Edward Adams's 2½" Gauge 'Monstrous'
I took the chassis to the club today and it ran fine on the track and had no problem negotiating the tightest curve on the track. It shouldn't have any problems really as Edward Adams ran it on his own track at home and that was only a circle of something like thirty feet radius.
When I got home I fitted the coupling rods to see how they ran and it was obvious that something was not right as there was a tight spot when the wheels were rotated. I narrowed it down to the two centre sets of wheels. I checked the centres of the coupling rod bushes and they were the same on both sides so it looked to be possibly a problem with the quartering of the crankpins. I decided to check the quartering on all four wheelsets to be on the safe side but how to do it?
I normally quarter my wheels in the lathe with the axles between centres so I used a similar setup again. The wheels were set up between centres and the crankpin nearest the chuck held against a square clamped to the saddle. This would ensure that all the wheels would have a common datum on one side.
The square was positioned so that the crankpin was approximately vertical above the axle. This wasn't critical as I was not trying to measure the actual angle, just make a comparison between each wheelset.
Each wheelset was held between centres and a couple of old gauge blocks set up between the top of the cross slide and the underneath of the other crankpin to leave a small gap. I then measured this gap with feeler gauges and compared the distance for each wheelset.
This method probably isn't super accurate but it would at least show if there was something drastically wrong, which there was. Two of the wheelsets gave almost identical readings and the third was pretty close. The wheelset with the cracked wheel was way different though and gave a reading approximately 0.029" less than the others. This was one of the wheelssets that were causing the binding on the coupling rods and this is why. I did a quick drawing in AutoCad and the error amounted to approximately 2.2 degrees which is a big difference. As this was the damaged wheel it's quite possible that whatever caused the damage had knocked the quartering out. It's also possible that it was the bad quartering that had ruined the badly worn bearing as incorrect quartering can put tremendous loads on the crankpins, bushes, and bearings.
In some ways this solved the problem of what to do about the damaged wheel. I had been reluctant to remove the wheel as I didn't want to disturb the quartering if possible but as it was way out anyway that was no longer a problem!
I guessed that the wheels were a press fit on the axles and I've always found them to be a pig to remove again. I was also worried about breaking the rim completely on the already damaged wheel! I do have a very cheap and nasty arbour press that I got off Ebay some years ago and that seemed the best way to remove the wheel from the axle. I had to rig up a very Heath Robinson affair to support the wheel assembly as the base of the press wasn't really big enough to take the supports at the sides of the wheels.
I found a couple of large Vee blocks to go either side of the wheels and supported then half on the bench and half on the base of the press. I then put two pieces of steel bar across these that the axlebox rested on. This would also remove the axlebox as well as the wheel which I wanted to do anyway to change the bearing,. I was very careful not to put any load on the damaged rim. I put a short length of round bar between the axle and the ram of the press. The bar was smaller than the end of the axle so that it would go through the wheel.
I then heaved on the operating lever and nothing happened. The axle wouldn't budge! I then heated up the wheel with a gas torch and tried again. Still nothing! Rapidly running out of ideas, I tried pulling on the handle and at the same time tapping the top of the ram with a hammer. Success! The axle started to move. By gently tapping the ram the axle was finally knocked all the way out of the wheel and the axlebox without any further damage to the wheel.
The ball race in the axlebox was very rusty and dirty. I'll order another two bearings which are the same as those in the big ends of the connecting rods. Unfortunately, I couldn't find any bearings of this size with rubber seals, only bearings with no seals at all. The old bearings only have a metal seal on one side so they can easily get grit etc. in them.
It was now easy to give the damaged wheel a really good inspection and I noticed that the crankpin boss is also cracked.
The boss was either cracked because the crankpin was too tight a fit in the hole in the boss or it was cracked when the end of the crankpin was rivetted over. I wish people wouldn't do this as it makes the crankpin extremely difficult to remove if it ever becomes necessary. I've had a couple of jobs where the wheel boss is cracked at either the axle bore or the crankpin bore. This is why I don't like press fits for axles and crankpins and prefer to use more modern methods e.g. loctite. It's so easy to get the fit wrong and crack the bosses. One of the driving wheels on Ayesha has a cracked boss, probably due to the axle being too tight a fit when it was pressed in.
