NSW 'B' class mogul

[Jim]

That's an offer too good to miss David.

Jim

[David]

Thanks Barry.

I started the day by making a longer union nut so it could engage with the undamaged thread on the inlet T. Lucky I made that male thread over-length. Only two failures before I got a usable one. Yes, I found two ways to mess up making a union nut.

I think I fixed the lubricator by accident - I misunderstood the problem and fixed what I thought was wrong which with luck has fixed what is actually wrong.

I suspected what Barry said, that the ball still wasn't seating properly against the o-ring. When I took the thing off again this morning I blew compressed air into the outlet and saw small bubbles in the oil. Not big glooping bubbles like the last couple of days but perhaps most of the air was getting blown aside as I was just shooting it out of an air gun. Anyway, I figured that proved the seating was no good and had the thought perhaps a longer or stronger spring was required.

I have neither of those so I decided to make two spacers - one which is in the design but I'd heard wasn't always necessary (which is why I didn't make it) and moves the whole o-ring/spacer/o-ring assembly downwards, and also a spacer to sit under the spring making it compress more which isn't in the design. Given the top spacer is part of the design I decided to try that one first and it seems to have solved the problem. I guessed at the length, hoping it wouldn't be so long it stopped the ram getting to where it would pump oil and got lucky, a bench test showed it still pumped.

I put it on the loco and ran it for about 30 mins and didn't see any bubbles and the oil level did go down so I hoped I'd fixed it. I took it down to the club this afternoon and Barry reckons it seems to be working as it should.

Barry mentioned if the holes that let oil get sucked into the vacuum between the two o-rings when the ram is on its way up break through too low in the pump body it can be a problem. You won't be surprised to know one of mine does.

I can only guess the spacer I put in is now blocking that breakthrough. I still don't understand what the problem is or why the pump would seem to work against my thumb but it must be something to do with air (or steam) trying to force its way back through the system and up through that slight breakthrough. Which also implies the ball and o-ring that form the check valve are not seating.

Someone pointed out there should be plenty of pressure from the steam inlet pushing the ball against the o-ring so I'm none the wiser as to what the real problem is or why it's fixed.

I also still has the problem of the pump barrel turning and undoing it's locknut when I try to do up the outlet union nut but I can't face taking it out and apart again to fix that right now. Barry suggested soldering a piece of brass to the part of it in the tank that will wedge against the inside of the tank which seems a simple enough fix. If I thought I had a good chance of making another pump barrel with all four holes coming out right I'd do that, plus make it so it would wedge itself against the tank body, but it seems unlikely I'd manage it - it's a bit beyond my pay grade.

Despite cleaning and theadlock one of the screws that goes through a die block unscrewed itself again today so I'll have to take that side of the gear out and do something more mechanical about keeping it in place. That's tomorrow's job.

Anyway, I pretty relieved the pump now seems to be working and the pipe can be screwed onto the inlet T properly.

[Shawki Shlemon]

David , you are doing a great job , your engine is excellent in my opinion . { he did get a lot of ribbing about it } , rivet counters produce nothing , just criticize , I say how did you do it ? they normally have no answer or a silly one . Your engine , if you are satisfied and happy that is all that matter .

[David]

Thanks Shawki. I know you've made a crazy number of locos. How's the current one progressing? Didn't you start a thread recently?

[Shawki Shlemon]

David , I am 81 now , I have few projects going , I am slower than before but they keep me busy . As for posting it has become more complicated to put photos on , I know it can be done but is overwhelming for me . Keep up the good work . Enjoy the great hobby .

[Jim]

Feb 2, 2020 1:55:19 GMT Shawki Shlemon said:

David , I am 81 now , I have few projects going , I am slower than before but they keep me busy . As for posting it has become more complicated to put photos on , I know it can be done but is overwhelming for me . Keep up the good work . Enjoy the great hobby .

