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Post by Rob on Oct 16, 2018 0:20:31 GMT
The next job was the crank pin holes. This was another procedure that I was worried about. My plan was to create a fixture that I can mount each wheel to in turn, to guarantee the holes are in the same place for every wheel. The first iteration of the fixture I intended to bolt through the wheel and into a T-nut, like so: IMAG1485, on Flickr IMAG1487, on Flickr Spotted the problem? I didn't until after I'd assembled it and looked really hard at what I was trying to achieve. The moment I undid the bolt, the fixture would move. So much for every wheel being the same! The next iteration of the fixture was held in position by a keats angle plate instead, with the wheel bolted to the fixture rather than the whole thing bolted to a T-nut. IMAG1582, on Flickr I don't appear to have taken any pictures of the drilling operation itself. I lined up the centre of the boss by eye, I couldn't think of a better way to do it given they were just rough cast surfaces and each was a little different. With the crank pin holes drilled I turned my attention to the keyways. I wanted these to be prototypical - in the thickest part of the boss directly in line with the crank pins. I also intended to use the keys as my means of quartering, so it was essential they were in the right spot. I went through a number of different ideas for the best way to achieve this. In the end I settled on making a pair of guides. Both are a light hand-push fit in the main axle bore and the crank pin bore. The relief in the main guide was so that I was able to get the 1/8" endmill deep enough to mill the slot to full depth. IMAG1581, on Flickr These are used like so, with the broach doubling as an alignment tool IMAG1500, on Flickr Once the guide is correctly aligned with the crank pin hole the whole thing was clamped down tight onto the guide so it could not move. I don't have an arbor press (they're more expensive than hydraulic presses, who'd have thought it?) so my pillar drill would have to do. The crank pin drilling fixture from earlier doubled as the ram - gripped in the chuck. IMAG1503, on Flickr Never a good idea to abuse your tools, but in this case I could think of no other way to broach the key ways. I milled a test keyway in one of the easy fit axles and did a trial assembly just to see if everything would fit together. IMAG1510, on Flickr Here are a couple of the wheels with keyways broached. IMAG1516, on Flickr Next came another daunting task: milling the keyways at exactly 90 degrees on opposite ends of the axle...
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Post by 92220 on Oct 16, 2018 7:38:36 GMT
Hi Rob.
The thinner viscosity Loctite will be OK as the wheels go up against a buttress on the axles to hold them square. If they didn't have that buttress then the thicker viscosity Loctite 648 would be better to hold them more concentric as it fills the space better, and thus more square to the axle.
You are right in trying to work on bits from the inside out, where possible. When fullsize locos were built, they could send smaller fitters and apprentices inside to assemble parts. Unfortunately we are not gifted with scale size hands for those jobs!!
Bob.
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stevep
Elder Statesman
Posts: 1,070
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Post by stevep on Oct 16, 2018 16:41:20 GMT
Rob, I seems that you are a little sceptical about Loctite or other glues. I can assure you that they work really well. When I made my Rob Roy, after completing the axles, I use a micrometer to measure over each pair of axles, both sides. I then used these dimensions to make the holes in the coupling rods. When I assembled the wheels to the axles, I glued one wheel on to each axle, then threaded the axles through the axleboxes, smeared Loctite on the other end of the axle, and fitted the wheels. Then I put the coupling rods on the crankpins and rotated the whole assembly until the Loctite cured. I then pinned the wheel to the axle in the normal way with a 1/8" pin, half in the wheel and half in the axle. After nearly 40 years, the wheels haven't slipped, and the engine is still running beautifully. www.youtube.com/watch?v=jlCDSfi2JJYSteve
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Post by Rob on Oct 16, 2018 20:29:35 GMT
Chaps,
It's not that I don't think they work well - was just worried that I might end up with the wheels slightly off if I don't have that positive location with a press fit. I'm more than likely being over cautious. I find it frustrating that ME plans don't specify fits, so I'm always guessing at what should be required.
As I say, I'm likely to use 603 on both the axles and pins anyway!
Steve - looks great! I don't have a micrometer large enough to measure between axles. I might set the frames up in the mill and use the DRO instead.
What fit do people usually aim for with their crank pin bushes? I understand there needs to be some allowance for suspension movement - but how much is too much?
