NSW 'B' class mogul

[David]

I don't like using nibs because I hate the thought of the cutter ramping up and down while cutting, even though the 4 flute cutters do seem to be centre cutting ones. Of course I considered them but I thought 0.2mm all around should be enough metal to hold it... if only there had been 0.2mm there.

The programming wasn't difficult but there was a lot of faffing around changing stock sizes so the cutter didn't go outside the stock meaning I could hold it in a vise, fiddling with cutter numbers because I often reuse them, changing entry points as I changed the stock size, massaging height and speeds, etc. I still don't have a single 'tool library' that just works, even after more than a year of occasional use and the toolpath default values for things like heights, passes, entry etc are never what I want.

It was only 4 drilling ops and 1 contour op but most times I program the thing it takes a hell of a lot of fiddling parameters and messing about to get toolpaths I'm happy with.

I was also working on nowhere near enough sleep which affects me badly. I wasn't thinking very well yesterday. Not sure what today's excuse will be!

Today's thoughts are on whether to cut the drawhook shank, put clearance for it in the stretcher it is fouling, or both. If I cut the shank too short I think I'll have trouble getting a nut on it due to the lump of steel on the back of the buffer beam - effectively the front frame stretcher.

I am also wondering about the method of securing the rods on the crankpins. At present the crankpins have clearance holes for custom 4-BA bolts with nuts on the back of the wheels. I don't have a socket or nut runner that will go through all the places it needs to in order to get these nuts done up meaning I have to use a spanner which is all but impossible and requires taking the axlebox springs and their studs out. I considered making a long thin nut runner and that will work for the front and back wheel sets but as far as I can see the eccentric straps still get in the way on the driving wheels.

The alternative is to open the holes in the crankpins out to 2BA tapping size and tap them, then make new rod retaining bolts with holes in them to use with a pin spanner. This would have been a great deal easier before they were loctited in the wheels and I could have used a smaller thread leaving the crankpins stronger. Plus I really don't want to break a tap in one of them. They are silver steel so I'll have to go easy if I choose this route and maybe use an oversize tapping drill.

No progress on the dome other than a bit more programming when we last spoke about it. Some 6mm ball ended cutters turned up on Christmas eve so I can have a play in F360 and see if they make a difference. But I'm really just putting it off on the assumption I'll stuff it up and waste an expensive piece of cast iron. I won't be surprised if the dome is last non-trivial part made, followed only by the dummy safety valve that sits on top of it.

[peteh]

Dec 28, 2019 23:59:06 GMT David said:

But I'm really just putting it off on the assumption I'll stuff it up and waste an expensive piece of cast iron. I won't be surprised if the dome is last non-trivial part made, followed only by the dummy safety valve that sits on top of it.

Why not glue some mdf of similar together to use as a dummy run / sanity check and save the good material until the program is good!

[mugbuilder]

I recommend the 2 BA option. It wasn't till after I had drawn the current arrangement that I realised how difficult it would be to tighten the 4BA nuts. Erics engine has retaining collars that screw in from the outside.Each collar has 2 small flats on it to allow a spanner to be used from outside. I may alter my 24 at some stage as the rods may need to come off after a few years service for adjustment.
Barry

[David]

I decided to tap the driving wheels at least because I could see no way a nut driver, however long and thin, could get past the eccentric straps on that axle. It all went well thank goodness and what a difference it makes being able to secure the rod retaining bolts from the outside with some o-ring pliers. I still think I might look for or make a nut driver for the other axles just because that's less work than tapping them and making 4 new bolts.

Here's the setup for opening out the holes in the crankpins and tapping them. One clamp was enough for drilling straight down - the existing through-hole only required opening out about 0.3mm.



Here's the new bolts.



This is a sketch I made of the new design after the fact. The original bolt went all the way through and had a 4BA thread with a nut securing it at the narrow end of the crankpin.



I've also decided I'll cut the shank off the drawhook where it should turn round and tap a hole in the remaining square part so I can screw in studs allowing me to experiment to get the best length. Then I can silver solder the stud in. I don't expect to haul a heavy train running tender first so I think a 2BA thread in the drawhook will be fine.

[jasonb]

I was using a 6mm ball ended mil the other day, will post in the dome thread so you can see how it cut.

[David]

Not much happening here since finally painting the frames on Thursday last week. Was very glad to have that done, mostly by Barry.

Obv before everything under the running boards can be assembled permanently, it all has to be painted - something I'd not really considered! I basically thought I could get the frames painted and have it all back together by about today.

I spent a couple of hours today cleaning the brake parts and a few other bits but painting will have to wait for tomorrow morning as the can of paint I'm going to try says not to use it over 30deg C and we don't see those mild temperatures much these days.

The frames, pony truck, a stretcher, and the little buffer beam reinforcing bits were done. We used a primer that Barry had, it was an epoxy one I think. The Caterpillar paint (yellow tin) was the topcoat. I'm going to try using the RustGuard Epoxy Enamel on some of these parts because apparently it doesn't need primer. If it doesn't work out I'll use the Caterpillar over the tin of etch primer sitting there. I'm only trying this shortcut on small and/or hidden parts.