I did some more clearing out of the shed today and fitted another shelf unit. I found about another 500 new plant pots that I didn't know I had!
After thinking about how to repair the damaged wheel some more, I decided to go with my original idea of machining a slot in the back of the wheel and letting in a piece of steel plate. A friend at the club had suggested machining the old tread off and fitting a steel tyre like I had done to the other wheels. That would have been a good solution but I was afraid that the cracked rim would break off completely when I tried to machine off the tread.
The wheel was clamped down to the milling table using some lengths of bar to lift it up so that the crankpin did not bottom out in the tee slot that it went in. I was very careful that the wheel was supported and clamped evenly to avoid putting any twisting forces on it that may break the rim completely.
I then milled out a one inch wide slot out of the rim centered on the crack in the rim and 1/8" deep to suit some 1" x 1/8" steel bar that I had.
While I was doing the milling, I decided to extend the slot along the broken spoke so that the new piece of steel could be fitted to include the spoke and used to reinforce that as well. The 'patch' will be fixed in place with countersunk screws and I'm also going to use JB Weld to glue it. I've still got to clean up the right hand end of the slot with a file to square the end off.
I used the new DRO on the mill for the first time for this job and it was wonderful! Mind you, I did have a Mr. Bozo moment when I first starting milling and went too far in on the right hand side of the slot and nicked the end of the good spoke. My excuse is that somebody a few doors away decided to start letting off some extremely loud fireworks and they made me lose concentration! It can be filled in with the JB Weld when I fit the patch.
I had to work this lunchtime but before I went I had a quick hour in the workshop and cut a piece of the 1" x 1/8" steel bar to make the patch for the wheel. I just roughly shaped it to fit and it will be finished when it's glued and screwed into place. I drilled and countersunk the bar in three places to take the securing screws. I put two 5BA screws into the rim and a 7BA into the spoke. This evening I drilled and tapped the corresponding holes in the wheel.
I then thoroughly cleaned the wheel and the patch with thinners to remove any grease and glued the patch in place with JB Weld. I also filled in the screwheads and any cracks etc.
I'll leave it for 24 hours to let the JB Weld cure properly and then see about finish machining it so it blends in with the existing flange etc.
I didn't take any photos of the machining of the patch but I roughly shaped the edge with saw and file and then mounted the wheel in the lathe. I machined a length of steel bar in the 3 jaw chuck to a good tight fit in the axle bore of the wheel to make a mandrel and then pressed the wheel onto that. It was then just a case of turning the edge of the patch to blend in with the existing flange using light cuts. I then turned the wheel around and machined the back of the patch to match the recess machined in the back of the wheel. A bit of work with files finished the job off.
I think it has made a satisfactory repair and it doesn't look too bad.
Tonight I refitted the repaired wheel to the axle but using Loctite this time instead of a press fit. I reduced the centre of the wheel seat on the axle slightly to give the 'Cotton Reel' effect to give a gap for the Loctite and then reduced the remaining portion of the seat to give a good running fit to hold the wheel square when it was fitted. The same method as before was used to set the quartering but instead of using gauge blocks and feeler gauges I used a couple of gauge blocks alone. I didn't want to mess about with the feeler gauges so I could set the crankpins quickly before the Loctite went off. Before fitting the wheel I pressed a new ball race to the axle box and the end of the axle. That was the easy bit.
It took three attempts to get the wheel on! The first time I fitted the wheel before I set the axle up between centres and the Loctite had grabbed before I managed to put the axle between centres and set the crankpins! I had to heat the wheel to break the Loctite bond.I then replaced the ordinary tailstock centre with a small diameter one held in a collet so I could slide the wheel over that before fitting the axle between centres (see Simply Longer page 5 for a similar method)
I could then slide the wheel onto the end of the axle with it all mounted in the lathe and the Loctite applied.
