uuu
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Post by uuu on Sept 10, 2023 9:22:48 GMT
I had to mill all the angles on Jessie to be square, too.
It helps a lot if you can get all the holes in the plates and angles accurately placed. You mention accuracy, too, so I'm not really saying anything new. Then when you loosely assemble the frames, there's nothing pulling things off-square; nothing fighting against you.
If you can make up some rods dead on the width between the frames, threaded in both ends, you can bolt these into any spare holes (bracket holes, brake hanger holes, etc) to help hold things true as you tighten up.
Wilf
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uuu
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Post by uuu on Sept 9, 2023 6:21:47 GMT
PM me with your size requirements and address.
Wilf
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uuu
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Post by uuu on Sept 8, 2023 20:59:14 GMT
The cylinder block on the Foden lorry s similar to a traction engine. It actually forms a steam dome with the regulator at the top and a cover plate to which the safety valves are fitted. This cover plate is made of steel, I am a little worried about corrosion. Would it be worthwhile to make a replacement? possibly stainless steel or aluminium? Am I worrying over nothing? I'd make it from the same material as the cylinder block. Wilf
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uuu
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Post by uuu on Sept 8, 2023 12:26:09 GMT
If you go to one picture and click "share" you can select the "Hotlink for forums" option and just paste it in here (no extra code required): Wilf
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uuu
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Post by uuu on Sept 6, 2023 7:15:00 GMT
I don't think there's a way of challenging a BI's judgement on an area where the UK code gives them discretion. Here's an obvious dispute area: c. Inspectors may, at their discretion, issue a certificate of hydraulic test with a shorter validity period where the Inspector considers that the above periods are inappropriate to the age and/or condition of the boiler. and "...to allow the Inspector to be satisfied..." and "...which is at an unacceptable level..." and "...check adequacy of screw threads..." There are so many areas where judgement is required. Here's the Federation website giving details of their services: fmes.org.uk/pressure-vessels-and-testing/This does offer a "contact us" section with a suggestion there's someone to contact with questions: "Safety Officer for questions relating to the proper conduct of tests, what must be tested and with regard to other pressure vessels such as for LPG" I suspect, without having used this service, that it might enable a clarification of the proper interpretation of the code. And the point I made above, where an inspector might argue that a shell re-test for a repair could require a more modern approach to the boiler's construction than the original design, might be just such a clarification. Wilf
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Post by uuu on Sept 2, 2023 12:46:53 GMT
Because the nuts are not particularly tight, you might consider a lock-nut to hold them once you've got the amount of squeeze you want.
Wilf
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uuu
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Post by uuu on Sept 1, 2023 14:58:09 GMT
Not as far as I know. Which is the source of many people's problems when dealing with older boilers. With so much left to the discretion of the inspector, you can get an easy ride or a hard one. Some inspectors err heavily on the side of caution, and insist on applying modern design requirements to repairs, which can be the devil's own job to implement. Or they expect features that are not even mandatory on new boilers, just recommended in the code. The code requirement in sub-paragraph "f" above for a "new initial shell test" can be interpreted as a need for the retested boiler to comply with all the new boiler standards.
Hopefully your inspector is more sympathetic, accepting the design standards of the original model. And hence my hope that your repair can be classed as non-structural.
Wilf
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Post by uuu on Sept 1, 2023 12:50:03 GMT
As with all things boiler related, your local club boiler inspector should be consulted. There's no point undertaking a course of action that they frown upon.
A relevant paragraph from the boiler test code is this:
12.5 The validity period of test certificates are as follows: a. The Initial Hydraulic Shell test is valid for the life of the boiler unless the boiler is subject to repair or modification which would affect the structural integrity of the boiler.
and:
f. Any structural alteration or repair of the boiler shall invalidate all current certificates. This will necessitate a new initial shell test followed by a 1.5xPW system hydraulic test and a steam test.
