brokenenglish

Great Planes "Ultimate" biplane. Here it is: https://outerzone.co.uk/plan_details.asp?ID=13254

Following my earlier post, a bit of Web browsing confirmed that the castings source I mentioned in Oundle was called "Woking Precision Models", and that their range was taken over by Hemingway around 2006.

I didn't dare mention it... We all have moments like that...

Here's the "other side" of my engine. Note the adapter, under the glow plug. I don't think the castings can be "Hemmingway" (whassat?), as this engine has been in my possession for more than 40 years. Your build threads have motivated me to run the Atom on sparks ASAP. I'm looking forward to it, but the weather is b-awful. I would expect the Atom to perform a bit better on sparks than on glow, but that's of no importance for me. "Nice running" is far more important than minor performance differences. I seem to remember that, decades ago, castings sets were marketed by a model engineering firm in Oundle, maybe my engine is from those.

Here's my Atom Minor running on glow, at a time when I didn't have an ignition circuit. I'll run it on sparks as soon as we get some decent weather (reasonable light for photos/video).

OK Here are the photos showing the engine id. Looking from the front, you can see E & D on the left and right, and Mk III below the shaft. Again, yours should be like this (it may be Mk II).

Again, I think there's misunderstanding. Re-read my post. The front bearing is the casting bolted onto the front of the crankcase. If you look between the bolt heads, on the front of the engine, you should see an "E" and a "D", in the top part of the casting (above the shaft), and "Mk II" or "Mk III" below the shaft. Are those markings not there? I'll attach a photo within the next few minutes (I hope!).

I've just noticed that you think your engine is "unmarked" (apart from the s/n). Surely it should be marked "ED" and "Mk II" or "Mk III" on the front bearing.

Good !

Sorry John, there's a misunderstanding. Your engine should have the dish-shaped prop driver like my photo. This driver has a square hole that locates on the crankshaft. On your engine, the prop driver has been lost and replaced by odd washers with square holes cut to match the shaft. Those washers aren't original! All Comp Specials have a dish-shaped prop driver with a square hole, no exceptions. And all prop washers, that go on the front of the propeller (only one per engine!) have normal round holes. Like I said, your engine's original prop driver and washer have been lost and replaced by several odd washers with square holes. In fact, I think the reason you have several washers is simply to cover the square length on the shaft. No Comp Special ever had a front end like that.

Your engine is from September 1948. Apart from the points already mentioned, the bits around the prop driver are not at all the way they should be. Here's one that's the same vintage as yours. Your engine should look like this. You can see the various differences for yourself. It's quite likely that your engine may run well. In good condition, they're super engines.

Jeff, I thought your propeller choice seemed a bit big, so I checked the original article. Laurie Sparey obtained best results with a 13x6, but his 13x6 must have been wood, i.e. far lighter than your MA & APC stuff (and easier on the fingers!). I'm lucky to have a huge collection of old propellers, and I would never use a modern composite prop on an old engine. Wood is best, or old soft plastic in the smaller sizes. Maybe a little more ether and a little less compression would be a good idea.

Shame the photo cuts off the top of your Owat.

The photo is a bit "untidy", but I don't see anything of any significant value that would interest a collector.

22 is a Majesco 2cc - Very rare indeed. 20 is a Dyne 10cc 18 is a Dyne 6cc 15 is an HP 3.5cc 23 is a Hallam diesel (I think!) All forties vintage rare English (and Welsh!) engines. I'll need to dig through documentation to identify the others.

TBH, I'd rather have my ED Bees.

Yes, you're right about the serial number. I forgot about the "L" and I'd run out of fingers. The S/N couldn't be '57. By 1957 the serial numbers were on the side of the case and I think the lugs were no longer scalloped. I'm not sure of the exact year they stopped scalloping the lugs, but it was before 1957.

There's no reason to think that it might have been "marine", the M prefix on the serial number is just the production month (December). Mike, this photo shows the way your engine should be. It's the first production configuration.

ED, just a bit of info. Not all Comp Specials have scalloped lugs. It was done to differentiate in relation to the Penny Slot (the Mk II). When ED stopped making the Penny Slot, they stopped scalloping Comp Special lugs, so "later" Comp Specials have normal straight lugs, probably around 50% of total production. The serial number on the OP engine is a normal Comp Special serial number (Dec. '47). So it's very early production (looks like the 64th Comp Special made). Finally, I tried an RC carb on a Comp Special, around 40 years ago and IIRC, it wasn't very successful.

Normally, I think your Comp Special should have sub-piston induction.

You don't need an RC carb to fly a nice old FF model. If you arrange the tank to give 3 or 4 minutes of engine run (in the air), you'll get between 5 and 10 minutes of glide and such flights are very enjoyable.

Hi Tim, You were a bit unlucky with the O&R 23 that you "happened to find". They were made from 1938 until 1952, and only the 1947 model (which you have) was lugless (radial mount only). However, there was a beam/radial mount adapter available, for beam mounting, and there was also a tank mount accessory (see photo). I have a lot of Ohlssons and O&Rs and I like them a lot. Shame you found the only model with inconvenient mounting.

David you've got your engines mixed up. I have a 45 and a 62, and the front bearing housings are parallel profile, not tapered like the one in your picture, i.e. as shown in John Rickett's photo above. Your engine is bigger and/or later than you think.

I think most cars are slightly cheaper purchased in countries other than their country of manufacture. The manufacturers consider that they have a "captive market" in their own country (i.e. people who will only buy a car from their own country). Conversely, they make a slight "pricing effort" for other countries, to gain export revenue. In France, there are flourishing businesses who import new cars from abroad (say importing Peugeot from Denmark or Germany), and then sell them to French customers at a price somewhere between the domestic price and the export price. You can save a bit if you don't mind the hassle.

Congrats! What a super result. +1 for the anodising process suggestion.