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Standard 4MT build - Scale 7


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Adrian

 

Its all looking very good.

 

You can buy tiny boring bars from J&L Industrial they are about £20 each, made from solid carbide and you can get them small enough to do a 3mm hole. They are very useful for telescopic axles as making a D bit that will bore to a depth of say 15 mm is difficult and time consuming, I have made them before but I would rather buy these.

 

 

Richard

 

 

Richard,

 

why not drill and reamer them to size, its a lot quicker and of a constant size. If you get a good reamer of course. As some will cut slightly big and some will cut slightly small.

 

 

OzzyO.

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enjoying this thread already, I have always fancied doing an MOK kit myself it would be the 8f, but back on track. Have you checked the fit of the axles in the bearings yet as they can be a few thou. up or down. Are you going to do the same on the bogie and pony axles?

 

Actually I haven't checked the fit of the axles so thanks for the pointer. The bogies and pony wheels will remain plain brass bearings - I had a look at fitting the ball races but there isn't enough meat around the castings to fit them in. As most of the weight of the loco will be through the drivers I hope this will be sufficient to notice a difference.

 

you could have a word with Bill at Premier Components and see if he would do you a set in steel.

 

Correct me if I'm wrong as it's a long time since I've seen any but I seem to think that the Premier rods are milled in a vertical milling machine as the fluting at the end of the rods stop abruptly, rather than flared in as can be achieved from a horizontal mill. Which is what I'd prefer.

 

 

You can buy tiny boring bars from J&L Industrial they are about £20 each, made from solid carbide and you can get them small enough to do a 3mm hole. They are very useful for telescopic axles as making a D bit that will bore to a depth of say 15 mm is difficult and time consuming, I have made them before but I would rather buy these.

 

Again thanks for the pointer - I've another couple of projects in the distant pipeline where this could be very useful.

 

Regards

 

Adrian

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Those instructions are a credit to the producer. I have long advocated photos of the actual items in various stages of the build. Other kit manufacturers take note B)

 

Producing instructions takes a lot of time and effort. If photographs are included then good quality paper and printing add further expense to do them justice. It's possible to absorb the cost more readily in a 7mm kit than a 4mm one, due to the higher overhead margins available in 7mm kit pricing. However, there is no excuse for instructions that dismally fail to show you how to build a kit (I have had some experience of those, too). Photos aren't neccessarily the best solution, whereas a good exploded diagram provides a lot of information.

 

The best (most user friendly) instructions I have ever encountered were for Robbe and Graupner R/C boat kits (I'm going back about 30 years). They had a full size set of drawings, a low cost text booklet and a high quality photo booklet. Of course, these were from companies selling relatively large volumes of fairly high cost kits. In particular the large scale drawings contained a lot of clear and valuable detail. By comparison, the UK kit R/C manufacturers were generally kitchen table producers, selling at much lower prices, which was reflected in the quality of both the product and the instructions.

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I haven't yet decided on a specific example of the class, although to link in with other projects a Shrewsbury/Cambrian based example seems appropriate, so 80135 is a contender at the moment

 

I know that engine well Adrian, have you seen my folder with the pictures.

 

I had the same idea as yourself with the ball bearings and bought some last week, but when I found the brass bearings are 5/16 and the ball bearings are 5/16, I decided there would not be enough "meat" left on the brass bearing for it to work and chickened out, now you have proved it can be done, I'll have to give it a gounsure.gif .

 

J.P.

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I know that engine well Adrian, have you seen my folder with the pictures.

 

I had the same idea as yourself with the ball bearings and bought some last week, but when I found the brass bearings are 5/16 and the ball bearings are 5/16, I decided there would not be enough "meat" left on the brass bearing for it to work and chickened out, now you have proved it can be done, I'll have to give it a gounsure.gif .

 

I have see the photo's and very useful they are too, it's one of the reasons I was considering 80135. For example in the kit for the front bogie it mentions two variants, with an optional skid plate underneath it like a sump guard. I've not found any mention of it in the RCTC book so I wasn't sure when they were so fitted. From your photo's it seems that 80135 doesn't have the plate, but did it when it was in service? There are a couple of photos in the transport treasury photo list so I might order them to see what they are like.

 

I've not finished the bearings yet so it's early days to say whether it's worked. I must admit it was a bit of a gamble as they are a tight fit.

 

Have you selected a number to model yet? It'd be nice to organize the Scale7 builds to be all different members of the class.

 

Adrian

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... For example in the kit for the front bogie it mentions two variants, with an optional skid plate underneath it like a sump guard. I've not found any mention of it in the RCTC book so I wasn't sure when they were so fitted. From your photo's it seems that 80135 doesn't have the plate, but did it when it was in service?

