Michael's Werkbank (Bavarian PT2/3)

[michael080]

I've come to a point where I need to wait until the F7 gearboxes arrive. Mick Roffe from the F7 crew was kind enough the resend the returned parcel, but the tracking number shows that it is stuck for 11 days at the Langley sorting center. I know there is a strike and I know that Christmas is coming, but I don't have much hope that the parcel will miraculously reappear.

All tiny bits and pieces that can be prepared have been prepared, but it is too cold to start priming the internals of the cabin and I need to prepare the bogies to develop a plan for the pick ups. I have a set of nice Roxey wheels that have one side isolated, but live axles. My idea is to have both bogies set up to pick up from one side either and isolate the bogies against the loco body. However, without the gearboxes, I can' do much.

Long story, simple conclusion: The kit goes back into some boxes and will be stored until I get the gear boxes.





As the holidays are approaching, I got another one of my favourite red boxes from the shelf:



I am sure David is already aghast that I mess up another of his precious kits.

Michael

 

[michael080]

Here is another small update. The MMP roadstone wagon is making good progress. I thought that it would be worth preparing a CAD-drawing of the standard RCH-brake blocks, so that they can be printed with a 3D-printer. This should solve the always present problem of shorthing the wagon throught the brake blocks.

The dimensions are straight from the RCH-drawing No.1021.




I have attached (I hope) the STL-file if anybody wants to use these blocks for own project. Please note that the STL-file is mm-based, but the part is 12" to the foot, so it needs to be scaled accordingly.

EDIT: I have moved the attachment to the "resources" and removed them here.

Michael

 

[simond]

Synchronicity….

I’ve modelled them too, but direct into 7mm.

I also have the 3’6” spring with pads for wooden under frames, and an RCH axlebox.

anyone who wants CAD or STL, I’m happy to share

cheers
Simon

 

[michael080]

I’ve modelled them too, but direct into 7mm.

The drawings are fractional and my brain works metric. Thinking about converting 5/32" to 7mm/1ft and then converting it to metric dimensions overloads my brain. Solidworks on the other hand allows to enter dimensions like 5/32" or 1' 6 3/4" directly into a metric drawing.

Michael

 

[Rob R]

Do we need to start a thread as a central repository for small files such as these so we can find them in 12 months time?

 

[adrian]

Do we need to start a thread as a central repository for small files such as these so we can find them in 12 months time?

It's been on my "todo" list for a little while now but once I've sorted out the software update on Thursday the next thing I've been looking at is creating just that sort of resource area for useful files and reference information.

 

[simond]

Rob,

I’m game, I suggested it to Adrian a wee while back. I think such a repository might need to be rather large, and would be prone to becoming outdated, so perhaps a directory of “who’s got what” might be easier to manage. You could then see who could provide the model you want, and PM them to enquire.

Michael,

I tried drawing at 1mm = 1” and rescaling but ended up tying myself in knots when I wanted to adjust dimensions to improve the print after scaling. I grew up with both metric and imperial systems, so it’s perhaps a bit easier. It would certainly have been easier to draw directly in full size.

Of course, if you‘re prepared to be a bit “relaxed“ about some dimensions, the job gets much quicker - 1/8” = 1/96’, so convert any small silly fractions to eighths of an inch, multiply by 7 and ignore the error. Eg. 3/4” = 6/8“ = 6/96’, ~ 0.42mm. Precisely, 0.75” scales to 0.4375mm. You won’t want to do it for big numbers but for little ones, it’s probably good enough.

Cheers
Simon

 

[SimonT]

An alternative method, should your package allow it, is to import the works drawing as a raster image (usually jpg) into the drawing space as a picture, which happens to be the Rhino command. Rhino allows scaling of individual axis, so that is done with the longest dimension given on each axis to bring the works drawing to 1:43. The drawing is then trued. This can be a problem if the original drawing wasn't flat on the scanner bed but can be solved with suitable cropping of the original raster image. This image is imported as a separate miny image and trued for the small amount of information on that image.

I then draw a layer that contains the major definitions of the model, such things as axle centrelines, boiler centre lines, etc. This is dimensioned to check that it matches a spreadsheet of all major given dimensions that converts the drawing office dimensions (including pesky fractions) into mm to two sig fig.

All the above exists in a master layer of source 2D information. The major definitions layer is copied into a Model master layer which will include all the 2D and 3D workings to build the model. This model layer has sub layers where everything drawn full size for the model, so all plate work is the thickness of the etch sheet.

Like Simon I happily work in both metric and imperial. When doing building work with my late father-in-law we used both. A piece of wood might be measured as 6ft2in and 4mm! Stangely it worked and we didn't crash our satelite into Mars. Even stranger is putting fuel into an aircraftat at American airfield. Fuel out of the bowser has to match fuel on the gauges exactly. The bowser load is in US gallons while the aircraft, despite being designed in US units, is gauged and operated in Kgs! One needs to know such things as the density of that particular load of fuel and its temperature.

