Large Scale Central

Tread Width for 1:20 wheels?

General Discussion
#1

I have a friend who is into the large size trains and takes them and track to a few of our local train shows. At the last show I sat with him as he was running his trains. I want to build a 55 foot McKeen Motor Car in 1:20 and hope he will invite me to run it on his track. All his large scale trains are Bachmann and I assume his track is also Bachmann.

I can buy an I Scale power truck from NWSL that is the wheelbase I need but they come with one of three different “tread” widths. They are 270, 236 or 172. I have to pick one but have no idea which I want. David at NWSL could only say that he thought the 172 was used as the wheels for “Fine Scale” models.

Does anyone have an answer or a suggestion?

Thanks, Bill

#2

Bill,

First, welcome aboard! This is one of the best places I have found for great people and information. Great project you are looking to tackle.

The assumption the track is Bachmann is a dangerous one. Most of the older Bachmann track is a stamped steel ‘hat shaped’ rail section. Only recently have they come out with a line of brass track suitable for what I would define as heavy or outdoor use. I would guess that if your friend has been doing has been doing his ‘road shows’ for any length of time, his track would be Aristo Craft, USA Trains or LGB, all of which are compatible with one another or the new Bachmann offering.

As for the NWSL truck you are referring to, I can only guess from their catalog page that the numbers refer to the tread width in thousandths of an inch. IF that guess is correct, I would recommend either the 236 or 270 tread width. This will be more compatible with possible later runs on other less hospitable indoor layouts or outdoor layouts where track work could be less than ‘perfect’.

My major concern is with the voltage rating of the unit. The catalog page clearly states the unit is designed for 12VDC operation. Most large scale trains are generally designed for the 18VDC range. The catalog page also clearly states that running over 18VDC may cause damage to the unit. This would cause me to step back and be either very careful how much throttle I give the unit, or try to in some manner restrict the voltage to the acceptable range. Another option would be to disable the track pickup on one truck and run the motors on two trucks in series. This make the motor voltage for the two motors in series 24VDC. Depends on how much work you wish to put in to it. You may be able to find an Aristo Craft motor block on eBay. USA Trains I believe sell them as parts. Another inexpensive alternative might be to purchase a Hartland Mac and use their motor block, a quite good one for the price of the loco.

Good luck and again, welcome aboard.

Bob C.

#3

What ever you buy don’t buy the code 172 wheels. They will NOT work with commercial 45mm gauge track. I would recommend the 270 wheels. I use 270 wheels on my GP9 locomotive without any problems on commercial track. The 236 “might” work, but I would stick with the known quantity. And yes the number is the thread width.

#4

About the voltage question brought up by Bob C. I have a few Heartland locomotives, and they too use 12 volt motors. Since I have a volt meter at my power station (housed in my feed and grain building), I can dial back my power so that it doesn’t exceed 12 volts. I failed to do that once, and burned out a motor in a Heartland 4-4-0. They were kind enough to replace the motor for me, since it was a new locomotive, but I was told to “not do that again”.

So I would head Bob’s advice, and either get a USA block that can handle the 16 to 18 volts most supplies can dish out, or build something into your McKeen that will limit the power to the motor block.

Incidentally, the McKeen is on my “someday” project list. Cool machine.

#5

Thanks Bob and Craig or the quick replies.

To Bob, thanks for the welcome. I have been a member for awhile and have watched a few different building threads.

I have 2 of the Bachmann 1:20 Old Time Passenger Cars with the “North Pole Southern” paint job. I bought them on ebay really cheap - $15 each. I also have 2 small caboose models by Lehmann that I bought about the same time. That was at least 4 years ago. I had thought about turning them into RailMotors of some kind.

I just measured the wheels on both, The Bachmann are 270, the Lehmann are 235 maybe really 236.

I will order the power trucks in 270 and tell David at NWSL what that means.

Most of my train models are HO, HOn3, HOn30 and On30. I have been installing Radio Control with Battery in them since 2007. I will run the Big McKeen by RC and Battery Power. David at NWSL did tell me about the voltage situation but then I reminded him that I will install RC in the McKeen.

My RC System has an optional voltage regulator that will hold the current that goes to the motor to 12 volts. I can even charge the battery if I have any track current while I am running it.

I will check prices at the places you all suggested before I buy a power truck. The nice thing about the NWSL units is that they have the 9’ wheelbase like the prototype. Since the Mckeen’s didn’t normally pull anything I thought I might get by with only 1 power truck and the other truck would be a dummy.

#6

David Maynard said:

Incidentally, the McKeen is on my “someday” project list. Cool machine.

David, The Mckeen line of engines, passenger-trailer and baggage cars and at least one yard switcher, are my overall favorite prototype or model train. My interest in the McKeen Motor Cars go back to 1954 when I was 14 and read an article about them in the March 1954, RMC, which I still have.

I have a bunch of them in the following scales, N, HO, HOn3, On18, On30, 1:35n2 and soon this one in 1:20.

I scratch built the N, On18, On30 and 1:35n2 models. The Hon3 was a bash using an HO resin model. In HO I have 6 different versions in Brass and 2 different versions as resin models.

#7

Welcome Aboard Bill, your ideas sound interesting.

#8

Bill, I hope you post some “as I go” pictures. I need some inspiration before I start mine. :slight_smile: