Sarf of the river, down Nine Elms way

[Martin Shaw]

As Steph's post above suggests we had a phone call this afternoon, which was most helpful, I would like to make public my grateful thanks for taking the time and interest to assist me. The fruits of this will become apparent in due course. He also suggested that the likely origin of the kit is Shedmaster, and more probably originally 4mm by Jidenco. This does explain some of the weirdness.

And now, for your Saturday evenings entertainment, "The Wheels Dilemma".

Firstly the prototype, the quoted diameter in Bradley et al is 6' 7", this would be new, the diameter would reduce with each turning of the tyre back to profile so could easily be 6' 4" by scrap size. This scales to 46.1mm - 44.4mm.

The crankpin is located 9" from the axle centre, 5.25mm scale.

The tyre width is 5", increasing on the face edge where the lips is to say 5 1/2", 3.2mm scale.


These are the wheels I have, the green one is off the model, coarse standard and uninsulated. It is possible that it could be finescaled and insulated but there isn't much meat in the rim for a resin filled gap, there is also a cost to this. Note also the 6BA brass screw inserted from the rear as a crankpin, less than desirable. The one on the right is of a finscale insulated set bought last year, and whilst not immediately as attractives as the green one, it is a rather better original casting with a clearly defined interface between the spokes and the central hub.

Dimensions, the green one is 45.6mm in diameter but the tyre width is 2.8mm so somewhat thin. THe crankpin is 7.5mm from the centre so some 2.25mm oversize, which scaled up is 3 3/4". It has been done like this to position the crankpin centrally in the boss and I suspect If I hadn't told you it was wrong, nobody would have noticed.

The unpainted one is 44.9mm, towards the bottom of the tolerance and indeed if the tyre had been turned down the rim width would have reduced as well, in this case it is 3.8mm which is oversize. More importantly from a visual perspective, the crank position relative to the axle is correct but because it isn't centrally on the boss it looks odd.

There it is, neither wheel is dimensionally spot on in all criteria, and they are also both compromised on aesthetics, the question therefore is which would you use. I appreciate it's ultimately my decision but I'm canvassing opinion here.

Alternatively the third option is neither and get a set from Slaters, but from memory they don't do a specific one for the D15 so again a compromise
would be needed, and I have spent money already.
Regards
Martin

 

[Brian McKenzie]

 

[Steph Dale]

Martin,

Happy to help. Now to be either very helpful, or not at all, depending on your perspective:
The D15 has the same wheels as the T9 (and L12, for that matter). These are available from Slaters as their item 7878sw. Not only is the hub and crank pin about right, they also have representation of the Eastleigh rim...

I tend to cut about 0.030" (0.75mm) out the back of Slaters wheels to improve appearance: Refining Slater's Wheels and:

Other than that, I quite like Brian's solution.

Steph

 

[Martin Shaw]

There has been a two week hiatus in progress, firstly my wife insisted we went away for a week staying in hotels and eating in restaurants, which was most pleasant, we even managed a whole evenings conversation one night, and I was allowed an afternoon for a ride from Whitby to Grosmont and returns. A Schools one way and a B1 the other, which frankly was the best part of the week but don't tell her I said so. On return the looming decorating wasn't to be ignored so another round of electrician(me), joiner, plasterer, painter, carpet fitter commenced, none of it particularly difficult but the disruption is enormous.

Thank you Brian for your suggestion, it seems a good way to go without purchasing another set of Slaters wheels which I really don't want to do.

I have been researching the frames situation which as they stand are odd. I have Bradleys book which has a good reproduction of the GA drawing if slightly on the small side, and from that it is obvious the the Shedmaster kit design made no attempt to reproduce the original. It looks like the frame plate curves upward at the front of the smokebox to form the location for fixing the valve chest, then dips again to a point about 1 foot above the running plate before following the curves around the splashers. The drawing also shows the massive driving axle hornguide casting with plenty of meat for fixing.



