The Unofficial Mamod and Other Steam Forum

RocDoc · Posted: Tue Mar 18, 2008 9:59 pm Post subject: Bowman safety values

Hi everyone,

Here is an interesting thing ... I have three different Bowmans (Seahawk, M140 and M167). Each has a different safety valve. In the photo below, the one on the left is from the Seahawk and fits the M167. The middle one came with the 167 and fits the 140 ... the one on the right came from Toy Train Spares (Bowman replica) and fits the 140 but not the 167. It only screws in about half way. Maybe this is because the thread on the right value is about twice the length as the thread on the other two valves.

Do Bowman valves vary between engine types even though the boiler is the same size (140 and 167)? Is the middle one a Bowman valve?

Confused from Lincolnshire

Pete

Atticman · Posted: Tue Mar 18, 2008 10:08 pm Post subject:

Hi Pete, the bowman boats we have all have no brass extension piece on either the filler plug or the SV like yours.

The middle one doesnt look like any Bowman SVs we have, but spose it may be a very early one, though as yous is a metal based I dont think its quite right.

All the Bowman SVs though are interchangable for ours between the boats and the engines.

Hope that helps

Mamodman123 · Posted: Tue Mar 18, 2008 10:14 pm Post subject:

The left is the same as the far right, but someone has crushed it a bit.

Not sure about the middle one, but the Bowman 101 did have a different style one, although the same thread I think

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johnreid · Posted: Tue Mar 18, 2008 10:28 pm Post subject:

My M135 has this style, much like the one on the right. However for the life of me I do not see how it can be tightened, it is a little weak in the spring and thus leaks at a lower pressure.

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Atticman · Posted: Tue Mar 18, 2008 10:30 pm Post subject:

The nut at the bottom of the stalk should be able to tighten John,

Mamodman123 · Posted: Tue Mar 18, 2008 10:34 pm Post subject:

I have one like Johns, and I can't tighten/adjust it either. You can only unscrew it from the top part.

Then I have another which you can adjust

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johnreid · Posted: Tue Mar 18, 2008 10:38 pm Post subject:

I notice that Roc Docs SVs have knurled ends whereas mine is smooth. I love the engine, it is an excellent runner sized somewhat between a Mamod and a Jensen. It has a lot of power to it also. I can definitely see why so many here brag up the Bowmans.
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RocDoc · Posted: Tue Mar 18, 2008 10:44 pm Post subject:

IndianaRog · Posted: Tue Mar 18, 2008 11:26 pm Post subject:

John, not clear what you can't tighten:

1) The two top parts outside the boiler are supposed to slide together on machined surfaces...those need to be cleaned/dremeled and oiled to work well IMO. The whole fitting is thus tightened onto the boiler by turning the knurled lower half as you would a Jensen SV

2) The nut retaining the spring is probably what you are having trouble adjusting...it does appear smooth vs. knurled. I would personally wrap a piece of leather around the upper knurled part and then grip that carefully with pliers. THEN grip the lower non-knurled spring retaining nut with pliers directly (it needs some knurls anyhow)...then see if it can be snugged up to compress the spring a bit or at least be removed so spring can be replaced.

I have an obscure piece of info that might be of use on the spring:
- it is 0.25 inches in diameter
- in uncompressed length it is 0.84 inches in length
- the spring itself consists of 8 turns

I can't vouch for this info, but it might be of use. Personally I have sacrificed a Jensen SV or two to get the spring...then used the remnants of the SV as an air compressor feed once a bit of tubing is soldered in the hole after the pin comes out.

cheers,
Rog
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tmuir · Posted: Tue Mar 18, 2008 11:32 pm Post subject:

RocDoc · Posted: Wed Mar 19, 2008 8:25 am Post subject:

tmuir · Posted: Wed Mar 19, 2008 11:48 am Post subject:

Atticman · Posted: Wed Mar 19, 2008 1:04 pm Post subject:

steamgranny · Posted: Tue May 20, 2008 4:59 pm Post subject:

I've dragged up this old thread because I need to change or tighten spring on my Bowman (158) SV.
Mine is identical to John's & MM's (see John's pic) , with the non-knurled bottom.
Have you succeeded in taking yours apart, John & if so, how? Or does MM confirm that it unscrews at the top rather than bottom end?
Any help gratefully received, as don't want to break anything

johnreid · Posted: Tue May 20, 2008 5:32 pm Post subject:

When I attempted to unscrew it all that happened is the metal wanted to bend, so I am assuming that it is not adjustable

I now have two Bowmans and the 158 has the adjustable variety so I should be able to swap them back and forth.
It needs a new spring also, but I think that for now I will put a gasket between the upper parts.
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