7mm Steph's modern traction workbench

Dog Star

Western Thunderer
Graham,
In this version I've got about 4mm clearance for a screw head between the prop shaft and the hole in the bogie frame, which is plenty. In addition I have the advantage that the Branchlines universal joint components can clip in/out of an otherwise-assembled bogie...
Maybe you need to persuade Peter to bring the Cl.37 along so you can see what you might face with that JLTRT kit, especially as fitting the ABC bogie means losing the body - floor fixing - gets in the way of the motor. There are some photos in my "S7 Odd Workbench "thread.

regards, Graham
 

mickoo

Western Thunderer
I'm certainly considering SDMP gearboxes for the JLTRT class 40 sitting patiently under the work bench, even considering a whole new inner frame with independent CSB suspension.
 

Steph Dale

Western Thunderer
Now here's a funny thing...

For some reason this evening I compared the bogie side frame castings with the inner bogie - and found they were 'out' by over a mm. Now some people would live with this, I'm afraid I pitched in and I decided to modify the parts...

Here's the nature of the problem. At the top, just about positioned in the (0.08" styrene) jig, is a sideframe which has been hacked into three parts. In the middle is an original and below is the first one through the process. You can see the discrepancy in the right hand side of the photo:
IMG_1552v1.jpg

Anyway, a few hours later with a bit of cutting, a lot of 145 solder, an age of filing and a quick wire-brushing I had four identical sideframes that had the axlebox centres matching the bogie frame. I've still got the equalisation beams to do before I kick off the next stage of assembly and here you can see one of the beams aligned with the bogie. Curious huh? Yes; it's asymmetric; the right hand side is fine and all the extra length comes out of the left hand beam.
IMG_1553v1.jpg

See? Funny, huh?

Steph
 

adrian

Flying Squad
Small discrepancies like that are really obvious when you have the wheels behind the side frames so full marks for modifying them - it's a really neat job.

As you say funny, if it was just shrinkage in the casting then you'd expect both sides to show a similar discrepancy, the asymmetry suggests an error in the original master. As the equalising beam shows a similar error then probably the error is in the original dimensions used. On the equalising beam the short flat on the widest part looks slightly longer on the left hand side. Are they supposed to be symmetric and is this where you'll be removing the extra length?
 

djparkins

Western Thunderer
Small discrepancies like that are really obvious when you have the wheels behind the side frames so full marks for modifying them - it's a really neat job.

As you say funny, if it was just shrinkage in the casting then you'd expect both sides to show a similar discrepancy, the asymmetry suggests an error in the original master. As the equalising beam shows a similar error then probably the error is in the original dimensions used. On the equalising beam the short flat on the widest part looks slightly longer on the left hand side. Are they supposed to be symmetric and is this where you'll be removing the extra length?

Sounds like a clever explanation but there is no discrepancy in the original masters. There is more shrinkage at one end that the other due to differential shrinkage during casting and this will always be at the end where the metal is last in the mould - it cools last but more importantly it is closer to the solidification shrinkage feeder head in the mould and so is pretty well unavoidable. The overall shrinkage also depends on how far into a casting session they are cast - the main beams could and do vary by 1mm easily. We could have done them in lost wax if the kit wasn't £199 but £495 instead - but even then it could happen.

In 17 years this is the first time anyone has mentioned it and personally it seems a lot of work for virtually zero gain - I bet if you put a set of these cosmetic sideframes on one bogie in modified form and unmodified form on the other it would not be immediately obvious which was which, especially with so much other detail added onto them to distract the eye still further. Still, each to his own!

Also earlier we heard how the tank & battery boxes sit at the wrong height - check your drawings - I have drawings from Brush and they simply do not. Its only if you raise the floor it becomes a problem - but then that is true of any kit - if you do not build it OOB and modify things - then other consequences will follow in relation to parts fitted later.

Anyway Steph - us manufacturers have to have broad shoulders as you will find out once your honeymoon period is over! It last 9-12 months in my experience. BTW - check you PMs.

David Parkins,
Modern Motive Power
 

adrian

Flying Squad
There is more shrinkage at one end that the other due to differential shrinkage during casting and this will always be at the end where the metal is last in the mould
Thanks for the explanation - I can see how that would cause the shrinkage always on one side.
personally it seems a lot of work for virtually zero gain - I bet if you put a set of these cosmetic sideframes on one bogie in modified form and unmodified form on the other it would not be immediately obvious which was which,
We'll have to agree to disagree on this, I think it would be obvious which was which. Building steam loco's getting the wheel base correct on the tender is critical, just 1mm discrepancy between the wheels and the axle boxes is painfully obvious, the symmetry of the wheel makes it very clear whether it is centred on the axle box or not.
 

djparkins

Western Thunderer
Thanks for the explanation - I can see how that would cause the shrinkage always on one side.

We'll have to agree to disagree on this, I think it would be obvious which was which. Building steam loco's getting the wheel base correct on the tender is critical, just 1mm discrepancy between the wheels and the axle boxes is painfully obvious, the symmetry of the wheel makes it very clear whether it is centred on the axle box or not.

