3/4" Raritan 2-4-0 build.

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NP317
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Re: 3/4" Raritan 2-4-0 build.

Post by NP317 » Sat Mar 06, 2021 12:54 pm

This inexpensive bench top hand press provides a 5.5" throat height:
https://www.harborfreight.com/1-ton-arb ... -3552.html
I have one and use it. 'Better than a vise.
RussN

RET
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Re: 3/4" Raritan 2-4-0 build.

Post by RET » Sat Mar 06, 2021 3:29 pm

Hi shild,

For press fits, you typically allow .001" to .0015" interference per inch of diameter. Coincidentally, the same numbers are used for a close slide fit. If you are going to do a press fit on a shaft, what I would do in your case is to turn the shaft down until it is close to the desired diameter, then machine a short portion of the end down so it is .001" to .0015" smaller and keep on doing this until the wheel just barely slides on the turned down portion. At this point, you have the rest of the shaft (.001" bigger in dia.) at the right diameter for your press fit.

For several reasons, in your case I would recommend Loctite (with the shaft machined for a close slide fit) or drilling and tapping the junction of the shaft and wheel for a "Dutch Key."
Dart Drive Wheel axle end.jpg
Dart axle end showing capscrew as a dutch key and capscrew plug for grease lubrication
Dart Drive Wheel axle end.jpg (38.67 KiB) Viewed 1714 times
The Dutch Key is relatively easy to do and it has the added advantage that you can easily remove and reinstall the wheel on the axle at any time in the future if you ever need to do so. All you have to do is to remove the capscrew and slide the wheel off. To reinstall, just slide the wheel back in position, line the threads up, replace the capscrew and snug it up tight. Simple, even I can do it!
Dart Drive Wheel.jpg
Larger view showing relative positions.
In the above view you can see that the plugs for greasing are in the crankpin as well as the axle.

Just something else for you to think about.

Richard Trounce.

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Greg_Lewis
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Re: 3/4" Raritan 2-4-0 build.

Post by Greg_Lewis » Sat Mar 06, 2021 9:09 pm

Richard's idea is a good one for drivers. For pilot and truck wheels I'd just do Loctite.
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 30 years of turning perfectly good metal into bits of useless scrap.

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milwiron
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Re: 3/4" Raritan 2-4-0 build.

Post by milwiron » Sun Mar 07, 2021 7:22 am

Correction: A few posts ago I suggested 638 Loctite for a rough finished bore and shaft, that should say 648 Loctite. Looking at 2 bottles on the shelf I just realized I mixed up those numbers and properties. 638 is thick, quick and wicked stuff to work with. 648 is thinner and a bit more forgiving before it sets. Both are amazingly aggressive and strong.
Denny
"Measure twice, curse once."

shild
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Re: 3/4" Raritan 2-4-0 build.

Post by shild » Mon Mar 22, 2021 3:12 am

Thanks for the replies everyone! Just finished the tenders wheels. Took a while because I also did the riding car and pilot truck wheels. Now it's axle time. Don't know if I mentioned but this will be the better looking but weaker small boiler version. Thinking about doing what those RC car guys do about underpowered cars and use ball bearings. I've got a couple of scooter bearings like this for the pilot. What do you guys think?
Attachments
IMG_0373.JPG
Tender is at this level now.
IMG_0374.JPG
IMG_0376.JPG
The loco will have the better looking but weaker small boiler.
IMG_0375.JPG
Thinking of using all ball bearings to help compensate.

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LVRR2095
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Re: 3/4" Raritan 2-4-0 build.

Post by LVRR2095 » Mon Mar 22, 2021 4:23 am

The copper tube for your boiler looks too thin.
I don’t think it would be safe. You need more wall thickness.

shild
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Re: 3/4" Raritan 2-4-0 build.

Post by shild » Mon Mar 22, 2021 4:41 am

LVRR2095 wrote:
Mon Mar 22, 2021 4:23 am
The copper tube for your boiler looks too thin.
I don’t think it would be safe. You need more wall thickness.
I think that's the one Joe Tanski provided. Just measured it at 7/64 or .1035. That's not thick enough? How thick should it be?

Mike Walsh
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Re: 3/4" Raritan 2-4-0 build.

Post by Mike Walsh » Mon Mar 22, 2021 5:36 am

0.1035" sounds about right. What does your print call out?

LVRR2095 - remember, this is a copper boiler, not steel.

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LVRR2095
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Re: 3/4" Raritan 2-4-0 build.

Post by LVRR2095 » Mon Mar 22, 2021 5:42 am

yup.....I was wrong. Bill Morewood’s drawings calls out .083” wall.
It just looked a little thin to me. All of my locomotives have copper boilers. And they all have .125” wall thickness.

But being wrong about...oh most anything, is my normal.....just ask my wife.
Keith

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Greg_Lewis
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Re: 3/4" Raritan 2-4-0 build.

Post by Greg_Lewis » Mon Mar 22, 2021 6:11 am

I've used skateboard bearings for trucks on 1 1/2 scale riding cars with success. The one in your photo looks rusty. I can't tell for sure but you will use good ones of course. I got mine from a skateboard shop and they were so cheap, I think less than $2 each. High precision bearings aren't needed for this.
Greg Lewis, Prop.
Eyeball Engineering — Home of the dull toolbit.
Our motto: "That looks about right."
Celebrating 30 years of turning perfectly good metal into bits of useless scrap.

Mike Walsh
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Re: 3/4" Raritan 2-4-0 build.

Post by Mike Walsh » Mon Mar 22, 2021 8:21 am

Regarding modifications/deviations from the original design...

Since this is your first locomotive build, and it seems you may be a little green in the steam/machining fields, don't deviate from the print much. The locomotive is a tried and true design, it will serve you well. If there were modifications needed, you'd know about them by now.

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NP317
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Re: 3/4" Raritan 2-4-0 build.

Post by NP317 » Mon Mar 22, 2021 10:03 am

I agree with Mike W. to follow the drawings for this locomotive.
The original wheel bearing design has served builders just fine for decades.
Bearing loads are light. Oil works well. Your build will progress faster.
RusssN

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