Scaling Drivers

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hobbysteam
Posts: 9
Joined: Fri Mar 15, 2013 7:09 pm

Scaling Drivers

Post by hobbysteam » Sun Feb 04, 2018 12:04 pm

Hello
I'm just starting in this hobby and I have a question that should be easy for most of you! I want to cast my own 80" drivers, having the 17 spokes, like a Pennsy. I have a prototype drawing, which is a 17 spoke center but my drawing is for a 72" center casting. I'm thinking that seeing as the tyres are approx 2 1/2 thick, and if you take that times 2, would make the center for the 80", finished driver, at least 75", is that correct? If that is the case then here is my question. Can I use my drawing for the 72" centers and scale it up that little bit, and will it still be correct?

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LivingLegend
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Re: Scaling Drivers

Post by LivingLegend » Mon Feb 05, 2018 12:09 am

2.5" is a bit on the thin side... Figure the tires at 3.5" thickness. Example: A Big Boy has a driver diameter of 68" with the center 61" making it's tire thickness 3.5".

Yes, you can scale up the drawing if needed.... But all you would have to do, tho, is lengthen the spoke itself. Use the cross section profile at the rim and at the hub, then stretch out the spoke's length between the two.

LL
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hobbysteam
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Joined: Fri Mar 15, 2013 7:09 pm

Re: Scaling Drivers

Post by hobbysteam » Mon Feb 05, 2018 11:26 am

Ok great, I'll try to find out exactly what the 80" driver tyre thickness was and then do the spoke thing as you outlined!
Thanks for the help!

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LivingLegend
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Re: Scaling Drivers

Post by LivingLegend » Mon Feb 05, 2018 12:36 pm

3.5" is the common thickness for driver tires.

FYI... Union Pacific FEF2 & 3 class 4-8-4 locos had 80" drivers with 73" centers. Chesapeake & Ohio L2 and L2a class 4-6-4 locos had 79" drivers with 72" centers.

LL
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
Blogs: Where people with nothing to say..... Say it

ebtfan
Posts: 81
Joined: Mon Jul 02, 2007 12:10 am
Location: Lancaster, PA

Re: Scaling Drivers

Post by ebtfan » Mon Feb 05, 2018 6:45 pm

Are you building a PRR locomotive? If so there are prints available depicting the prototype dimensions including hub, rim, counterweights, etc. I currently do not have access to my prints otherwise I would offer you the dimensions. The prints are available from the Pennsylvania State Archives. Here is a link to the archives.

http://www.phmc.pa.gov/Archives/Researc ... wings.aspx

hobbysteam
Posts: 9
Joined: Fri Mar 15, 2013 7:09 pm

Re: Scaling Drivers

Post by hobbysteam » Wed Feb 07, 2018 7:44 pm

I think I have found what I need in an old Cyclopedia but I am taking note of your Archives tip non the less.
Thanks for that!

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