Allen Models making changes.

[10 Wheeler Rob]

I also pitched the brittle castings for my ten wheeler when an tried straightening one and it snapped in two. I used 6061 T6 Aluminum and manually milled them.

303 Stainless water cut blanks would interest me for future engine builds.

Rob

[PeterCraymer]

I heard a number of stories about the stock cast aluminum rods causing problems related to breakage and or the design of the connection of the front rod to the rear rod. I am not a huge fan of the fishback style rods either and wanted to have them with flutes cut into the sides. That known, I made all my rods out of 6061 (with pressed in bushings for bearing surfaces) after making my own drawings based on Gene's dimensions on the prints. The fluted areas are painted black and the entire rod is clearcoated after brushing them to keep corrosion and staining away. I also used 4 screws to lock the pin in place at the connection to the back rod and have had no issues at all from any part of the setup. All that said, I think that as was stated above, the best answer is to make them from steel and finish to your liking. I would nickel plate them. Brass or bronze could be done and plated as well, but native steel could be clearcoated or oiled if someone wanted realistic colored rods but not the expense of plating. I know it has worked for many folks for a long time, but cast aluminum that thin can be done but has risks of porosity and not great to machine threads and such which leads to other issues.
Just my $.02.
Peter

[pat1027]

I'm not building an Allen model, but I plan on aluminum rods machines from bar. I think a machined rod has a more prototypical finish than cast rods. I chose aluminum to be able to leave it unpainted.

[makinsmoke]

'Course the majority of locomotive rods were painted to prevent rust
because they were plain steel. Only later when alloy steel rods started
being used were the rods polished and left unpainted.

A period locomotive would have painted side and main rods.

Paint would have to be removed for the periodic magnaflux tests.

[NP317]

And I believe the FRA outlawed paint on locomotive main and connecting rods, to allow better and more frequent visual inspections for cracks.
~RN

[Harlock]

I will add my voice to the chorus for steel rods, water jet cut. They have the right finish and the strength. There is also no headache of maintaining the patterns and using specialty suppliers.

On John Heald's B-Class locomotive, the big rods are waterjet (the main rod and connecting rod for example.) The holes are left out for final sizing, with the separate marine bearing insert actually welded in once the distance is determined. The split bearings are faked with a solid bushing pressed in instead.

Shorter 3D profile walchaearts linkages are fabricated and welded together with the welds ground seamless. This is not a need on the Allen engines for the most part since most use stephenson.

-M

[makinsmoke]

No disrespect however, no paint applied to wheels and couplers.

There are many of photos of in service steam locomotives up to the end of steam
showing painted rods unless they were alloy and polished.

Back to the thread. I bought the rod castings from Gene but hope to have some
made from steel for many of the reasons above. Fluting would be one plus.

Thanks for all you are doing Steve. The fact that you are even asking is a big deal.

Take care,
Brian

[Cary Stewart]

For what it is worth, Charlie Dockstaeder used 7075 aluminum for the rods on all of his engines. He ran the journals on the reamed rod ends. The El Gub. had over 30,000 actual miles on it when he re did the rod bearings. 7075 is tough and nearly as strong as steel. Not as easy to machine as 6061 but not that bad.
Cary

[Harold_V]

7075 is tough and nearly as strong as steel. Not as easy to machine as 6061 but not that bad.
Cary

Yep, it is, but only in the proper aged condition (T6 or T651). It cuts hard and crisp, but easily, assuming sharp tools.
If strength is a concern, 6061-T6 would be my third choice. 2024 is wonderful stuff to machine, and comes close to the strength of 7075. You'd want to select T351 or T4, and for an even (marginally) stronger advantage, T861.

Harold

[BClemens]

Ditto what Harold V said.... 7075 is ideal as far as strength and machinability goes but it is not easily welded and it corrodes like crazy although anodizing seals it against corrosion. It is a perfect material for a small cnc machine shop with a bare bones (no coolant) machine. It sheds the cutting chips like steel so you can walk away. 2024 is not weldable at all and it too corrodes badly. 6061 is a gum ball to machine without coolant (or constant attention with CRC or WD-40) but welds very well and is not as susceptible to corrosion as 7075. 5000 series aluminum is corrosion resistant, welds nicely but requires coolant to machine similar to 6000 series.

Steel is great all around but rust is its pitfall. Never use cold rolled steel - it will warp and draw out of shape so much so that maintaining bearing alignment is impossible. 303 SS is similar to 1018 and will warp too. Open hearth hot rolled steel with a flash of nickel plating is perfect for side rods. They could even be case hardened for slip fit bushings.

just another pair of pennys...

BClemens

[rwmorris]

I'm huge fan of water-jet parts... The rods are a perfect candidate for this process.

[NP317]

I'm huge fan of water-jet parts... The rods are a perfect candidate for this process.

I would expect water-jet to cost more that laser cut. Anyone have info on relative costs?
The water-jet I had in my University shop had high consumable and cleaning expenses.
But they surely work wonders.
~RN