Allen mogul siderod project

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John_S
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Allen mogul siderod project

Post by John_S » Sun Oct 05, 2014 4:14 pm

One of the things I never liked about my Allen mogul were the aluminum siderods and main rods. I machined them a long, long time ago when I was first teaching myself machining and they were, well, not so great.
rods0.jpg
Original cast aluminum rods.
I drew up the new rods in DraftSight and sent the drawing over to a local shop and had them laser cut out of 1/2" HRS. Then a lot of face milling ...
rods1.jpg
Face milling the rods to the correct thicknesses.
rods2.jpg
Face milling done.
I used a 3/8 ball end mill to machine the fillet around the bearing areas.
rods3.jpg
Machining fillets.
One of the design flaws was the way the front rod was connected to the rear rod: A steel pin, threaded at one end, that screwed into the aluminum casting. Over time the threads get beat to death by the rods and the pin will work its way out. This happened to me not once but twice at Mid-South ... on two different visits! The engineer's side at last year's fall meet and fireman's side at this year's spring meet.

So, I redesigned that pin (as many others have) and made it like this:
rods4.jpg
Connecting pin fix.
(more to come in next post... )

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John_S
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Re: Allen mogul siderod project

Post by John_S » Sun Oct 05, 2014 4:18 pm

rods5.jpg
Connecting pin fix.
I've got one side all done and reinstalled on the locomotive. Finishing up the other side now.
rods6.jpg
New rods!
Closeup of the new final connecting pin:
rods7.jpg
New pin.
The one other major change from the original design is I'm using Delrin AF for all the bushings. The oilcups are for decoration only. I've heard mixed comments about Delrin AF, from "It's the best thing ever" to "It'll beat your crankpins to death."

We'll see how it does in a couple weeks when I take the loco out to run.

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Fred_V
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Re: Allen mogul siderod project

Post by Fred_V » Sun Oct 05, 2014 5:20 pm

I like the castrated nuts!
Fred V
Pensacola, Fl.

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LivingLegend
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Re: Allen mogul siderod project

Post by LivingLegend » Sun Oct 05, 2014 6:04 pm

How do you castrate a castle nut?

LL
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John_S
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Re: Allen mogul siderod project

Post by John_S » Sun Oct 05, 2014 7:03 pm

LivingLegend wrote:How do you castrate a castle nut?

LL
Edit: I just realized Fred's mistake and your joke, heh! :)

They're not too much to make on a rotary table or an indexer, but I went the easy route and ordered mine from McMaster-Carr. :)

Mine are all 3/8-24 thread, and I actually started to make them myself, but realized it was worth the couple of dollars to just order them.

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LivingLegend
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Re: Allen mogul siderod project

Post by LivingLegend » Sun Oct 05, 2014 7:54 pm

LOL.... I was making light of Fred calling them castrated nuts. I've made many castle nuts in my day from 5-40 up.... Some with non standard thread diameters and TPI single point threaded. Once worked as a prototype machinist/modelmaker/toolmaker.

LL
Last edited by LivingLegend on Mon Oct 06, 2014 8:40 am, edited 1 time in total.
Do it right.... Or don't do it at all
I have no life. Therefore, I have a hobby
It's not that I'm apathetic, I just flat don't care
An Intellectual is nothing more than an Over-Educated IDIOT
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ccvstmr
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Re: Allen mogul siderod project

Post by ccvstmr » Sun Oct 05, 2014 8:05 pm

...I would have thought a "castrated nut" had no flats for sides! :roll: Made a few of those in my time...might even share a recent (similar) experience here in the next few days. Carl B.
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Harold_V
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Re: Allen mogul siderod project

Post by Harold_V » Mon Oct 06, 2014 12:19 am

John_S wrote:to "It'll beat your crankpins to death."
Blink! Blink!
Delrin AF will beat crank pins to death? :shock:

One of the most absurd comments I've heard in a long time. Did the individual who dispensed this little tidbit happen to manage to describe the mechanism by which that would work? To me, it sounds a lot like denting an anvil with a feather.

Harold
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Bill C
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Re: Allen mogul siderod project

Post by Bill C » Mon Oct 06, 2014 7:08 am

John, your new rods look great! Thanks for posting the update.

Bill C.

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Marty_Knox
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Re: Allen mogul siderod project

Post by Marty_Knox » Mon Oct 06, 2014 6:25 pm

John, your rods look good! If you add a pin in the back of the knuckle pin you can tighten the nut without it spinning - this is full size practice. The Allen/Harpur Mogul was designed to be simple, low cost, and easy to build. It lends itself well to refinements and improvements like yours.

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John_S
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Re: Allen mogul siderod project

Post by John_S » Mon Oct 06, 2014 6:37 pm

Marty_Knox wrote:John, your rods look good! If you add a pin in the back of the knuckle pin you can tighten the nut without it spinning - this is full size practice. The Allen/Harpur Mogul was designed to be simple, low cost, and easy to build. It lends itself well to refinements and improvements like yours.
Thanks Marty! Are you making changes to the drawings to improve the pin's design? I know there's been a bunch of different methods folks have used (I saw at least four different solutions at Mid-South last spring!) to remedy the problem.

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Marty_Knox
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Re: Allen mogul siderod project

Post by Marty_Knox » Mon Oct 06, 2014 8:06 pm

John_S wrote:Thanks Marty! Are you making changes to the drawings to improve the pin's design? I know there's been a bunch of different methods folks have used (I saw at least four different solutions at Mid-South last spring!) to remedy the problem.
I want to update all the drawings eventually. For some reason, I think the first one that will be done is the boiler.

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