The second attempt failed as well! I got the wheel on, quickly set the crankpins and thought job done. When I took the wheel assembly out of the lathe I saw that the wheel had not gone on far enough. Doh! Off came the wheel again using heat. The third attempt went fine thank goodness!
The wheels were all fitted back into the frames and I tried fitting the coupling rods again. To my relief everything rotated smoothly this time with no tight spots so the quartering must be pretty close. It took some getting there but it all seems fine now.
I've only done a few hours a night on Monstrous and not enough to give a daily update.
I've been working on the expansion links and the expansion link brackets and getting those ready to fit back on the chassis.
One of the cross stays that support the ends of the expansion link brackets is just a simple bar and one side was bent so needed to be straightened again.
That was soon sorted out and the rest of the brackets were cleaned up and refitted to the chassis. The brackets that hold the front end of the expansink link brackets bolt to either side of the frames and also support the ends of the slidebars for the outside cylinders.
I then had a look at the radius rods and the expansion links and it was obvious that the die blocks were a very sloppy fit in the expansion links and the radius rods could be moved backwards and forwards in the links. I disassembled the links and it was obvious why - the die blocks were a terrible fit in the slots in the expansion links with the die blocks being maybe 1/16" narrower than the slots.
The slots looked quite well machined and had perhaps been milled on a jig or rotary table but it looked as though the die blocks had been hand filed and not very well at that.
I didn't fancy setting up the rotary table etc. to make a new set so decided to try a different approach. A lot of people seem to use circular die blocks so I decided to make some of those which would be a simple turning job from silver steel bar. These were drilled and reamed 9/32" to suit the pins on the radius rods and then turned to give a good fit in the slots in the expansion links. Actually, I had to make them a pretty easy fit as the slots were worn a bit unequal along their length and I had to make the blocks to suit the narrowest part of the slot. They were still a much better fit than the old blocks though!
I had to round off the outside edge of the blocks as the bottom of the some of the slots had a radius on the bottom rather than a sharp corner. Also, the pin in one of the radius rods was undersize and loose in the hole in the radius rod so that was replaced as well. Ideally I should have probably cleaned up the slots in the expansion links by re-milling them on the rotary table but I didn't want to go to all that trouble at this time.
The expansion links were then reassembled and refitted to the brackets in the frames.
The next job will be refitting the outside cylinders.
Well, today it was raining for most of the morning and afternoon so a good excuse to spend the day in the workshop. Too wet for gardening!
I wanted to get the outside cylinders fitted to the chassis so spent the day doing that, which took longer than I expected (doesn't everything!). I had to do some fettling on the slidebars to get the crossheads to move smoothly from end to end and had to add some shims to the spacer blocks between the slidebars as a couple of them were too thin. On the right hand cylinder if you tightened the screw that holds the slidebars to the cylinder end cover then the crosshead locked solid. I noticed that the top slide bar was badly galled again along with the corresponding face of the crosshead and that was probably why. I had to add a 10 thou brass shim to get the crosshead to run nicely and a 5 thou shim at the other end. The left hand cylinder just needed a 2 thou shim at the far end of the slidebars.
When I came to fit the cylinders to the chassis I had to do more fettling on the brackets that support the slidebars as they were miles out. I had to elongate the bolt holes in the brackets on both sides so that they lined up with the threaded holes in the top slidebar otherwise the bolts forced the slidebars out of alignment. On one bracket I had to shim the bottom of the bracket where it bolted to the frame as the brazed joint on the fabrication wasn't exactly square. On the other bracket I had to file the face that contacted the top slidebar as the bolting face was too low. Eventually I got both crossheads to run smoothly when all the bolts were tightened up but it took a lot of fiddling about.
Originally the cylinders had a gasket between the bolting face and the frames, presumably to seal the exhaust passages, but if I had fitted a gasket again it would have pushed the slidebars further out and made the alignment with the support brackets even worse. Instead, I bolted the cylinders directly to the frames with a smear of gasket cement around the exhaust ports.