I know what you mean Shawki, I'm 80 and while for the most part I don't feel it, I am slower and I do lack a bit of enthusiasm for loading things up and heading off to rallies etc as compared to earlier times. On the the other hand I have lots of projects on the go to keep the mind busy and active.

As you say it's a great hobby and one I love.

Jim

[David]

That's the one downside of this site - having to put the photos on some other hosting service and then linking to them when posting. It's far more painful than most message boards.

I think I have figured out why the die block pin unscrews itself. I made a new one yesterday when I noticed the old one was a bit loose in the non-threaded side of the valve rod fork where the bore of the bush is oversize and eccentric (although it should not be either of these things). When I put the new pin in I found the valve rod swung freely when the die block was at the top of the expansion link but when at the bottom things were rubbing and the valve rod was obviously pointing off to one side.

This triggered the thought that the die block pin seems to unscrew itself while running in reverse, and it is always more difficult to put one valve rod into the spindle clevis and I'm guessing it's this one.

So I think that rubbing is causing the pin to unscrew.

I used high strength retaining compound on the new die block pin thread this time so no doubt the damned thing is stuck in good and proper now but I think I should take it apart and redo the bushes on that valve rod to avoid excessive wear.

[David]

A friend had a eureka moment and thinks they figured out what was wrong with my oil pump based upon the fix.

If I understand it, the ram is too long and after all the oil has been pushed past the ball the ram is bearing directly on the ball. For the first part of the up stroke the pressure from the ram pumping oil out has gone but the ball can't seat from the back-pressure because it's still held down by the ram so now oil or steam can come back past the ball. Then with one of the oil feed holes broken through too low this allows the back-pressure to get to the tank, getting around the top o-ring somehow.

By adding the top spacer and moving the o-rings and ball down I have effectively shortened the ram so it no longer hits the ball. The top spacer may help seal the broken edge from the oil feed hole. Moving all the o-rings down may help compress them a bit if they're now touching the rim of the outlet pipe if they didn't before.

So many "may"s is quite frustrating. I can see the operation of the pump is beautifully simple but to get a working one it seems to rely on a good understanding of how it works to get the various heights/lengths correct (and there are not many numbers on the original plan which was sent to me by John/baggo overnight - it must assume a competent person is making it), and good manufacturing to hit the numbers and not stuff things up like the oil holes coming out too low.

I know everyone else has can make one while eating breakfast but it seemed a bit beyond me! I did notice a Stirling Single had a flurry of questions about the oil pump on this board a few years back when I was googling for the original Ewins article, so at least someone else didn't find it trivial! I have EIM vols 1-3, it was in vol 4 :-\

[suctionhose]

David, I don't think people "make stuff over breakfast" with much success.

I might be repeating myself but things work for reasons not dumb luck.

This miniature stuff is very demanding. That is a large part of its attraction I would say.

Knowing what the average "skilled" person is capable of in the workforce - you are not exposed to that - the generic concept of "Fitting & Turning" is not in the same league by any stretch.

I've witnessed tradies shim a motor aligned to a pump and could not get it closer than 2mm out of line. I kid you not!

Even beyond following a decent drawing, one must understand what should happen and prove to oneself that it does happen. Anything less is a lottery.

Every part of your engine performs a function. Mostly you have been very thorough. But anything left to chance will come back to bite.

That is the nature of machinery. Multiply that by some factor for sake of a miniature and you get and idea of just how demanding the task is.

Many get their machines to work ok but only small proportion of them really nail it. The devil is in detail!

It's going well. Final assembly coming up!

[David]

Feb 5, 2020 6:22:29 GMT suctionhose said:

Even beyond following a decent drawing, one must understand what should happen and prove to oneself that it does happen. Anything less is a lottery.

That's certainly where I dropped the ball with the lubricator, I just didn't get how it worked so didn't have the knowledge of what measurements were important and interrelated.

