Pistons

What grade or specification alluminium should I use to make pistons which run in cast iron sleeves. Alluminium to specification 6068 expands to much and the pistons seeze up. I allowed 0.05mm (2 thou) play, for a 40mm diameter sleeve/piston, between the sleeve and the piston.

Hi Joey.

I had a look at one of my i/c engine books (miniature internal combustion engines by Malcolm Stride).

And according to his reference you could use the following :

Cast : LM51

Machined from barstock: HE 15 OR HE 30.

For small compression engines (Diesel ) He recommends cast iron but no spec supplied .

I imagine these designations change from one country to the next etc so you may need to search for an equivalent on the internet .

There have been many articles in Model Engineer regarding engines so try there .

Alternatively try the MODEL ENGINE NEWS website as they have masses of info on many types of engines .

With a 40MM bore i would guess that you are using piston rings ?

Are you sure that it is not them that is seizing in the bore (ring gap too small )

And if you are using rings try a little more piston to cylinder clearance say 3-4 thou .

Are the pistons oval ? Should be smaller accross the wrist pin (gudgeon pin hole ) to allow for deflection or any flexing .

Ian

I've used HE30 (6082) on several IC engines but would be looking at more like 0.004" clearance.

What sort of IC is it? slow reving hit & miss or higher reving 2/4 stroke? What rings are you using?

J

The engine is a 40% scale Anzani W 3 cylinder model of the engine which was used by Bleriot when he completed the first flight from Calais in France to Dover in England.

I am using cast Iron piston ringss and the pistons have beem ground oval ( smaller across the gudgeon pin) by 0.05mm ( 2 thou)

I will check out the the suggested remedies and report back at a later date.

The engine is presumably slow revving with atimed exhaust valve and an atmospheric valve. In its current configuration it turns a 31 inch (diameter) X 12 inch (pitch) propeller at 2800 rpm, full throttle and Idles at 700 rpm.

Thank you to everybody that posted replies so far,