Model Boat Mayhem
The Shipyard ( Dry Dock ): Builds & Questions => Steam => Topic started by: Geoff on March 28, 2025, 05:10:14 pm
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Hi,
I've been asked to have a look at this engine and get it set up for a friend and have some questions:
- I was told its a double acting oscillating engine. Is this correct or is it only single acting oscilating?
- Who makes this engine - it seems familiar but I can't quite remember?
- There are number of steam leaks with the water level sight glass, specifically where the brass screws into the boiler. Should I just use a high temperature sealant or would a fibre washer (with sealant) be better?
- Whilst the unit comes with a pressure gage it does not properly screw into the pipe fitting. You can turn it endlessly when screwing it in so I suspect the thread is wrong. Does anyone know the correct thread?
- What pressure would this typically operate on - I suspect about 25 to 30 psi.
Thank you in advance
Cheers
Geoff
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Bonjour Geoff,
I will be happy to try to answer to your questions as well as I can ok2
- I was told its a double acting oscillating engine. Is this correct or is it only single acting oscillating?
Based on what I see, I guess an inverter if so it is a double acting engine
- Who makes this engine - it seems familiar but I can't quite remember? I don't recognize major bands, the mix brass aluminum mix is unusual for me so I would lean towards doing it by a private individual on plan
- There are number of steam leaks with the water level sight glass, specifically where the brass screws into the boiler. Should I just use a high temperature sealant or would a fibre washer (with sealant) be better?
Personally, I like using either a 0'ring of the diameter of the glass pipe or sometimes tightly rolled Teflon tape to make an O'ring and moderate tightening and for screws, Teflon tape and thread sealant like Loctite 542 or equivalent
- Whilst the unit comes with a pressure gage it does not properly screw into the pipe fitting. You can turn it endlessly when screwing it in so I suspect the thread is wrong. Does anyone know the correct thread? Mine, bought in France, are 5 x 0,5 mm and I don't know English threads
- What pressure would this typically operate on - I suspect about 25 to 30 psi. For all my steam machines, 2 Bar / 30 PSI is my favorite pressure and it is well suited to an oscillating machine because, especially if the springs are weak, the cylinders will come off their plates. Before operating my machines, I like testing them on air and they should start moving with 2/300 g / 2/5 PSI of pressure, example : https://youtu.be/OE6CSYMIotc (https://youtu.be/OE6CSYMIotc)
I hope this will help you,
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Single or double acting? The simple way to check, if the bottom of the cylinder is open then it is single acting, if there is a gland to seal the rod it's double acting.
Jim
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Most simple oscillating design steam engines have only 2 ports in the face of the standard, being the admission port and the exhaust port, so are single acting
If the engine has 4 ports in the standard face, then the engine would appear to be double acting
Some oscillating engines of higher design, have a gland bush on the rod side. however this is to assist the piston to maintatain alignment and not to wear the cylinder bore prematurely
Derek
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The problem with using a fibre or copper washer to seal the sight glass fittings is that when precisely the correct pressure is applied to seal the joint the fitting might not be in the correct alignment with the other fitting. As the position of the two fittings of the glass is critical you invariably end up having to either over tighten the fittings and risk splitting the washer or worse, breaking the thread, or you have to back off the fitting and so run the risk of a leak as the washer is not tightened correctly. The best ways to seal the fitting thread are either with PTFE tape or a medium hard sealing compound. The best way to set the fittings position is first remove the top cap then, with a piece of brass or steel rod of the same diameter as the glass you can check to ensure perfect alignment as you tighten the fittings up. When the jointing compound is set the glass can be slid in place through the 'O' rings and the gland nuts.
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Hi all, My thought would be that if the 2 pistons were 90 degrees apart then they would be double acting and as has been said a mirror might reveal a lower gland on the cylinder.
If single acting then they would be 180 degrees apart.
Derek, do you read your P.M.s? I almost passed your address a month or so back when our son and I were in Bowral at tea time.
Just been to see a proposed 10 1/4 gauge miniature railway set up.
Roy
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Mirror is a good idea Roy ok2 .....I last posted do you on......"roycv (https://www.modelboatmayhem.co.uk/forum/index.php?action=profile;u=356) December 27, 2024, 12:41:23 AM
Derek
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Looking at the pictures it is definitely single acting with a simple throttle valve :-))
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By way of an update we have had the engine running on steam and it's self starting so is double acting. It performs well in the open launch ans steams for nearly 15 mins. I think it's a Modeen engine.
Cheers
Geoff⁹