When all you have is a hammer, everything's a nail...

Where users can chronicle their builds. Start one thread and continue to add on to it.

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OddDuck
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Re: When all you have is a hammer, everything's a nail...

Post by OddDuck » Wed Sep 06, 2017 11:37 am

Houston, we have a problem... Did a test fit on one of the wheels yesterday, didn't quite make it. I put the wheel on the barbecue grill on high for an hour or so, gave it a good soak to make sure the temp was even. Put it on the assembled axle and gave it a few whacks to help seat it. Not quite. It wound up about 1/4" from seating against the shoulder. Uh oh.
Even though the axle was a fairly straightforward turning job, I didn't really want to do it over if I didn't have to. So, set about separating them today. Made a drive punch out of a handy 3/8" bolt, applied heat to the hub for twenty minutes or so, and with a few whacks with the attitude adjuster they came apart, no harm no foul. Didn't even ding up the end of the axle.
I am going to put the axles back in the lathe and see if I can file off a whisker, after all, it nearly went on, and I want a good tight fit.
I also got the spring pockets ans upper spring plates cut and mounted, and the springs cut down to size. They are ex-valve springs, I get them every now and then when I melt down an old cylinder head. I wanted some fairly robust springs, this little critter should be pretty hefty after it's all together.
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"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

OddDuck
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Re: When all you have is a hammer, everything's a nail...

Post by OddDuck » Wed Sep 06, 2017 11:38 am

Some pics of the springs, etc.
Attachments
IMAG0269_1.jpg
IMAG0268_1.jpg
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

OddDuck
Posts: 158
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Re: When all you have is a hammer, everything's a nail...

Post by OddDuck » Wed Sep 06, 2017 6:18 pm

Success! After a little judicious file work, and more wheels on the barbie, they are all assembled! Wheelsets done, on to chains and motor mounting!
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IMAG0278_1.jpg
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

Harold_V
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Re: When all you have is a hammer, everything's a nail...

Post by Harold_V » Thu Sep 07, 2017 1:20 am

OddDuck wrote:I am going to put the axles back in the lathe and see if I can file off a whisker, after all, it nearly went on, and I want a good tight fit.
Please take note that I worked as a machinist/toolmaker for the bulk of my productive years. I am very outspoken on this topic, and do NOT endorse the use of files for establishing fits of this nature.

Filing anything you wish to be an acceptable fit is likely going to create other problems. The likelihood that you can remove metal uniformly, resulting in a straight and round piece of constant diameter is highly unlikely. You may reduce the size such that it goes on easier, but it may provide the perfect opportunity for the resulting fit to oscillate, which will result in a wheel that falls off when it's worn enough.

If you wish to reduce a diameter a trifle, I strongly recommend you use strip abrasive cloth. Hold an end in each hand (keeping your hands well apart), so it can't get wound up on the spinning item, then as carefully as you can, apply the abrasive uniformly to the spinning item. If the surface is rough (a turned finish), you can remove a half thou quite quickly, especially if you're using a relatively coarse cloth.

I would suggest to you that you are making a mistake in changing diameter, however. If it removed as easily as you say, the fit is likely already marginal. You can eliminate assembly problems by simply heating the wheel to a hotter temperature, and to assure slower heat transfer, chill the axle with dry ice if necessary. When you get the temperature correct, the two will slide together effortlessly, assuming you have both surfaces clean, and they are properly aligned.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

OddDuck
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Re: When all you have is a hammer, everything's a nail...

Post by OddDuck » Thu Sep 07, 2017 11:35 am

Thanks Harold, good info as usual. Just out of curiosity, would using a backing plate with the sandpaper help, or does that lead to some of the same issues as using a file?
I checked the axles as I trimmed them up, and made sure the diameter was consistent. I think my problem was that I just made them a few thousanths too thick. Unfortunately I also lack the two things you mentioned, and absolutely zero budget to remedy the lack. So, had to use what I had on hand. Also, my machine work on the whole is slightly less than accurate ( working on it... ) so "close enough" and "that works" will have to do.
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

Harold_V
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Re: When all you have is a hammer, everything's a nail...

Post by Harold_V » Thu Sep 07, 2017 4:12 pm

OddDuck wrote:Just out of curiosity, would using a backing plate with the sandpaper help, or does that lead to some of the same issues as using a file?
A good question, one I may not be able to address, as one can't speak for the ability of others, and technique, in this instance, would be critical to success.

I can offer one example, however, and the backup, using a parallel, was quite successful.

The last job I held, prior to starting my own humble shop, I was called upon to make a pair of stepped plug gauges. Sadly, the shop had only surface grinding capabilities, and the job required cylindrical grinding.

I resorted to the only process at my disposal, the one of grinding (after heat treat), using a tool post grinder. Anyone with experience in precision grinding will readily understand that such a solution is, at best, a considerable compromise, as the degree of precision isn't improved (a lathe is still a lathe, and is never a cylindrical grinder), plus the resulting finish typically leaves something to be desired. Fortunately, in my case, hitting size wasn't too challenging, but finish was. I was not satisfied with the grinding results, so I gave thought to spin polishing to, hopefully, improve the finish. I didn't want to polish the entire ground surface, just remove the peaks of the mountains, so to speak. I chose to try polishing by backing the strip abrasive, and was rewarded with an exceptional finish. I had to use care to apply pressure where it was needed, otherwise taper would be readily introduced. I can honestly say, the finished gauges were very acceptable.

So then, yeah, with care, you can back the abrasive with a known flat surface and improve the results, but it can backfire on you just as well. The one real benefit is that abrasive removal in lieu of file removal is a slower process, so you have a better opportunity to control the end result.
I checked the axles as I trimmed them up, and made sure the diameter was consistent. I think my problem was that I just made them a few thousanths too thick.

To help you better understand fits, a "few thousandths" isn't likely what your problem was. The difference between a slip and press fit on small diameters is just a few tenths. That's why you shouldn't use a file, as you can remove a thousandth and ruin the fit all too easily.

If you make a fit such that it goes together easily, it will come apart easily as well. That's why I suggested that you simply heat the wheel hotter, and not to alter the diameter. That's assuming you had a measured fit with a difference of a thou or a little more.

With the task accomplished, all you can do now is to see how the fits perform. Watch for unexpected movement of the wheels on the axles. If you see signs, it will be just a matter of time before you experience a failure. In order for the wheels to remain in place, it's important that they can't "oogie", or walk about, on the axle. That type of movement leads to failure, as it feeds upon itself, creating greater and greater clearance. That's why it's important for the axle/wheel interface to be straight, and (an adequate) shrink, or press, fit. Note that knurling is not an acceptable method of making the fit, as it, too, will fail.

H
Wise people talk because they have something to say. Fools talk because they have to say something.

OddDuck
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Re: When all you have is a hammer, everything's a nail...

Post by OddDuck » Thu Sep 07, 2017 5:22 pm

Thanks. I fully expect to remake these axles at some point, we'll see how they do in the meantime. After putting the wheels on, they look a little small proportionally to the body. But, they are all I had, so a little mismatch will have to do until I cast some more.
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

OddDuck
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Re: When all you have is a hammer, everything's a nail...

Post by OddDuck » Sat Sep 16, 2017 4:28 pm

Last week I made quite a bit of progress, got the wheels on, got the rest of the sprockets made, and more or less got it assembled. After a few alignment issues (chain wouldn't stay on... ) it was ready for a powered test. Hooked all the electronics up, and scrounging up a couple of batteries I tried to fire it up and nothing. Hmm. So, I went over to a friend's place to see if we could figure out what was going on. Since I figured the batteries that I tried may have not been up to snuff we used his set. Still nothing. We decided to try the spare motor that came with the pile of ex wheelchair guts that I am using, and still nothing. So, we took the back cover off the spare motor to see what was going on. Well, the built in brake was rusted up, so we decided to surgically remove it, figured we could replace it with a resistor if the controller didn't like that. We also cleaned up the commutator and checked the brushes. The controller still wouldn't move it, so we hooked it up to straight battery and off it ran.
Since I was out of time for the day I packed up the works and brought it home.
Yesterday I decided to take the cover off the motor I have on the loco. Oh, crap. This one looked like I had dredged it up off the bottom of a lake. I wound up drilling the brushes out, they were stuck so badly. Also, one set of the hardware that kept the brushes in place was completely corroded away.
So, since I needed this gearbox because the other one had the output in the wrong direction, I reworked this one as best as I could. Had to thoroughly sand the commutator and stole the brushes and associated hardware off the other motor. Luckily the motor wasn't stuck, the bearings were okay. Pulled out the batteries, hooked it up, and after a few false starts, away it went! Phew. Now I just need to figure out a controller.
I also added some pics of the way I am attaching the shell to the deck, I made a couple of locating pins, and drilled recesses for some small rare earth magnets in the front and a couple of bar magnets in the back. Holds it down to the steel deck pretty snugly, but is still easy to remove.
Attachments
IMAG0283_1.jpg
IMAG0281_1.jpg
IMAG0282_1.jpg
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

OddDuck
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Re: When all you have is a hammer, everything's a nail...

Post by OddDuck » Sat Sep 16, 2017 4:32 pm

Oh, a few pics of the chain setup.
Attachments
IMAG0279_1.jpg
IMAG0280_1.jpg
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

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PRR5406
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Re: When all you have is a hammer, everything's a nail...

Post by PRR5406 » Sun Sep 17, 2017 11:03 am

You have remarkable persistence, Pete. When one considers the design is your, the aluminum foundry work is yours, the gear drive is yours, and the motor(s) came from Hell, I can't help but be impressed. I can't wait to see her pulling with an engineer at the throttle.
"Always stopping my train, and risking my ankles, with American made, New Balance sneakers."

OddDuck
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Re: When all you have is a hammer, everything's a nail...

Post by OddDuck » Sun Sep 17, 2017 8:28 pm

Gave it a paint job today, and I made a neat find, I found a sheet of embossed aluminum from an ex storm door, looked a lot like diamond plate, and was even reasonably close to scale to boot. So, now I will have a little extra detail.
Attachments
IMAG0285_1.jpg
IMAG0286_1.jpg
"If you took the bones out they wouldn't be crunchy!" -Monty Python's Flying Circus

Pontiacguy1
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Re: When all you have is a hammer, everything's a nail...

Post by Pontiacguy1 » Mon Sep 18, 2017 8:57 am

I've used that stuff before on the running boards of a steamer. Screwed it down with some #2-56 brass hex head model bolts. Looked real good too.
Scrounging and taking something you find and making it into something completely different is one of the best parts of this hobby to me.

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