I have the LHS valve gear out at the moment because an eccentric bush is causing some binding in reverse (but not forwards!) which is causing the die block pin to unscrew. The opinion at the club this morning was to take the reverse eccentric rod off and linish off a bit of the expansion link until the binding goes away. Simpler than what I was going to do, but I'm still annoyed it isn't straight and neat like the other side. I'm sure I'll forget about it if it doesn't cause trouble in future. I'm worried it will wear either the die block pin early or the hole in the die block itself. I guess pins have to be replaced sometimes so when that time arrives I might fix it properly but now I've used the high strength loctite (before I realised what was happening) I don't feel like heating it up to break the bond.

Software development is similar to what you say. Some people just get it and are good at it. Some people learn it and their code is workable but you don't admire it. I've worked with some people who I couldn't believe thought they should be programming for a job. I guess most things are like that. Lets hope we all get the good surgeons who really get it when we need them!

[David]

No progress yet on fixing the problem but having had a close look at the B class Barry is finishing off I think I see why my pony truck wheels don't clear the guard irons. The pony truck on mine seems to be something like 3 - 5 mm too far forward.

I've just checked my parts and they seem to agree with the drawings, but at least two other B classes have been built to the same drawings and don't have the problem so the likely explanation is that I've put it together wrong.

I think the easiest fix is an eccentric pin for the pony truck to move the pivot point back a few mm.

[David]

Some progress now. I made the pin with 3mm eccentricity. 4 or 5 would have been better but it's difficult to judge these things. The wheel flanges still clipped the guard irons so I continued with plan A and persuaded the guard irons out further and that finally got things clear.

I'm not convinced with how they look from the front but I'm sure I'll get used to it and forget it's not quite right! If I ever get really bored I can make another pin with greater eccentricity and whack the guard irons back into shape. I lost a painted bolt somewhere along the line too. I'm sure it will turn up as I start to tidy the workshop up now this part of the job can be called about done.



This is a little hole for a pin to stop the whole thing turning when you're doing up the nuts. In the case of the eccentric pin it also aligns the eccentricity so the pony truck is moved back.

[David]

I put the dummy leaf springs in last night and had another look at the guard iron/pony truck wheel situation. It looked like there should be enough clearance to have the guard irons bent as they should be so I took one off, eased the bends, put it back, and it was fine. Did the other one and it was fine too. No idea what was happening the night before. The paint on the guard irons is now looking pretty tired.

Then I drilled 4 rivet holes at the top of the front of the smokebox. The design has a headlight there but I'm going to skip that and do a pre-electric generator model. Every rivet on that smokebox is exactly where it should be due to CAD and DRO coordinate drilling. Except one of these 4 where the carbide drill I was using didn't go where it should in the pop mark. Yes, I am extremely annoyed about it. I used a HSS drill for the other 3.

Having said that when I walked into the workshop this morning (to do my real job - the workshop is also my home office) and saw the painted frames with all the rods etc on and the smokebox sitting in place - I couldn't see that rivet clearly - my first thought was "that looks pretty good".

[David]

The loctite is setting on the handbrake clevis which has been put back on with the machining mistakes facing the frames this time. I'll put a pin in it tomorrow.

An unwelcome discovery this morning was my cab sides were rusting badly after soldering the angles on. My guess is the bakers fluid was sucked under the riveted strips and angles and not flushed out when I washed the parts after soldering.

A wire brush got a lot of the rust off and luckily the angles aren't pitted anywhere much I can see. Small wire wheels in a dremel did a reasonable good job of getting at the worse bits. It's happened all along the curved angles and all down the angles where the spectacle plates screw onto the cab sides.

Sample of probably the worst area after a wire handbrush:



After the dremel:



I assume this is going to continue. As I see it, the options are from least to most effort:

• Keep an eye on it and take the wire brush to it when rust shows up.
• Give it some undercoat to keep the air off it. This can be a coat and be stripped off before proper painting.
• Unsolder the angles and take the riveted strips off and clean the steel and angles properly. Then put it them all back on. But what flux to use on steel if not bakers?

