Don Young's Black 5

[delaplume]

Hello all,

Don, that's my take on it as well.....Just for interest sake here is another type of brake shoe, this time it has one central web for mounting ( Loco is GWR Pannier )

[steamer5]

Hi Alan,
Almost on track.......
An old neighbor worked as a guard on the Fell Engines that ran up & back a step incline.... here’s a couple of links

www.fellmuseum.org.nz/history/the-incline/
www.rimutaka-incline-railway.org.nz/

On every return trip the brake blocks were replaced! Done during the servicing of the loco & swap of the wagons, he said it wasn’t unusual that the were still a dull red when the maintanence guys started the swap out!

Cheers Kerrin

[runner42]

Before we leave the brake block saga, you will note from the drawing that the brake block is not symmetrical. So which way is up, ie the big end or the little end?

Brian

[RGR 60130]

You'll need to look at the brake hangers to see how they mate up. I suspect that this design will prevent the brake blocks flopping down and rubbing on the wheels.

I found from bitter experience on my A1 that when I assembled the brake gear with the chassis upside down the brake blocks stayed clear of the treads. However when I put the chassis the right way up, gravity came into effect and the blocks started rubbing with the brakes in the off position. Remaking the brake hangers with a modified profile sorted the issue.

Reg

[oldnorton]

Hi Brian

Your figure of the brake shoe was from Drawing No. 3. There is a better drawing, that makes clear it is a slot, on Drawing No. 8 and here also the erection of the shoes is shown.

Norm

[oldnorton]

I have read somewhere (dangerous thing to do) that the brake hanger pins are not set square to the frames, but are angled at the same pitch as the wheel tread so as to present the shoes square to that tread. This mystified me until I realised that if the hanger pins were parallel to the axle, and the shoes cut with a tapered radius, then the side thrust forcing the shoes outwards would put a considerable load on the hangers and significantly increase wear.

Question: how many model designs seek to replicate this?

Now, a question for you Alan as a chap who has been there and done it: I assume what I said above is universally applied to all use of blocks on tapered wheel treads? or are there exceptions? And are the new brake blocks machined with a blend of two radiuses to match the different inner and outer contact points?

Norm

[mbrown]

Yes, this is certainly full-size "mainline" practice. It is always dangerous to generalise, but I am not aware of it being usual practice on small narrow gauge locos although they too will have coned treads. It may be that there is a point where the side forces are containable and the cost and "faff" of inclining the hangers is not justified.

If that is correct, the only reason to do it in our scales would be fidelity to prototype (a perfectly good reason, of course!)

Malcolm

[delaplume]

Hello all,

I can only answer you from my own BR experiences ie}---- The new shoes fitted were "As cast" and not machined as far as the main profile was concerned, although I suspect any holes to accept the pins might well have been pre-drilled...possibly in a simple jig...before delivery to the MPD Stores.

Apart from having to match the curve on the block to the radius of the flange/tread on the wheel the shoes went straight on...which leads me to think that they were not "handed" and thus the matching angle was incorporated within the design of the brake hanger bracket, this being a permanently fitted item....

Regarding any side thrusts generated}----Remember this is only a 2 degree taper and each L/H shoe is connected to it's opposite R/H side by a connecting bar which would balance out any lateral forces and also centralise the assembly....

In any event I don't think it's a good idea to make use of a fully working brake system on a loco. up to 5" gauge as the tendency will be to lock the wheels and generate "Flats"....unless it's part of a complete system of course..

[coniston]

Neville Evans design angled brake hangers and angles on the beams for his Penrhos Grange








And no taper on the brake blocks.


Chris D

[runner42]

Apr 21, 2020 9:34:47 GMT oldnorton said:

Hi Brian

Your figure of the brake shoe was from Drawing No. 3. There is a better drawing, that makes clear it is a slot, on Drawing No. 8 and here also the erection of the shoes is shown.

Norm

Thanks Norm, so the big end is at the bottom.

Brian

PS If one was constructing the locomotive in the stages outlined by Don Young in his words and music then the tender would be completed first so one would concern themselves with the drawing no 3. However, I didn't  do that and started the locomotive first but haven't yet done the brake gear, because I have no means of cutting a 3 3/16" radius for the brake blocks. I did look at the locomotive brake gear some time ago but forgot it was a slot. 

[delaplume]

Hello Chris,

Yes, on reflection I made a mistake saying that the shoe would have a taper cast in didn't I ( see my initial reply ) .... If they did then they would be "handed"......much easier to design it into the hanger arrangement --- as shown in the Penrhose Grange drawings --- and just mass-produce a single, non-tapered shape for the shoes....

Slaps wrist and says}--- 3 "Hail Gresley" as a penance ( joke !! )

Alan

[runner42]

The steam brake shaft trunnion and brake shaft are fabricated assemblies, the brake shaft being installed in the brake shaft trunnion, held in position with two PB bearings. However, as far as I can see it is impossible to install the brake shaft into the trunnion, the width of the trunnion being 7/8" and the brake shaft being 1 3/8", unless the brake shaft is made in separate pieces, ie the 9/32" dia shaft part of the brake shaft assembly is pushed through the two holes in the trunnion with the actuating hub being held in position. However, the drawback of doing this is that the actuating hub needs to be fixed to the shaft, because the two PB bearings are there to provide the bearing capability, not the actuating hub bearing on the shaft. Difficult to understand, but I cant articulate it any simpler. Given the problem, what solutions are there to change the design of the brake shaft because I have already made the trunnion?

