Twin in-line engine

[makila]

Hi,

I am a bit late in posting this engine - a twin cylinder in-line 62cc engine design from WWW.cad-modelltechnik-jung.de

The plans are quite easy to follow and I have made just about all of the parts as can be seen from the picture. I had not taken pictures of the various stages of machining as I had not intended to post this one but as I had some cam questions on the tea break section, I thought I would put it in should others be making a similar engine from modelltechnik.

Although it was an easy-ish engine to make, the heads required some thought to make as there is no instructional text that comes with the plans. Another point was perhaps the rather technical crankshaft which sports no less than 5 rather large bearings so it looks like a tough beast.

Anyhow, I have just the camshaft to complete, once I complete my cam grinding jig, and have some confirmation from the designer that the cam drawing is correct (see the Tea Break thread cam profiles). The crankshaft is made up from 7 sections and these are pressed and bolted together to make one rotating assembly.

It is a rather square looking engine with a belt driven cam shaft and has a few quirks to overcome during machining but otherwise it seems to be taking shape. It is a glow plug type ignition so that has eliminated making a timed spark system and saves construction time. The downside is it will require that nitro type of fuel that model flyers are familiar with. Anyhow, the next installment should be completing the cams on a cam grinding jig that's taking forever to build but will be useful for other projects.

Till then, thanks for reading.

Steve

 

[petertha]

Beautiful work. Cant wait to see it run.
What did you make the cylinder liners out of & how did you finish them (meaning lapping or whatever)?
How about the rings, did you follow his method or do you have your own recipe?

 

[makila]

I used a 50 x 180mm piece of Meehanite cast iron to create the liners and rings from. The bore was bored to 34.5mm and honed the rest of the way to 35mm. I used the expanding 3 legged type of honing tool, they took a long time to do and I wore three sets out during the process. The Pistons were made following the honing to ensure .5mm sliding fit.
The rings were made from the same stock, then cut with a chisel (carefully on a smooth anvil and sharp chisel) then opened the ends up to hold onto a 6mm piece of square rod. The rings then we're heated to a red glow before they fell off under their own weight and allowed to cool. Then used a small file to square ends targeting about .005 to .010 (imperial) gap in the bores. There is an attrition rate however, so I made 5, shattered 2 during chisel breaking and one failed during heating and ended up with 2 good ones.

 

[petertha]

Great thanks. Not sure if you saw this but Terry made a ring cleaving device, post 211
http://www.homemodelenginemachinist.com/showthread.php?p=252921&highlight=ring#post252921

What's the plan for camshaft hardening once you get the lobe orientation confirmed? I take it its turned from solid, not hardened lobes attached to a shaft?

 

[IC-man]

With regards the snapping of the rings, and I have made many, I use this method, grip the ring with 2 pairs of flat nose pliers ( as close as you can get them) and just snap them I have never broken one yet. try it on a scrap ring

 

[Johno1958]

Now that is nice. Did the plans come in English?
John