So an obvious question is: Does this repair affect the structural integrity and/or is a "structural alteration or repair"?
Clearly if you wanted to solder in some blind bushes, you might loosen some other joints with the heat. However, just re-tapping for fatter screws, or even larger for screw-in bushes, might be considered not to be a structural thing. Only if your inspector shares this view of course.
Or you might not be frightened of a full two-times shell retest.
Wilf
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Post by uuu on Aug 27, 2023 19:31:04 GMT
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Post by uuu on Aug 25, 2023 20:28:55 GMT
That puts my theory to bed then.
Wilf
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Post by uuu on Aug 25, 2023 10:10:56 GMT
Do you have two people driving, like a traction engine? The chap on the regulator would be the senior person, and go on the right, with the steersman on the left.
Here's a passage I found online - relating to showman's engines etc.:
On these vehicles there is, first of all, a driver. He is, in fact, an engineer. He is the man who is responsible for getting steam up, applying the brakes and generally looking after the firing and mechanical side of the engine. When the engine goes downhill the driver or engineer has to see that his fire is properly damped down, that he has not got too much steam up, and that his brakes are properly on. At the same time he is giving the necessary signals to the men behind on the different trailers. They can pull three enormous trailers and a watering cart, a train of five vehicles travelling along the road. The engineer blows a whistle and each man who is in charge of the different trailers behind has to apply the brakes at the proper time, or take them off, as the case may be. This Clause does not affect these men. The driver-engineer would continue to have a licence, but he is not the man who steers the vehicle. The man who steers the vehicle is a steersman. He is the man who actually turns the small wheel which directs the front wheels of the vehicle along its course on the road, and this Clause, if it goes through as it stands at present, will mean that the steersman will not need to have a licence. Anyone will be able to steer one of these big machines—a lunatic, or a half-wit, or even the fat lady in the show, if she is able to get into the small space available. On the other hand, of course, you might have the driver who goes round "The Walls of Death."
Wilf
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uuu
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Post by uuu on Aug 21, 2023 7:33:45 GMT
EKP supplies still list graphited yarn for sale - there are probably others too.
It often comes as square section - so the method is to cut two or more tiny lengths to go round your rod with as little gap as possible - a bit like a piston ring. And, as with a piston ring, you put them in with the gaps on opposite sides.
Wilf
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Post by uuu on Aug 21, 2023 7:23:25 GMT
Looking up the coefficient of expansion of Steel - it shows as 0.0000065"/(in x deg F)
So for a 5.5" rim, that is 0.00003575" for each degree F.
400 degrees, and the expansion is 0.0143"
So you can get it to grow 14 thou in a domestic oven. And Phil's dull red is about 750F - grows about 26 thou.
Wilf
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Post by uuu on Aug 19, 2023 7:13:56 GMT
The late president of the Isle of Wight club had a Ken Swan "Wren" locomotive. Its cast iron wheels wore badly on the steel bar rails at the club - after a lot of use, it has to be said. And it's a hefty loco on only four wheels.
So he turned down the cast iron treads and added heat-shrink-fit steel tyres, which lasted better.
The loco always gripped well, so I can't say whether rail adhesion was affected. It might be thought that cast iron would slip more easily.
So that's how I'll go with my own loco. Start with the cast iron and, if it wears out, fit tyres at that point.
