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Post by David on Nov 6, 2023 9:53:48 GMT
Thanks guys. I did put a groove in the middle of the axle shoulder for this purpose but not the crank pins. I did twist the crank pins as I put them in so with luck some loctite got into whatever bits of rough were left by the reamer. Here's how I put the wheel back onto the mill to ream the hole. Think of how much easier this would have been RIGHT AFTER THE LAST DRILL as all the others were done! I was able to put this wheel over one of the others and have both crank pin and axle go through so it's pretty good. That only worked for one other wheel so there are tiny differences between them - hopefully less than 0.001" The wheel is sitting on the wheel making jig which has a 1/2" reamed hole to locate the axle hole and another one of those at crank pin distance on one side, and a clearance hole for drilling and reaming opposite - which is under the crank pin hole in this photo. Then a centre was used to put the crank pin hole under the spindle and everything locked down. Here are the other new bits.
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Post by racinjason on Nov 6, 2023 22:16:20 GMT
Those wheels look good David, it's satisfying machining wheels from solid and that exhaust should let it breath. when I use Loctite on pins or axles, I leave the finish a bit ruff a drilled hole is good then make the shaft a push in fit this give a surface for the Loctite to key to also put the Loctite on the shaft not the bore this will push it down the shaft as it goes in. Regards Jason.
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Post by David on Nov 7, 2023 6:23:13 GMT
The tyres look fantastic in person, a really great finish. The steel wasn't anything special, just MS covered in mill scale.
I wish I'd left the counterweight flush with the boss and tread - would have saved time, wear, and looked better! I'd also make the spokes thinner. Pretty happy with them for a first attempt and only scrapped one because I used the wrong cutter.
I'm considering making 3mm bosses for them because I think they'll look a bit silly with a 3mm bush bringing the rods out to the correct spacing.
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Post by racinjason on Nov 7, 2023 8:15:54 GMT
David, did you turn the tread on the mill?
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Post by David on Nov 14, 2023 9:53:54 GMT
Yes, the treads were done with the CNC lathe head.
I've made the front crank pins just a bit too long, thinking too long was better than too short. I was wrong! The instructions do say the crankpin is very close to the crosshead and that is true. The crankpins are loctited into the wheels now so it's going to be a bit of a mess getting them out but I assume some heat will do it so I can shorten them. I'd have been tempted to file them back but they have a counterbore in them that a top-hat bush goes into and the bush will bottom out if I do that so the excess has to come off the rear of the pins. I might re-measure in the light of a new day and see if that will work because it will (may?) save a lot of faffing around. Unless I get it wrong and have to buy a new length of silver steel to make new ones.
Far worse is that I read a drawing incorrectly and thinned the front axleboxes down to 1/2" over all rather than 5/8". I didn't check the existing ones to confirm the measurement either. This means they're too thin to have the spring pockets drilled into them. So that's many hours and much careful work wasted. I took great care and thought through the process to make all four in a way that would cancel out errors and I reckon I probably got them all within 0.001". There's no chance I can repeat that given the centres are a little off fore-aft, but they were all off the same amount! Plus I need to buy another stick of cast iron and machine a great deal of it away, again.
Quite a frustrating session with the measuring sticks finding all that out tonight!
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uuu
Elder Statesman
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Post by uuu on Nov 14, 2023 11:06:52 GMT
At the Pump House we've found removing crankpins with an arbour press is effective. A bit of heat helps, but we've never had to get them really hot - the press seems to do the work.
I think we're on the third set of pins for John's loco, (so far).
Wilf
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stevep
Elder Statesman
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Post by stevep on Nov 14, 2023 12:32:08 GMT
Can't you clamp the wheels on their back to the milling table, and gently machine off the excess?
If you need to drill and tap them deeper, you could 'clock' them true to the spindle.
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Post by David on Nov 17, 2023 8:15:09 GMT
Steve, that probably won't work for various reasons. I don't have enough material to make new ones so I'm trying to go the safest way.
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Post by David on Dec 2, 2023 10:56:19 GMT
Nearly back to where I was 2 weeks ago! I got one more axle box out of the original cast iron and my father-in-law gave me a scrap of his that I could get the other from.
As expected they have a different error to the originals. I still don't know why I can't get these holes in the middle - it should have been a simple case of an edge finder on the jaws of the vise but damned if I could get it. I was close on the originals as evidenced by the rods going over the axle ends ok (a few thou out) but these ones are much worse, relatively.
The design calls for 8.625" between axle centres. Using an edge finder on the milling machine I ended up with 8.641" +/- 0.001. So I reckon I managed about 0.012" error on these ones!
As best I can measure the current rod boss centres are 8.633".
I'll knock the front bush out, put a new undersized one in and try to bore it at the correct length and see what happens.
I also cleaned the axle boxes up height-wise. I trimmed the bottoms all to the same length from the axle centerline and then did the tops. I hope this means distortion of the geometry due to the axles being at slightly different heights will be minimised. Why weren't they all the same already? I have no idea, I tried very hard but didn't get it.
Spring pockets and oil galleries still need to be done on the axle boxes too.
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Post by David on Dec 7, 2023 8:14:10 GMT
Spring pockets are done. The old axleboxes didn't have oil galleries to get oil to the sliding faces. I think I might add some on the new ones because the axle oil goes in the end of the axle rather than in the top of the axlebox so I have some room. I could use the CNC machine to put a fancy pattern on them.
All the measuring I did seems to have come to nothing. I made a new bush for a coupling rod, drilled while it was in the rod clamped on the mill, indexed against the middle of the rear bush, and it's sticking in the same place the old one did - when it pins are furthest from the front. Back dead centre?
Doesn't make sense to me. I might put off worrying about it until the wheels are quartered. Trying to move a rod when there's only wheels on one side seems to be a bit iffy.
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Post by racinjason on Dec 7, 2023 9:51:42 GMT
Yes, trying to rotate the assembly with only one side on will jam up every time it's too easy for the wheels to get out of phase. I wouldn't worry about fancy pattern the oil goes everywhere anyway.
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Post by David on Dec 12, 2023 9:51:02 GMT
In an attempt to recover from this axlebox misadventure I've made a measuring stick to check the distance between axles. I still can't quantify the distance but I'll try and use these to scribe a mark where the hole needs to be in the bush.
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Post by racinjason on Dec 12, 2023 10:39:36 GMT
David You could machine a flat on the outer edges leaving it say 5mm from center then you can easily measure with a vernier and subtract 10mm to get the correct distance.
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Post by David on Dec 12, 2023 20:28:38 GMT
I don't have a vernier long enough!
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mbrown
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Sisyphean
Dec 12, 2023 23:22:20 GMT
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Post by mbrown on Dec 12, 2023 23:22:20 GMT
I am going to have to locate the vertical plane of my driving axle in order to attach the expansion link brackets at the right distance from the axle. Like you I haven't got a vernier or caliper long enough, so a copy of your trammel would be just the job.
Thanks for the idea - I'll put it on my 99 3462 thread when I get back in the workshop and have a chance to make one.
Malcolm
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