Nusky/Mercer 0-4-0 driver width?

[Sandiapaul]

Hi all,

I'm building a 0-4-0 camelback. The drawing for the drivers shows 2 different dimension for the tire width, depending on gauge. For 7.25(which is what I am building) shows an overall width of .875". For 7.5 gauge it shows the IBLS recc width of .750".
Anyone know why its like this? Only thing I can think of is it would allow so extra room to run the 7.25 version on 7.5 track.

Thanks,
Paul

[ChipsAhoy]

Is the narrower driver on the wider guage to help prevent having to move side rods, valve gear or perhaps cylinder outboard? Or in other words having a narrower driver causes the flanges to be further apart by default.
Scotty

[GO&PRR]

Hi Paul,

Looking at the two drive wheel views, the top one is for the 7-1/4" gauge version which has the wider tread at 11/16" and a flat back.

Comparing to the next drive wheel view for the 7-1/2" gauge version, has a 9/16" tread. NOTE that this wheel has a 1/8 boss on the backside. This simply moves the flange out for the wider 7-1/2" gauge. Thus the axles can be made the same for both gauges for that design.

In my opinion, I prefer the wider treads also for the 7-1/2" versions. To do that, turn the wheels like the 7-1/4" drawing and then lengthen the axles by 1/8" on each end, keeping the 1" length thru the wheel. The 'revised' cylinder castings (Mercer now offered by IHS) offer more meat at the mounting face so that they can be machined with the extra 1/8" distance. Older builds may have used a 1/8" spacer. A thrust washer can be introduced between the drive wheel and the journal box.

Hope this helps.

[Sandiapaul]

Thanks for the info Ed. I'm almost ready to make the drivers so this is good info.

[JohnHudak]

(Mercer now offered by IHS)
Hope this helps.

Ed, does IHS have a website?

[PRR5406]

Hooray! Another A5a joins the fleet!

[Fender]

Watch the clearance between the crosshead and the crankpin on the lead driver. Pretty close clearance there.

[GO&PRR]

Hi John,
Do not have a web site yet but is on the list to do's.
Send a note to ihsc775@gmail.com and can reply with a price list showing what is currently available on the A5a.

[Sandiapaul]

Thanks for all the responses guys!