I had noticed that the motion had been very stiff to turn over before I disassembled the chassis and I think it was purely because nothing lined up properly. Plus the bent slidebar on the middle cylinder of course!
I decided that I may as well fit the coupling rods at this point and they went on easily. I did have to replace the bolts that retained the rods on the two rear crankpins as the threads on the originals were almost completely stripped. The originals would have been 1/8" whitworth but I retapped the crankpins and used 5BA instead. I did have a look on the internet for suppliers for small Whitworth bolts and there are a few companies sell them, including EKP who I use a lot, but they are silly money! No one seems to sell anything smaller than 1/8" diameter anyway.
However, before finally fitting the rods I took a little bit off the diameter of the outside crankpins with carborundum paper to ease the fit of the ball races for the coupling rod big ends. As mentioned previously, they had been a right pig to remove and were far too tight a fit. They should be a tight push fit now as opposed to a 2 pound lump hammer fit!
I was standing back admiring my handywork after fitting the cylinders and then realised that I had dropped a clanger! The front and rear covers of the cylinders have steel covers that fit over them and I had forgotten to fit the rear ones which should have been done before I fitted the slidebars, crosshead, piston and piston rod. Oh bother (or words to that effect!). So I had to take everything to bits again. It only took about an hour to do both sides but it was something I could have done without!
Must tidy the bench!
I had to remove the expansion links again so that I could work on the slidebar brackets. I'll refit them after I've fitted the connecting rods which will be the next job..
I took the chassis to the club today and pushed it around the track to see how it ran now that the coupling rods had been fitted. It seemed to cope with the sharpest curve with no problems. It was amazing how much crap the wheels picked up from the track and I had to clean the wheel treads with paraffin when I got home.
Tonight I fitted the connecting rods with the new bearings in the big ends. The connecting rods are different, one has a bored recess to take the bearing and the other has a bore all the way through. Not sure why!
The recessed bore was a really tight fit for the bearing and also the bore was tapered so I decided to remachine it (I do wonder if the original bearing was damaged due to the really tight fit). I thought that the best way was to mount the connecting rod on the milling table, centre the bore, and then bore it parallel with a boring head. The connecting rod was clamped to the milling table and the bore centred with the milling spindle using a dial test indicator held in a collett in the spindle. There is a very nice tool for doing this but I can't remember the name of it at the moment! (coaxial indicator). Anyway, I managed with the dial test indicator.
Once the bore of the big end was centred, I zeroed the DRO so that I could move the table if necessary and then return to the correct position (I really do like the new DRO!). The bore was then machined parallel using the boring head. I have to confess that I took a bit too much out of the bore and the bearing was a very easy fit so I just held it in place with some bearing retainer!
The big end bearing was now a nice tap fit onto the crankpin after I had reduced the diameter slightly and I thought it best to machine up a thin brass washer to fit between the bearing and the coupling rod to prevent the bearing moving on the crankpin and to align the connecting rod with the crosshead. After fitting the washer the connecting rod was tapped onto the crankpin and the crosshead pin fitted. I was pleased that the wheels still rotated smoothly with the connecting rod in place. I was expecting some alignment problems but everything went ok.
The other connecting rod was bored all the way through and was actually a good fit for the bearing so I just pressed the bearing in and centred it in the big end using a washer to get it in the right position. I again machined up a suitable washer to fit between the bearing and the coupling rod to prevent the bearing moving on the crankpin.
I also machined up a washer to fit between the bearing and the eccentric crank, again to prevent the bearing moving outwards on the crankpin but also to act as a shield to keep dirt out of the bearing,
When the second connecting rod was fitted, everything still rotated smoothly with no tight spots so I was very pleased.
Next job is to refit the expansion links and the rest of the valve gear.