Will this keep happening after it's painted or will the paint keep the air off it and make it stop?

What would you guys do?

[mugbuilder]

I use 965 low melt silver solder flux with good results. Much better than Bakers but not as easy to get.

[Roger]

Feb 12, 2020 23:09:09 GMT David said:

The loctite is setting on the handbrake clevis which has been put back on with the machining mistakes facing the frames this time. I'll put a pin in it tomorrow.

An unwelcome discovery this morning was my cab sides were rusting badly after soldering the angles on. My guess is the bakers fluid was sucked under the riveted strips and angles and not flushed out when I washed the parts after soldering.

A wire brush got a lot of the rust off and luckily the angles aren't pitted anywhere much I can see. Small wire wheels in a dremel did a reasonable good job of getting at the worse bits. It's happened all along the curved angles and all down the angles where the spectacle plates screw onto the cab sides.

Sample of probably the worst area after a wire handbrush:



After the dremel:



I assume this is going to continue. As I see it, the options are from least to most effort:

• Keep an eye on it and take the wire brush to it when rust shows up.
• Give it some undercoat to keep the air off it. This can be a coat and be stripped off before proper painting.
• Unsolder the angles and take the riveted strips off and clean the steel and angles properly. Then put it them all back on. But what flux to use on steel if not bakers?

Will this keep happening after it's painted or will the paint keep the air off it and make it stop?

What would you guys do?

Fertan is very thin and would wick into the joint and convert the rust. That's what I would use.

Personally I would avoid using Soft Solder altogether unless there are no other alternatives. Things like Brass water tanks are one such case, but almost anywhere else you can use Silver Solder.

[David]

Thanks Roger. Amazingly we can get something called Fertan here, although it's not made by the same people as the ones I see listed in the US & UK. I'll have to assume it has the same stuff in it.

www.chemtech.net.au/cr_op_fertan.html

I'll get some within the next few days if I can find it out here, or order some if not.

One thing I don't understand is how people use phosphoric acid to protect steel, like Jelonite (which I've never seen down here). If I leave phosphoric acid on steel for too long it eats away at it.

The loctite didn't set on the handbrake clevis and I could still move it around by hand with some effort. I took it off and cleaned both parts and it's having another go overnight.

[Deleted]

Feb 14, 2020 11:24:03 GMT David said:

The loctite didn't set on the handbrake clevis and I could still move it around by hand with some effort. I took it off and cleaned both parts and it's having another go overnight.

Hi David

How good is the fit? it may be that you're using the wrong spec Loctite, they all work to different gaps/fits...some are much stronger than others

Pete

[Roger]

Feb 14, 2020 11:24:03 GMT David said:

Thanks Roger. Amazingly we can get something called Fertan here, although it's not made by the same people as the ones I see listed in the US & UK. I'll have to assume it has the same stuff in it.

www.chemtech.net.au/cr_op_fertan.html

I'll get some within the next few days if I can find it out here, or order some if not.

One thing I don't understand is how people use phosphoric acid to protect steel, like Jelonite (which I've never seen down here). If I leave phosphoric acid on steel for too long it eats away at it.

The loctite didn't set on the handbrake clevis and I could still move it around by hand with some effort. I took it off and cleaned both parts and it's having another go overnight.

I imagine it's similar. Mine is brown and very watery. When you apply it to clean Steel, it looks like it's not going to do anything, but it eventually leaves a brown surface. Whether that's converted something in the Steel or just dried out and changed colour I can't tell.

[David]

Hi Pete, it's a different brand then loctite but is meant to be equivalent to the high strength retaining compound. It says for slip fits of parts on shafts with up to 0.15mm gap so it should be fine. I used it on these parts before and it worked so I'm guessing I didn't clean inside the bore of of the clevis well enough.