Originally Posted by gkamysz
CNC has very little to do with model engine cylinders. CNC is just a tool. The fine fits require know how.
I've never seen a bore taper published for a reliable model diesel. I suppose it's easy enough to measure, but I haven't measured a diesel. Materials come into play as well. Modern is one thing, but comparing something like current F2C engines to CS and grouping them together as "modern" is simply wrong.
I've never had any problems hand starting a glow to diesel conversion. Heck, I run ringed diesels and they hand start. But, I also have engines like the MDS 1.5 tether car diesel that was so poorly built the cylinder head didn't seal as supplied, and then broke a wrist pin when that was remedied. One day, I will piece together a running engine from the 3 I have and my own parts.
Like anything else there is quality and there is product made to look like it works. Unfortunately, you can't tell until you attempt to use it.
I have this thing about how people compare the current world to how it "used to be". Th truth is the world is virtually the same with respect to people. People make the decisions about the way things are. If they want to make a world class engine, they will do so. If they need to unload scrap metal at retail engine prices they will do so. How many low quality diesels were produced 50-60 years ago? I only know of a few names, but you guys know which ones I'm talking about, Gotham Deezil, etc. Is that really any different today?
Yes I agree that in "those" days there were rubbish diesels too. Over here we used mostly diesel engines in our CL planes espescially Webra and Taifun
and we always did handstart them. (who had heard of electric starters then anyway? besides these are a nono in any case) I know nothing of CNC, can a correct taper be machined on CNC ? What I do know is that lapping is not for everyone's skills and understanding. I have learned it from old friend Harry. It is all a matter of FEEL. When you turn around a Benno Schlosser you feel (or do not feel ...) the delicate springy-like compression : that's high class workmanship. When I first started my Mk-1 and 2 tiny fragile Frogs I had some doubts but they sprang alive quickly. One funny thing : I have had a few CNC lathe operators visiting and when they stand in front of my Myford they raise hands not knowing what to do ! It is a different handling of machinery I suppose ?