Valve timing a 5″ Tich

[Kevin BennettParticipant @kevinbennett25223]

Hi Has any body have information on static timing a 5" Tich as i have been on it for 6 1/2 hours with on luck.

I think i had it at one point then lost it again it bit the end of my finger at one point . one of my problems is i have a memory problem and keep forgetting what i have moved.

so any tips please or photos of the left and right side of the engine.

Thanks Kevin

[Kevin BennettParticipant @kevinbennett25223]

Valve timing a 5″ Tich

[Fowlers FuryParticipant @fowlersfury]

Kevin, you haven't witten which of LBSC's alternative valve gear you have made for Tich.
Assuming you've made it with Walschaerts, it might be helpful to look at some valve timing vids on YouTube. Though not for a Tich, there's one vid (of many) which explains clearly enough the process. https://www.youtube.com/watch?v=rRGGSr68miQ

[Kevin BennettParticipant @kevinbennett25223]

Hi Thank you it is the Walschaert type and the video was spot on a big thanks .

Thanks Kevin

[Richard KellawayParticipant @richardkellaway]

I would recommend looking at EIM April 1982 where Jim Ewins describes Walschaerts valve gear in detail and how to set it. I redesigned the valve gear on my 'Mountaineer' in line with the article and the results were perfect.

Be careful as some of these videos can be misleading. For example in the video above:-

The method of setting the front and back dead centres using a felt tip pin is not accurate. You need to be more precise as a small rotation in the crank will cause the expansion link to move out of position, which he even points out in the video. You need to use scribed marks on the wheel and use a pair of dividers to find the mid point between the two marks.

Don't pay too much attention to the return crank setting being at 90 degrees. This is only applies if the expansion link tail pin is at the same height as the centre line of the coupled wheels. This is often not the case.

He is correct in saying that at both front and back dead centres there should be no movement of the valve when lowering and raising the die block. If this cannot be achieved it is likely to be caused by one or more of the following:-

• Return crank position set incorrectly
• Return crank length incorrect
• Eccentric rod length incorrect
• Incorrect position of expansion link tail pin hole (sometimes referred to as 'Backset' )

He refers to the use of a dummy/adjustable eccentric rod to try eliminate any errors. This should be treated with caution as changing the length of the rod is likely to require repositioning of the expansion link tail pin hole!

He is correct in saying the valve should be set so the amount of Lead is equal at both ends. In fact this is really the only adjustment you have available on this valve gear and no adjustments here will be able to compensate for geometric errors elsewhere.

He talks at the end about cut-off but does not explain this is determined by the length of the valve and reducing the length of the valve (same amount from both ends) will result in an increased cut-off.

I hope this will be of some use

 

Edited By JasonB on 16/11/2020 06:51:43

[Nick Clarke 3Participant @nickclarke3]

Don Ashton's articles and book (available from Camden Miniature Steam) are extremely useful, but I find Martin Evan's books less so.

Edited By Nick Clarke 3 on 16/11/2020 12:41:17

[Kevin BennettParticipant @kevinbennett25223]

Hi Guys thanks for your help i did take all the linkages off both sides to check the dims,and found no errors.

I did get it running today it needs some fine tuning i also need to look at the pined linkages as some of then started to creep out and i have to look at the reverse but overall it works.

I will see if i can get the Camden book.

Thanks Kevin

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