uuu
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Juliet
May 1, 2020 10:25:20 GMT
Post by uuu on May 1, 2020 10:25:20 GMT
I'm quite fond of Station Road Steam's approach on their "Stafford" loco. All except the rearmost horn have elongated fixing holes. So you do the back horn up first. Then the back axle goes in, and its front horn is adjusted for a nice fit. then the front axle in, with the coupling rods - and its horns are adjusted until it all goes round.
Wilf
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smallbrother
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Juliet
May 1, 2020 10:35:14 GMT
Post by smallbrother on May 1, 2020 10:35:14 GMT
Here is a better photo with a partially machined cylinder included. Pete.
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Post by ettingtonliam on May 1, 2020 10:36:27 GMT
For what its worth, when I was building Juliet, and helping Dad with his Speedy, many years ago, to get the rod lengths to match the axlebox centres we made an adjustable jig, like this. Turned 2 bushes from silver steel, drilled and reamed to suit the size of the holes in the rods, before fitting the bearing bushes, and one end turned down to fit the axlebox bores. Piece of flat steel, size doesn't matter, but nice and stout. Drill holes in the flat for the jig bushes ,about 1/8" larger than the axle diameter, to suit theoretical axle box centres, but open up one of them along the line of the flat, so there is about 1/16" movement either side to the nominal position. One jig bush is pressed into the flat (or Locset) and the other has a thread to take a thin nut and washer. Harden bushes, tempering isn't necessary. Fit jis bushes to steel flat, leaving nut loose. Assemble to axleboxes, and then lock up the nut . Check that jig is a nice sliding fit in axleboxes, and when it is, use the jig to drill the coupling rod blank. Repeat the whole exercise for the other side, in case the axlebox centres are slightly different from one side to the other.
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Juliet
May 1, 2020 10:37:49 GMT
Post by ettingtonliam on May 1, 2020 10:37:49 GMT
I'm quite fond of Station Road Steam's approach on their "Stafford" loco. All except the rearmost horn have elongated fixing holes. So you do the back horn up first. Then the back axle goes in, and its front horn is adjusted for a nice fit. then the front axle in, with the coupling rods - and its horns are adjusted until it all goes round. Wilf Do they then dowel the front horn to the frames?
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uuu
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Juliet
May 1, 2020 12:14:16 GMT
Post by uuu on May 1, 2020 12:14:16 GMT
I don't think so. I think it's just the fixings holding it. I've got this from their kit instructions - just reading them for amusement.
Wilf
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Post by builder01 on May 1, 2020 12:34:19 GMT
Hey Pete, photo posted just fine! Thank you. Which holes need to be closer, the holes in the rod? A method I used to set the distance, was to measure the distance between the axles. This should be the same distance between the holes on the rod. Does not matter what the drawing shows, the holes in rod must match the axle centers. I measured over the axles with them pushed together and another measurement over the axles with them pushed apart. You may have to get someone to manipulate the axles while you manipulate your caliper. The average of these two measurements is the center distance between the axles. (minus the diameter of one axle!) This is also the number for the distance between the holes in the rod. I assume you have a mill to accurately position the holes. Drill and ream one hole, turn the hand wheel the distance you have for the axle centers and drill and ream the other hole. No, you were right about the average... I use this method for finding the centres of any feature. It works even if the hole or axle sizes are different. Oh yes, if it is the averaage, the measurement over the axle diameter is taken into consideration as the other measurement is taken between the axles. Thanks Roger!! At any rate, the wheels on my 0-6-0 all went round and round the first time with no binding.
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Juliet
May 1, 2020 18:15:29 GMT
Post by delaplume on May 1, 2020 18:15:29 GMT
Don't forget that before the introduction of alloy steel for the rods in full size, and more accurate manufacturing methods, the rods were adjusted to suit by taking them to the forge and having the smith stretch them or shorten them by 'bumping'. Very true !!.........GWR used plain Carbon steel for their coupling rods, hence the large size and fishbelly shape..........Compare them with rods from A3 /A4 etc which I believe were of a High Tensile steel ??
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smallbrother
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Post by smallbrother on May 9, 2020 15:18:49 GMT
Almost there with milling the portface. A flash of hungover inspiration just now to set up the gauge as shown to check the dimension to the bore which should be 0.75". Another 5 thou needs to come off. Not doing it today as still feeling hungover. Work holding and measurement taking are quite challenging for us beginners but most days I learn something - either by trial and error on my own or from the helpful experts on here. Pete
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uuu
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Juliet
May 9, 2020 15:38:16 GMT
Post by uuu on May 9, 2020 15:38:16 GMT
Your workholding is clearly effective - see all the swarf. It just looks really scary! It's not nice when things move during milling - I tend to have more clamps - belt and braces. But, as I said - you've made plenty of swarf.
