Help with 'Speedy' valve gear and other issues...

[Roger]

I've just finished making the washers and Split Pins for the pivot pins on the fillers and fitted them

PXL_20231018_102648556 by Billy Roberts, on Flickr

I bought some Nickel Chromium resistance wire for these ones, adding the flat using the Mangle I used for the others that were made from Florist's wire. I thought these ones needed to be made of something that wouldn't rust, but Stainless Steel would have been a bit of a challenge to make into the necessary 'D' shape.

PXL_20231018_102705249 by Billy Roberts, on Flickr

The filter isn't shown on this picture. I may make some different ones that have a floppy sack that can be tucked into the tank so they can be filled more easily without spilling over the tank top.

PXL_20231018_102716814 by Billy Roberts, on Flickr


You can see some Grey overspray on the above photo that's got onto the tank top from when I was lining the side. I hadn't realised that it wasn't masked sufficiently. Below, I've given it a very light going over with T-Cut, which has removed most of that. It might need a little more and then polishing all over, but it's rectified most of the bloom.


PXL_20231018_111827237 by Billy Roberts, on Flickr

I managed to get a lot more on the side of this filler...

PXL_20231018_110516294 by Billy Roberts, on Flickr

... so I gave that the same treatment. I may need something finer to restore that Full Gloss finish. Maybe something like Silver Polish?

PXL_20231018_110922157 by Billy Roberts, on Flickr

[Roger]

I'm trying to get the Pannier Tanks completely finished, but I'm concerned that the PLA printed gears might absorb enough water over time to cause issues. Any plastic is potentially going to have this issue, but I thought Fluorosint might be a better choice for the small gear because it's so slippery. The mechanism has to work with pretty small forces, so I decided to make one from that.

As a reminder, this is the general arrangement. There's no seal between the Try Cock indicator and the gear, the connection is through magnets attracted to each other through the thin walled Phosphor Bronze tube. The angle of the Try Cock indicates the water level. I'll put a Red dot on the end of the handle that is normally not visible when the tank is full.

20190520_200416 by Billy Roberts, on Flickr

The material is extremely soft, and difficult to cut cleanly, even with really sharp tools.

PXL_20231018_142505595 by Billy Roberts, on Flickr

I've made a containment region for one tooth, and used the 4th axis to step around 16 times to cut all of the teeth.

Here they're being roughed out with a 1mm cutter which won't quite reach down to the root...

PXL_20231018_153737264 by Billy Roberts, on Flickr

... and this is a 0.8mm PCB burr being used to finish the profile. I'm treating the tooth just like any other 3D machining operation, using 50micron (2 thou) overlap so as to get a nice smooth tooth form. Obviously the tooth is tapered and I'm not following the geometry of the tooth in the usual direction, but it doesn't matter. As long as the 3D model is correct, it will generate the correct profile in slices at whatever angle is chosen.

I'll do the same for the Brass Quadrant gear, when the plate arrives.

PXL_20231018_201607938 by Billy Roberts, on Flickr

The flat is so that the assembly can fit through the opening in the end of the Tank.

PXL_20231019_103906857 by Billy Roberts, on Flickr

I'll keep the mount and 'C clip as PLA and leave the whole thing in water for a few weeks to see what happens.

If necessary, I'll make the mount out of Brass too.

PXL_20231019_111601888 by Billy Roberts, on Flickr

[Roger]

This YouTube 'short' just came up on my feed. My Son-In-Law bought a tracked model Snowmobile so it could be split in two and the tracks modified to fit the foot of his R2D2 Robot. I made a gearbox to connect it to a 12V Windscreen wiper motor such that it was completely hidden in the foot and leg arrangement.

You can see the Frames of 1501 on the bench while I was sorting out the axleboxes.

[Roger]

One of our club members has his own garden railway, and today was an open day and Steam Up for Members, friends and family.

Although the weather forecast wasn't promising, I decided to take 1501 along to see how it would ride on the track, and loosen up some of those tight spots.

