Cooling an air-cooled engine

[xwhatsit]

You know, with all the time out from riding, I've been doing a lot of thinking... which is normally a bad thing, but this idea I have seems less stupid than the usual ones so I thought I'd post it up on here.

Now, I'm not planning to do this, but I'd love to give it a shot once I'm out of student life and have a real job, I want to get a bucket racer and try all these silly ideas I have just for kicks.

I'm not a biker originally, I'm from the land of blinkenlights and electronics and nerdy stuff like that. In this scene, kids like to tune their computers to make them faster doing something called `overclocking' -- essentially, over-revving their computers. This generates a lot of heat, so they've come up with all kinds of innovative ways to cool their computers. Big heatsinks, fans, water-cooling, liquid nitrogen, Peltier devices...

So I was looking at some overclocking pics the other day, and I thought... well my bike gets hot in traffic, could I not apply some of the principles here? My particular idea is to water-cool the bike, in classic overclocking style, by taking some thin copper tubing and bending it around in a spiral between the cooling fins on the cylinder head and barrel. Through this you pump water, which goes to a reservoir where you cool it with a condenser or radiator or something. Obviously it's not anywhere near as efficient as a proper water-cooling system like they build into engines, but it seems to be a hell of a lot better in computers than just a plain heatsink and fan setup (which is what an air-cooled bike uses). Also, as the water is contained within the copper pipe, you don't have to worry about hydraulic lock if you blow a head gasket.

Is my idea blindingly stupid, can anybody see anything wrong with it? I'd love to attempt this with a shitty little bucket to see if it would work.

[jrandom]

Cooling the coolant with a condenser is a great idea. Reminds me. Have you ever tried leaving the fridge door open on a hot summer's day to keep the kitchen cool? Works a treat. Try it some time.

[terbang]

I remember the old Ford prefects that used hot water rising and cooled water descending to circulate the coolant. There was a term for it, can't remember it, though it saves having to fit a pump.

[TerminalAddict]

thermo cyclic ??

[Ixion]

Thermo siphon it's called. Was used on many old cars, and the Scott and LE Velocette. Works perfectly well, so long as the radiator can be placed well above the cylinder head (which is why it is not seen now).

Back when bikes had cast iron heads and barrels it was by no means unheard of for people to cut the fins off, and solder a copper jacket on. An old radiator, a bit of hose and Bob's your Mummy's special friend.

Knew a few folk did it for various reasons, with varying success.

Never could quite see why though. Airt cooled bikes don't overheat in this country.

[xwhatsit]

Cooling the coolant with a condenser is a great idea. Reminds me. Have you ever tried leaving the fridge door open on a hot summer's day to keep the kitchen cool? Works a treat. Try it some time.

Lol, so you would need a radiator or summat? CPUs can get pretty hot... hot enough to boil the water... but an engine is a bigger lump I suppose.

[jrandom]

Lol, so you would need a radiator or summat? CPUs can get pretty hot... hot enough to boil the water... but an engine is a bigger lump I suppose.

I was being facetious, inasmuch as a condenser is a way of moving heat from A to B that, being an imperfectly efficient device, inevitably generates more heat in the process.

One way or the other, you'll eventually need a radiator, or you'll just have a bike that overheats its condenser before it overheats its engine...

[terbang]

Thermo siphon it's called.

Thats the words I was racking my brain for. There has obviously been too much brown bubbly stuff consumed since I last heard those words used..!

[xwhatsit]

Thermo siphon it's called. Was used on many old cars, and the Scott and LE Velocette. Works perfectly well, so long as the radiator can be placed well above the cylinder head (which is why it is not seen now).

Back when bikes had cast iron heads and barrels it was by no means unheard of for people to cut the fins off, and solder a copper jacket on. An old radiator, a bit of hose and Bob's your Mummy's special friend.

Knew a few folk did it for various reasons, with varying success.

Never could quite see why though. Airt cooled bikes don't overheat in this country.

Interesting... I thought it might've been attempted in the past, all of my ideas are somebody elses first (bathtub curve? Who woulda thought?!).

As for why... well my bike gets pretty bloody hot in Auckland traffic. Surely it's better on the engine for it to run cooler, and definitely better for my heart so I can stop thinking about seized pistons? Of course, that would be of little use on a bucket, as it's travelling at speed (relative speed, of course ;)), but I've heard that highly-strung air-cooled strokers do have the occasional problem with heat?

At any rate it would be fun to try.

[imdying]

Never could quite see why though. Airt cooled bikes don't overheat in this country.

There's your answer.

[Ixion]

Interesting... I thought it might've been attempted in the past, all of my ideas are somebody elses first (bathtub curve? Who woulda thought?!).

