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Author Topic: Doll 360/3 Annoying Knock  (Read 319 times)

Nick

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Doll 360/3 Annoying Knock
« on: June 20, 2020, 08:08:15 pm »
Any tips for curing this knocking? At first I thought the screws were going in too far and being hit by the pistons as the decorative caps were dented in a little... I was able to round them back out with a wooden dowel and hammer

Runs quietly with the screws out, but any back pressure and the knock gets quite loud  :-\



Nick

yozhek

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Re: Doll 360/3 Annoying Knock
« Reply #1 on: June 21, 2020, 02:50:34 am »
Hi Nick,

That is quite violent at higher pressure :o
Just a thought, can you retard the timing of the steam valve? As you know i know nothing about steam but looking at the rather insubstantial crank and bearings i hazzard a guess there is a fair amount of free movement there to create knocking if the timing is too advanced. Or maybe the crank has got bent in the centre where it is unsupported upsetting the timing?
Apologies for sticking my nose in if you have already tried this ::)
Best wishes
Ade

Nick

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Re: Doll 360/3 Annoying Knock
« Reply #2 on: June 21, 2020, 09:53:56 pm »
Hi Nick,

That is quite violent at higher pressure :o
Just a thought, can you retard the timing of the steam valve? As you know i know nothing about steam but looking at the rather insubstantial crank and bearings i hazzard a guess there is a fair amount of free movement there to create knocking if the timing is too advanced. Or maybe the crank has got bent in the centre where it is unsupported upsetting the timing?
Apologies for sticking my nose in if you have already tried this ::)
Best wishes
Ade

Thank you for the help Ade, and yes it is a very violent knock. I have taken it apart enough to adjust the timing, unfortunately it's a toy and many of the parts are pressed on, so changing the timing is going to be a little more difficult than I had hoped...
Nick

parallelmotion

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Re: Doll 360/3 Annoying Knock
« Reply #3 on: June 22, 2020, 06:56:59 am »
Nick,
Maybe you could use slo mo video to figure out what's causing the knocking. Could be some wear/slop in the holes in the con rods that ride on the crankshaft--they tend to get oval-shaped over time. Another place to look is wear in the con rods where they join the piston rods. In either case the best fix would be to make new rods, although reaming and bushing them might also be possible. If there's this kind of wear you should be able to see and feel it.
Brent

Dan-c

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Re: Doll 360/3 Annoying Knock
« Reply #4 on: July 02, 2020, 03:20:10 pm »
Sounds like big end knock are the ends worn oval ?

Tadfafty

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Re: Doll 360/3 Annoying Knock
« Reply #5 on: July 02, 2020, 10:22:01 pm »
Something worn being moved by the pressure?
If I had the storage space... And the money... I'd have a few more engines.

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