio do you intend to run), or is it just something you want to "try"

By that I mean, have you a design for an engine in mind that has very high cylinder compression and needs such a cooling system to cope?

If you go to the effort of water cooling a head (it's not really that hard,but it will take a little time) you want to have an engine that really benefits from increased cooling, otherwise it will bring you quite small gains!

[wbks]

Well if you were going to put an air cooled engine into a different chassis with less air flow it might be needed for reliability rather than HP gain.

[saxet]

I'm thinking of taking an old GP100 motor and taking the tuning to a serious level, getting around the carb limits on the 125 I presently run and still intend to on tight tracks.
I'm looking at a GP100/125 based motor for things like Battle of the Buckets and the Bucket GP.
I want it to be GP based çause I'm stubborn.

[SS90]

I'm thinking of taking an old GP100 motor and taking the tuning to a serious level, getting around the carb limits on the 125 I presently run and still intend to on tight tracks.
I'm looking at a GP100/125 based motor for things like Battle of the Buckets and the Bucket GP.
I want it to be GP based çause I'm stubborn.

Ok, that's a good reason!

As you are aware, to get a 5 speed engine competitive, you need to have a good amount of low RPM torque, as well as a good amount of "overrev" in the top RPM, to enable you to run exhaust port timing that will give you good power.

High cylinder compression is a good place to start for Torque, and water cooling the head is needed for such ratios.

The first thing I would give consideration to is how I would drive my water pump.

There is loads of options there, but first, (if you are interested), I can help design you an ignition (retarding), so you get more gains from that high compression,and that also provides 12V's, so you have the option of running an electric water pump (that saves on weight and difficulty of setting up a mechanical drive system)

If you have access to a lathe, you can make it yourself, using second hand parts from a wrecker.

If you don't have accsess to a lathe, PM me, and I'll help you from here.

[speedpro]

Everyone I know who has watercooled a bucket motor say the same thing - the water pump caused the most headaches. I've been there and I agree with SS90 (can't believe I said that) - go electric. You can get some nice little bilge pumps from boat supplies - LVM pumps. The only drawback is they don't like being pressurised. On my TS/RGV motor I made the pump from scratch & fitted it where the oil pump used to live and drove it with a custom shaft. Total pain in the arse.

[k14]

I thought that was what a thermostat was for
or tape over the radiater

I believe that you run the rs125's at about 70 degs

50 deg+ (water temp)
No... RS125's run at between 50-60. If I can get mine to run about 52 I am happy but not too worried if its 57-58. Its quite easy to regulate the temperature (remembering they have no thermostats) with duct tape on radiator. After a while it becomes quite easy but if you stuff it up you could loose a race because of it.

[SS90]

No... RS125's run at between 50-60. If I can get mine to run about 52 I am happy but not too worried if its 57-58. Its quite easy to regulate the temperature (remembering they have no thermostats) with duct tape on radiator. After a while it becomes quite easy but if you stuff it up you could loose a race because of it.

Yes, for sakes of simplicity, running without a thermostat is a good idea (in my opinion)

As in an two stroke GP bike, they have no thermostat, you are required to "warm up the engine" correctly BEFORE riding...(cold seizure will result otherwise...although as a GP100 has no exhaust port bridge, it's not as much of a concern....but still required), and regulate your temperature by tape on the radiator.

If Saxet goes the way of a electric water pump though, he can just have a thermo switch to control the flow of water (off when it's cold)

My experience has been to OVERCOOL and engine, not overheat. (when I used mechanical operation)

Electric does make controlling things a little more of a science (which is nice)

[F5 Dave]

A friend made a conversion using a Honda Beat scooter pump which is handily belt driven. On his GP100. That would be by far the easiest. Actually thermo-syphoning would be easiest. And fairly effective bearing mind the modest heat energy to disperse.

General rules exist for both methods, but be careful of welding into heads as they can get porous if not careful (you know this) & can make them warp. Sometimes have to heat treat, but that is expensive & makes them brittle.

But a decent std head with channels cut should be big enough mass to avoid this if done minimalistically.

