FireFly 46 liner

I have made a mistake and started making the liner out of cast iron instead of EN8. Will this work with a cast iron piston or do I need to order some EN8 and start again.

I dson't know how I made this mistake as I always look at the drawings before ordering the metal but I had it in my mind that it was cast iron from the start and never checked until I was reading the latest issue of ME

What an idiot

Havn't built IC engines, but as far as I go, CI, on CI is fine. I think there is an engine building thread, in the IC eng department of two engines built, one with a steel liner, and the other with CI. The experts will come and shot me down. Ian S C

The thread I was thinking of was ED Racer 'times two' by Ramon Wilson, its worth reading. Ian S C

I've used iron liners a lot in combination with iron rings on several slower reving IC engines but not sure how it works at the higher revs of a glow engine. As Ian has suggested Ramon is far more knowledgable and his article would be worth reading or drop him a PM if he does not reply here.

J

PS Cheap e-bay Tacho arrived in the week so will see what revs I'm getting later.

J, is that one of the non contact laser tachos? Ian S C

Yes, one of these

Got side tracked doing the final assembly on my 1/2 scale Domestic so will run the Firefly tomorrow and report back, may also get that going with luck.

J

Found a short length of EN8 on ebay so I am going to remake the liner as per the drawing. Just got to wait for the postman.

It only a couple of quid so not a big mistake.

I used to run cast iron piston, ring and liner up to maximum of 15,000rpm in my flash steamer (113mph)

Windy

Mike - For what it's worth - as mentioned by Ian I have used cast to make a liner which machined easily and produced a good finish however the initial piston/liner fit reduced slightly upon running compared to all the other 'cast iron piston in steel liners' set ups made. The one difference , and one readilly apparent, to using a steel liner is the truly black exhaust gunge!

I have explained elsewhere but from what I have subsequently read it appears the best combination of material for these small engines up to about 25mm bore - without recourse to any form of hardenening and potentially the subsequent need for grinding - is a cast piston in a leaded steel eg En1a liner. This info became apparent after the 'Racers' were made and evidently this combination has been used by several manufacturers in commercially produced engines.

All the engines made since have used this combination with great success, both in the machining and lapping and giving a very good piston seal. At first I had doubts about the possible longevity of such a set up but further reading particularly about commercial use has since allayed this worry.

Now you have it, using En8 as called for will be fine but personally, were I making one, I would now use En1a

Good luck witjh your build

Regards - Ramon

Jason, that's the same tacho as mine but at twice the cost - now theres inflation for you