Not a lot done today but tonight I had a look at the lubricator and cleaned it all up. There was quite a bit of gunk in the bottom of the tank and some debris inside the pump itself which wouldn't have helped it's performance. The brass tank on the bottom of the lubricator was a bit beaten up with a few dents in it so I flattened it all out again on a steel block. It was soft soldered together and one of the joints had cracked so I resoldered that.
I thought at first that the shaft that drove the lubricator was bent as it had a tight spot but it turned out to be the securing nut that held it into the 2 to 1 lever shaft was too tight and it just needed loosening a touch. It all seemed to work fine when everything was reassembled again. It seems to pump oil ok but the test will be when/if the chassis runs on steam.
I decided to spend today in the workshop again as I wanted to get the chassis completed as much as possible and see if it would run on air. I want to spend next week building the new axle assemblies for the driving truck so that I can use it on the 10th at a rally.
Unfortunately, I didn't take any photos of today's work. I intended to but got too engrossed in what I was doing and forgot!
The first job was to clean up the valve chests and to make this easier I unscrewed the outside valve chests from the middle one so that I could work on them individually. As mentioned earlier, all three valve chests are screwed onto the steam pipes that connect them and have to be removed and refitted as one unit.After cleaning them all they were screwed back together and fitted to the cylinders with new gaskets. The valve faces seemed fine with no scoring so I just gave the face a quick rub on some carborundum paper to polish them.
It's a bit fiddly to replace the outside valve chests as you can't really see inside the outside valve chests (they are a one piece casting with no separate cover) and you have to get the valves in the right place for the valve rod and nut to fit into them. I managed it after a few attempts. Unfortunately, I had to take the valve chests off again as I had screwed the left hand one onto the steam pipe one turn too far and after I had screwed the valve chest into place the others didn't line up with the fixing bolt holes! I got it right the second time.
Then it was just a case of cleaning up all the valve gear parts and refitting them which all went fairly smoothly. Everything seemed to fit well this time.
Still haven't tidied the bench!
At this point I hadn't reset the valve timing but I decided to try running the chassis on air to see what happened. I connected a pipe from the compressoer to the steam inlet on the middle cylinder and tried it on about 20psi. To my amazement it ran and ran quite well. I wasn't expecting that at all! Needless to say, I was pretty pleased. The timing is obviously out as it's very lumpy at very low speed but it runs faster pretty well so the timing can't be that far out.
So it just remains to set the valve timing properly and I can see that not being an easy job. The middle valve should be easy enough as you can remove the valve chest cover to see the valve but you've got to set the outside valves first as altering the timing on those affects the timing of the middle valve. The outer valve chests just have two screwed plugs in them which I don't think even line up with the ports. They are only about 0.25" bore so you can't really see anything through them anyway. I did try shining a torch down one but couldn't see a great deal. I don't think the holes are big enough to fit my endoscope through them which would have helped.
The outer valve spindles are threaded at each end and screw into the valve rod guides at each end and you are meant to adjust the timing by rotating the valve spindle and screwing it in and out of the guide blocks.. The front end of the spindle has a screwdriver slot in it to facilitate this but it means removing the front guide block and the linkage to the 2 to 1 lever. I can see this being fun, not!
I'm at work in the morning but might have a quick look at it tomorrow afternoon. Then I really need to get back to the driving truck.
I did have another look at the chassis this afternoon. I took the middle valve chest cover off and roughly set the valve and this did improve the running somewhat. I tried checking the timing of the outside cylinders by taking out the cylinder drain cocks which I had loosely fitted back to block the holes in the bottom of the cylinders! I rotated the wheels by hand with low pressure air connected to the steam inlet and tried to judge when the valve opened by seeing when air came out of the draincock hole. The timing didn't seem far out but the chassis was still very lumpy when running at slow speed. What I did notice was that there was a lot of air escaping straight up the exhaust as soon as the air was connected and I think it's probably the piston packing leaking on one or more of the cylinders as I don't think that the valves are leaking. I was debating whether to repack the pistons before I reassembled the cylinders but I didn't bother as the original packing didn't look too bad. It looks like I should have done!