As for why... well my bike gets pretty bloody hot in Auckland traffic. Surely it's better on the engine for it to run cooler, and definitely better for my heart so I can stop thinking about seized pistons? Of course, that would be of little use on a bucket, as it's travelling at speed (relative speed, of course ;)), but I've heard that highly-strung air-cooled strokers do have the occasional problem with heat?

At any rate it would be fun to try.
Never heard of an "ordinary" four stroke air cooled engine piston seizing in NZ conditions. Two smokers can be another matter but two strokes always are. And if a two smokers made up its mind to seize, seize it will, water cooling or not.. In general, the hotter and engine runs the better. Air cooled engines are meant to run hot. Use good oil, change often and don't worry about it.

[xwhatsit]

Ah, so when my engine runs better in cold conditions, it does so because of cold intake air, rather than colder barrel/head? That makes sense actually.

So, heat is only a problem when it reaches seizing-levels or causes air leaks? Sweet. So the problem I really want to solve is not cooling my bike, but to stop getting a heart-attack when I can see heat-waves coming off my engine lol.

[TLDV8]

I remember the old Ford prefects that used hot water rising and cooled water descending to circulate the coolant. There was a term for it, can't remember it, though it saves having to fit a pump.

Boxer twin cylinder Bradford's too. :yes:

Maybe Jowett's also .......1953 or so sporty version,took it at a Pukekohe race day.

[Ixion]

That's the Jowett Jupiter. Nice car in its day, if you could keep it in crankshafts

[sAsLEX]

Ah, so when my engine runs better in cold conditions, it does so because of cold intake air, rather than colder barrel/head? That makes sense actually.

So, heat is only a problem when it reaches seizing-levels or causes air leaks? Sweet. So the problem I really want to solve is not cooling my bike, but to stop getting a heart-attack when I can see heat-waves coming off my engine lol.

Cold air means denser volume of gas entering the cylinder which means more oxygen which means more boom

[xwhatsit]

OK, here's another thought; why not cool my intake air then? How you would do that I don't know lol. A bit trickier than cooling a hot bit of metal.

[jrandom]

Cold air means denser volume of gas entering the cylinder which means more oxygen which means more boom

He already knew that.

I pity the fool who doesn't already know that.

[xwhatsit]

He already knew that.

I pity the fool who doesn't already know that.

Lol! You, and Squeak the Rat, are about the only people I know that can make me literally laugh out loud over the internet :D. I don't know why, it must be the glorious unexpectedness :sunny:.

[Ixion]

OK, here's another thought; why not cool my intake air then? How you would do that I don't know lol. A bit trickier than cooling a hot bit of metal.
A very long pipe, connected to some place where the air is very cold would do the trick. Like Antarctica for instance. But , seriously, yes, racers are aware of the power gains to be had from using intake air that is as cool and dense as possible.

[TerminalAddict]

does a dense rider have the same affect :shifty:

[xwhatsit]

A very long pipe, connected to some place where the air is very cold would do the trick. Like Antarctica for instance. But , seriously, yes, racers are aware of the power gains to be had from using intake air that is as cool and dense as possible.

:angry: I hate you guys, with your reason and common-sense and knowledge! You never let me play around with anything cool! Like alternator-powered Peltier devices attached to my airbox!!! :angry2:

[sAsLEX]

OK, here's another thought; why not cool my intake air then? How you would do that I don't know lol. A bit trickier than cooling a hot bit of metal.

An intercooler would do it........

[jrandom]

You never let me play around with anything cool!

Ba-dum, tsh.

Seriously, though. You're committing Engineering Design Error #1 by falling in love with an intermediate hypothesised solution rather than focusing on your true requirement.

Your true requirement is to make the bike go faster.

Burning more fuel in each engine combustion cycle is an excellent brute-force way of achieving that, but cooling the air intake is not the only way of burning more fuel in each combustion cycle.

For that matter, burning more fuel in each combustion cycle is not the only way of making the bike go faster.

[xwhatsit]

Ba-dum, tsh.

Seriously, though. You're committing Engineering Design Error #1 by falling in love with an intermediate hypothesised solution rather than focusing on your true requirement.

Your true requirement is to make the bike go faster.

Burning more fuel in each engine combustion cycle is an excellent brute-force way of achieving that, but cooling the air intake is not the only way of burning more fuel in each combustion cycle.

For that matter, burning more fuel in each combustion cycle is not the only way of making the bike go faster.

Wrong! My true requirement is to play around and generally amuse myself by playing with copper tubing, in much the same way I used to play around and amuse myself with Lego when I was a wee lad (not that long ago).

Well, displacement is an easy way of course. Burning more fuel... instead of cramming it in there with squishier air, just make more room to cram it in. So that's why I always get pwned by the Gixxer thou at the lights...

[Disco Dan]

Wrapping copper pipe between the fins of your air-cooled engine would lessen the air cooling effect of the fins.. unless you plan to run it all the time? Thermostat maybe?

