Wartime piston

Having problems with a Seagull? - ask an expert here

Moderators: John@sos, charlesp, Charles uk, RickUK, Petergalileo

Salvtecmarine
Posts: 9
Joined: Tue Oct 13, 2015 8:26 pm
Location:

Wartime piston

Post by Salvtecmarine »

Hello all.

I have a wee question regarding an Sdp I have, I am in the process of restoring the o'l girl, I have dismantled it with no problem, no rusty or seized bolts, but the question is, why is there no circlips in the gugeon pin?

Finding the lack of a little bit odd.

I would be glad of any advice on this.

Thanks all
Phil
headdownarseup
Posts: 2484
Joined: Thu Apr 04, 2013 2:26 pm
Location: bristol

Re: Wartime piston

Post by headdownarseup »

I've often wondered the same.

Dont worry though, it is perfectly normal for these motors.
A LOT of the earlier 102 models (both short and long water jacket) were fitted with a non-circlip gudgeon pin. They are a sort of "floating" pin if you like with a domed ally cover at either end.
Does your crankshaft have a hollow big end to it? If so, then the crank is original to the motor.

Internals seem to change slightly at some point in the early 50's to something most people would be more familiar with i.e with circlips on the gudgeon pin.

Nice motor the SDP.
Do i have it's data yet? :P

Jon
Salvtecmarine
Posts: 9
Joined: Tue Oct 13, 2015 8:26 pm
Location:

Re: Wartime piston

Post by Salvtecmarine »

Hello Jon

Thanks for the reply, put my mind at rest.
I checked the piston and it is the original hepolite, the big end has the hollow end cap on it too, it has the short water jacket and the piston and cylinder are in quite perfect condition for an engine built in the 40's,
Engine number Sdp8969

I just want to get it to an original working state, it has taken a few years to get its scars and scrapes, only things missing are carb, flywheel cover plate and bayonet cap for the tank.

Thanks
headdownarseup
Posts: 2484
Joined: Thu Apr 04, 2013 2:26 pm
Location: bristol

Re: Wartime piston

Post by headdownarseup »

Not entirely sure that SDP's ever had a bayonet fuel cap for the tank. (mine certainly doesn,t)

There is still an awfull lot that we still dont know about these, and as for a "standard spec" on parts, it's quite a difficult thing to answer with any clarity.

As with a lot of old engines that have seen a lot of use over the years, bits and bobs get swapped around all over the place which only makes things more difficult to work out what is still original to the motor.

Some pics of the motor in question would be good to see. Gives others a chance to see if there are any differences in their's.


Jon
Salvtecmarine
Posts: 9
Joined: Tue Oct 13, 2015 8:26 pm
Location:

Re: Wartime piston

Post by Salvtecmarine »

See, Jon, every day's a school day, I didn't know about the tank and cap, what tank should it have?
I have the engine in bits so when I get back from sea I will take some pics and post them.

Thanks again
User avatar
Charles uk
Posts: 4951
Joined: Wed Feb 27, 2008 4:38 pm
Location: Maidenhead Berks UK

Re: Wartime piston

Post by Charles uk »

To the best of my knowledge all of the wartime motors SN, SP, SD, SDP & the HSD had steel tanks with the bayonet fuel cap, some chromed & some unplated brass all with integral air bleed nipples, sorry but there was no mention of aluminium, screw fuel caps in any of the wartime part lists I seen.
Make it idiot proof and someone will make a better idiot.
Salvtecmarine
Posts: 9
Joined: Tue Oct 13, 2015 8:26 pm
Location:

Re: Wartime piston

Post by Salvtecmarine »

The tank is steel with the bayonet cap fitting, so this is the correct tank as far as I was aware?
all I need is the cap then and all is well. :roll:
Thanks again chaps
User avatar
Oyster 49
Posts: 3311
Joined: Tue Oct 26, 2010 6:55 pm
Location: Derbyshire, UK

Re: Wartime piston

Post by Oyster 49 »

Charles is quite right in what he is saying, the bayonet cap carried on into the D and C post war engines and also the early AD and AC engines, albeit with a brass tank by then.

Let's keep the advice correct please.

Unfortunately the bayonet caps are obtainable but the air bleed screws are not, quite desirable parts to seek out, which is of course all part of the fun.
headdownarseup
Posts: 2484
Joined: Thu Apr 04, 2013 2:26 pm
Location: bristol

Re: Wartime piston

Post by headdownarseup »

Sorry chaps, i made a booboo (not the first time i guess)

My SDP also has a steel tank with bayonet cap (i was thinking of something else at the time i was typing. Far too many things on the go at once)


If anyone has a couple of brass tanks with the bayonet fitting complete with caps, i'd be very interested in doing a deal.


Jon
Adrian Dale
Posts: 758
Joined: Wed Apr 16, 2014 7:58 am
Location: Tasmania, Australia

Re: Wartime piston

Post by Adrian Dale »

bit late with this due the time difference, but the Parts list for the Sd's publication #26 Page L126/1 part #s 28, 29 and 30 clearly shows the steel tank bayonet cap and chain with clip that I still have to pay you for Charles!

These tank caps are like rocking horse xxxx. I have two, shared between three engines

Interestingly on the same page part #19 shows the gudgeon pin fitted with ally pads.. never noticed that before and have not seen them fitted, but as the pin and ally pad has the same part number they were not sold separately.. Full description as per list: Pin, Gudgeon steel, hollow type, with al pads. (fully dimensioned)


AJ
User avatar
JERSEYMAN
Posts: 665
Joined: Sun Jul 31, 2011 2:47 pm
Location: Jersey, Channel Islands

Re: Wartime piston

Post by JERSEYMAN »

If I remember right, the early gudgeon pins had ally pads that were coated with stellite to prevent the pads wearing.

As far as the bayonet caps and tanks, I have a model C and a D (1946 ish) which has a brass tank with a bayonet cap which both look original, the last steel tank with a bayonet cap I think was on the SDP.
Salvtecmarine
Posts: 9
Joined: Tue Oct 13, 2015 8:26 pm
Location:

Re: Wartime piston

Post by Salvtecmarine »

That's good to know, the tank is steel, also in a relative dent free order too.

The pin had no pads fitted, also I have checked the bore adjacent to where the pin would be and it's absolutely perfect, I was a bit worried the floating pin would mark the bore.

Thanks again chaps
User avatar
Charles uk
Posts: 4951
Joined: Wed Feb 27, 2008 4:38 pm
Location: Maidenhead Berks UK

Re: Wartime piston

Post by Charles uk »

Can you post a picture of both ends of the pin, so we can ensure it is safe to run your motor with that pin, the wrong pin can destroy a cylinder during a boating Saturday.
Make it idiot proof and someone will make a better idiot.
Salvtecmarine
Posts: 9
Joined: Tue Oct 13, 2015 8:26 pm
Location:

Re: Wartime piston

Post by Salvtecmarine »

Hi Charles

As soon as I return I will post some pictures.

Thanks again
Adrian Dale
Posts: 758
Joined: Wed Apr 16, 2014 7:58 am
Location: Tasmania, Australia

Re: Wartime piston

Post by Adrian Dale »

I guess what you are saying here Charles is that if a standard pin made for a clip is fitted into a piston without the clip groove then the end profile of the pin will be too sharp, (square cut off) and as it floats will score the bore. This is something I must now check with my SD as it has been overhauled in the past. When I inspected it I did know about this detail although the pin is floating I did not check the end profile simply assuming it was correct. Thus my comment on not having seen the al end caps.

AJ
Post Reply