Seized and Sheared Safety Valve Help

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Seized and Sheared Safety Valve Help

sebdickson
Forum Newbie
Joined: 11 Oct 2017, 11:31

12 Oct 2017, 14:42 #1

Hi All,

New to the forum, and got a few questions about this Mamod (I think) stationary engine that i want to get going again. 
The safety valve has at some point seized, and the previous owner  took his pliers to it (wince), causing it to shear off at the threads. 

The rest of it is covered in grime but is all there (including burner), and with a few drops of oil is spinning quite nicely. The cobwebs in the chimney are fluttering when i spin the flywheel which implies that the cylinders are still sealed quite well and the pipes are free. 

DSC_0087.JPG

The top of the safety valve is held from coming free by the bottom of the bob, which is trapped beneath the remaining threads (you can just about make out where they start in the boss, here: 
DSC_0090.JPG
 
Question 1 is: Where could i get a replacement SV? All the spares websites I have found do not have anything that resembles it, only the newer style round versions.
Question 2: if no spare is available, I am more than happy to turn my own, but what thread should I use? (Cannot seem to download any of the files on the 'toy steam thread sizes' thread before anyone points me there!)
 I can get all the other measurements, but I'm presuming that i will not be able to get a decent measurement on the threads when/ if i can extract them (and I have no idea how Imperial thread standards work anyway, so wouldnt know what to measure and how to get the depth right)

Question 3: How would you recommend getting the old threads out? There is not very much to get a purchase on, and if they were stuck fast enough to shear the top, i'll presumably need to get some way of loosening that first because the amount of torque I'd have to apply to shift it is more than i really want to put through a thin, somewhat ancient boiler sheet!
Unwilling to resolder a new boss in. 

(Current plan is to saw through the shaft of the bob, letting it drop into the boiler, then use an 'easy out' on the inside of the remaining section of SV)

Bonus question: How is the whistle meant to work? handle doesn't seem to do anything, so i'm assuming it is seized as well, and again I am not going to force anything. The whistle itself unscrews quite happily from the boiler.
Cheers
Seb
DSC_0086.JPG
DSC_0086.JPG
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TeamBlue1
Forum Newbie
Joined: 06 Sep 2017, 23:58

12 Oct 2017, 15:11 #2

Hi Seb, I have sent you a PM.
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Mamman
Forum Newbie
Joined: 22 Dec 2016, 09:36

12 Oct 2017, 15:52 #3

sebdickson wrote: Hi All,

New to the forum, and got a few questions about this Mamod (I think) stationary engine that i want to get going again. 
The safety valve has at some point seized, and the previous owner  took his pliers to it (wince), causing it to shear off at the threads. 

The rest of it is covered in grime but is all there (including burner), and with a few drops of oil is spinning quite nicely. The cobwebs in the chimney are fluttering when i spin the flywheel which implies that the cylinders are still sealed quite well and the pipes are free. 

DSC_0087.JPG

The top of the safety valve is held from coming free by the bottom of the bob, which is trapped beneath the remaining threads (you can just about make out where they start in the boss, here: 
DSC_0090.JPG
 
Question 1 is: Where could i get a replacement SV? All the spares websites I have found do not have anything that resembles it, only the newer style round versions.
Question 2: if no spare is available, I am more than happy to turn my own, but what thread should I use? (Cannot seem to download any of the files on the 'toy steam thread sizes' thread before anyone points me there!)
 I can get all the other measurements, but I'm presuming that i will not be able to get a decent measurement on the threads when/ if i can extract them (and I have no idea how Imperial thread standards work anyway, so wouldnt know what to measure and how to get the depth right)

Question 3: How would you recommend getting the old threads out? There is not very much to get a purchase on, and if they were stuck fast enough to shear the top, i'll presumably need to get some way of loosening that first because the amount of torque I'd have to apply to shift it is more than i really want to put through a thin, somewhat ancient boiler sheet!
Unwilling to resolder a new boss in. 

(Current plan is to saw through the shaft of the bob, letting it drop into the boiler, then use an 'easy out' on the inside of the remaining section of SV)

Bonus question: How is the whistle meant to work? handle doesn't seem to do anything, so i'm assuming it is seized as well, and again I am not going to force anything. The whistle itself unscrews quite happily from the boiler.
Cheers
Seb
Hi Seb, I'm sure you'll get plenty of welcomes from the members of the forum. May I be one of the first.

I don't know if you realise what you have there, but it is the holy grail of Mamod stationary steam engines, a  c.1939  SE4. This is very rare and can fetch nearly £1000 in good condition.

Because of its value, take your time before doing anything drastic. The whistle unscrews about 1/2 a turn to operate, as it works a bit like a bleed nipple on a cars brake system. As far as I know, nobody is making replacement safety valves of that type [ if they are, I'm sure a member will let you know] . As far as removing the existing one is concerned, as you say if the previous owner broke it trying to unscrew it, the thread is well and truely stuck. The best way would be to unsolder the boiler end cap and then unsolder the boss, [ which is usually soldered from the inside]. I know you said ' no soldering' , but because of the value of it, it would be worth paying to have the work done if you were unable to do it yourself.

                                     Chris.
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Nick
Steam Supreme Being
Joined: 15 Dec 2007, 17:40

12 Oct 2017, 18:58 #4

Another SE4 turns up! Very nice find!

And as Chris said be careful doing anything with this engine, a very valuable piece 😉  Many here will recommend that you don't even polish it.