Below is a short video of it being towed.

PXL_20231028_114147784.TS by Billy Roberts, on Flickr

Finally home after a couple of miles running and a bit of a drowning. It's definitely a little easier to move, and there was a small smear of blackened oil around some of the bearings.

It's got properly christened with rust from the Steel rails, and the oil has attracted a lot of dirt.

It's currently very nose heavy with the massive rear Stretcher missing. even so, I think it might need even more than that to make it sit evenly on all six wheels. I do have a big lump of Lead which can be melted into a suitable shape if there's room under the footplate. If not, I could cast a piece to sit in the bottom of the Bunker.

PXL_20231028_142808837 by Billy Roberts, on Flickr

[uuu]

Next time, you could try towing it backwards - is there an argument to say that will apply wear to the surfaces more used in forward running on steam?

Wilf

[Roger]

Back to the Water Level Gauge in the LH Pannier Tank.

The original 3D printed version is in the foreground, but this is again going to be made in Brass so that it can't absorb any water. I decided to just 3D machine it, disregarding the fact that it happens to contain gear teeth.

I simplified the clearance around the teeth, removing the shallow chamfer, but that's all.

The original used a Brass arm that was bolted to it, but I decided to extend the arm and attach it directly to the float.

PXL_20231024_192537967 by Billy Roberts, on Flickr



PXL_20231024_203548967 by Billy Roberts, on Flickr

The area around the teeth was defined with a Containment Region, then worked on with ever smaller cutters.

PXL_20231025_080847001 by Billy Roberts, on Flickr

The problem is that the gap between the teeth at the root is only about 0.9mm. That means you can't rough it that close to the full depth, even with a 1mm cutter.

PXL_20231025_191549069 by Billy Roberts, on Flickr

Using radial machining, and a 0.8mm PCB burr, it is possible to get pretty deep into the teeth taking small cuts and lowering the cutter over several steps.

PXL_20231026_061112280 by Billy Roberts, on Flickr

Finally it was possible to take one Parallel Finishing pass very slowly across the teeth to the full depth...

PXL_20231026_074040361 by Billy Roberts, on Flickr

... gradually working away with 25micron (1 thou) overlap to avoid breaking the cutter and to get an acceptable finish.

PXL_20231026_101347361 by Billy Roberts, on Flickr

Five hours in, and only about half way!

PXL_20231026_112956696 by Billy Roberts, on Flickr

Then after about 12 hours, this is the finished item. Yeah, a slow way to produce something like this, but easy to do.

PXL_20231026_190320194 by Billy Roberts, on Flickr

The profile was roughed and finished with a 3mm cutter...

PXL_20231026_214341950 by Billy Roberts, on Flickr

... and the quadrant was hollowed out to reduce the weight. I want this to be heavy on the arm end so that it can turn the gear when the level drops.

PXL_20231027_095218282 by Billy Roberts, on Flickr



PXL_20231030_102012968 by Billy Roberts, on Flickr

I wanted the float to be as light as possible so that it could provide a substantial force to lift the arm and turn the gear. The ratio is 4:1, so there isn't a lot of torque available to turn the indicator.

This is one of the end caps of the float. It's hollowed out so that there's still a 1.5mm flange to solder on to.

PXL_20231030_122102599 by Billy Roberts, on Flickr

i should have partially parted this off much longer, then taken several cuts to stop it warping. A rookie error really.
I squashed it flatter in the vice, but managed to punch a hole through the middle where the pip was. Not my finest moment. You'll see later where there's a blob of solder in the middle to seal that up. It's not great, but it's just a float.

PXL_20231030_124622574 by Billy Roberts, on Flickr

The other end has a tab, so I left a little more on the thickness at this end ie 0.5mm total, and included a small rib to support the tab. Here it's being held by the tab, the cuts being taken very gingerly because it's not a robust setup.

PXL_20231030_191453757 by Billy Roberts, on Flickr

The tab finally gets a 3mm hole to hold it on to the arm.

