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MTA · Posted: Fri Mar 20, 2009 7:38 pm Post subject: College project

As part of the course I am doing, I have to do a 'project'. This can be anything that takes my fancy, and I have chosen to do a rolling road for my 32mm gauge engines (as well as 45mm too). I was taking some pictures for my project portfolio today, but I have taken some more for those here with an interest.

First, the progress so far. This has taken me a month so far (one day a week), including the odd cock up Embarassed

The sides were clamped together and machined as a pair; to aid alignment of holes, slots and the ledges.

Just last week I finished the ledge (which took me one day shared over two days owing to other tasks and setting up time). For this I had to use a 'long series' end mill cutter to give me the depth I needed, the problem with this is that because the cutter is so long that it can flex slightly when it comes into contact with the material as this photo proves.

The cylindrical spacers were made in under half an hour, drilled 20mm in from either end and tapped M8 to take the M8 25mm CSK screws (in black). The bar was chosen over the square variety as there are no edges to dig into your hands as you lift it!

Today, I have been machining the bases for the sliding roller carriers. These measure 50 x 65 x 10 (L x W x H) and I have to make them as accurate as possible to ensure they slide along without friction on the faces against the ledge in the rolling road.

For this, I used one of our Bridgeports. The one I used is unrefurbished, we have another unrefurbished one as well as a refurbished one.

I mounted a 12mm (in diameter) end mill in the chuck (with the appropriate collet) and set the speed to 550rpm. A quick 'touch on' and I skimmed the surface to remove the rough surface created when I cut the workpiece in the powered hacksaw.

Once the surface was smooth, I ramped the speed up to 920rpm and skimmed the surface by only 0.1mm and a slow feed (by hand) to give a very nice, smooth finish perfect for measuring.

The workpiece was then turned through 180 degrees and the other surface was machined to give a nice surface. A measurement was taken and incremental cuts of 1mm at a time were made until it was close to the final measurement of 65mm, then a finishing cut was made of 0.1mm at 920 rpm. Then a final reading was taken with a set of vernier callipers, suffice to say it was spot on! Who needs a DRO?

I made two more of these, and they were all put on the rolling road frame. The third one isn't pictured.

You will notice a gap between the bases and the ledge sides, this is so that I can silver solder some plates on the sides of the bases for the rollers to attach to.

As time was running short, I decided to saw off lengths of 3mm diameter silver steel (or High Carbon Steel) for the pins which the rollers will revolve around. These were then faced in one of our five Harrison M250 lathes.

The silver steel was put in close to the chuck (as silver steel is very brittle, it has a tendency to flex if the tool is brought in too quickly)

the speed set to 1500rpm and the feed to 0.25mm/min. Next I ground up a tool from High Speed Steel, mounted it in a tool holder, and by placing a live centre in the tailstock I checked that the tip of the tool was at centre height.

Then, all six pins were faced off at both ends.

As an aside, here's a drawing in AutoCAD that I drew in half an hour. It shows the roller components and a general assembly of the rollers and roller carrier.

I hope that has been of interest. If you have any questions, need any terms explaining etc. please ask!

More on Tuesday, as I will be machining the rollers.
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SillyBilly · Posted: Fri Mar 20, 2009 7:46 pm Post subject:

Very interesting, what's the name of the course you're doing?
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Cheers,
William a.k.a Silly Billy
www.billsrailpics.fpic.co.uk

"To the best of my abilities, I have taken great pains with it." - James Spooner c.1836

MTA · Posted: Fri Mar 20, 2009 7:49 pm Post subject:

BTEC National Diploma (inc. NVQ Level 3), Mechanical Engineering.
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MTA · Posted: Fri Mar 20, 2009 7:52 pm Post subject:

Oh, I forgot to include the technical specification!

Size: One half (that pictured in the first picture) = 400 x 83 x 100mm

Current weight: 6.5 kg ( Embarassed

)

Total length: 800mm (although I'm planning on finishing one half, as time is tight!)
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Spokesmann · Posted: Fri Mar 20, 2009 9:13 pm Post subject:

Interesting stuff, takes me back to my metalwork days!
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avenger · Posted: Sat Mar 21, 2009 8:55 am Post subject:

MFSteam · Posted: Sat Mar 21, 2009 9:09 am Post subject:

I remember writing reports like that for my portfolio. Sad

To much writing and not enough cutting is what I can remember about my course.

What material are you making it out of Si?
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www.mfsteam.com the home of the MFTwin and replacement parts for Mamod, Bowman, Hobbies and Cyldon Steam Engines

Mamod Collector · Posted: Sat Mar 21, 2009 5:28 pm Post subject:

Very interesting, will be nice to watch the rolling roads progress till completion Very Happy

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Mike
My personal website, with pics. Smile

www.mikes-steam-engines.co.uk ™

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