Piston repair - best way?

[Peter S]

Tim,

Just wondering what type of engine this is? You seem to get some interesting jobs!

[Evan]

I would guess that it was originally designed for pumping water and has been adapted to power a canal boat.

[Timleech]

Originally Posted by Peter S

Tim,

Just wondering what type of engine this is? You seem to get some interesting jobs!

It's a National DM2, built by the National Gas & Oil Engine Co of Ashton-under-Lyne. They later became part of Mirrlees National, I suppose what remains is now part of MAN.

They were built under license from Russell Newbery, initially because RN were offered a contract for more units than they could handle for a new fleet of Narrow Boats for the Grand Union Canal Carrying Co. in 1933. RN (well, their successors, at one time they were owned by the makers of Sterling machine guns) still make them in very small numbers, some history here:-

http://www.russellnewbery.co.uk/history_1.html

This is a 2-cylinder, 18 bhp @ 1000 rpm, hand start only, they were built in 2- 3- & 4-cylinder versions mainly for generators or marine propulsion. Nationals made them for a number of years, as well as a scaled-up version, and then developed their own variant with conventional overhead valves.

Tim

[Timleech]

Here's the end result:-


Ring grooves skimmed out for new oversize rings, crystalline material faced off the piston crown, then bored out.



Bronze top hat sleeve made for piston plug, shrunk onto the plug & then finished to size & put in freezer.



Piston heated, ice cold plug pushed in & then held in place in the press until cold. Bronze flange turned off to match profile of crown. Nut & washer fitted with loctite retainer & thread peened over.





Tim

[A.K. Boomer]

Nice work, on the formula v engines we used to over cut the ring land grooves and install a thin metal spacer - on the power stroke side (bottom of the groove)

Do you have enough piston material for the under nut to grab or did you have to make up a reinforced washer? (due to the diameter of the bronze).

I swear that damn piston reminds me of an oil can er sumthin...

[RetiredFAE]

Originally Posted by A.K. Boomer

I swear that damn piston reminds me of an oil can er sumthin...

Looks like the old Kerosene fuel can we used to fill the lanterns on the ranch when I was a kid in the 50's. Got used every winter when the power went out until we finally got a generator.

[Timleech]

Originally Posted by A.K. Boomer

Nice work, on the formula v engines we used to over cut the ring land grooves and install a thin metal spacer - on the power stroke side (bottom of the groove)

Do you have enough piston material for the under nut to grab or did you have to make up a reinforced washer? (due to the diameter of the bronze).

I swear that damn piston reminds me of an oil can er sumthin...

No problem over the washer area, the original (actually a tough steel packing piece about 5mm thick) just needed a whisker skimmed out to clear the bronze.

Tim

[wierdscience]

Good looking job Tim,if that works loose there isn't another thing that could be done to stop it.