Wilf
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stevep
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Juliet
May 9, 2020 15:39:46 GMT
Post by stevep on May 9, 2020 15:39:46 GMT
Pete,
I hope the setup you show here is just for the measuring. Machining the port face whilst the vice just holds the edge of the casting is, in my opinion, courting disaster.
Having determined how much has to come off, I would remove the bar through the bore, and lower the casing down in the vice so it is gripping nearly all the end faces. Use the clock to make sure it's level, and then machine off the 5 thou.
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smallbrother
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Juliet
May 9, 2020 16:17:06 GMT
Post by smallbrother on May 9, 2020 16:17:06 GMT
I was very wary of this set-up I must admit, and expected it to go wrong. I have taken light cuts and only along the Y axis.
I think Steve I will take your advice and move it down. I can tackle the flanges with a bit more confidence then.
With the benefit of hindsight I could have moved it much earlier in the process, but like I said, I learn new things every time.
Pete.
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uuu
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Juliet
May 9, 2020 16:19:40 GMT
Post by uuu on May 9, 2020 16:19:40 GMT
You might not get the same alignment if you move it - and with only 5 thou to go, you might be better just to carry on. It hasn't moved so far.
Wilf
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Juliet
May 9, 2020 20:20:27 GMT
Post by chris vine on May 9, 2020 20:20:27 GMT
Hi Pete, You are making grand progress! My observation on milling vices is that they are not as rigid as one might think. As you tighten the jaw it can tend to lift - especially if they are gripping near to the top of the jaw only. A clock on the jaw as you tighten it will show how much.
In your set up, the jaw may lift and mess up you accuracy a bit. But also it won't be presenting a flat face to the small bit of the casting you are holding, so it is in a bit of danger of tipping round.
However, as you are going gently it will probably be fine for you...
All best Chris.
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smallbrother
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Juliet
May 9, 2020 21:11:48 GMT
Post by smallbrother on May 9, 2020 21:11:48 GMT
Hi Pete, You are making grand progress! My observation on milling vices is that they are not as rigid as one might think. As you tighten the jaw it can tend to lift - especially if they are gripping near to the top of the jaw only. A clock on the jaw as you tighten it will show how much. In your set up, the jaw may lift and mess up you accuracy a bit. But also it won't be presenting a flat face to the small bit of the casting you are holding, so it is in a bit of danger of tipping round. However, as you are going gently it will probably be fine for you... All best Chris. Hi Chris - yes there is a tendency for a bit of lifting as I close the jaws. Is this a quality issue or do they all do that? I check as the jaws close and if necessary give a tap with a soft hammer to keep it in position. Pete.
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Post by chris vine on May 9, 2020 22:06:20 GMT
Hi Pete, I think all vices will do this a tiny bit. It isn't necessarily the jaw lifting off its guides, but metal is much less rigid that we give it credit for. You only have to watch a youtube clip of rails going round a curve to see this!! www.youtube.com/watch?v=O4kC262exiw&list=PLdqXzKAYu85zsw3gK4uSZxZjvgS-3Mw46&index=23&t=160sabout 2 mins in... I find the best way is to put parallels (or an old bearing race) under the work in the vice, so the parallels are sitting on the base of the vice. Then you can tap the job down with a lead hammer. You can even make one of these yourself. Once the parallels are nipped tight under the job, then you know it is down flat. Chris.
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uuu
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Juliet
May 10, 2020 6:52:13 GMT
Post by uuu on May 10, 2020 6:52:13 GMT
I think your vice is a "drill press" vice rather than a milling one. But it's a chunky one. The milling ones have more support for the moving jaw, so it won't twist as easily and, in theory, won't lift. But all but the very best do seem to lift (and they get really heavy), so I wouldn't rush to change if yours if proving to be satisfactory.
Wilf
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smallbrother
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Post by smallbrother on May 11, 2020 13:14:06 GMT
Did I see somewhere that you can use a piece of round bar between the work-piece and the moving jaw to stop the lift?
Pete.
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uuu
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Juliet
May 11, 2020 13:55:56 GMT
Post by uuu on May 11, 2020 13:55:56 GMT
Yes, I do that sometimes. But it does reduce the hold-down of the piece as it's only the other jaw stopping it pulling out - the roller can, um, roll.
Wilf
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smallbrother
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Juliet
May 11, 2020 14:24:20 GMT
Post by smallbrother on May 11, 2020 14:24:20 GMT
I just tried it while doing the pump stay. Seems to have worked OK.
Pete.
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uuu
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Post by uuu on May 11, 2020 14:44:41 GMT
Doing a bit of googling, I've found this treatise on the subject: John F's workshopWilf
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