By comparison the model frames are designed to fit under the running plate which is why the driving wheel bearings are nearly at the top and is going to make sprung axleboxes a challenge. The body has a step at the rear of the smoke box so I can gain some frame height, and as can be seen the bearings themselves are a bit hit and miss, and the whole thing is too narrow due to its coarse origins. It is though the correct length. I was going to measure and draw this and subsequently modify it, however I have now decided to design the frames directly from the body, I have wheel centres and footplate height so it should be possible to come up with something that works, better than what I have although some way short of modern kit design.
Regards
Martin

 

[Martin Shaw]

The joiner who was supposed to turn up this morning, didn't, some confusion over dates saw him in an airport somewhere in the world. No matter he is coming at the end of the week. The suddenly available time gave me an opportunity. Dusting off Turbocad and struggling to remember how to drive it I started with the known dimensions, frame length 218mm, height above the railhead, 4' on the drawing or 28 mm scaled, buffer plank and drag beam height 8mm, and the measured sizes of the wheels to hand and their centres. Plotting this out was relatively easy but filling in following the contours of the existing frames challenged things however I am not trying to produce an accurate representaion, more capturing the essence of where it started so I'm ok with where I've got to, which is this.


As you can see I have gained a 5mm height increase on most of the frame length which helps a lot for sprung hornblocks, purely down to how the body is constructed, and there is now plenty of material above the rear bogie wheel. I have allowed a 1mm gap between the bogie wheels flanges and the frame cutouts, do you think this enough? I could push it another 0.5mm and worst case I would raise the footplate by 0.5mm if needed. I have also discovered that on the prototype the main frames were joggled inwards at the extremities of the bogie, essentially the width of the frame 1.25", not easy to do and probably not adequate for model curves anyway. I'll have to consider this and there is yet much to do, but pleasing.
Regards
Martin

 

[Martin Shaw]

I realise there has been something of a dearth from me of late, largely due to the ongoing house refurbishment alluded to previously. The original plan was to do the living rooms following on from the two bedrooms finished last year. This very quickly grew to include the hall stairs and landing, all needing walls plastered, floors sheeted and new skirting, painted and carpeted, with a little bit of electrickery to eliminate a previous owners bodgery.

Completion saw us at the end of September so I thought this years flurry was at an end and modelling could rise to the top again, unfortunately my wife and I had a discussion which went like this, "what do you think about the kitchen", I replied "it's very tatty and is somewhat shown up by everything else, I was thinking maybe next spring". "Wouldn't it be good", she somewhat artfully suggested, "to benefit from this years momentum", I could see where this was headed so I tentatively sort of agreed to be landed with "it will be finished for Christmas , won't it"? Well to my great benefit it was, started on the 21st November and completed on the 21st December, Christmas dinner was duly the first proper meal from the new cooking appliance. Without being too immodest coordinating plasterer, kitchen fitter, painter, joiner, and tiler, as well as my own plumbing and electrics input into 4 weeks work is something I'm quite proud of. This rather wordily explains my uncharacteristic quiet for the last few months.

The D15 last resided at a point where new frames were to be made and a discussion about the wheels and their choice was underway. Following that Steph Dale donated the etches of a Shedmaster D15 kit if they could be of some use, along with a rather nicely made bogie c/w with wheels. This was immensely generous and has furthered thinking about what to do. I contemplated the wheels dilemma for a while, until the Linlithgow O gauge show at the end of October. Meanwhile a root around the stores produced this,


and you may well be asking, what has this got to do with the D15. Apart from sharing Drummond as a designer it is the last of my originally coarse wheeled locos that I hadn't done anything about replacement wheels. Whilst at Linlithgow I showed this to Dave Brooks of JPL who thought it would be easy enough to shave 20thou of the backs of the flanges and rim insulate one side and he also thought that he could do the original D15 wheels as well which made a decision for me, worst case I have the bought replacements as a next choice. So the 700 has to have its wheels removed and along with the D15's packed off to Manchester for works attention.

Richard very kindly sent me the dimensions of the Finney7 Drummond axlebox which won't realistically fit the frame dimensions available so its back to start from scratch which will be the next bit for attention. I really do hope to move this glacial progress somewhat more quickly in the new year.

I know some of you have a hifi interest, this arrived in November after three abortive attempts to get a working Quad PA1, I then gave up on Quad and they have subsequently withdrawn the product from the market so obviously quite serious. I like it a lot.

