99 3462 Build diary

[mbrown]

Many thanks Roger.

Today was the repeat of last weekend. The second motion bracket went together just like the first, so now we have two....


IMG_20201031_181049 by malcolm brown, on Flickr


IMG_20201031_181034 by malcolm brown, on Flickr


Everything seems to match, so there shouldn't be any dimensional issues between left and right.

Tomorrow should see them finished off with the slidebar seat machined, then I will have to put in a long stretch at the mill, cutting down 13 mm black steel angle to make the long angle that runs along the top of both frames from the rear buffer beam to the cylinder....

Malcolm

[steamer5]

Hi Malcolm,
Those look great!
On the angle front, have you got a bandsaw? I've got something similar to do in the future & that's going to be the weapon of choice to remove the bulk of the material & then clean up with the mill. The plan is to set up the fence on the saw table so that I hopefully can keep the cut straight!

Cheers Kerrin

[mbrown]

Hi Kerrin.

No, I don't have a band saw (I wish I did, but no room...) but it wouldn't help with this job. The angles I have are 13 mm x 13 mm x 3 mm. I need to thin them down on both legs to 2 mm max, then trim one leg back to 9 mm - so the angle will be 12 mm x 9 mm x 2 mm. I will be milling the outside flats and then taking one leg down a bit, if that makes sense.

Lots of slow handle-winding, lots of swarf, not much excitement!

Best wishes

Malcolm

[steamer5]

Hi Malcolm,
Gotya!! Sorry thought you just had to cut the legs down to size. Better go check what I need & I may need to put an order in with you as you will be an expert by the time you've done yours!

Cheers Kerrin

[mbrown]

You'd have to pay me extra to compensate for the boredom! I love things like the complicated fabrications but repetition work and long slow machining jobs don't appeal much....

Malcolm

[steamer5]

Hi Malcolm,
Just checked & I'm going to have to do the same! The only difference is the legs are the same length! So will be watching to see how you get on as I can see the angle going pear shaped...GROAN!

Cheers Kerrin

[mbrown]

I have milled the long angles down to the right thickness - I will cut back the short leg by a similar method.

These angles are 16" long, and I didn't fancy trying to clock them parallel over such a length, so I clamped the angles down to the edge of a T slot. This meant they were aligned to the table itself on the relevant axis. It depends, of course, if the inside of the angle is true - in my case it was.

I used three clamps. Having milled down an inch of so at one end, I then put a clamp over the part that had been cut back and set another clamp about 2" further off from the 3/4" end mill. Working Right to Left, as the cut approached the end mill, I brought the right hand clamp up as close as possible to the cutter, and then moved the middle clamp another 2" to the left. At all times, the angle was held by a minimum of two clamps, so it didn't move. It was a long, slow, job which used virtually the whole traverse of the table. In fact, because of space limitations in my workshop, I had to move the X axis handwheel to the left hand end of the lead screw to avoid it hitting the wall...

Here it is, a couple of inches into the cut. (The spanner is following delaplume's advice to Pete [smallbrother] - there are a number of gouges in the table dating from its previous employment long before I acquired it!)

IMG_20201101_165404 by malcolm brown, on Flickr


And here is one length of angle compared to the 3 mm stock as purchased. After milling both sides, there was just a tiny bit of bowing over the whole 16" - easily dealt with by hand pressure with an end in the vice.


IMG_20201101_173931 by malcolm brown, on Flickr


I want to mill down some further lengths next weekend, for use elsewhere on the loco. Trying to get as much of this tedious work done with one set-up....

Malcolm

[mbrown]

Today's other job was finishing off the motion brackets. The seating for the slide bar needed to be put in at the same 20 degree angle as the alignment of the piston rod. I therefore used the same jig I used for the cylinder bores. By packing up the motion bracket the same amount as I did for the cylinder, and setting it against the fence which is fixed at 20 degrees to the cross slide, the height and angle had to be correct.

Because of the orientation of the motion bracket, I had to have the fence at the rear of the cross slide - this in turn moved it further away from the headstock, and I found that the lead screw swarf guard was fouling the gearbox before I could get a slot drill up to the cut. Fortunately the swarf guard is only fitted on with two nuts, so off it came.

Here is one of the motion brackets in place, prior to clamping down.

IMG_20201101_154226 by malcolm brown, on Flickr


And here's the other with the slide bar slot just milled in. I also used the same setting to drill the slide bar bolt hole.



IMG_20201101_161648 by malcolm brown, on Flickr



After doing the first one, a dreadful thought struck me.... since doing the cylinders, I had replaced my cross slide with a new long travel one. What if they were not the same height above the lathe bed? It is not an easy dimension to measure, but when I lay one of the cylinders on the jig, the piston rod centre coincided precisely with a centre point in the headstock, so all was well.

So the motion brackets can now join various other parts waiting to be fitted to the outside of the frames before the frames, buffer beams and stretchers are assembled as a unit (which will be some weeks off as there is a lot more to do.)


Best wishes

Malcolm

[terrier060]

Great fabrication job on those brackets Malcolm. Much tidier than mine were for the Terriers, but fabrication is very satisfying.
Ed

[mbrown]

I spent several hours today milling down further lengths of 13 mm black steel angle for various locations on the loco.

The angle along the top of the frame required two 16" lengths plus two 4" lengths, each with one leg reduced to 9mm high. Then a length with both legs at 9mm to make the long guard irons (cowcatchers?) below the front and rear buffer beams. Then a few more feet of reduced thickness angle for various other brackets etc (and in case I make any mistakes and need to make bits again).