As for cooling the air? Just look at your fridge for clues. A radiator inside your air box flowing with cold coolant would chill the air to some degree... If you need a very small square radiator, a mini uses one in the cab for the heater... hot engine water flows into cab through little radiator and back to engine again - fan behind it blows through, heats up... viola. Go ask skidmark for his heater matrix... heck its not as if he needs it now! hahaha!!

[jrandom]

My true requirement is to play around and generally amuse myself by playing with copper tubing...

Build a pipe organ.

No, really.


displacement is an easy way of course

I was thinking N2O...

[xwhatsit]

Wow, I'm learning shitloads. Is that how NoS/NOS/Nos/nOS/WTF works... it condenses the air heaps, like a turbo.

Hahah no I'm not building no fricking pipe organ. I did extensively modify my trumpet though, the mouthpiece and lead pipe especially... I had it sounding a lot like a flügelhorn by the end of it heheh.

[jrandom]

Wow, I'm learning shitloads. Is that how NoS/NOS/Nos/nOS/WTF works...

I never went to university; I just stay up all night reading Wikipedia (http://en.wikipedia.org/wiki/Nitrous_oxide#Internal_combustion_engine).

[xwhatsit]

I never went to university either, just the exams... no wonder my results last semester weren't quite top percentile haha.

I see this has diverged quite a bit from the original topic, which was never meant to boost performance anyhow. What I was wondering though, is why (reading some bucket threads) do the bucket racers put water jackets on their motors?

[Mr. Peanut]

To keep them moist?

[car]

Wrong! My true requirement is to play around and generally amuse myself by playing with copper tubing

Oil cooler mods: one of the many fun things to do with a VW engine.

http://www.type2.com/library/cooling/oilcoole.htm

Citroen 2CV perverts do similar things, IIRC.

[imdying]

Wow, I'm learning shitloads. Is that how NoS/NOS/Nos/nOS/WTF works... it condenses the air heaps, like a turbo.Nope, but there's heaps of good books on the subject.

[xwhatsit]

Heh, one day I'll build my own engine. I'll re-invent the concept of pushrods or something, and believe I'm the first one to ever do it, along with fuel injection. Wait... I already know about pushrods... how about pullrods? You could tie some string to the valves, and route it through pulleys :D.

It's obvious my education was based in computer science, isn't it?

[stanko]

If you want extra cooling for your overclocked motor, first overclock it. port the head fit a water tank to your bike with a small pump like a windshield washer pump have some spray nozzles that spray water onto the motor a kind of unjacketed water cooled bike, total loss system. have a button to turn the pump on . You will only need it at the lights onlookersa will think you have burst a hose. ride into the petrol station an filler up for free.

not too many bucket racers fit waterjacket to their bikes, that was in the 80's when water cooled bikes were rarer than rocking horse shit. Now you just buy an FXR and go racing.

A CO2 fire extinguisher would be even more spectacular than the water spray cooling but may result in cold siezures

[Ixion]

Heh, one day I'll build my own engine. I'll re-invent the concept of pushrods or something, and believe I'm the first one to ever do it, along with fuel injection. Wait... I already know about pushrods... how about pullrods? You could tie some string to the valves, and route it through pulleys :D.

It's obvious my education was based in computer science, isn't it?

Sorry.Too late. Ducati made a well known pull rod engine. Try again

[Motu]

Never heard of an "ordinary" four stroke air cooled engine piston seizing in NZ conditions. .


Sidevalves do,for the same reason 2 strokes do - huge cylinder distortions.Having an exhaust valve and port in the cylinder is not too good an idea.

I seized my B31 once when I had a high comp piston with a chamfered lower edge - I wondered if it sliced off too much oil on the downstroke and starved the bore of oil?

[xwhatsit]

Ah, you see, I first started to worry about my bike overheating after recently re-reading ye olde Zen and Art; early on he talks about seizing his CB350 or whatever that beautiful bike was. Now, America is of course much warmer (in places) than NZ, but an old 60s engine like that would be sidevalve, wouldn't it?

I think I should just trust my bike to not seize... at least as long as it's put back together correctly, lol. It all looks so delicate inside, I can't believe such an intricate mechanism can contain such violent explosions.

[AllanB]

Just add a oil cooler to deal with oil temp.

Save the copper pipe for your still.........

[xwhatsit]

If you want extra cooling for your overclocked motor, first overclock it. port the head fit a water tank to your bike with a small pump like a windshield washer pump have some spray nozzles that spray water onto the motor a kind of unjacketed water cooled bike, total loss system. have a button to turn the pump on . You will only need it at the lights onlookersa will think you have burst a hose. ride into the petrol station an filler up for free.

not too many bucket racers fit waterjacket to their bikes, that was in the 80's when water cooled bikes were rarer than rocking horse shit. Now you just buy an FXR and go racing.