Here is mine running after a clean-up:

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Dr. Rog
Steam Supreme Being
Joined: 30 Dec 2008, 17:53

12 Oct 2017, 19:28 #5

🤓
Welcome Sebdickson, what a wonder you have there.
I suggest you disconnect the boiler from the engine by unscrewing those hex nuts, and the boiler band; strip off anything you can then dip it on its side in vinegar to soften whatever scale is causing the problem. Then there is a chance you may be able to use a stud extractor.

A junior hacksaw blade may go in the hole and cut the SV blob, but would damage the thread. The options above would replace the whole insert so would be less original anyhow.

What is the inside of the boiler like?
Cheers Rog https://www.youtube.com/user/DrRogB/videos New positive, and successful motto for 2017: carpe diem
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sebdickson
Forum Newbie
Joined: 11 Oct 2017, 11:31

12 Oct 2017, 23:35 #6

Hi All,
Ah, yes I realise now that this is quite a valuable piece!
It goes without saying (before i receive any more offers) that it is not for sale!
Thanks for all your suggestions - I've now sorted that particular problem, with help and advice of the University Engineering Dept Model steam group and detailed how below, but managed to extract the old safety valve without any damage to the plug and therefore no soldering!

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The history of it is that my great grandad bought it, it was then played with by my Grandpa and then my Dad and his brother before disappearing into a cupboard for the next 30 years.
When i was 8 or 9 and a budding engineer I got a TE1A for christmas (still have it and run it in circles whenever I'm bored). Took it to my grandparents when we visited and my Grandpa said that he had one when he was a boy and went and dug it out. The safety valve then came off and he got a stern telling off from my Granny for being clumsy. Fast forward 10 years and after he died, it went to me. I've had it kicking around waiting for the time to look at it for  a year and finally got round to it today, thinking it would be much more complicated than it actually was!

I'm absolutely not going to sell it as the sentimental value is very high- and it sits quite nicely next to my Traction engine and SP5!
 Similarly, I'm not going to restore any paintwork as the reason why it is in the state it is in is because 3, and now 4, generations of my family have got much fun from it over the last 80 years and so to repaint and make it look fresh from the factory seems silly!  However I will dismantle and degunk, and i do like the polished brass on yours

In the end, took a dremel to the plunger of the safety valve to remove the free half.
Then, at the suggestion of one of the model engineers,  carefully turned down a rod in the lathe to an exact fit of the aperture in the remaining lower half, then loctited it in place. Waited 40 minutes, had more tea, then it came out with barely more than a tweak- bit of gunk on the threads so someone might have once tried to seal it? 
Highly recommend this as a solution, if someone else is faced with a similar issue. The filed in spanner flats on the bar were in anticipation of rather more force being required! 


DSC_0092.JPG

Then we tentatively ran it off the compressed air line, bringing the pressure slowly up to 1 bar. Whistle works exactly as Chris said it would - thanks! 

After getting that far, couldn't leave it without steaming it! Went and got the gear from my traction engine and tried the safety valve on the off chance it would fit and it did! After reaching a firm boil it was still refusing to turn over more than a few times until it suddenly ejected an enormous amount of rather disgusting, limescaley, oily muck over everything within 2m from the exhaust pipes and then ran really rather sweetly!

Things still to do:
I need to extract the bottom half of the plunger (with spring) form inside the boiler, (any tips?)
Re solder the end pot on the burner, which is slightly loose, and replace all the wicks with something not carcinogenic
Turn a new safety valve (again, any tips?)

I dont know what the inside of the boiler is like, but i will flush it a few times with vinegar if that is the consensus? 

Thanks for your help
Seb
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Mamman
Forum Newbie
Joined: 22 Dec 2016, 09:36

13 Oct 2017, 08:23 #7

 Hi Seb,  that's a great tip with the loctite and rod. I have bought engines from areas with hard water, where the limescale was so bad that the threads were  locked solid and had to be soaked in vinegar for days ! If your boiler is relatively free of limescale, I personally would not use vinegar in it. Brass can be very variable in quality and thickness and if water was left in the boiler at any time in its life when stored away, could have the start of dezincification  internally. This would be accelerated if you used an acid, and would do more harm than good.

    Getting the remains of the SV out of the boiler is a tricky problem. If the spring has come free of the brass stem it will be easier, but I have spent hours shaking upturned boilers and probing with cocktail sticks with blobs of adhesive on the end ! ...... But leaving them inside is no real problem.

     The engine runs well. I agree about leaving it as it is, a family heirloom with the wear and scars of previous generations [ less the snapping of the SV thread of course ! ]

                        Chris.
  
                     
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kevin
Steam Supreme Being
Joined: 14 May 2012, 13:34

13 Oct 2017, 09:59 #8

if you need details on the valve I have made several of them in the past, nice engine and welcome to the forum
Im not a megalomaniac, I just want to rule the world !
www.ITA-SHOP.co.uk
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Dr. Rog
Steam Supreme Being
Joined: 30 Dec 2008, 17:53

13 Oct 2017, 20:38 #9

Well done!
Cheers Rog https://www.youtube.com/user/DrRogB/videos New positive, and successful motto for 2017: carpe diem
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sebdickson
Forum Newbie
Joined: 11 Oct 2017, 11:31

18 Oct 2017, 12:01 #10

kevin wrote: if you need details on the valve I have made several of them in the past, nice engine and welcome to the forum
i have pm'd, thanks!
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