All very tedious and nothing worth photographing, but another stage toward getting the frame assembly together.

Malcolm

[mbrown]

I am gradually getting the bits together that will be attached to the outside of the frames. All the angles are now done - and, by the way, I forgot to mention that when milling the thickness down, it is vital to arrange the cut so that the rotation of the end mill pushes the angle against the edge of the T slot and not away from it. Guess how I found out.....

Today's items were the pivots for the equaliser beams. The suspension is equalised between the first and second, and between the third and fourth axle, so I need four pivots.

They started as a length of 5/16" x 1 3/32" bar, with steps milled down each side.


IMG_20201108_153857 by malcolm brown, on Flickr



Then it was turned on its back in the milling vice, and a 3/8" slot was run down the back with a slot drill - and as the equaliser beams are themselves 3/8" deep, I took off an extra 20 thou each side to give a little clearance.



IMG_20201108_160552 by malcolm brown, on Flickr



Finally, each part was cut off with a 1/32" slitting saw, the central pivot hole drilled (under size at present) and after one had been drilled for the four bolt holes, it was used as a jig to drill the others.


IMG_20201108_172018 by malcolm brown, on Flickr



I meant to press on with the spring hanger brackets which are identical to those on the tender. The various bits have all been cut out, but I keep forgetting how early it gets dark now the clocks have changed and, as my brazing hearth is outside the workshop door with no exterior light, sticking them together will have to wait.

That's it for another week....

Malcolm

[David]

The motion brackets look great, and very casting-like!

[mbrown]

Thanks David.

The real castings actually have quite a rough finish - I pondered whether I should do something to make them look even more casting-like in that respect, but decided I would be more likely to mess them up!

Malcolm

[David]

I think by the time you scaled the cast finish down it would be pretty smooth. Yours look good, and it's nice to have the ribs and not just flat edges - I think that is what makes the difference with fabricated 'castings'. I tried to add them to an inside motion bracket in 7mm scale... it did not go well! There were 4 slidebars per cylinder too so two cross shaped openings.

[Deleted]

Nov 9, 2020 10:11:36 GMT mbrown said:

Thanks David.

The real castings actually have quite a rough finish - I pondered whether I should do something to make them look even more casting-like in that respect, but decided I would be more likely to mess them up!

Malcolm

Hi Malcolm

When I fabricated my expansion link brackets I sprayed them in a textured primer which gives them that 'cast' look. I found Halford's own brand textured primer gave a very pleasing finish.

Regards

Pete

[mbrown]

Thanks for that tip Pete - I have not come across textured primer before. Worth a try, but I will test it on something else first!

Malcolm

[Deleted]

Hi Malcolm

IIRC, when I did mine I found a sanding sponge worked well in reducing the texture if it looked too heavy. Yes, testing first is always wise...

Pete

[mbrown]

After several hours in the workshop today, I believe I must qualify for full membership of the Honourable Association of Railway Rivet Counters (HARRC)....

The job was to drill the frames for the rivets which attach the heavy angles along the top edge. These are tucked under the running board and are hardly ever visible in photos, but I do have the picture below which shows two rows of rivets fixing the angle to the frame. The problem was to work out the spacing.


577728_651517734953261_3154313139901192022_n (1) by malcolm brown, on Flickr



The other source of information I have is a video of the loco, taken from a low enough angle and with the light about right to pick up some of the relevant detail. Freeze-framing the video, I managed to work out that the lower row of rivets is pretty evenly spaced - there is a rivet directly over the centre line of each axle, as far as I can see, and I counted 10 spaces between each axle. As my axles are exactly 89 mm apart (accurately drawn in CAD and then laser cut) it was easy to space those rivets at 8.9 mm on the DRO in the mill.

The top row, however, is clearly not set at the same spacing - the rivets vary in relation to the bottom row, apparently on a somewhat wider spacing. I guessed that the upper rivets also attach a smaller angle to the inside of the frame - I worked out the presence of the inner angle from the pattern of rivets above footplate level) and those angles do not run the full length of the frame. So, taking a guess, I set the upper row at 12 mm spacing, and only in the areas where an inside angle would be attached.

I was also able to mark out and drill holes for other bits and bobs like the brake hangers, some of the stretchers and so on. Other bits, like spring hangers, will be marked off from the piece itself.

Anyway, here are the frames after drilling and de-burring the outsides. With well over 100 holes to do, de-burring on four surfaces is not a quick job....


IMG_20201114_182741 by malcolm brown, on Flickr



I also managed to make progress on the eight spring hangers - these just need the profile finishing and the holes drilling. There are then a few more brackets to make which will need to be fitted before the frames are assembled and, looking ahead, I can see that the steam brake cylinder will also be easier to fit while the frames are separate, so that is a job for the near future.

In a week or two, the frames should be ready to go together, and I suspect that will feel like a lot of progress in a short time. For now it feels like a bit of a slog....

Malcolm

[coniston]

Great job Malcolm and lovely attention to detail, every little job done is a step forward, keep at it.

Chris D

[mbrown]

Thanks Chris,

I sometimes wonder if I am getting obsessive about having things exactly as on the prototype.... if most of those rivets are invisible on photos of the real loco, they are unlikely to be noticed on the model. And none of the stretchers and stays between the frames are visible at all except, in full size, from a pit. But I have still cut out all the bits to the right shapes and sizes.

I guess it is just one sort of model engineering psychology - we get all sorts on the forum and all are justified - and entirely harmless compared to all the ills of the world.!

Best wishes

Malcolm