 

Well, I can't see anything on my pic of '064 or this pic of '151:

 

post-6908-127629673918_thumb.jpg

 

Perhaps not a Brighton thing?

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Have you selected a number to model yet? It'd be nice to organize the Scale7 builds to be all different members of the class.

 

It will have to be one of the Whitby engines for me, which is 80116 to 120, think I've about decided on 80116. Incidently 80135 now has the boiler from one of the whitby engines, but for the life of me I cannot remember which one.

 

You have to be careful using preserved engines for referance, it's been about 46 years since it last ran on BR and especially now that a lot of our engines are being fitted with TPWS etc for runing on Network rail to Whitby. One thing I can garantee is that the Livery is non genuine, which is a shame because I think it really suits green.

 

I'm hoping to take some more pictures this coming week.

 

J.P.

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A quick progress update. Whilst still sorting out axleboxes and suspension I thought I'd progress with a few more of the individual components. The next part of the instructions covers the ashpan, and as with a kit of this quality there are ten etchings that go into making the ashpan.

post-91-12763883617_thumb.jpg

 

6 of the etchings require various folds before assembly and a recent purchase of a hold'n'fold from Perfect Miniatures helped a lot. The sides of the ashpan have a reverse fold, one which is very close to the edge of the etching. You can just make this out on the lefthand etching near the large radius turn, where it was difficult to get a clean fold. As shown in the photo I dressed this fold using a small anvil and a pin hammer. Note the face of the pin hammer is highly polished, when I put it away in my toolbox I have an old sock I use to protect the finish. Many moons ago I enrolled for a few jewellery making evening classes with the specific intention of learning a little bit of silversmithing because I have long admired the work of Gerald Wingrove. I would heartily recommend jewellery making courses for any one looking to improve their model making skills. I got a lot of practice in the art of silver soldering, I made a couple of broaches using repousse techniques and did a little bit a silversmithing, with bowls and cups. This hammer was one of the tools I acquired from this experience, because the face is highly polished it minimises the tool marks on the ashpan etchings when I hammer the fold into shape.

post-91-127638837449_thumb.jpg

Once everything is folded up then assembly can commence. The kit uses a series of slots and tabs to hold everything together before soldering, this is the first kit I've built that has used this technique and I was a little apprehensive that the slots wouldn't be etched fully. However it all fitted together beautifully without any fettling required, but as the instructions make clear you do need to get all the fold angles right to slot everything together.

post-91-12763883894_thumb.jpg

So the finished item - well nearly finished, this is just the assembly and twist tab stage, I've still to solder anything thing and trim the tabs to tidy it up.

post-91-127638840361_thumb.jpg

 

In the meantime I've been cutting out the frame spacers and inner frames. The chassis design builds up using a main set of frames over which a set of etched cosmetic frames are added later. There's probably a dozen various frame spacers plus the ashpan.

post-91-127638841854_thumb.jpg

So I'm back on sorting out the suspension - I reckon I might have a "simple" solution for fitting "continuous springy beams" to the loco so that might be the next thrilling instalment if I can work out the details in time.

 

@Pinkmouse re: "sumpguard"

 

Actually looking back through the instructions I think I misunderstood what it was describing and in fact the photo you posted does show the "sumpguard". It's actually described as a bottom cover and is fitted to the bottom of the casting around the axle and not to the bottom frame of the pony truck. A whisker to the right of the dropper from the coupling there does appear to be something there.

 

 

Regards

 

Adrian

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Hi Adrian,

 

neat work there as usual. I too was impressed with the slot and tab arrangement when I built the Q1, in fact the tender body framing and cladding looked finished with just the tabs twisted, every thing being so square and acurate - can't wait to start another - in a few weeks time once the Inspection Saloon is finished.

 

As a matter of interest, which size Hold & Fold did you get?

 

regards

 

Mike

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Correct me if I'm wrong as it's a long time since I've seen any but I seem to think that the Premier rods are milled in a vertical milling machine as the fluting at the end of the rods stop abruptly, rather than flared in as can be achieved from a horizontal mill. Which is what I'd prefer.

 

If your doing 80135 the rods , should'nt be fluted.

 

Found out it's 80116's boiler on 80135 so at least some of my chose engine still exists.

 

Couple of pictures of the front bogie, no sign of a guard, but that does not mean that it may have had one in BR days.

 

J.P.

 

post-7730-127680409283.jpg

post-7730-127680411042.jpg

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If your doing 80135 the rods , should'nt be fluted.