Brian


Brake shaft trunnion and shaft by Brian Leach, on Flickr

[Roger]

Hi Brian,
Agreed, that's not feasible. I imagine since it's slated as being a fabrication, it's expected that the shaft is separate. Even so, if that was the intention, the drawing should indicate how it's supposed to be held in place. I'd probably use a separate shaft with a flat on it and a small grub screw with a hex head.

Why are the ends of the shaft so long?

[stevep]

I may be miscalculating, but the trunnion has oversized holes, for the separate and removeable bearings. I suspect that you can thread one end of the brake shaft through one hole (from the inside) and then align it with the other hole. Then when you fit the bearings (from the outside) they keep everything in place.

I think that's why the shoulders of the brake shaft are rounded.

I seem to remember there's something similar with the brake shaft on Pansy.

[uuu]

I'm going to ask a contrary question: Why is the body of the pivot assembly so narrow?

Given that the bearing fixing holes are tapped, I'm supposing the bearings are fitted from the outside. So if they have 1/8" flanges, it answers Roger's question - 7/8" spacing of the trunnion plates, plus two times 1/8" plate thickness, plus two 1/8" bearing flanges matches the 1 3/8" shaft.

But the pivot assembly is only 11/16" wide flapping about in the 7/8" gap. Unless the bearings project into the space, but they only have 1/16" wall thickness.

Wilf

[uuu]

May 1, 2020 9:09:12 GMT stevep said:

I may be miscalculating, but the trunnion has oversized holes, for the separate and removeable bearings. I suspect that you can thread one end of the brake shaft through one hole (from the inside) and then align it with the other hole. Then when you fit the bearings (from the outside) they keep everything in place.

I think that's why the shoulders of the brake shaft are rounded.

I seem to remember there's something similar with the brake shaft on Pansy.

But the body of the pivot assembly at 11/16", plus one shaft end at 11/32" (the other shaft end is in the hole) adds up to 1 1/32", which you're trying to swing into a 7/8" gap. You might gain a bit with the shoulder going into the hole, but it feels too tight.

Wilf

Edit. I've sketched it out - I don't think it fits.

BrakeTrunnionQuestion by Wilf, on Flickr

[Deleted]

Hi Brian

I'm sure if you find the drawing for the bearing, all will become clear.
To me the bearings will have a collar which fits into the trunnion and held by the 4x10 BA bolts either side. The shaft will be seperate. Bearings may well be blind to stop the shaft from pushing out, their collars being of a length to hold the brake shaft central.
Assembly would be one bearing cap fitted first, brake shaft placed into the trunnion from below, shaft pushef in to engage the brake 'pivot' and lastly the other bearing cap to hold all in place.
It's a similar layout on Doncaster but the shaft is integral and has a spigot either end to stop it from moving and thus the earings are plain, no cap but they do have the collar.
You could make life easier and do the same, ie, a spigot either end of the shaft to hold it central and thus the bearings can be plain with no cap, just a collar like Doncaster. You'd need to make the bearing collar thicker to match the spigot...not that there's anything wrong with a 1/16 wall ..iirc that's the size of the collar on Doncaster.

On second thoughts, now that I have my thinking cap on...lol...you may find that the shaft is indeed a fixed item and that will some giggling, you can get the shaft into the trunnion as a solid piece. That is the bearing collars once removed from the trunnion allow enough play to seperate the two parts. With bearings fitted all is held securely, and thus no cap required on the bearing...
I would say it's my latter suggestion which is how Don intended, again, it's the same on Doncaster although I have two trunnions, one rither side of the frames but it does involve some giggling to get the shaft in which can not be done with the bearings in situ...hope that makes sense
To summarise, forget my first suggestion as I think the latter one is how it should work, I'll leave the first in this reply in case I'm wrong with the latter idea, I don't think that I am though.


Pete

[ettingtonliam]

OK, if you can't wangle the shaft assembly into the trunnion before fitting the bearings, then try this. Make the shaft assembly in 2 parts, that is, the shaft and the lever. Insert the lever into the gap in the trunnion, poke the shaft through from the outside, fixing it to the shaft either with Locset, or by pinning, or both. Then assemble the bearings on to the shaft ends and bolt to trunnion.

[springcrocus]

May 1, 2020 10:13:46 GMT ettingtonliam said:

OK, if you can't wangle the shaft assembly into the trunnion before fitting the bearings, then try this. Make the shaft assembly in 2 parts, that is, the shaft and the lever. Insert the lever into the gap in the trunnion, poke the shaft through from the outside, fixing it to the shaft either with Locset, or by pinning, or both. Then assemble the bearings on to the shaft ends and bolt to trunnion.

I think the shaft should be separate, too, but would suggest that this is the perfect opportunity to insert the bearings from the inside and let the shoulders act as positioning pieces for the trunnion. And I would use a taper pin to lock it together, one tap with the hammer to fit, one tap to knock it out again.

Regards, Steve

[d304]

Hi Brian

Looking at the bottom drawing of the trunnion there, to me, is a 1/2 slot. This would allow the shaft to enter the hole and freely swing up through the slot. The bearings then correctly position the shaft. Why a 1/2 slot for a 13/32 hole is another question. I would make slot 13/32 for a better fit.

regards 

David