Finally, thank god I hear, my wife produced some bottles of delicious Australian Shiraz for the festive season named Jam Shed, subtitled Rich, Jammy, and Smooth. I can do the last two but the first might be tricky I said, there was naught but a laconic chuckle. Having bored everyone rigid may I wish all my fellow WT'ers a very Happy New Year, I hope it's good for you.
Regards
Martin

 

[Martin Shaw]

I have spent the last few days madly doodling on bits of paper in a way that would earn a 3 year old plaudits, and I have managed to come up with a design of axlebox and horns. This was going well until I thought to look at the Z dimension, the available space on the axle having subtracted the gearbox. Originally I had planned to reuse the original and elderly JH, but this measured 22.0 across the gearbox leaving 7mm for the rest of the gubbins, too tight really, a newer JH is slimmer at 19.2mm but 8.8mm is still a might fine, and that's without any clearance. Fortunately I had a helical gearbox which is only 15.8 wide giving a generous 13.2 to play with which is good but it is 10mm higher than the JH, however it seems to fit in the loco okay. The one I have is I think 30:1, I may well get a 22:1 to give it longer legs.

Obviously these are the original frames which will fit with this motor, in the new ones the frame spacers can be placed differently so I may yet get a bit more clearance. Now I have got past the difficult decisions I can CAD the bits and produce manufacturing drawings.

Whilst this has been going on I have given some thought to the philosophy of what I'm trying to achieve and I fear I may have overcomplicated the whole project, so in essence I am going to take some sensible shortcuts. The finescale wheels purchased last year are going to be used as is, I realise they aren't perfect, but neither were the originals , and as it is once they're in and painted, hardly noticeable. Secondly the chassis is going to have no more adornment than the original, bar the substitution of sprung suspension instead of fixed plain bearings. I did consider making the axleboxes from bronze which is good engineering but more expensive than brass which will be perfectly satisfactory. I have far too much stuff and this has been going on for far too long, there is a danger of achieving nothing.
Regards
Martin

 

[Martin Shaw]

I wonder sometimes whether resorting to RTR Hornby in 4mm scale might be a tad more simple and relaxing. The last few days of head scratching, sketching and eventually CAD has produced an enormous quantity of variants, none of which quite worked, either a lack of space , insufficient room, or bits in the way. Re-engineering to fit the existing body is challenging and I reckon starting from scratch might have been easier. Anyway I have ended up here,

I found out how to export direct from CAD to forum. The axlebox is 9mm square and 6.5mm deep, the hornguide 12mm high by 4mm deep. I am going to make up an axles worth to work out the springing and prove to myself that I can work to the required precision. The DRO on the mill will resolve to 5 microns, so any dimensional discrepancies are purely operator error.
Regards
Martin

 

[Martin Shaw]

After considerable prevarication, procrastination, and generally sitting around doing nothing much, I have now made solid bits of metal that are pretty similar to the drawings above, and despite saying I was going to make two in fact I've only done one.


The camera somewhat cruelly shows the gap twixt axlebox and hornguide as a gaping chasm, it really isn't but having said that the box slides sweetly and there enough play for it to freely operate but not so much that it binds. I think it would be fine in a loco, except it probably isn't going to be the D15. It is somewhat obvious to me now, and probably some time ago to the rest of you that the design of the kit is fundamentally flawed in the arrangement to separate a body from a chassis. There is just not enough frame available even with my increase in size to make all this springy stuff fit, so in this particular case I'm back to fixed bearings, which frustratingly is where I started, drat.

It has had a benefit though, there has been very useful learning curve for making small components on the lathe and mill, and were I to do it again I have a better idea of how I would do it differently. I see Mickoo on his latest build is using a very nice looking box/guide unit which can't be too expensive so for new builds and where space on existing models allows it's probably the better way to go. This modelling lark does take you down some alleys, even if they're occasionally dark.
Regards
Martin

Addendum 27/3/20 I have decided to send this project on a sabbatical, I have struggled to find a way forward that satisfies me and after two months of near enough nothing it can await a better day.