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Post by Rob on Oct 16, 2018 21:04:57 GMT
On to the axle keyways. But first, somewhere in between the last lot of pictures and these, I fancied playing about with some soviet era electronic technology and made a Nixie tube clock. Nixie Tube Clock, on Flickr My method was to use a square block with a collet mounted in it. Mill one keyway, rotate the block 90 degrees and mill the other keyway. I hope it's good enough! IMAG1514, on Flickr IMAG1512, on Flickr The numbers are there to ensure I got the orientation right! Would hate to have one axle with the keys in the opposite direction. With each of the keyways broached in the wheels and milled on the axles, I couldn't put it off any further. I had to break out the files. IMAG1532, on Flickr I tried to break up the monotony by spending only an hour a day on this, and I was very glad when it was finally done. I'm sure I could probably spend many more hours perfecting them, but I'm not sure how great the castings on the full size 15xx would be anyway! I also had to quickly knock up another smaller eccentric sheave for the oil pump as I managed to bell mouth the one I made a few years ago trying to adjust the fit to an axle. IMAG1521, on Flickr IMAG1524, on Flickr This picture also shows the oil pocket in the top the axle boxes, with the twin oil holes. I need to make some form of cover for these I think, to keep the dirt out. The grub screws are metric. I just feel they look better than the hex headed set screws. IMAG1536, on Flickr The next project was the eccentric straps. For these, I felt I needed some protection from the jaws. So I knocked up these out of some 2 mm aluminium sheet. IMAG1531, on Flickr IMAG1530, on Flickr
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Post by GWR 101 on Oct 16, 2018 21:45:03 GMT
Rob, some very neat work there. Must admit I still use bits of brass in between the job and the jaws which of course keep falling out. Resulting in some very choice words, perhaps if I spent a bit of time making something like yours the time would soon be recovered. Regards Paul
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don9f
Statesman
Les Warnett 9F, Martin Evans “Jinty”, a part built “Austin 7” and now a part built Springbok B1.
Posts: 960
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Post by don9f on Oct 16, 2018 22:31:10 GMT
Hi Rob, great job on your wheels & axles! I would have thought that if all your quartering and coupling rod lengths (between bush holes) is accurate, then the bushes need only be a couple of thou oversize to start with.
Cheers Don
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Post by Roger on Oct 17, 2018 6:12:46 GMT
I'd like to echo the others and praise your workmanship and methods, 1501 is going to be a cracking locomotive. With regard to the fit of the bushes, the chances are that you'll end up with what Don suggests, but I'd err on the side of a closer fit to begin with, if only to shake out where any tight spots are. If you can get it to turn smoothly with say 10 microns clearance, then you know it's spot on. Adding clearance is easy once you know it's moving nicely if you want. I've left mine a bit on the tight side in the hope it will sort itself out on the track.
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Post by Rob on Oct 17, 2018 20:59:27 GMT
Rob, some very neat work there. Must admit I still use bits of brass in between the job and the jaws which of course keep falling out. Resulting in some very choice words, perhaps if I spent a bit of time making something like yours the time would soon be recovered. Regards Paul Thanks Paul. It was exactly the little bits of aluminium constantly falling out that prompted me to make those protectors. I thought that with the length of time I've spent setting up jobs, dropping the little bits in the swarf tray and trying to fish them out, rinse and repeat, investing some time making something a little better was worth it in the long run! Hi Rob, great job on your wheels & axles! I would have thought that if all your quartering and coupling rod lengths (between bush holes) is accurate, then the bushes need only be a couple of thou oversize to start with. Cheers Don Thanks Don, I hope that the quartering is accurate! Time will tell. I think I'll make test rods first, just to see how close (or far out!) I am. I'd like to echo the others and praise your workmanship and methods, 1501 is going to be a cracking locomotive. With regard to the fit of the bushes, the chances are that you'll end up with what Don suggests, but I'd err on the side of a closer fit to begin with, if only to shake out where any tight spots are. If you can get it to turn smoothly with say 10 microns clearance, then you know it's spot on. Adding clearance is easy once you know it's moving nicely if you want. I've left mine a bit on the tight side in the hope it will sort itself out on the track. Thanks Roger, though for me it'll be one of either 1506 or 1507 as these were based in Newport for 9 years. I need to find a 5" gauge 86B shed plate, as well as a set of number plates! I doubt very much I'll have the accuracy anywhere near 10 microns. I'd be pleased if I had it within 50!
