Progress so far...

[ejbrush]

So, I'm putting together the second diesel motorcycle. Here is what is done so far.
http://img513.imageshack.us/img513/7239/1000455lu4.jpg
Normal Yanclone power, Ariel transmission, scooter shock assy. for the seatpost, Honda 360 front end, repro Harley WL rear fender, lots of DOM tubing.
I don't want to talk about the clutch, beyond saying that if what I copied can cope with a 15hp garden tractor it ought to stand up to a 9hp motorcycle. It is cheap and ugly.
Clipped the fins off the flywheel, removed all shrouding. Have not yet run the monster to see if it gets too hot, I'm betting no. Don't dare run it untill the lack of brakes is addressed.

[pietenpol2002]

Great job! Now get that thing on the road and educate us as to your experience with the free air approach. Many of us would love to go there. And how about some pics of that "ugly" clutch. I have a hunch regarding what you've done, but we need the visuals and then a report of how it works. And BTW, where in Wisconsin are you located?

Cheers,
Ron

[Darren]

I ran my Hatz 1B30 with no fan for a while - the head gasket weeps a bit of oil now....

I spoke to the man who developed the first Hatz 1B30/Enfield conversion at the behest of Hatz. He said they found that the engines would overheat in traffic without the fans fitted.

[arnaud]

Why did you clipp of the cooling fins??
Do you think that the riding wind will be sufficient?

[Darren]

The nylon fan is screwed onto the steel flywheel.

It was missing when I bought the bike - took me a while to sort out a replacement.

[Diesel Dave]

There are many benefits to going fanless as well as just as many drawbacks.

For a start every petrol/air cooled motorcycle I've ever had will overheat in summer when stuck in heavy traffic - for a start all of the fins are laid horizontally so they actually trap hot air when stationary. the best option was the 45 degree fins used on the Panther singles as this would work in both directions.

Most oil cooled bikes don't have a fan to take the heat from the rad when stationary either.

Only water cooled stuff manages to keep the engine at a steady temperature, petrol or diesel - that's why there are no air cooled cars, trucks or busses anymore.

Ok enough of the history.

Diesel fan cooled motors have some extra restrictions:
1) the fins are much shorter
2) they are designed for a sideways air direction so unless you are installing with an inline transmission (BMW et al) they won't naturally cool in the motorcycle movement without a fan.

There is much to be gained from going fanless:
1) lighter flywheel frees up HP to push the bike forward
2) thinner engine profile
3) faster heat up times in winter

Remember that these engines are designed to operate in 40 deg ambient temperatures when shut inside a concrete mixer. If you look at the Indian Greaves unit compared to it's parent Lombardini lump you will see that the fins have been increased by 100% to operate in the Indian summer climate. Also the iron barrels don't cool as well as the Yanma alloy ones.

In a transverse fitting the action of the motorcycle travelling forwards will reduce the amount of air thet the fan will circulate - venturi affect of air passing sideways over the fan intake will try to suck air back out of the fan.

I'd estimate you could gain as much as 5% by going fanless and lightening the flywheel however I would also do the following:

1) Construct an air scoop to direct air sideways accross the motor when travelling forwards.
2) Install and electric fan on a heat switch to suck air past the motor when stationary & hot.
3) Construct a decent flywheel cover.

For those of you that have diesel bikes on the road with fan cooled transverse motors try the following (safety caveats apply). After running/riding the bike for half an hour; feel the airflow exiting the shrouding when stationary - nice and warm and lots of it. Now repeat this test when running full pelt down the road and despite the general airflow try feeling the hot air exiting - much less because of the venturi effect sucking air back from the fan intake.

From my 4 years of riding a diesel bike I've never suffered a hot leg or anything else even in the height of summer - however the BMW boxer has nearly melted my boots off me, and the 500 petrol Royal Enfield got so hot it dropped a valve seat. Interestingly the boxer motor has fins that work in both air directions - forwards and upwards, but the bike's handbook contains clear warnings not to let the motor idle for more than 5 minutes when stationary without additional cooling air being provided.

If you want to go fanless I'd say go for it, but don't just dump the fan and shrouds without at least fitting a cylinder head temp gauge before doing the conversion so you have some data to compare against. in the case if the fan being cast into the flywheel consider having the balance factor checked beforehand and re-balanced afterwards.

It's all experimenation at the end of the day and whetever works in the UK's abysmal climate would not apply to someone else in the outback of Aus or the Nevada desert. My worst fear in the UK is riding the beemer on a blisteringly hot summer day and then be faced with a river crossing 'ford' with ice cold water being blasted over the pots. A definite receipe for disaster.

Best of luck everybody.

Dave

[oldbmw]

I suspect that the power loss is considerably more than the 5% you suggest. Volkswagons use several horsepower for their fans, ( admittedly belt driven)
you could fabricate a forward facing airscoop to assist the fan when rolling forwards. But I think you are right that a thermostatically controlled fan is probably the best solution.

[Stuart]

Don't forget that the cast fans are considered to be part of flywheel and removing them can cause all sorts of problems apart from just cooling.

[sbrumby]

Just acouple of points on this subject, your engine looks similar to my yanmar 6hp in that it doesnt have a barrel and head that is covered in fins, the fins that the engine has is covered with a smooth aluminium cover over the fins and as such requires the metal cover to be present to force air sideways. I also agree with Stuart that on cast flywheels like my ruggerini`s, removal of this would adversly effect balance and most importantly tickover capabilities. I would also question how much power it takes as 5hp = 3600watts that would be a hell of a cooling fan. Two other points its easier to clean a cover than fins, the flywheel is a big lump but you have to drive something on the other side, cog case or cvt all helps to balance the appearance.

[andrewaust]

Certainly will be interesting to see how hot the engine gets and if balancing problems occur.

If the engine does get hot maybe an air dam to force air through the fins while riding might work, long periods in traffic I'd avoid .



Cheers

[jeremy]

Thank you Diesel Dave for an insightful piece on fan-cooled pro's and con's. I know secretly or otherwise I'd love to strip all semblance of lawn-mower-dom from my project, incl. pull-start cords, cooling shrouds, etc. and feel authentically motorcyclish--perhaps to the point of being unscientific about the honest effects of doing so, or not. Thankfully, my Hatz 1B30 has a starter and a 14-amp alternator, but still is encumbered with the need for its cross-flow cooling system--or is it? Your entry gives pause, and I'm considering the need for at least a scoop on that side to maintain effective air flow through the factory system at speed. It being brand new and pricey, I'm reluctant to both cut away at it, and possibly fry it. To anybody else who plays around with this--let us know your findings.

Of course--the venturi-effect! Somewhere in the back of my mind I was wondering just that.

[oldbmw]

I would also question how much power it takes as 5hp = 3600watts that would be a hell of a cooling fan.

I just wonder where do you get your 5HP figure from ?

[sbrumby]

The 5 hp comes from me missreading 5%