Can you detect it on Simon Varnam's Class 47s?
 

Steph Dale

Western Thunderer
David,

Many thanks for your comments. I suspected that the issue might have been casting shrinkage and understand the issues involved in getting whitemetal castings and etched brass assemblies to align; you're also quite correct about the use of lost wax brass in similar situations. My observation was most definitely not meant as a criticism!

I'm not surprised I'm the first person to attempt to reduce the sideframes, I'm not even really sure why I decided to check them against the inner bogie...

I'll be having a good look at available info on the underframe details. In the major part that's because I'm not hugely familiar with the prototype. From the built-up models I've seen the height of the tanks above the rail looks about right to me, so I'm intending to build that area up pretty much as the kit provides.

Thanks for your comments about the broad shoulders too; by your estimate of 12 months honeymoon period mine ended about 15 years ago!

Cheers,

Steph
 

adrian

Flying Squad
Can you detect it on Simon Varnam's Class 47s?
I've no idea to be honest - I don't think I've had a good look at one in the flesh, all I'm saying is that when I do see tenders built with a small discrepancy in the wheelbase compared to the axle box then it can be obvious.
 

mickoo

Western Thunderer
Also earlier we heard how the tank & battery boxes sit at the wrong height - check your drawings - I have drawings from Brush and they simply do not. Its only if you raise the floor it becomes a problem - but then that is true of any kit - if you do not build it OOB and modify things - then other consequences will follow in relation to parts fitted later.

The reason the floor needs to be raised is to better model the fish belly section under the engine, there is a distinct sloped section here which is not present on the kit, OOB or not, the end result is that the tank support brackets are not attached to anything substantial and appear to float in mid air
http://www.7mmlocomotives.co.uk/gallery2/main.php?g2_itemId=781.

I suppose the biggest consequence of modifying things and not building out of the box is that it might actually look right?

Image1.jpg

Sorry David, but you are one of the strongest and respected advocates to doing the best you can and model as best you can, yet when ever anyone tries to make it better they get poked. For some of us 1mm matters and yes I did go quite a few steps further and modify virtually the whole floor with ribs and sections, and yes! It probably won't be seen, but that's my choice and is not....for I've forgotten how many times I've publicly said this.....a criticism of the kit.

I have no criticism of MMP kits, I think they are very good, I better had as I've got quite a few, seven locos in all and I will continue to support the brand as and when items I require come up.

I have modified my initial posting, so that it will not mislead anyone else in the future.
 

djparkins

Western Thunderer
The reason the floor needs to be raised is to better model the fish belly section under the engine, there is a distinct sloped section here which is not present on the kit, OOB or not, the end result is that the tank support brackets are not attached to anything substantial and appear to float in mid air
http://www.7mmlocomotives.co.uk/gallery2/main.php?g2_itemId=781.

I suppose the biggest consequence of modifying things and not building out of the box is that it might actually look right?

View attachment 19306

Sorry David, but you are one of the strongest and respected advocates to doing the best you can and model as best you can, yet when ever anyone tries to make it better they get poked. For some of us 1mm matters and yes I did go quite a few steps further and modify virtually the whole floor with ribs and sections, and yes! It probably won't be seen, but that's my choice and is not....for I've forgotten how many times I've publicly said this.....a criticism of the kit.

I have no criticism of MMP kits, I think they are very good, I better had as I've got quite a few, seven locos in all and I will continue to support the brand as and when items I require come up.

I have modified my initial posting, so that it will not mislead anyone else in the future.

You totally misunderstand. I am full of admiration for your raising of the floors on the locos.

However as I read your posting you were saying that OOB the tanks were at the wrong height and I was just trying to correct that!

I cannot see how the tank support straps/brackets appear to float in mid-air though when they locate into either slots in, or onto tabs folded down from the loco floor [all eight of the castings]. If you are talking about the longitudinal girders then yes, I applied to same logic to these as I did with regard to not raising the floor. As I say, you are a brave man to try it though - full marks!

We put in as much detail as we could for the price, [as with the 08] and there is for sure more more to be added, as you rightly say but in these times price rules - you ain't gonna sell many diesels @ much more than £250 a kit.

Regards,

DJP
 

mickoo

Western Thunderer
You totally misunderstand. I am full of admiration for your raising of the floors on the locos.

However as I read your posting you were saying that OOB the tanks were at the wrong height and I was just trying to correct that!

I cannot see how the tank support straps/brackets appear to float in mid-air though when they locate into either slots in, or onto tabs folded down from the loco floor [all eight of the castings]. If you are talking about the longitudinal girders then yes, I applied to same logic to these as I did with regard to not raising the floor. As I say, you are a brave man to try it though - full marks!

We put in as much detail as we could for the price, [as with the 08] and there is for sure more more to be added, as you rightly say but in these times price rules - you ain't gonna sell many diesels @ much more than £250 a kit.