 

Sorry, I wasn't too clear in my comments -although thanks for the reminder, I had realised that 80135 had the deeper rectangular rods, I should have made it clear I was referring to the conn rods and the rest of the motion which was fluted. I've been going through the RCTS noting all the differences and there seem to be a few. The book reckons all those built after 80079 in March 1954 were fitted with the rectangular rods, the tanks vents were moved forward and speedo's were fitted for 80059 onwards, 80000 to 80120 had LNER pattern return cranks and 80121 onwards had the LMS pattern 4 bolt return cranks. Then various other regional variations - eg 4 lifting brackets on the cabs, tablet mechanism's, bi-directional water scoops, lamp bracket variations and even one with a snow plough.

 

If you want a CSB plot, Adrian, just let me know...

Well now since you've offered I'd appreciate it if you wouldn't mind checking my numbers and any other feedback. I've gone through the CLAG notes and tried to work it out for myself. However as it's the first one I've tried to calculate, a check of my numbers and any comments would be appreciated to give me a bit of confidence before I commit to it.

 

I started with the Black 5 settings then suitably tweaked for 7mm and the 7'7" - 7'9" wheelbase for the 4MT.

post-91-127680861699.png

 

So for the wheelbase :

  • p (7' 7") = 53.08mm
  • q (7' 9") = 54.25mm

My original calcs ended up with d=22mm however when I tried to lay this out on the chassis it came close to a frame spacer behind the rear driving wheel that is used as part of the rocking assembly if it were to be a compensated chassis. I then thought I could use this frame spacer with a suitable hole drilled as the actual fulcrum point D - but this then reduced d slightly and fixed it at 20.25mm.

post-91-127680863234_thumb.jpg

 

 

So I have revised the dimensions to

  • a=19.75mm
  • b=28.5mm
  • c=30.5mm
  • d=20.25mm

Am I on the right track here - I reckon it makes the centre drivers a little over 10% softer loading than the outer wheels.

 

Regards

 

Adrian

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Adrian

 

Looking at the picture it looks as if you will be having the ball race bearings on the outside of the horn blocks?

 

Will this not put a lot of vertical loading on the out sides of the frame and over time cause a twist around each axel?

 

Where as if they were on the inside of the horn blocks you would have the shortest horizontal distance between the ball races and the frame will stay square.

 

It's something I noticed.

 

Pete

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Hi Pete,

 

This model is being built to S7 standards, so there would not be enough room to fit the bearings in that position, not even in f/s either come to that. I expect that Adrian had just placed them in that position to show a rough idea of how the chassis will go together.

 

ATB, Martyn.

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Looking at the picture it looks as if you will be having the ball race bearings on the outside of the horn blocks?

 

It's something I noticed.

 

Pete

 

Sorry about that, the photo is a bit misleading - the ball races are on the inside of the hornblocks. Both frames are showing the inside faces, the bottom one needs flipping over left to right to match the top frame. I was just laying it out to mark up for the CSB fulcrum points.

 

Regards

 

Adrian

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So I have revised the dimensions to

  • a=19.75mm
  • b=28.5mm
  • c=30.5mm
  • d=20.25mm

 

That's extremely close, Adrian, but I've finessed the front axle deflection to be exactly the same as the rear one:

 

a = 19.5mm

b = 28.25mm

(c and d unchanged from your dimensions)

 

These dimensions keep the centre driver 10% softer than the outer ones.

 

I haven't got a proper feeling for what that type of large 7mm loco should be weighted at, apart from what I'm learning from Ken (Jazz), but my gut feel is that your loco might be in the region of 1.6 to 1.8kg overall (??), and in which case you'd be looking at a probable CSB diameter of 0.7mm, or maybe 0.8mm diameter if your pony and bogie are supporting a bit less compared to what they do on the prototype.

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That's extremely close, Adrian, but I've finessed the front axle deflection to be exactly the same as the rear one:

[snip]

 

I haven't got a proper feeling for what that type of large 7mm loco should be weighted at, apart from what I'm learning from Ken (Jazz), but my gut feel is that your loco might be in the region of 1.6 to 1.8kg overall (??), and in which case you'd be looking at a probable CSB diameter of 0.7mm, or maybe 0.8mm diameter if your pony and bogie are supporting a bit less compared to what they do on the prototype.

 

Many thanks for that, I really appreciate it. It's nice to know that I was on the right track. Just the etches and the packets of castings tips the scale at a whisker over 1.6kgs. So by the time I add the wheels, motor and gearbox and loose the scrap etchings and sprues it probably be about the same. The pony truck and bogie are sprung but I think only lightly. I'd estimated 600g per axle and I have some 0.9mm spring wire - so again your comments are reassuring.

 

Regards

 

Adrian

 

 

 

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I'd estimated 600g per axle

The prototype had just over 60% of its near 90 tons loco weight on the drivers, so if you were to replicate the loading of the prototype with your 600g drivers you would be looking to have an additional say 1200g for the pony and bogie loadings (apportioned say 420g for the pony and 780g for the bogie). In models, the extent of this carrying wheel support isn't strictly necessary of course, but even so, I feel you should be looking at supporting at least an additional 600g apportioned between pony and bogie for overall loco stability purposes, so your overall weight would be a minimum of (3 x 600) + 600 = 2.4kg. (Which would mean adding an extra 800g minimum of lead to your current parts.)