PXL_20231030_193221096 by Billy Roberts, on Flickr

Originally I was going to use 0.5mm shim until I realised how heavy that would make it. This is 0.1mm shim instead.

PXL_20231030_201242420 by Billy Roberts, on Flickr

I 3D printed a former to help support the inside and get the shape right.

PXL_20231030_203523726 by Billy Roberts, on Flickr

That was left inside while tacking the end on.

PXL_20231030_204719785 by Billy Roberts, on Flickr

The overlap is about 1.5mm. I cleaned up the Brass inside and out and used a PCB liquid flux to help get the joint to seal.

PXL_20231030_205942706 by Billy Roberts, on Flickr

I made the end flanges 0.4mm over the location, even though the sheet is only 0.1mm thick. That was filed back when the soldering was completed. Soldering was done mostly with a Soldering Iron, but I did use a Hot Air gun to reheat it with more flux to level it out and get it into the joints.

As you can see, it's really light.

PXL_20231031_113319687 by Billy Roberts, on Flickr

I was going to lighten the arm if it turned out to be too heavy, but it turns out that it's about right.

PXL_20231031_114008286 by Billy Roberts, on Flickr

It has no problem moving the gears and Indicator. As a reminder, the indicator is magnetically coupled to the small gear to minimise the force required to turn it, and eliminating the need for a seal.

PXL_20231031_114012441 by Billy Roberts, on Flickr

[Roger]

The float turns out to be too close to the back of the Pannier Tank, causing it to jam. This is the necessary clearance being created on the back...

PXL_20231103_210823961 by Billy Roberts, on Flickr

... and this is the spacer to move the float over.

PXL_20231103_213724280 by Billy Roberts, on Flickr

The 3d printed mounting is now going to be made from Leaded Bronze because I've got loads of this.

PXL_20231105_113837931 by Billy Roberts, on Flickr



PXL_20231105_121505680 by Billy Roberts, on Flickr



PXL_20231105_123052595 by Billy Roberts, on Flickr



PXL_20231105_135157364 by Billy Roberts, on Flickr

Machining the Arm clearance and through hole for the Gear created a lot of swarf. I don't worry about trying to remove it because it has little to no effect on the way it cuts while roughing.

PXL_20231105_171213434 by Billy Roberts, on Flickr

That was all cleaned up to size...

PXL_20231105_171358179 by Billy Roberts, on Flickr

... and a 4mm cutter cleaned up the inner corners.

PXL_20231105_202914967 by Billy Roberts, on Flickr

After parting off, the bracket was machined to the final thickness.

PXL_20231105_211145914 by Billy Roberts, on Flickr

The 3D printed part had this Arm retainer included, but it's easier to machine the bracket without it and bolt one on afterwards.

PXL_20231107_102003351 by Billy Roberts, on Flickr

[Roger]

This is a piece of Delrin being machined into a 'C' clip to retain the small gear on the Water Level Guage.

PXL_20231109_210109540 by Billy Roberts, on Flickr

The Stainless 'E' Clips turned up today, so I fitted those to the pivot. The original version had the pin pressed into the 3D print, and the other end didn't have a retainer for the arm.

PXL_20231109_210445236 by Billy Roberts, on Flickr

I decided to have a retainer on the shaft to make sure it didn't rely on the plate next to the gear to keep it in place.

The plate is held on by two M1.6 x 4 CSK screws which are on order. There isn't room for the head of a bolt because that would foul the inside of the Tank Flange.

Hopefully that's all I need to do to finish this. It's taken a lot longer than I anticipated because I've been so busy with other things.

PXL_20231109_210546415 by Billy Roberts, on Flickr

[92220]

Lovely job Roger!!! Especially that minute 'T' tap handle on top of the cover. Blink and you might miss it, it's so small!!!

Bob.

[Roger]

Returning to the Pressure gauge, here's a reminder of where I left the design. The Bezel is to scale, and the now flatter Bourdon Tube is 12.7mm diameter. Originally this was going to be more oval, and be made from Phosphor Bronze, but that proved to be way too brittle.