Loco brakes, another stretcher, and the bottom of the dummy well tank of the tender.



Some small parts to be done.



I did spend a bit of time reworking the model of the dome because I wasn't happy with the transition into the flare, I felt it was too abrupt. I raised the point where the blend starts by 5mm and made that end of the 'guide rails' for the loft operation very gently curved.

Before:



After:

[jon38r80]

Like the pigs nose bolts, Have you made a two pin spanner to fit? Or will you use circlip pliers and Loctite. ( got shanghied by the predictive text so had to edit out Lottie whoever she is )

[David]

Circlip pliers and loctite Jon. I didn't know they were called pig nose bolts!

That last batch of painting went pretty well and I was able to put one stretcher and the buffer reinforcing brackets on, plus the brake hanger stand-offs.

Continuing with the work required to put the lower half of the loco back together I tapped the crankpins of the front and rear wheelsets yesterday and made the bolts today. I made six on the well known basis of there not being time to do it right, but there's always time to do it twice.



I thought I could put the pony truck back in but there are two problems.

1. I missed a little strip of metal that was added to the stretcher to support the pony truck's pivot arm. I only noticed it in the photos yesterday when I was looking at which way around the stretcher goes into the frames and saw a piece of metal that mine didn't have. So I have to make the strip and paint it before I can put the pony truck in. The photo above shows the stretcher now has the holes drilled for the bolts to attach this strip. The strip is in the phosphoric acid to soften the mill scale so it's easier to clean up.

2. The pony truck axleboxes have a 1mm thick flange on them and these have broken on both boxes. Barry said the loco he's fixing up at the moment also had this problem and I think he said a solution is to mill the flange off and replace it with a square piece of 1mm steel, I assume screwed to the front of the axleboxes. So I had to heat up a wheel to break the Loctite and get the boxes off. The photo below shows the broken flanges and there's a big crack forming in the one on the right.

[Jim]

Great progress David, you should be really pleased with the progress to date.

Jim

[David]

Not much to show for this week. I've spent most of the workshop time fixing the axleboxes and finding more nuts, bolts, and bits that need painting. The painting of bits is still going on.

I filed the flanges off the axleboxes then faced both ends off to remove most of the broken / cracked iron and the rough cut at the rear end I never cleaned up. I brought them to length, cut a couple of bits of 1.6mm steel to make the new outer face/flanges, and coordinate drilled the holes. They're tapped 8BA in the axleboxes. I found the centre of the axle holes by screwing the plates on and scribing around the inside of the bush then drawing a square around that and scribing from corner to corner. I'm not sure why I couldn't get the axle holes t in the middle when I made the boxes but they're not.



I used a step drill to open out the hole in the plate. Because the holes aren't in the middle and the plate is on back-to-front this isn't a clean as I'd like.



Then I found I'd not drilled the spring pockets so I made a little transfer punch to mark where they should go and used a 2fl 6mm endmill followed by a 3/8" one to make the 2mm deep pockets.



Finally I put countersunk screws in (they're hidden by the wheel bosses) and after this photo was taken sanded them smooth and painted them.



I thought today was going to be the day I put it all back together but found the flanges of the pony truck wheels fouled the guard irons. I'd never checked this before painting the frames with the guard irons bolted on. I took the guard irons off to leave for another day and found / cleaned the nuts and bolts required for the pony truck stetcher but then decided I'd paint them too before putting them in for good. So that's the state of play at the moment. I'm away this week so nothing else is going to happen.

I thought I'd have to make new guard irons with the iron offset a couple of mm forward from the bolt holes but I'm hoping bending the existing irons out a bit more will provide the necessary clearance. I don't want to make them thinner as they will not look right in profile. Assuming I'd made the bar behind the pony truck too long I checked my parts against the drawing and they are correct so if fits on two other locos of the same design it should fit on mine.

Then I went to put my painted nuts and bolts back in the workshop after I'd left them drying in the sun to find a gust of wind had got under the cardboard they were sitting on and flung them around on the driveway! I'd painted them on the side of the workshop I felt had the least wind but clearly go that wrong.

The cylinder drains all felt pretty loose when I removed them before painting other than the one I fixed recently. But they're not just falling out and I think some loctite 567 will help them seal and the operating rods will keep them from unscrewing. Not sure why these holes are so bad.

I'm still glad I chose to try and 'complete' the frames etc. All these problems would have had to be fixed anyway.

[David]

Now to complete the lubricator and get it in place. I finally purchased the one way roller clutches a couple of weeks ago.

I tried the tank in place to see how things were looking.



So that's not great. I fitted the lubricator tank a couple of years ago before I had the pockets for the springs in place and now the tank doesn't fit. I had to mill 1.5mm or so off the block that holds the tank off the frame and has the threaded holes in it so it would even fit between the frame stretcher angle and the spring pocket. That means the holes no longer line up. I also milled the block down 0.75mm because I felt the outlet of the lubricator was too close to the forked end of the valve rod where it joins the spindle and it looked like it would foul so this brought the outlet further away from the valve parts.