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  • 6 months later...

My apologies for the lack of posts over the last 6 months - circumstances have forced a sabbatical for 6 months. As much as I'd like it to be otherwise the modelling is just a hobby for me and it had to take a back seat for a while. Anyway just before Christmas things started to calm down a bit and I've managed to blow the cobwebs off my workbench. I had made progress with the chassis but just before Christmas my trusty Weller soldering iron packed in and Christmas money from the Mother-in-Law meant that I treated myself to a nice variable temperature soldering station - an ERSA RDS80. It took a while to turn up due to the snow but once it had arrived I wanted to test it out. Hence the renewed effort on the workbench.

 

As a change from the main chassis work I wanted to to build a separate unit so I decided to get back into building the kit by starting on the front pony truck. So rather than waffle on I bet most folks are more interested in the few photo's.

 

So these are the myriad of parts for the pony truck, depending on the version built there are 17 bits just for a pony truck! In the RTCS book there is a great photo of 80135 (fig 26 page 30) climbing Talerdgig bank so that is the one I've decided to model so as far as I can tell I don't need the bolster skid plate but everything else is used.

post-91-0-65856100-1293933447_thumb.jpg

 

The thought that has gone into this kit is superb everything just fits. The following photo is an illustration of why I decided Scale7 was right for me. As I'm building the Scale7 version of the kit, the pony truck components have been widened appropriately. With the castings supplied in the kit there are still some of the narrow gauge (32mm) items, which on the front of the pony truck bolster there is the lateral control spring. This photo shows the Scale7 item fitted to the bolster and below it is the item you'd have to use if you had the standard 32mm gauge kit. Now you might say that there is only 1mm difference in gauge, which over a track gauge is only 3% error, so nothing to get worked up about. However to my eyes on something like this spring which is just under 3mm in diameter the aspect ratio for the 32mm item is wrong, with the tighter tolerances the 32mm itm is 14mm wide verses 16.5mm for the Scale7 item which equates to over 17.5% difference between the two.

post-91-0-54204700-1293933555_thumb.jpg

The main bolster castings has bits cast for what I assumed was pinning - so these were drilled out for a bit of nickel -silver wire to be inserted.

post-91-0-89243300-1293933532_thumb.jpg

 

So the bolster is then soldered together

post-91-0-93073000-1293933491_thumb.jpg

Once that was completed I turned to the bearings - this consisted of the main casting and a couple of etchings and the spring castings.

post-91-0-14188500-1293933470_thumb.jpg

 

Bolster, bearings ant bottom etching were then assembled.

post-91-0-54608700-1293933483_thumb.jpg

 

I then soldered on then the guard irons on the front of the truck. Hopefully this is the one item overlooked in the Scale7 kit, I dare say in the 32mm version it 's fine but because in S7 the main etched frame is wider and the probably because he wheel sets are narrower, then the guard irons were too wide for the gauge, as shown below.

post-91-0-38479400-1293933514_thumb.jpg

 

So this is how far I've got with the front bogie. The instructions suggest leaving the main pivot bearing until the chassis is up and running, hence that is missing. The eagled eye viewers my have noticed the main bearings, the castings as supplied are for 3/16" axles, however the Scale7 supplied wheels for the carrying wheels use a 5/32" axle. So I turned a small PTFE bush as a tolerance fit in the castings, reamed 5/32", for the pony wheel, hence the small "plastic" bearing in the photo.

post-91-0-70846800-1293933546_thumb.jpg

 

There are a couple of small details to finish off, the front of the pony truck looks a little bare so I think it needs some additional detailing as discussed in this thread

http://www.rmweb.co....746#entry277746

 

So ther are a few more updates in the pipeline - hopefully I can keep the momentum going!

post-91-0-24957300-1293933502_thumb.jpg

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looks superb!

Cheers for that, but that's all down to the kit, rather than my abilities. I would seriously recommend something like this as a kit for a beginner as everything fits perfectly.

 

However I forgot to mention a big thanks to the guys at Transport Treasury . They have a great selection of photographs, in my opinion good prices too. So I have a cracking set of photo's of 80135 for which I'll use to build my model.

 

 

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... Also a motor and gearbox is required, it's designed around an ABC unit but I dare say many others would fit without too much trouble.

 

Adrian

 

Adrian

 

Do MOK say which particular ABC unit is recommended?

 

I will be following this thread with much interest, although mine, when I get it, will be a 'narrow gauge' version ;)

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