A CO2 fire extinguisher would be even more spectacular than the water spray cooling but may result in cold siezures

Oh I didn't see you up there. Lol@faux-steam engine :scooter:!

Question still remains though why they did bother to put natty little jackets on their bikes? I mean, it wasn't just for rocking-horse shit bling factor?

[stanko]

on a 2 stroke it means you can run closer piston to bore clearences, and they dont go "off" like an aircooled 2stroke when they overheat

[The Pastor]

bro just do it and make sure you take alot of pictures! It might work fine.....

[Dadpole]

And do yourself a favour. Throw away ye olde Zen and Art book. A load of bollocks IMHO.

[xwhatsit]

Lol I never understood the vitriol motorcyclists direct at Zen and Art; I think it must be to do with being pissed off it's got nothing to do with motorcycle maintenance haha. If you read the book as a beginner's guide to philosophy, it's actually quite fascinating if you're into such things. Which I'm clearly not, as I'm a tough motorcycle dude *ahem*

[Ixion]

Maybe because he rode a Honda ? Though the CB77 was a jolly good bike in its day. I owned two and I'd buy one and restore it if I could find one

[xwhatsit]

Ah yes, CB77, that's right -- 305cc, not 350. Superhawk. I remember reading though that they are really bloody expensive though... collector's items. Upon some casual googling though, it appears that it's not a sidevalve, it was one of the first overhead cam models and had a 9200RPM redline lol.

Maybe the engine seized just because Pirsig was such a dry old bugger?

[jrandom]

I can't believe such an intricate mechanism can contain such violent explosions.

I had an almost identical reaction the first time I looked inside a (fucked) CV joint. I was amazed that such a clonky-dinky bit of steel had ever worked at all, let alone spun away quietly for years under torque that would rip my arm off in an instant.

Any sufficiently advanced form of metallurgy is indistinguisable from magic.

I prefer to get my fixes these days playing with guns - the oldest and simplest, yet still most ejaculatorily-compensating, form of internal combustion engine.

And I don't think Pirsig's engine ever actually seized; that was just a plot device to hang more MOQ shite on.

[scumdog]

Ba-dum, tsh.

Seriously, though. You're committing Engineering Design Error #1 by falling in love with an intermediate hypothesised solution rather than focusing on your true requirement.

Your true requirement is to make the bike go faster.

Burning more fuel in each engine combustion cycle is an excellent brute-force way of achieving that, but cooling the air intake is not the only way of burning more fuel in each combustion cycle.

For that matter, burning more fuel in each combustion cycle is not the only way of making the bike go faster.

Haven't read the whole thread but relating to the above; to make heat you have to burn fuel, at idle (when there's not much airflow over the engine) your bike is not burning sufficient fuel to make heat of damaging proportions. (Unless you have a fairly high 'idle' speed of course!).

Example: My 7 litre hot rod engine has no fan, I can fire it up from cold and let it idle and it will take 15 minutes or more before it gets to normal running temperature, if I hold the revs at 2,000rpm or so it will overheat in just over 5 minutes.

[frogfeaturesFZR]

Persigs bike was a BMW was'nt it ?:yes:

[MikeyG]

Have you ever tried leaving the fridge door open on a hot summer's day to keep the kitchen cool? Works a treat. Try it some time.

Fridges use a heat pump to pull heat out of the insulated box and push it out the back. Leaving the fridge door open should have no effect at all in the long term. Short term effects are noticed from all the stuff you have in it defrosting.

[MikeyG]

Wrapping copper or other tube into the cooling fins would rely on heat being conducted through the fins and into the tube, for highest efficiency you will need good joins with large surface area between the fins and the tube. Soldering the tube to the head with big blobs of solder may help.

Or when you are sitting at the lights you could just turn the bike off until the light goes green.

[jrandom]

Leaving the fridge door open should have no effect at all in the long term.

... apart from heat dissipation from the compressor motor gently warming up the surrounding area.

[Ixion]

Persigs bike was a BMW was'nt it ?:yes:

His was a CB77 Honda. His companion (John ?) had a BMW

[xwhatsit]

Wrapping copper or other tube into the cooling fins would rely on heat being conducted through the fins and into the tube, for highest efficiency you will need good joins with large surface area between the fins and the tube. Soldering the tube to the head with big blobs of solder may help.

Or when you are sitting at the lights you could just turn the bike off until the light goes green.

I was thinking about using large blobs of thermal paste. Solder too would help, didn't think about that.

What I should really do is keep the connected copper tubing up, but use it to boil water... what can I do with that? Make coffee, for one. Run a small turbine?

[Dadpole]

You could install a boiler and small funnel. That would get people wondering WTF.