Valve Gear Problems

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Valve Gear Problems

Post  Heavyhaul on Wed 23 Aug 2017, 10:54 pm

Hi everyone has anyone especially the second batch builders, had any problems with the valve rods hitting the side of the valve chest, and if so how did you overcome this problem.

Kind regards
Steve Honey (Heavyhaul).

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Valve Gear Problems

Post  Simon C on Thu 24 Aug 2017, 6:44 am

Hi Steve
Yes I did is the answer and you aren’t going to like the work about to follow.
The connecting rods on my showmen’s valves hit the block wall and had bottomed in the front fork ends so could not wind them in any further. At the valve plate end I did not have enough threads behind the valve plate to shorten it enough that way ether.
The solution was to remove the valve stems (no mean feat as this involved cutting in situ to release them) lengthen the thread (if required in my case that was 5mm) at the fork end and then remove about 8mm this was already removed by the in situ cut amount, from the end of this thread.
The movement that this created meant that the valve stems no longer hit the block wall and I also have enough extra movement for setting the timing.
I think the above will make sense to you Steve but if not P.M your Number and I can probably explain better over the Phone.
Simon
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Re: Valve Gear Problems

Post  Mark the spark on Thu 24 Aug 2017, 8:24 am

I just finished doing this yesterday I had to add about 10mmto the lenth of the thread and also had to tap the thread a bit deeper in the sliding fork but all fine now and the timing is spot on now at least until its steamed for the first time and I have to reset the timing again

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Valve gear problems

Post  Heavyhaul on Thu 24 Aug 2017, 10:51 am

Morning Simon,
Thank you for your reply I'm glad I'm not the only one having problems, I'm about to remove the valv e rods after measuring and commence with the alterations.

Regards
Steve.

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Valve gear problems

Post  Heavyhaul on Thu 24 Aug 2017, 10:57 am

Morning Mark,

Thanks for your reply I was wondering about tapping the valve fork as the valve rod doesn't seem to screw in far enough even with the locking nut left off, did you have to shorten the valve rod at all, and if so by how much.

Regards
Steve.

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Re: Valve Gear Problems

Post  Mark the spark on Thu 24 Aug 2017, 5:17 pm

Hi Steve
I did not shorten the valve rod I just added about 10 mm extra thread and taped the fork a bit deeper and all worked great
Mark

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Re: Valve Gear Problems

Post  Capricorn1 on Thu 24 Aug 2017, 9:40 pm

I cut around 10mm off the 8mm thread and then ran a die down to leave the same length of thread on both valve rods, this brings both valves towards the crankshaft and stops them hitting the front end of the steam chest.

However at the LP side I found the valve guide bore in the weigh shaft bracket was not on line with the cylinder block and while it is possible to screw the valve spindle into the guide (fork), on the first steaming it made the engine rather tight and left wear marks along the valve guide.
So I set up a DTI to measure the deflection on the valve rod as I screwed the two items together, the mis-alignment is 0.6mm horizontal and 0.35 vertical.

I did ask Steve for a new valve guide without the 8mm tapped hole so that I could off-set it on the 4 jaw chuck and drill a hole off-set to the above amounts, but STW only have a stock of finished guides and don't have time to make a one-off.........

This was a few months ago and what with working away and other things I've not been able to get the issue resolved, so the plan this weekend is to set the valve guide (fork) up in the lathe, drill out the threads and then silver solder in a plug, then off set the guide in the 4 jaw chuck and re-dill and tap the threads to bring the hole into line with the valve spindle stuffing box (gland).

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Re: Valve Gear Problems

Post  gwr1475 on Sat 26 Aug 2017, 6:05 pm

Hi all,

Just wondering if the second batch was when STW changed to the open both ends cylinder block?

Mark
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Re: Valve Gear Problems

Post  Capricorn1 on Sat 26 Aug 2017, 8:46 pm

Without having any detailed drawings to check the dimensions of the valve spindle bores in the cylinder block or the valve guide bores on the weighshaft bracket it's difficult to determine where the error is.
When I set the bracket to the boiler barrel the setting tool for the HP side screwed on perfectly, so I decided to leave it as moving the bracket around the barrel would only throw both guides out of line.
The new design of cylinder block does not effect the spacing of the valve spindle stuffing boxes as these are still part of the block.

With a little patience I off set the LP valve guide in the 4 jaw chuck and after double - double checking things I re-drilled & tapped the M8 hole having previously drilled out the threads and silver soldering in a plug.
The valve spindle now screws into the guide easily on the engine and the valve, spindle and guide move freely.

So having washed out the boiler, sorted out the few leaks that appeared at the first steaming and put things back together, filled the boiler and added some water treatment we're already for lighting up tomorrow morning.


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Valve Gear Problems

Post  Heavyhaul on Sat 26 Aug 2017, 9:01 pm

Hi Mark,
yes the second batch has the modified cylinder blocks.

Regards
Steve.

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Re: Valve Gear Problems

Post  gwr1475 on Sun 27 Aug 2017, 1:11 am

Thanks Steve.

Not sure if mine is from the second batch or not, but I do have both end open cylinder block. Just wonder if I will run into the same valve gear problem. Has STW fixed this issue?

regards

Mark
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Re: Valve Gear Problems

Post  Mark the spark on Sun 27 Aug 2017, 9:22 am

gwr1475 wrote:Thanks Steve.

Not sure if mine is from the second batch or not, but I do have both end open cylinder block.  Just wonder if I will run into the same valve gear problem.   Has STW fixed this issue?

regards

Mark
If you tap your sliding fork a bit deeper before you fit it you will be half way there
Mark

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