Make sure there is a good amount of material so it doesn't warp. Make the passages thin, old heads are too big (read up about barrier layers). Pipes in thermo should be wide (but my old MB used normal hose & worked quite well). My MB100 uses an NSR pump welded into the cases driven off clutch with an idler in the correct direction at correct speed so it should be the biscuits, but untested as yet.

I'd do the barrel as well, helps piston. Don't get too close to ex port with jacket, that's what killed my MB.

[saxet]

Well I'm looking at thermo syphoning (perhaps). An electric pump as per Speedpro would'nt be too hard.A thermostat would also be good but brings up the issue of mounting it. As to the design of the water jacket..well thats whats bugging me at the moment as I think it could be easy to stuff it up! E.g. uneven cooling.

The cutting of channels seems to be a good way to go but the layout would be important. Looks like I'll have to do more research tho off the top of my head I'd assume the best way to go would be the water inlet entering a cylinder water jacket at the lowest point(therm-syphon), flowing around each side of the barrel, into the front of the head above the exhuast outlet and flowing, via channels formed in the head outer surface and inside the top of the water jacket for the head,around each side of the combustion chamber then out and back to the radiator.

I've never even looked at one. Anyone local got something in pieces I can look at?

[Buckets4Me]

http://www.rscycles.com/images/thermostat/therm_guhl.htm



Thermostat system for your two stroke machine. This system maintains two coolant loops. A constant flow around your engine to avoid hot spots and not cavitate your water pump and as temperature raises the systems blends into the radiator loop to maintain a constant temperature. This will greatly simplify your jetting as well as bring the motor up to temp much quicker. When full open you system stays as cool as the radiator's capacity.
A must have for those cooler spring and fall races.

[Buckets4Me]

would make it easier and less hassels

but cost a bit more than a $20 roll of duck tape

[speedpro]

I did an AC50 20+years ago & went with a thermosyphon system. I had a little radiator about 120mm square by 1cm thick and had to put duct tape over the whole front except for about 1-2cm. If it rained I had to tape the front and back completely to get it to warm up. Don't get too technical with channels and flow rates, just build it, it'll be fine.

[saxet]

I did an AC50 20+years ago & went with a thermosyphon system. I had a little radiator about 120mm square by 1cm thick and had to put duct tape over the whole front except for about 1-2cm. If it rained I had to tape the front and back completely to get it to warm up. Don't get too technical with channels and flow rates, just build it, it'll be fine.

Cheers dude!

[saxet]

Well i don't have access to a lathe myself but I can badger someone, I hope.
I've come to think a thermostat and cooling pump would be best to regulate temp. These bring up the problem of pressure on the pump and mounting a thermostat.

[F5 Dave]

Fins come off quickest with angle grinder & a cut off wheel. Mill might be easiest to cut square type channel around chamber (I'd offer but now is going to be seriously busy for me) & then just make a lid that gets welded over the top along with a couple of pipes in & out (funniest one I saw was a head with only an outlet, they'd forgotten that there was no connection to the water cooled barrel).

If you are going to consider doing the barrel later you may consider where the inlet is positioned so it can be u jointed to the barrel, or if you get flash blank it off & drill passageways in between.

[saxet]

Take it the baby has arrived...congrats to you and your lady.

[F5 Dave]

Thanks, but no, we are still expecting, but by the weekend is sure.

[boostin]

I did an AC50 20+years ago & went with a thermosyphon system. I had a little radiator about 120mm square by 1cm thick and had to put duct tape over the whole front except for about 1-2cm. If it rained I had to tape the front and back completely to get it to warm up. Don't get too technical with channels and flow rates, just build it, it'll be fine.
Would it be possible to put a tap in the return part of the system as a temp control? Allowing less of the heated water to rise?

[F5 Dave]

probably no reason why not, but why add complexity?, if the thermosyphon was really over efficient (unlikely) then a smaller rad would be a lighter less bulky solution.

[speedpro]

Kiss . . . . . . .

[TZ350]

My only experiance with thermo siphon cooling is with old single cylinder stationary millking machine motors.

But isn’t a thermo siphon more or less self-regulating, with the flow increasing/decreasing in proportion to how hot the cylinder/head is?

And I think that by raising/lowering the radiators height above the cylinder head the rate of flow can be varied a lot. Lower is slower and hotter, higher is faster and cooler within limits.

.