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Post by Rob on Oct 17, 2018 22:00:49 GMT
I started on the larger of the eccentric straps by filing off the high spots and setting up in the mill to start cleaning up the casting. IMAG1534, on Flickr Then off to the lathe to face the front and back. In retrospect, this was backwards - I should have faced first before setting up in the mill. I did it this way around for the smaller of the two. I left them 20 thou over size so I could finish them after they were split and bolted. I drilled the bolting holes, and then cut them in half using a 1mm slitting saw. I had intended to use a 0.5mm saw, but I was seeing a large amount of axial run out. There was still axial run out in the 1mm saw, but by rotating the saw in the arbor and remeasuring, I managed to get this down to what I considered to be an acceptable level. The saw still had radial run out, but it seems from reading that most if not all slitting saws exhibit this! IMAG1555, on Flickr There are lots of horror stories on the web about using slitting saws, so I was feeling apprehensive about how this would go. I calculated an RPM of 200 or so for the correct cutting speed and left the mill in high gear with the VFD set near minimum hoping the mill would stall before anything was flung across the room. I have to say all the worry was for nothing, the whole process was easy. I started off taking tiny cuts of a few thou but quickly realised I could ramp this up. I believe I settled on 50 thou cuts in the end, but think I could probably have taken a full depth cut in one pass. The radial run out probably helps in this regard as the cut effectively 'ramps up': getting progressively deeper as the saw rotates. I realise that LG2 is soft material and the story may be different in steel. IMAG1556 by Defiance Industries, on Flickr I made a set of fitted bolts for positive location of the two halves - I did not want there to be any slop with clearance around threads, and then it was back to the lathe for facing and boring to final size. These next pictures are a mixture of the smaller and larger straps as I seem to have taken different pictures of each stage on each one! IMAG1578, on Flickr IMAG1583, on Flickr IMAG1584, on Flickr IMAG1570, on Flickr With a little fitting to get the two halves together, one was done! Well, done all bar the filing the 'as cast' edges and removing machine marks. Oh, and drilling the oil hole and milling the slot for the ram. Close enough. IMAG1571, on Flickr On to the second! I faced this in the lathe first before setting up in the mill, learning from the larger strap. IMAG1580, on Flickr And then there were two! Here I think you can really see the difference between the ML7 and Warco lathe. The sheave on the left was made on the new lathe, the sheave on the right was made on the ML7 and the machining marks are that much more noticeable. It may just have been that my ML7 was particularly worn out. IMAG1586, on Flickr And with that I'm completely up to date. I've recently had a delivery of some new materials for the pump and the coupling rods and bushings. Is it just me that finds a draw full of metal satisfying? Cranks pins first, then a test coupling rod I think. IMAG1573, on Flickr
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Post by Rob on Oct 20, 2018 9:54:12 GMT
Only a very quick update. I have been kept out of the workshop for a few days as I realised I could not start on the crank pins until they were redesigned to match the more accurate to full size, redesigned coupling rods. Unfortunately, I haven't re-done the coupling rods yet so I couldn't do the crank pins!
As drawn, everything is very over size and the rods don't match the GWR profile at all. The recesses in the coupling rods are also on the wrong side. I started by slimming down the trailing end to a more accurate thickness, including the bush, and then attempted to update the rear half of the coupling rods to the 'fish belly' shape. I seem to have found a bug in the 3D modelling software's elliptical tool I'm using which rendered the work I had done last night a waste.
I'm itching to cut some metal, so I think I'll attempt to turn up the brake blocks to fit the GL5 wheel profile today. I can't complete them until I sort out the design for the brake hangers as they're wrong too, but the wheel profile won't change and I can use the unmounted wheel as a plug gauge without removing the blocks from the lathe.