Bourdon tube in housing by Billy Roberts, on Flickr

The latest effort uses 0.08mm thick Beryllium Copper shim, folded into a flat shape with rounded corners. Folding that is tricky, because I only want a small overlap for the joint, else it ends up very rigid.

This is a former to help bend the sheet back past 90 degrees on the corners. It's been roughed out with an 8mm cutter and finished with a 3mm Corner Mill with a 0.5mm corner radius...

PXL_20231112_110200750 by Billy Roberts, on Flickr

... then parted off and tidied up with a file.

PXL_20231111_210624035 by Billy Roberts, on Flickr

The shim is cut to the right width, and then set on the first former using a Toolmaker's clamp, which then hands it to the vice...

PXL_20231111_111501976 by Billy Roberts, on Flickr

... like this.

PXL_20231111_112216335 by Billy Roberts, on Flickr

Once folded this far, it lines up nicely with the triangular former to get it the next step.

PXL_20231112_112655548 by Billy Roberts, on Flickr

It's then folded flat onto the Titanium Sheet former which is a piece of 4.2mm wide sheet, 0.2mm thick.

PXL_20231111_212348559 by Billy Roberts, on Flickr

That was then fluxed and Silver Soldered.

PXL_20231111_214446382 by Billy Roberts, on Flickr

The Titanium formed can be easily pulled out.

Here's my latest attempt at making a former that can be removed once it's been rolled into the desired arc. These are Piano Wire hairpins to make it easier to get hold of them to pull them out. The previous attempt used the Titanium former, but I couldn't remove it afterwards!

PXL_20231112_124851228 by Billy Roberts, on Flickr

It was fiddly to get them into place...

PXL_20231112_131024783 by Billy Roberts, on Flickr

... but I managed to form them around the mandrel.

PXL_20231112_144259683 by Billy Roberts, on Flickr

However, being Piano Wire, they sprang straight back again, so that's not going to work either.

PXL_20231112_145621971 by Billy Roberts, on Flickr

However, I found some really thin Shim Steel, 0.05mm thick, and that proved to be easy enough to thread through the Bourdon Tube, even though it wasn't straight.

PXL_20231112_151815082 by Billy Roberts, on Flickr



PXL_20231112_151948091 by Billy Roberts, on Flickr

That worked much better. The little rolling machine isn't that good, but it can be adjusted to prevent any wrinkles forming while it's being formed.

I can see why Beryllium Copper is a good choice for this sort of application. It's easy to form, but is springy and doesn't crack. Obviously it's not a material you want to have filings of or breath in any dust.

PXL_20231112_212459080 by Billy Roberts, on Flickr

The big question is just how much will this move when pressure is applied? It feels fairly flexible, but I'm going to have to design the mount and get it to the point where I can do a physical test. If it doesn't move enough, I'll have to see if I can source some even thinner shim.

[chris vine]

Hi Roger,

Looks good to me!

Here's a maths/physics problem for you:
If it doesn't deflect enough (and it is difficult to make from a thinner shim material), then if you squeeze the tube a bit to flatten it, (after making it) so it is flatter, then will it deflect more for a given pressure?

There seem to be two opposing ideas here:
1, as the tube gets flatter, the rigidity in bending will become much less, so it should deflect more.
2, as the tube gets flatter, the difference in area between the inside curved wall and outside curved wall (it is this difference which causes it to deflect) will be reduced - so it should deflect less!

I wonder which one wins, or if they cancel each other out?

Without doing the maths, I feel that the flatter tube might deflect more because all bourdon tubes are flattened. If it didn't make any difference, they would probably be round tube, but bent into a curve!

Happy puzzling!
Chris.

[Roger]

Nov 13, 2023 10:32:53 GMT chris vine said:

Hi Roger,

Looks good to me!