Wilf
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Post by uuu on Aug 14, 2023 12:41:05 GMT
Just to validate the simplicity of the required G-code, I drew a round-cornered rectangle in my CAD program, 204 wide and 104 high, with 2mm corner radius, and generated the required code:
G0 X-100.0 Y52.0 G1 Z-1.0 G3 X-102.0 Y50.0 I0.0 J-2.0 G1 Y-50.0 G3 X-100.0 Y-52.0 I2.0 J0.0 G1 X100.0 G3 X102.0 Y-50.0 I0.0 J2.0 G1 Y50.0 G3 X100.0 Y52.0 I-2.0 J0.0 G1 X-100.0 G0 Z3.0
The I modified the corners to take the wider course, as shown in the sketch given, and here's the result:
G0 X-100.0 Y52.0 G1 Z-1.0 G1 X-100.25 G3 X-102.0 Y49.75 I0.25 J-2.0 G1 Y-50.0 G1 Y-50.25 G3 X-99.75 Y-52.0 I2.0 J0.25 G1 X100.0 G1 X100.25 G3 X102.0 Y-49.75 I-0.25 J2.0 G1 Y50.0 G1 Y50.25 G3 X99.75 Y52.0 I-2.0 J-0.25 G1 X-100.0 G0 Z3.0
Save yourself $10, and write it by hand!
Wilf
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Post by uuu on Aug 14, 2023 9:34:10 GMT
I've been thinking about the modification to the G-codes to bring about the new cutter path. As you note, it shouldn't be difficult.
If I imagine the curve pictured above to carry on to be a complete circle, then I think the centre of that circle is the same point as the original. So we can modify the X,Y coordinates of the start and end of the curve, and make equivalent adjustments to the I,J offsets to get the same centre point.
So, if the centre of the circle is at coordinates x,y and the radius r, the original G-code could be this:
Approach: G01 X(x+r) Yy Curve: G03 Xx Y(y+r) I(-r) J0 Departure: G01 X(wherever) Y(y+r)
And the modified code, for a cutter offset of 0.25:
Approach: G01 X(x+r) Y(y+0.25) Curve: G03 X(x-0.25) Y(y+r) I(-r) J-0.25 Departure: G01 X(wherever) Y(y+r)
Does that work?
Wilf
Edit - Since you're describing a rectangle, and one corner is achieved with only three lines of code, it should be trivial to write the 12 lines needed for the whole plot by hand. No CAM program needed. Edit - only eight lines of code - four straights and four curves. Edit - PS - I know you like your CAM program to output curves as a series of line segments, but in this case it's so much easier to use the G02, G03 approach. I've used the I,J figures as relative to cutter position - I know you can ask for an absolute I,J setting, but I never use this. Edit PPS = analysing your required shape to use the centres of the corner radius as primary inputs is helpful when you're drawing multiple coloured lines, as they'll all share the same four corner values - just different radius.
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Post by uuu on Aug 12, 2023 18:16:58 GMT
Jim Ewins did some experiments measuring temperatures around a model loco in use. Looking up an old post on another forum, these are described as being written up in Model Engineer 18th March, 1st April, and 20th May 1966. I've not got these so can't see the figures, but I suspect they include internal smokebox temperature- the outside can't be too far below this. Wilf See also this Youtube video, where temperatures of 260-270C are recorded: www.youtube.com/watch?v=Bl_FZnzpWp4
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uuu
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Crab
Jul 24, 2023 10:42:38 GMT
Post by uuu on Jul 24, 2023 10:42:38 GMT
I can't get your link to work - you may have posted the private editing rather than public viewing version.
Wilf
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Post by uuu on Jul 17, 2023 6:29:57 GMT
If I'm reading your description right, the extra bit is the first bit to be engaged, and ends up poking into the boiler when the thing is done up. The position of the four holes has already been determined, and the thread removed doesn't change the final position of the flange (it only affects the beginning), then it will be OK.
You can test this yourself with an ordinary nut and bolt. Screw the nut all the way onto the bolt, and mark it's position. See that it always ends up in that position. Then cut a bit off the end of the bolt. This won't change the way the nut ends up.
Wilf
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Post by uuu on Jun 30, 2023 19:27:53 GMT
I can't help with your particular design. My own loco has a tube, round which there's a skirted wrapper - so the sealing is easier between front and rear rings and the tube. And it's in steel.
But - it uses real rivets to hold it all together. So I was wondering if you could use proper rivets?
Wilf
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