Garden Railway Forum

I have been fixing the Mamod SL3 model for a while and I gave up. But now I want to trouble shoot the issue again. problems after problems arise that I have ever seen it run since I acquired the locomotive in Ebay nearly a year.

The current issue is that after I replaced new pistons, which have the rubber rings it seems the rubber rings make it too hard to run on the meth burner. I observed water boiled quite vigorously, and some spitted out from the safety valve but it seems not strong enough to push the pistons. The problem is during the replacement I bent one of the old pistons so I can't put it back. The old pistons do not have rubber rings. If someone has recommendations to overcome this issues, please let me know.

By rubber rings do you mean the type with the stuffing gland nut on the the piston rod end of the piston? If so slacken these right off and run in (loco on blocks) using plenty of oil on the piston rods. Once it's all freed off finger tighten the nuts until steam stops blowing past, any more will be too tight and caust the o-ring to grip the piston rod.

You'll be needing an inline oiler with these

Hi, I had a problem with my sl1 that sounds very similar.
I fitted a cylinder upgrade kit, after fitting the chassis was very stiff.

I thought it was the pistons, annoyingly the problem got worse when the model got hot. I could just about get the chassis to run on compressed air but only at high pressures and very erratic.

After much head scratching I food the problem to be the uprated cylinder springs, they were just too tight. I refitted the original Mamod springs and it ran like a sewing machine. Its done a few running hours now and just gets better.

I presume the springs just held the cylinders too tight against the valve faces for them to move.

Its worth a check, hope it helps

daveyrd11:105852 wrote:Hi, I had a problem with my sl1 that sounds very similar.
I fitted a cylinder upgrade kit, after fitting the chassis was very stiff.

I thought it was the pistons, annoyingly the problem got worse when the model got hot. I could just about get the chassis to run on compressed air but only at high pressures and very erratic.

After much head scratching I food the problem to be the uprated cylinder springs, they were just too tight. I refitted the original Mamod springs and it ran like a sewing machine. Its done a few running hours now and just gets better.

I presume the springs just held the cylinders too tight against the valve faces for them to move.

Its worth a check, hope it helps

Thanks for the information, I will look into the springs and probably, they need to be loosened a bit. After the springs were fixed, did you run the locomotive with the upgraded cylinders with the rubber rings?

DVT Dweller:105846 wrote:By rubber rings do you mean the type with the stuffing gland nut on the the piston rod end of the piston? If so slacken these right off and run in (loco on blocks) using plenty of oil on the piston rods. Once it's all freed off finger tighten the nuts until steam stops blowing past, any more will be too tight and caust the o-ring to grip the piston rod.

I tried those things but it was too tight. I think it can be both the rings and springs are too tight.

Hi, yes, my loco runs with the full dream steam cylinder upgrade minus the uprated springs. I find the pistons seal really well now, when cold the chassis is quite stiff to rotate with no flow of steam, but when in steam with lots of good quality steam oil it runs very nicely.
However it did run well before the conversion so I had the advantage of knowing everything else on the loco was correct!
Best of luck, hope you get to the bottom of it soon, they are a great little loco when running well

I suggest you go back and re-read the original Discussion you raised on the other Forum as we answered your question fairly comprehensively there - http://modelsteam.myfreeforum.org/Mamod ... 73793.html

New 'O' ring pistons need bedding in. So it is beneficial to fit the original cylinder pivot springs (at least until they have been bed in properly), it is advantageous to use very light oil initially (I inject 3 in 1 type oil into the cylinders when they are first assembled, and I run my oscillator locomotives on Roundhouse 220 steam oil), and you need to fit a lubricator as well. I'm not going to start the dead leg/inline lubricator argument again but in my experience they both work equally well, although the dead leg lubricator generally using less steam oil per run.

Chris Cairns

Chris Cairns:105872 wrote:I suggest you go back and re-read the original Discussion you raised on the other Forum as we answered your question fairly comprehensively there - http://modelsteam.myfreeforum.org/Mamod ... 73793.html

New 'O' ring pistons need bedding in. So it is beneficial to fit the original cylinder pivot springs (at least until they have been bed in properly), it is advantageous to use very light oil initially (I inject 3 in 1 type oil into the cylinders when they are first assembled, and I run my oscillator locomotives on Roundhouse 220 steam oil), and you need to fit a lubricator as well. I'm not going to start the dead leg/inline lubricator argument again but in my experience they both work equally well, although the dead leg lubricator generally using less steam oil per run.

Chris Cairns

Chris,
It's nice to hear from you. I just added more oil in the cylinders and push/pull them hundreds of times manually. Interestingly, it seems they loose up a bit and I can feel how much less stiff they are now. I will test run tomorrow. Since I got the Regner Willi I was lazy to troubleshoot the Mamod but this coming holidays is a good time to revisit the problems.