3D printed MR Brake

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Andy W
Posts: 870
Joined: Thu May 21, 2009 8:11 am

3D printed MR Brake

Postby Andy W » Fri Apr 10, 2020 10:56 am

I've not been active in the hobby for a good few months, and it's surprising how developments move along so quickly when you're not looking. 3D printing is just one of the areas that have advanced recently. I was given a Bill Bedford MR Brake van before the virus hit so I thought I'd make it the first victim of my "Shelf of Shame" attack. On opening the box what surprised me was that it appeared to be a semi RTR model. I know a printed kit should be like that, but to an old school kit builder like me it was a pleasant surprise.

The kit took me about 10 evenings to complete - but really it should have taken a lot less. I made some mistakes, and hit a couple of problems which I wanted to share so others don't trip over the same stones.

The main problem was in fettling the brake gear etc to get the wheels fitted. I'm used to carving and cutting soft plastic kits, but this material is far more brittle. I managed to break the footboards and pull rods by being too heavy handed.

Underframe.JPG
Underframe.JPG (108.33 KiB) Viewed 630 times


Once repaired I realised the printed underframe meant I couldn't use my usual Brassmasters' axle spacer.

JIG.JPG
JIG.JPG (127.73 KiB) Viewed 630 times


So I made one up with plasticard using an old (I think Bill B) jig, and attached an inside bearing.

Jig wide.JPG
Jig wide.JPG (117.02 KiB) Viewed 629 times


Jig used.JPG
Jig used.JPG (106.73 KiB) Viewed 629 times


It did the trick. Normally I would add lamp irons etc, but I decided not to drill into the body because of my previous setbacks. Also I didn't use the supplied buffer heads as I couldn't get them to spring so drilled out some MRTs instead. I didn't trust the strength of the hooks either so replaced them - which is a shame as they're terrific.

I know it's relatively early days for 3D printing, but it really felt like I had a glimpse into the future for our hobby with this kit. I like scratch and kit building, but this technology is an exciting advance for our hobby. I just need to be less heavy handed with the material!

MR Brake.JPG
MR Brake.JPG (81.57 KiB) Viewed 630 times
Make Worcestershire great again.
Build a wall along the Herefordshire border and make them pay for it.

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Guy Rixon
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Joined: Sun Mar 27, 2011 6:40 pm

Re: 3D printed MR Brake

Postby Guy Rixon » Fri Apr 10, 2020 1:21 pm

This kit does not have a drop-in, etched chassis? Weird; I though Bill was onto a winner with those.

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Paul Townsend
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Joined: Mon Sep 14, 2009 6:09 pm

Re: 3D printed MR Brake

Postby Paul Townsend » Fri Apr 10, 2020 4:50 pm

Bill seems determined to make entire kits 3D printed. I think thats a mistake for underpinnings. Small parts tend to be too fat and/or too brittle.

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Guy Rixon
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Joined: Sun Mar 27, 2011 6:40 pm

Re: 3D printed MR Brake

Postby Guy Rixon » Sat Apr 11, 2020 10:25 am

He may have his eyes on a different market. Removing the brass bits simplifies the build and attracts those who don't do conventional kits. It probably lowers the cost, too.

Brake parts are at the limit of printability, but can be done well enough. Compared to mouldings, they can be much finer. Axleguards are the problem, IMO.

billbedford
Posts: 709
Joined: Tue Oct 02, 2012 2:40 pm

Re: 3D printed MR Brake

Postby billbedford » Sat Apr 11, 2020 2:12 pm

Andy W wrote:
The main problem was in fettling the brake gear etc to get the wheels fitted. I'm used to carving and cutting soft plastic kits, but this material is far more brittle. I managed to break the footboards and pull rods by being too heavy handed.


I'm not sure what you needed to fettle on the brakes. The pips from the supports can be cut off with a sharp scalpel.

Normally I would add lamp irons etc, but I decided not to drill into the body because of my previous setbacks.


There should be no problem drilling the thick part of the body, either by hand or with a dremel.

Also I didn't use the supplied buffer heads as I couldn't get them to spring so drilled out some MRTs instead.

The hole may need chasing out. Ideally, 6mm x 1.1 mm plus a through-hole of 0.6mm, though you could get away with 1mm & 0.5mm drills.

I didn't trust the strength of the hooks either so replaced them - which is a shame as they're terrific.


These have been tested with a 120gm load. A Bachmann 24, tested at the same gave a drawbar pull of around 80gm, so they will work perfectly in most situations.
Bill Bedford
Mousa Models
http://www.mousa.biz

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Andy W
Posts: 870
Joined: Thu May 21, 2009 8:11 am

Re: 3D printed MR Brake

Postby Andy W » Sat Apr 11, 2020 4:39 pm

All points accepted Bill. It’s a fine kit, I’d definitely build another.
Make Worcestershire great again.
Build a wall along the Herefordshire border and make them pay for it.


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