Here's a maths/physics problem for you:
If it doesn't deflect enough (and it is difficult to make from a thinner shim material), then if you squeeze the tube a bit to flatten it, (after making it) so it is flatter, then will it deflect more for a given pressure?

There seem to be two opposing ideas here:
1, as the tube gets flatter, the rigidity in bending will become much less, so it should deflect more.
2, as the tube gets flatter, the difference in area between the inside curved wall and outside curved wall (it is this difference which causes it to deflect) will be reduced - so it should deflect less!

I wonder which one wins, or if they cancel each other out?

Without doing the maths, I feel that the flatter tube might deflect more because all bourdon tubes are flattened. If it didn't make any difference, they would probably be round tube, but bent into a curve!

Happy puzzling!
Chris.

Hi Chris,
Those are great questions. I have seen some tubes that are more oval, I don't think I've ever seen any that are round. My instinct says that the flatter the better, but I'm not sure. There's also the influence of the seam, which I've put on the outside, reasoning that the outside being stiffer ought to promote more bending as the inside expands. Who knows. I'll give it a try as it is and see what I get.
I know some people have used Brass Shim, but that's far from ideal. The melting point is very low, and I think Silver Soldering is the best option for the seam.
All good fun!

Edit:- I've just found some 0.05mm sheet on eBay which isn't too expensive, so I've ordered some of that. A couple of listings claim to go down to 0.02mm, but those don't appear in the drop-down box, so you can't order them. To be honest, that might be too thin anyway.
Unfortunately, this has to come from China, so there will be a small delay. I'll press ahead with the rest of the design though. 

[chris vine]

I tried to find a calculator for bordon tubes, but the maths is super complicated. Now one would just use FEA.

Good luck,
Chris.

[dhamblin]

This is a commercial offering from the 1950s - seam on the outside

Pressure Gauge by Daniel Hamblin, on Flickr

A great start Roger, looking forward to future instalments on the gauge build.

Regards,

Dan

[Roger]

Nov 13, 2023 21:26:58 GMT dhamblin said:

This is a commercial offering from the 1950s - seam on the outside

Pressure Gauge by Daniel Hamblin, on Flickr

A great start Roger, looking forward to future instalments on the gauge build.

Regards,

Dan

Thanks for that Dan, it's good to see the shape of the tube as well as where the seam is.
I'm working on the scale positions of the needle and pivot, and looking at the different internal arrangements others have used. I've got articles by C.R.Amsbury which I think Julian sent me, and he recommends gears to give a more linear range. There's 100 degrees of travel on the GWR gauges, so that's an awful lot of movement to get from the Bourdon Tube.
Anyway, we'll see how that progresses as I flesh out the construction.

[ettingtonliam]

And now this amazing man is making his own pressure gauge! Makes me want to go and hide under a stone in shame-----.

[Roger]

Nov 13, 2023 23:55:16 GMT ettingtonliam said:

And now this amazing man is making his own pressure gauge! Makes me want to go and hide under a stone in shame-----.

That's very kind of you, but don't be too impressed. I'm following in the footsteps of others who did this without the benefit of CAD, CNC machines and eBay to source otherwise difficult to find materials. It's much easier to do this sort of thing in 2023 than it was decades ago.
It's just another interesting puzzle to solve.

[oldnorton]

Roger, I presume that you will want to make a new dial face. Have you got a nice method? I will start a new thread in case there are some good ideas out there.
Norm.

[Roger]

Nov 14, 2023 9:39:34 GMT oldnorton said:

Roger, I presume that you will want to make a new dial face. Have you got a nice method? I will start a new thread in case there are some good ideas out there.
Norm.

Hi Norm,
I haven't given it much thought yet. Off the cuff, I'll probably try printing it on a sticky label using the Office printer as a first port of call. That can add the Red line too. I don't know what the resolution will look like, but it might be good enough.

[jma1009]

Hi Roger,

There is something in the post for you in the next few days. There is a thread on here about Freddie Dinnis and his FSD pressure gauges.

Marvellous work as ever on your part!

Cheers,

Julian