 

[Rob Pulham]

In Fusion 360 you can easily set up a user parameter which allows input in feet and inches and auto convert to 7mm or whatever scale you enter into the parameter.
I may have done a short video on how to do it. If I did I will post it.

 

[chigley]

In Fusion 360 you can easily set up a user parameter which allows input in feet and inches and auto convert to 7mm or whatever scale you enter into the parameter.
I may have done a short video on how to do it. If I did I will post it.

I tried this 3D printing lark but i couldn't get on with the blue and red glasses

Ken

 

[Rob Pulham]

Here we go, apologies to Michael for high jacking his thread

 

[michael080]

I like the idea of a repository for such small parts.

thanks for the comments. It's an interesting thing with the fractional and metric world. I am a (continental) mechanical engineer, so reading drawings, designing parts in 2D and 3D is my daily work. Still I always note that it is really complicated for me to do something like subtract 5/32" from 5/8". I know the maths, I know that you do that easily, I don't. I belive that the main reason is that I have been living in a strictly metric world for the first 50 years of my life. You people from the island grew up in a fractional world. Obviously, it need a long time to adjust. Nevermind!

I love these old drawings, it is always interesting to see how these draftsmen 100 years ago knew their business and the limitations of their time. I love it even more if I find a mistake they made 100 years ago like in the drawing below. There is at least one dimension missing for the caster to build his mould. Can you find it?



Michael

 

[ICH60]

Here we go, apologies to Michael for high jacking his thread

Is it me, but I not seeing a link

Ian

 

[ICH60]

Is it me, but I not seeing a link

Ian

sorry It seems the Garage I sitting in waiting my service of my car blocks Youtube!!

 

[Crimson Rambler]

Doing 7mm scale in inches/Imperial is easy! Indeed you can do the fractional conversions in your head.

One inch is 22.966 thousands of an inch - but for a few inches in length rounding up to 23 thou suffices so for example 3 inches becomes 69 thou.
For the fractions of an inch substitute 24 thou equals one inch - now you have a direct easy connexion to the fractions used on the prototype.

Thus say 2 1/4 inches becomes in 7mm scale (46 + 6) = 59 thou.

Much easier I suggest than trying to get 7mm into 12 inches!


Crimson Rambler

 

[simond]

Doing 7mm scale in inches/Imperial is easy! Indeed you can do the fractional conversions in your head.

One inch is 22.966 thousands of an inch - but for a few inches in length rounding up to 23 thou suffices so for example 3 inches becomes 69 thou.
For the fractions of an inch substitute 24 thou equals one inch - now you have a direct easy connexion to the fractions used on the prototype.

Thus say 2 1/4 inches becomes in 7mm scale (46 + 6) = 59 thou.

Much easier I suggest than trying to get 7mm into 12 inches!


Crimson Rambler

it might be easy, but it’s still daft.

If anyone had any sense, 0 gauge would be 1/48 if imperial, or 1/50 in metric (choose one or the other, I’m not suggesting that both would have been an improvement!), and would have been dead scale, but the powers that be had other ideas, including some demented theory that locos looked somehow nicer on less than scale track. I think that was Greenly but I have repeatedly failed to find the reference.

and one real inch is 0.5833mm in 7mm, so just type that multiplied by whatever into Solidworks.

 

[michael080]

Thanks all,

KISS*!

but this confirms my opinion that drawing in original scale is the easiest solution. If your CAD-system allows, take dimension in their original notation (imperial or metric) from a drawing and sketch your part. No scale conversion until now.
There will only be one conversion afterwards to transfer it to the desired scale. Furthermore, I will need these parts in 7mm, but if someone wants to use them in 00, 10mm, H0, Z or whatever, one scaling step will do the job.

No volunteer to look for the missing dimension in the drawing?

Michael


* Keep It Simple, Stupid

 

[simond]

I should be able to spot this not least because I also recently modelled it, but I’m being dim tonight. The draft angle doesn’t appear to be there, but can be inferred, as can the radius of the middle hole trunnion, and Madame is just about to drag me to a lecture about fascists & the Spanish civil war…. I shall look forward to seeing the answer on my return!

 

[michael080]

So, I printed the brake blocks only to notice that a scale block won't look right on an oversize wheel .

Here is the new version that is too wide but it looks ok on a Slaters wheel.










There is more to come in the next days .....




The RCH drawing missed either dimensioning the center of the red circle or the red angle.



Michael

 

[michael080]

Oh,
I forgot to mention that the gearboxes for the Class 40 are only 30km away now. There is still hope that the customs office won't return them to Cawood for a second time. It looks like the parcel will take about 45 days for the 980km trip. About 0.9 km/h.

Michael