It's not too big a job to remove the pistons again. You can just remove the front cylinder covers, remove the crosshead pins, slide the pistons right to the front of the bore and unscrew them from the piston rods. I'm not going to do it now though and will leave it until after I've sorted the driving trolley. At least I know that the chassis runs and there are no major problems with it. So no more updates for a week or so.
Well, it's been a bit longer than a week or so but back onto Monstrous again. I've decided to try PTFE rings again for the pistons so I ordered a length of 40mm diameter PTFE bar. After some thought I decided to try putting O rings under the PTFE rings to help spring them against the bore. For smaller cylinders I have had good success with just using the PTFE rings on their own but these cylinders are 1.5 inch bore and I am not sure that just the rings alone would have enough natural 'springiness' to keep them in good contact with the bores.
The original grooves in the pistons are quite large so the rings will be wide compared to those that I have used before. I've ordered some 1.78mm section O rings to put underneath the rings and as the grooves in the pistons are about 8mm wide, it will need 4 or 5 of these side by side to fit in the grooves. This will mean that the rings themselves will be about 4mm deep and I will be fitting two rings per groove with the gaps at 180° apart as usual.
I cleaned up the grooves in the pistons by making a dummy piston rod held in a collet in the lathe, screwing the pistons onto this and then machining the grooves with a parting tool. The original grooves were quite rough and the sides were not parallel or the bottoms level. I made all the grooves to the same depth but the width does vary from piston to piston., indeed the width of the pistons varies as well! I didn't bother making them all the same as the width of the rings can be made to suit the width of the slots.
I'm waiting for the O rings to arrive but in the meantime I put the PTFE bar in the 3 jaw chuck and machined the outside diameter to match the cylinder bores which are all the same at 1.5050 inches. I then drilled and roughly bored the bar to size. I'm not sure yet what the bore wil need to be to give a suitable compression of the O rings and hence the pressure of the PTFE rings against the bore. I don't think that it will need to be much as the rings will expand with the temperature and help seal them against the bore. I think that once again it will be a matter of 'guesstimation and trial and error'!
The O rings arrived yesterday so I spent this afternoon making the new PTFE piston rings and refitting the pistons.
As the grooves in the piston were quite wide I had to fit four O rings to each groove.
The O rings do not completely fill the width of the groove but that shouldn't be a problem.
I came across an article in Engineering in Miniature about PTFE piston rings which recommended a pinch of 0.010" to 0.015" for the O rings so I decided to give that a try. The inside diameter of the PTFE was bored to 0.015" less that the diameter over the O rings and the outside diameter machined to that of the cylinder bores. The individual rings were then parted off such that two would fit the grooves with about 0.005" side clearance in the grooves to allow for expansion. The rings were then split with a knife and a piece taken out to give about 0.030" gap, again to allow for expansion.
The rings were then fitted to the pistons with the gaps 180° apart and the pistons refitted to the piston rods in the cylinders.
The gap looks very big in the photo above but the rings need to be compressed to fit in the cylinder bores.
The cylinder covers were refitted along with the front buffer beam and the lubricator assembly and the chassis tried on air again. No improvement! There was still a big leakage of air from the exhaust! Choice words were uttered and it looked as though one of the valves was not sealing. Maybe the old graphite packing was not leaking after all but I'm sure that the new PTFE rings will be an improvement.
I bit the bullet and removed the valve chests again which is a pain in the proverbial as all three have to be removed at once. Once they were removed it seemed that the cutout in the gasket on the lefthand valve chest was not big enough and the valve was sitting on top of the gasket and so not seating on the valve face. This was quickly sorted and the valve chests refitted. The valve chests needed to be removed anyway to cure the leak from one of the steam pipes that I had found earlier so that was sorted at the same time.
The chassis was again run on air and the blow from the exhaust was considerably reduced. There is still a bit of a blow at one point in the rotation of the motion however so something is still not sealing properly. Further investigation is needed.
The chassis is now a lot tighter than it was before but hopefully it will free up once it has run on steam and the rings have sorted them selves out.