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Post by Rob on Oct 20, 2018 21:09:38 GMT
The brake blocks were quite a simple procedure. Set the ring up as near as damn it to running true and crack on. IMAG1596, on Flickr Face the back just to clean up the casting. Unfortunately, there were a couple of 'chilled' spots right at the extremities of the 'pointy' parts. Not sure if they'll pose problems in future. IMAG1599, on Flickr Next, bore with a 3 degree taper to match the GL5 wheel profile, until the wheel fits snugly like so: IMAG1600, on Flickr The only problem I have now is determining how thick the blocks should be. It's difficult to work it out from photographs. I'm assuming that they didn't profile the blocks to sit in the radius at the root of the flange, but I have no pictures to back up that assumption. It also looks likely that the blocks stop before the chamfer at the outside edge of the wheel. IMAG1601, on Flickr IMAG1602, on Flickr IMAG1603, on Flickr How do you usually make yours? In the picture above, the middle section is flush with the chamfer, the raised block areas sits out over the chamfer so there is a gap. The inside edge is snug with the start of the flange radius. The casting twisted a little when I removed it from the 4 jaw - I hadn't experienced that with cast iron before, only LG2. I didn't think I was putting that much tension in it through the jaws, but perhaps I was. As the only critical dimension with these is the wheel contact patch, no harm done.
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don9f
Statesman
Les Warnett 9F, Martin Evans “Jinty”, a part built “Austin 7” and now a part built Springbok B1.
Posts: 960
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Post by don9f on Oct 20, 2018 22:50:26 GMT
Hi Rob, I personally would profile the inner edges of the blocks so they sort of match the radius of the wheel flange root....doesn’t have to be a perfect fit here, just so the blocks can fit to the width of the wheel treads without overhanging the outer edges of the wheels....obviously the way the blocks fit to the wheels is influenced by the way the brake hangers fit in relation to the wheels and how much play there is in the whole system, including side play of the wheel sets / axleboxes etc.
Although not a problem for models, in full size it is undesirable for brake blocks to overhang the outer edges of wheels (where the chamfer is) because it can aggravate conditions where this outer edge can start cracking....not something you want with wheels!
So in my opinion, you probably don’t need to machine any more out of your ring of blocks, just radius or profile each block by hand on its inner edge, once liberated from the ring.....that’s how I’ve always done mine.
Cheers Don
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Post by David on Oct 21, 2018 0:57:55 GMT
I used an electric die grinder to freehand a relief for the flange root at the back of each shoe. They flop about a bit so even if they’re not meant to be rubbing against the flange they might do so.
Nice job on the wheels and axles.
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dscott
Elder Statesman
Posts: 2,438
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Post by dscott on Oct 21, 2018 1:32:32 GMT
I recognise the Mill!! They are superb except my yellow box split on the blobs of weld!!! However We went to the Midlands via Leek to pick up a 1500 chassis rolling with machined cylinders! Then camp overnight and meet up with Roger and others the next day. Yes we were first in the queue Friday!!! I have a master drawing of the to scale 1500 frames so this will be dismantled and milled down to size. On the cylinders they just need bolting to a backplate which has some realistic webbs let in all round. The Black Five and Class 2 do this very successfully. If I start tomorrow, I may have all the realistic rivet holes drilled by Christmas. Then there is the Jinty. Bothersome engine coming as she did with a spare set of the wrong wheels 14 spokes? So it was either Upset friend Chris Eden-Green with building an E2 Billingtons. Or do 2 Speedys. Go Great Western won!! They are all machined up and just ready to fit onto their axles! Best David, and Lily, who does not mind the chassis sitting next to the Black Five tender in the sitting room!!!
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Post by 92220 on Oct 21, 2018 8:18:59 GMT
Hi Rob.
As Don says, radius the back edge of the blocks. They needed as much surface contact as they could get, for maximum braking force. You are right though, that the blocks stop at the edge of the chamfer on the wheels. So basically, your brake block width will be whatever it is from the flange face to the inner edge of the wheel chamfer, less any slop in the brake hangers, to make sure the brake blocks don't overhang the edge of the chamfer. I know there is a large age gap, but that is how BR brake blocks were fitted, and I would guess that it was common practice pretty well everywhere.
Bob.
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stevep
Elder Statesman
Posts: 1,070
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Post by stevep on Oct 21, 2018 8:56:53 GMT
I don't think you need to over-think this.
Remember the old adage (Churchward?) that says the engine pulls the train and the train stops the engine. You want efficient brakes on your passenger or driving trollies, but the brakes on the engine are for parking.
