gmedson

In the Everything Diesel thread, Three Cylinder radial model diesel engine , started by earlwb, YouTube links feature three such engines running. These appear to be WOHM engines, built by a German craftsman, based on Hermann Fricke's basic design but perhaps with Taifun pistons and cylinders.

Here is some information about Herr Fricke and his FMO engines. A good bit of this is supplied by my friend Luitpold Fiess in Germany.

A former watchmaker, Hermann Fricke started building his engines in 1959. FMO stands for Fricke Motoren. His flat twin diesel and glow engines soon developed a reputation for running well. He offered different sizes up to 16cc (0.96 cu in). In 1984 he started building a small number of three-cylinder radial diesel engines. This was the first time a model diesel engine was built as a three-cylinder radial type! A YouTube clip shows a Fricke reed valve radial diesel running. http://www.youtube.com/watch?v=MWQwlkZJwf8.

Luitpold and I each have an FMO radial diesel. Displacement is 3.54 cc. Cylinder bores are 11.9 mm and stroke 10.6 mm. Capacity of each cylinder is 1.18cc. Crankshaft is one-piece, running in bronze or aluminum bushings. There are three crank throws, 120 degrees apart and pistons cycle in unison. If it were a flat, opposed-cylinder engine, we would call it a boxer. All cylinders fire at the same time, and forces are balanced so that there is negligible vibration. The two versions of the engine are reed-valve and rear rotary-valve induction. The reed-valve version has its carburetor between two cylinders, as shown in the YouTube clip at http://www.youtube.com/watch?v=MWQwlkZJwf8&NR=1. The rear rotary valve model has its carb centered at the rear, behind one cylinder, as shown in my accompanying pictures. An M4-threaded propeller stud screws into the front of the crankshaft, and the prop driver is retained by a brass collet. Carb is a simple rotary drum type with no air-bleed adjustment.

Like many other model diesels, steel cylinder sleeves are threaded into the crankcase, each having three radial exhaust ports with three transfer ports between, milled into the inside of the cylinder walls. Pistons are cast iron. Each cylinder has a cast iron (or sometimes steel?) contrapiston in the top of its bore, and finned aluminum head muffs, each bearing a tommy bar-style compression adjuster. The engine rear cover and rotary drum housing includes a radial engine mount.

I have not dissembled my engine enough to get a really good look inside, so I can't tell you much more. However, Luitpold says that each aluminum connecting rod has a cap and two-piece bearing at its lower end. Cylinder is steel and the piston is ductile cast iron. Fits and finish are first rate. Of course the aluminum castings don't look as nice as those from the major manufacturers, such as OS and Saito, but the minor casting "flaws" (shallow voids showing molten metal flow) add to the charm of a handmade engine! Compression of all three cylinders is superb and the engine turns over very smoothly with no indication of any slop, such as at crank journals and wrist pins.

One of my pictures shows the grooved spinner nut and pull rope Herr Frick made for me that harkens back to the olden days when some model engines were so equipped.
Luitpold gives weight as 215 g (7.6 oz), and he has a reed-valve model. My rotary-valve engine weighs 224 g (7.9 oz).

And now to the two-cylinder engines. Herr Fricke has made these in boxer configuration since 1959 in sizes up to 16cc as both diesels and glows. Clanford shows three of these in his Pictorial A to Z of Vintage and Classic Model Airplane Engines. You can see a 1.5 cc FMO diesel running on YouTube http://www.youtube.com/watch?v=k0irFW5ypQg. This appears to be the same engine as mine, which is actually closer to 2.4 cc. For a 6cc FMO, see http://www.youtube.com/watch?v=jfp-lRYfDMQ. Notice how nicely the smaller one runs! Sweet! But the dog seems unimpressed...

My FMO boxer diesel uses the same pistons and cylinders and associated other bits as the radial described above. Therefore, displacement is 2.36 cc. Front cover, back cover/radial engine mount, prop driver, propeller stud, exhaust stacks, cylinder muff, and compression tommy bars are the same too.

Considerable variation appears among FMO engines through the years, both in major aspects such as size and rotary or reed induction, but also in minor details. My three-cylinder radial has bronze crankshaft bushings. But my boxer has aluminum. There is a separate aluminum bushing in the front crankshaft housing, and the rear cover is reamed for a running fit.

Speaking of fits, they are not as good for my boxer. Piston fit is too tight, at least for one cylinder anyway. And connecting rod fits are looser than in the radial but within the range expected for most engines.

The final picture below shows Luitpold (with engine) and Hermann Fricke (in white) at an engine collectors event in Germany. Herr Fricke is now 86 years old and he no longer makes his wonderful engines for sale.

As you have likely guessed, my friend Luitpold brokered the deal for me to acquire my two FMO engines. I thank him for this and many other kindnesses, including a lot of the information in this article.

Regards. -Gary

Hobbsy

My Feedback: (102)

Good stuff Gary and thanks, when I was growing up in western Pa in the 50s our neighbor had a Fricke steam traction engine of about 20 hp.

gmedson

Hi Hobbsy - Thanks. A steam traction engine? Was this by the same Hermann Fricke I wonder? He would have been in his 30s then. Perhaps before he started model engines... Regards. -Gary

Hobbsy

My Feedback: (102)

Gary, I'm embarrased, I'm going to be 69 in couple of weeks, we'll just have to let that one slide. The tractor was a Frick, here's a picture anyway and I won't steal any more of your good, informative thread. Could be Fricke Americanized though.

gmedson

Hi Hobbsy - Well, I am going on 71 and my less-nice son calls my episodic mental misfires "oldtimers disease". So far, the grandkids have not picked up on this.

Neat traction engine. First one I saw was when I was about ten at YMCA Camp Meehan, across Spirit Lake from Mt. St Helens, Washington State. Rusted tractor was at abandoned Sweden mine near the camp. Great attraction for the campers!

There. See. I can lead the thread astray too!

Regards. -Gary

Hobbsy

My Feedback: (102)

Thanks Gary, I'm going to make an assumption here, the fact that these engines run makes me think, (no, actually know) that Herr Fricke sat down and planned these out taking into account bore and stroke ratios, fuel transfer velocities, rod angularity, the compression pressure would have to be set in the middle of the contra range. Lots of things to get straight in your mind before ever turning on the lathe. I'm more of a beauty is in the function guy, but these have the best of both worlds. Thanks again for sharing.

PS, I remind my wife now and then that as long as I can get Harley upright I ain't old yet.

earlwb

Thanks for the information. It is very interesting.

fiery

My Feedback: (2)

Does anyone else think the flat twin boxer and radial FMO's are engineering works of art?

I can't decide which I like most ... my heart says the radial, for the sheer "wow": factor, but .... my viscera the twin.

[I ride a BMW R1100S so I am predisposed to boxers! ]

If they were remanufactured again, I would zack up ..

Hobbsy

My Feedback: (102)

You ride a great bike Derek, I have watched for a 60s 500 for years, I saw an R-27 250 single once, one of them would bring big bucks now.

I agree that the lil Diesels are works of art, does the fact that they run take them out of the art catagory? Not a chance.

AMB

few years back a buddy of mine had the boxer twin what a great machine to ride will never forget it awsome martin