Leaving that aside I moved onto figuring out how to fit the clutches. I'd made one part that had a 4mm bore and gets one of the clutches in one end but hadn't done the counterbore for the clutch back then because I didn't know what the OD of the clutch would be. I realised I wouldn't be able to get the current bore and the counterbore concentric and given the part was made short anyway I decided to remake it. Despite spending a great deal of effort to bore a press fit for the clutch (including having made a bore gauge) it ended up being a slip fit and retaining compound was required.

Next I made the driving mechanism. I managed a press fit this time and silver soldered the arm on with 55% silver solder.

Going back to the tank I put some brass screws into the existing holes and then some soft solder for good measure and then transferred the frame holes onto the mounting block. I managed to keep the new holes blind. Here are the bits. You can see where the mounting block has been milled down the left hand side



I put the tank onto the frames and tried to fit the brake hanger standoff that goes between the two tank mounting bolts. It fouled the left bolt head. I didn't want to elongate the hole in the painted frames and move it again on the mounting block so I turned down a hex headed bolt into a cheesehead screw that barely fits. It's ugly but it will be hidden high up under the running boards so won't be seen.



Here's the $%^$# contraption finally in place. It's been a very troublesome piece of work! Not helped by my random order of building things on the loco, and usually having it in bits on the bench meaning I really stuffed up the placement of the mounting holes.



It used to work so I'm hoping it still does. I'll give it a good clean before I try it again.

[mugbuilder]

Make sure that you prime it before finally installing it as it needs oil all through the pump or it will have trouble picking up the first time.

[David]

A small job today, the rod to drive the lubricator. Now I feel like I've made some progress on this part seeing it driven from the eccentric strap.

The stunt bolts will be replaced before it's all considered done, possibly with custom made ones to help avoid unscrewing etc. If I need to use one of the upper two holes in the arm I'll need to make another clevis for the rod as they bind on this one.



You can see how tight things are. Despite how it looks the valve rod and clevis are not touching the lubricator.

[Jim]

That's all looking very good David and you should be pleased with the continuing progress. Things do look tight but then lots of things on our locos are very compact and with little clearances.

You're doing very well indeed.

Jim

[David]

Continuing to make life difficult for myself I put the cylinder drains and their operating mechanism on and found the control rod passes right under the lubricator outlet. That means there's not enough space for the pipe from there to be bent as required to go on its way to the inlet plumbing.

So I made a 90 degree elbow from 1/4 dia brass with a nut & tail soldered to it and went from there.





I'm finding a lot of things that don't fit correctly at this point due to the aforementioned random build order and not having everything in place when fitting other things on. This area seems to be particularly nasty but I haven't solved the guard iron problem yet either. Bending them further out didn't help the clearance problem. So I'm sitting on that one for now - I can't adjust the pony truck so I may have to just take material off the back of the current guard irons or make new ones offset forward from the bolting location. There's not enough meat around the holes on the current ones to slot them to give the necessary offset.

I had a quick go at making the cylinder covers from a baked bean tin but it didn't work. If I understand what Barry says the tin was rolled across the grain of the metal so when I tried to tighten up the curve I ended up with a lot of sharp corners in it along lines of the grain. I tried rolling it the other way and it worked better but I'd already cut out the notches for the drains and the lines from the first attempt are still visible so I can't use it. But it did prove the metal could be rolled the other way successfully and I can use it as a template. Here is the dud result.

[suctionhose]

Talk to James Sanders...

[David]

Hi Ross, I did talk to James on Wednesday and he told me about the drink cans when I showed the baked bean tin effort. I have two small dia cans sitting on the bench waiting to be tried tomorrow.

The general consensus was that the aluminium is a bit light and 0.7mm or 1mm steel would be better but I'm not sure how well I'd go bending that. It won't take long to try the drink cans in any case.

[coniston]

I think my concern with the aluminium can is how easily it would get dinged or scratched. Personally I have used brass sheet with success, not tried steel but that may end up being even better.
All looking good though, great perseverance on overcoming these niggles. well done.

Chris D

[Deleted]

Jan 24, 2020 18:34:55 GMT coniston said:

I think my concern with the aluminium can is how easily it would get dinged or scratched. Personally I have used brass sheet with success, not tried steel but that may end up being even better.
All looking good though, great perseverance on overcoming these niggles. well done.

Chris D

I'll be using Brass too Chris, I bought what I needed some time back, can't recall the thickness.. 10 thou or less comes to mind. It's K&S sheet which is ideal for what I need being only slightly wider and having nice square corners to line up with... I'll get around to fitting it one day...

Pete

[Jim]

For what it's worth David I bought a small sheet of tinplate (6"x8" appox) from the local hobby shop for the cylinder cladding. It worked well.

Jim