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Post by Rob on Oct 21, 2018 9:55:15 GMT
Hi Rob, I personally would profile the inner edges of the blocks so they sort of match the radius of the wheel flange root....doesn’t have to be a perfect fit here, just so the blocks can fit to the width of the wheel treads without overhanging the outer edges of the wheels....obviously the way the blocks fit to the wheels is influenced by the way the brake hangers fit in relation to the wheels and how much play there is in the whole system, including side play of the wheel sets / axleboxes etc. Although not a problem for models, in full size it is undesirable for brake blocks to overhang the outer edges of wheels (where the chamfer is) because it can aggravate conditions where this outer edge can start cracking....not something you want with wheels! So in my opinion, you probably don’t need to machine any more out of your ring of blocks, just radius or profile each block by hand on its inner edge, once liberated from the ring.....that’s how I’ve always done mine. Cheers Don Hi Rob. As Don says, radius the back edge of the blocks. They needed as much surface contact as they could get, for maximum braking force. You are right though, that the blocks stop at the edge of the chamfer on the wheels. So basically, your brake block width will be whatever it is from the flange face to the inner edge of the wheel chamfer, less any slop in the brake hangers, to make sure the brake blocks don't overhang the edge of the chamfer. I know there is a large age gap, but that is how BR brake blocks were fitted, and I would guess that it was common practice pretty well everywhere. Bob. Thanks Don, Bob. I'll do as you both suggest and hand form the profile on the inside edge until the block sits at the chamfer. If I can avoid re-chucking the ring that's a good thing, I'd like to avoid distorting it any further. Bob, when you refer to the large age gap, do you mean the gap between GWR and BR practice? If so, the 15xx was only ever operated under BR, they weren't built until 1949. I think BR practice is the one to go for. I used an electric die grinder to freehand a relief for the flange root at the back of each shoe. They flop about a bit so even if they’re not meant to be rubbing against the flange they might do so. Nice job on the wheels and axles. Thanks David, and good point. I hadn't considered they'll effectively be free to pivot and move about. I'm looking forward to seeing some more pictures of the B class build! I recognise the Mill!! They are superb except my yellow box split on the blobs of weld!!! However We went to the Midlands via Leek to pick up a 1500 chassis rolling with machined cylinders! Then camp overnight and meet up with Roger and others the next day. Yes we were first in the queue Friday!!! I have a master drawing of the to scale 1500 frames so this will be dismantled and milled down to size. On the cylinders they just need bolting to a backplate which has some realistic webbs let in all round. The Black Five and Class 2 do this very successfully. If I start tomorrow, I may have all the realistic rivet holes drilled by Christmas. Then there is the Jinty. Bothersome engine coming as she did with a spare set of the wrong wheels 14 spokes? So it was either Upset friend Chris Eden-Green with building an E2 Billingtons. Or do 2 Speedys. Go Great Western won!! They are all machined up and just ready to fit onto their axles! Best David, and Lily, who does not mind the chassis sitting next to the Black Five tender in the sitting room!!! Hi David, I like the mill, it works for me, and it's a damn sight better than the vertical slide in the ML7 I was using previously. I think I've mentioned before it has a number of short comings though, for example the Z axis is useless for milling. I don't think you need to over-think this. Remember the old adage (Churchward?) that says the engine pulls the train and the train stops the engine. You want efficient brakes on your passenger or driving trollies, but the brakes on the engine are for parking. Steve, I'm interested for appearances sake, rather than braking efficiency - I doubt they'll ever be used in practice. I'd like the model to be as accurate as I can get it. Unfortunately, I haven't had the privilege of seeing 1501 at the SVR up close, so all I have to go on are photographs.
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Lisa
Statesman
Posts: 806
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Post by Lisa on Oct 21, 2018 13:12:21 GMT
I can't speak for the 15xx class, but I've seen plenty of worn out brake blocks from loco's and rollingstock with a very clear root radius on them, if that's any help.
Random little tale of brake blocks: I went to a Hangi* once, where, lacking any volcanic stones, they used railway brake blocks to heat the pit.
*A Hangi is a Maori cooking method, involving burying food wrapped in banana leaves in a pit filled with hot volcanic stones and water; it makes for some very tasty food!
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Post by 92220 on Oct 22, 2018 7:43:42 GMT
Hi Rob.
I was forgetting that most important point about 'age'. Stupid me! Mind you, that could be MY 'age'!! 'Corse it was BR!!!! So Yes, the BR practice would be relevant.
Bob.
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