Regards,

DJP
David,

My sincere apologies for misunderstanding your comments, I'd blame it on the meds...or lack of...but that would be a lame excuse!

You are quite correct, my initial comment was regarding the water tank height, I went and looked at Simons site and re looked at my efforts and found that where I had added the fish belly floor to provide the correct height you have provided longitudinal girders (Part 1), I'd forgotten about that part and it does space the tank the correct height, hence my original comment, now amended.

Your right, I was talking about the eight longitudinal parts with lightening holes in them, the outer ends have no primary longitudinal beam to support them, I.E. an extension of part 1.

To be fair, to represent the fish belly floor would take a lot of effort in etch work, there's no easy half way approach, your either all in or not. With the kit employing a [_] body format of construction where the floor is joined to the walls and thus the floor is flat, then trying to replicate the fish belly engine section would actually make it look worse I think.

One side effect of the floor rework is that you can no longer use a vertically mounted motor or large in line motor as the motor openings are now sealed, hence Steph's drive (with a little prodding from me here and there LOL) toward a lower below floor gear box and motor arrangement to fit your motor bogies, all in an effort to get that 'air' between the bogies and body when viewed at low angles.

I understand the pricing constraints on design, but lets be fair, if the only faults are 1mm in the bogie side frames and other minutia, then I'd say they were pretty good value for money.

The only other issue I found down below thus far is the drag box side valances (part 6), the etched tab slots would have you solder this tapered valance parallel to the cab side, in real life this part widens so that it meets the body side at the rear cab door hand rail. If the etched slots are followed this would give an incorrect distance between the valance and the cab door kick plate at the lower edge.

The other area that so often gets built wrong is the small triangular fillet at the cab door upper hinge area, a lot of models have the cab door flat where as it should have a inward kick from where the base of the window is and the body side part near the top should have a small radius, often this whole area is soldered up flat which means then that the roof doesn't fit correctly or that the roof panels cant rail radius doesn't match.

Image3.jpg

Regards
 

djparkins

Western Thunderer
The other area that so often gets built wrong is the small triangular fillet at the cab door upper hinge area, a lot of models have the cab door flat where as it should have a inward kick from where the base of the window is and the body side part near the top should have a small radius, often this whole area is soldered up flat which means then that the roof doesn't fit correctly or that the roof panels cant rail radius doesn't match.

View attachment 19323

Regards


Mickoo -

Fully take the point about the side valances.

On the door - this fillet is provided for on the kit. Perhaps its not apparent until you look from both sides on the etch and then slice down with a scalpel - but the etch is cut right down to waist level on both front and back so that you can angle-in [so to speak] the door and shape the curve on the small section behind.

Regards,

DJP
 

mickoo

Western Thunderer
Mickoo -

On the door - this fillet is provided for on the kit. Perhaps its not apparent until you look from both sides on the etch and then slice down with a scalpel - but the etch is cut right down to waist level on both front and back so that you can angle-in [so to speak] the door and shape the curve on the small section behind.

Regards,

DJP
David,

Yes, it is indeed LOL, but it's beyond me why it is not used in a great many cases? People just build the cab door flat which as can soon become quite obvious, cause problems getting it to fit with the resin roof and roof panel just behind.

Regards

Michael
 

djparkins

Western Thunderer
David,

Yes, it is indeed LOL, but it's beyond me why it is not used in a great many cases? People just build the cab door flat which as can soon become quite obvious, cause problems getting it to fit with the resin roof and roof panel just behind.

Regards

Michael

Michael,

I think we should have mentioned it in the instructions but I suppose I thought it would be obvious [!!!] - but will do so next time around. We used just a narrow cutting line to mininmise the gap but of course you then get the 'gold leaf' effect at the middle depth of the line [which requires a light touch with a blade] and I suppose it can look as if it is only etched from the front and hence is just surface detail.

Regards,

DJP
 

mickoo

Western Thunderer
David,

All points appreciated, mind I tend to be a bit blasé and view instructions as guidance, but then I only tend to build what I know enough about or have researched long enough to be comfortable with.

Not with standing that, the fillet does make a large difference to the 'look' of the Brush type 4 face so it's an important part to get right.

The thin etch is clever and I was in luck, the Postman had already split the doors from the side sheet in these areas for me LOL.

Regarding the future, it's a crying shame you don't make the Class 40 bogies as a separate etch sheet <sigh>....it'd save me a job.... or other diesel bogies as stand alone kits for that matter. I understand the idea behind one piece cast resin bogie side frames, but they do lack some fidelity in certain areas, areas where built up bogies surpass.

Regards

Michael
 
S

SteveO

Guest
I'm just going to stick my oar in - in a general but positive way. I absolutely love the fact that a kit designer/producer is talking so openly and candidly to a builder about their products in an open forum. This would normally only happen in private through emails or telephone calls so full mark to both of you, but especially David for putting his mouth where his money is. It seems so easy for someone in David's position to hide behind anonymity these days.

OK chaps, as you were.
 
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