Arch bar trucks

[johnny]

What is the best material for making the bars in an arch bar truck? I see strength and malleability or bendability as trade offs here. I saw some nice ones made of aluminum, but they were for 1" scale. Hot rolled, cold rolled steel? What would be easiest to bend like wrought iron, but strong enough to hold its shape once bent and support a few hundred pounds of riders? Also, I have seen posts discussing metals identified by numbers. Is there a source that describes metals and their properties for newbies? Any help appreciated.
Johnny

[willy]

I will be making my trucks out of 1018 cold rolled. I have made others in the past with hot rolled, and have worked out fine that way. The hot rolled I heated up with a torch (cherry red)till it bent easily.

-willy-

[ccvstmr]

Johnny,
First of all, there were many different kinds of arch bar trucks. Some had 2 of 3 bars bent plus one flat member, others had 3 of 3 bars bent. On some arch bar trucks, one of the members was thicker than others. Lots of styles to choose from.

I will be using cold rolled steel as mentioned in the previous post. I plan on making a set of forms with an insert (depending on which bar is being formed) so that all similar bars will be pressed the same way. The forms will also include bolt hole locations to secure the journals and pedestals. I have heard of some modelers using a bench vise to form the various bars, but a press will be much easier on the hands and arms. In particular if you're building more than (1) set of trucks.

The advantage of using a form/die is to ensure that all of the members are nearly identical. Small amounts of error in bending and/or drilling could result in a truck that tries to "crab" as it rolls down the track. In other words, you don't want your axle journals skewed. You want the same distance from the bolster centerline to the axle centerline for each side frame and from side frame to side frame on the same truck.

Anyone else have experience making arch bar trucks (I think Dick Morris has)? cb

[willy]

Definately use a jig. If you bend it ar press it. You will want some way of verifying its accuracy.

-willy-

[Bruce_Mowbray]

Johnny,
I like to use hot rolled steel to make my trucks. It bends easy doesn't have much springback like cold rolled steel does. I make dies (one male amd one female) out of aluminum plate with the same thickness as the bar is wide and bend them either in a press or in an old milling vise. With hot rolled steel the shape of the dies is almost the same as the finished part.

[pat patton]

I have a set of arch bar trucks made from 1/8" x 3/4" aluminum. They are over 20 years old and in good shape. They've been under a wood flat car and held up well.

Pat Patton

[UnkaJesse]

Willy, That is one weird looking arch bar truck in your attachment. [img]/ubb/images/graemlins/confused.gif"%20alt="[/img] Never seen one like it. What road used them configured like that? [img]/ubb/images/graemlins/crazy.gif"%20alt="[/img]

Unka (who thought he had seen it all but was wrong as usual) Jesse

[UnkaJesse]

Carl, I have made several arch bar trucks from hot rolled steel and they have all perked werfectly. Simple bending jig in a good bench vise or press will bend them all alike. The formed trucks are very strong and "look right" (because they are right) . I have one set of Cannonball cast aluminum "arch bar" trucks under my wooden gondola which perform well also, but do not look as good as the steel ones.

Unka Jesse

[C_Wilkes]

I recognized it as a truck from that Dunkirk he is building. Those engines are really unique. dunkirk at geared steam

[Dick_Morris]

I have made a couple of pairs of arch bar trucks. One is based on Gene Allen's castings. I thik there is a detailed description on the old board. I used 1/8" by 1/2" CR steel. I thought the arch bar material in Gene's was over scale compared to all the drawings I have found. I also thought a sharper bend looked better that the was provided. The edges on HRS are quite rounded compared to the CRS.

One caution, I believe it's Mountain Car Companythat lists their arch bar trucks as having significantly less capacity compared to a Bettendorf. Not a problem with my tender or a short car appropriate to the era for my locomotive, but something to be aware of.

Personnaly, I'd steer clear of aluminum. The extra weight and strength of steel are both advantages.

One trick I've heard of is to silver solder the joints where the arch bars come together. I may try that on a set - it would probably help with strength and rigidity.

I only bent one bend at a time. It worked OK, but it takes care. On my things-to-do list is a bending jig. The only problem is that each type of truck takes a different jig and I'd like to make several variations. V&T has and interesting one with extensions of the bars used to hang brakes at the front and rear of the trucks.

Sigh, so much to do, so little time.

[johnny]

Dick,
Thank you for the feedback. I found your old posting on arch bar trucks. In it you said: "Arch bars were formed using a die made from a couple of sections of 1-1/4" heavy angle iron with guide rods to hold the pieces of angle parallel." Do you have some pictures of the die? I've practiced bending steel strips, one angle at a time in a vise and am having trouble getting the bends all the same. Both the angle and the length between bends vary despite careful marking and lining up of the piece. Also, the angle is not very sharp. I think a die would help here.
Johnny

[johnny]

Willy,
Thank you for the feedback. What is 1018 cold rolled steel? This is one of the "metals identified by numbers" that I referred to in my original post. Is there a listing somewhere of metals by number and properties so I can ask about materials without looking too newby? Thanks,
Johnny