Wischstadt Arch Bar Trucks

Scotty Lewis sent these plans for publishing on the IBLS website, October 2023.


 * This is an article to add to your collection, written about 1985 by Chuck Wischstadt. I found it maybe useful for new people to the hobby. Use bar stock or strap iron, aluminum blocks or steel, I've even seen hardwood without bearings; just grease and when you smell wood burning re-grease!


 * Chuck is the Son of Ace Wischdadt. Most old timers knew Ace on the West Coast. He was the talker of the 3 guys who were the founding fathers of Chula Vista Live Steamers.  Both Ace and Chuck have passed away about 10 years ago. Chuck was an artistic guy, lots of talent very creative, always had a refrigerator car full of chips and salsa and Coors beer. Even now at live steam meets someone see the CVLS tee shirt and asks "Did you know Ave and Chuck?"



Arch Bar Trucks

By

Chuck Wischstadt

Many arch bar trucks have been built in various scales, from the 1 inch to the foot variety on down to the "Z" scale size. The following is my version of an arch design I've seen on many standard and narrow gauge railroad cars. I'm currently modeling in 1-1/2 inch to the foot. I've seen many types of arch style trucks and many types of construction methods for 1-1/2 scale. Here I hope to explain how I build my trucks clear enough so other builders can use the information to build their own.

After machining your wheels and mounting them on 11-3/4 inch long axles, finish turning the tread and flanges of the wheels with the axles mounted between centers. This way assures that the wheel tread and axle is concentric and will run true in operation. The axle stub ends (the part that is outside the wheels) need to be turned down to accept ball bearings. I use surplus aircraft type bearings with a 3/8 inch ID and a 1 inch OD and 3/8 inch thick. First measure 0.625 inch outside the wheel face and mark the axle at this point. The end of the axle needs to be turned down to accept the bearing leaving a square face (shoulder) on the axle for the bearing to ride against. Make sure you leave a small radius but not so large to interfere with the bearing. The stub end diameter should be a thou or so under to allow the bearing to slide on the axle freely. Put the bearings on the axles and mark off about 0.020 inch outside the bearing, and then cut off the remaining stub end of the axle. Now we've got our axles ready for the side frames.

The first part of the side frames that need to be made are the journals. I use 1-1/2 inch square aluminum bar stock. If you have some cast journal boxes use them, they make better looking trucks when you are finished. Cut the 1-1/2 inch stock off at 1-1/4 inch long. Of course you'll need 8 of these. Lay out all of your journal blocks finding a center, then center punch all the blocks. After that is done the bearing bores need to be cut out. Mount a block in a 4 jaw chuck on the lathe and bring the center in till she's running fairly true. Then center drill the block, and clean up the face with a cut across the face. Drill the center out with a 3/8 inch drill about 3/4 inch deep. Then start turning out the bore with a boring bar. I take the bore out to 0.005 inch larger than the bearing. This gives the bearing room to move around when the side frames of the trucks are twisted. This is something that is necessary. I'll explain later on. Take the bore down to 0.750 inch deep, but don't clean up the bore bottom (leave the drill point chamfer in the bottom of the bore). This is for the clearance of the axle ends.

If you've been lucky enough to get a set of castings for your journals, the following is an explanation on how I machine them. First the upper and lower surfaces need to be faced off. Mount the casting in a 4 jaw chuck so that upper surface will be turned off square. I set up the casting so that the four corners of the upper surface run approximately the same distance from the cutting tool then secure the jaws to the casting. Then start cutting the surface down flat. Cut it down till you just break through the lobe of the journal box lid mount. Remove the casting from the 4 jaw and turn the opposite face the same way as the upper surface (push the casting against the chuck face then tighten the jaws). Turn the casting down till the overall height is 1-9/16 inch. Remove the casting from the 4 jaw and rotate the casting so it will be mounted in the chuck to turn the sides (ears). I just face off the tips, leaving about a 1/4 inch area that has been surfaced. Repeat the process on the opposite side. Now all the mounting surfaces have been faced off square. Rotate the casting mount in the 4 jaw so that the inside surface can be surfaced off and bored. Find the center and center punch. True the center in the 4 jaw and face off the inner surface. Bore the bearing bore in the same manner as I've described above (for the aluminum block style journals). Of course you've got to do this on all 8 journals.

The next parts we need to make are the bars of the side frames. I use 1/8 inch by 3/4 inch hot rolled steel strap stock. You'll need 8 pieces 12 inch long, and 4 pieces 13 inch long. Now we need to bend the bars. There are many ways to do this. Some builders have made a special fixture that fits in a hydraulic press to bend the bars. This works great, but I don't think all the extra work put in to the fixture in worth it. Sure it's handy, but most of us builders aren't in major production. In other words we only make maybe one or two sets of trucks. I hand bend my bars using a vise and a ballpeen hammer.

First take one of the 12 inch bars and mark off the center. Yea that's at 5 inches from the ends. Then lay all the bars side by side and flush with the ends, hold them together and using a combination square mark all the bars with one stroke of the pencil. Now using the full size drawing, lay one bar on edge over the upper bar image and mark both of the bends that are close to the center. Make the marks square across the bar. Next put the bar in a vise so the upper edge is flush with the top of the jaws of the the vise. Using your free hand push on the end in the direction you want to bend the bar then hit the bar (close to the vise jaws) with the ballpeen. Thump it a few times till you think your close to the angle you need (if you have a machinist type protractor it would help here). You might need to check the angle with the drawing from time to time, till the bar looks about right. So go ahead and take the bar out of the vise and check it over the drawings. That's how I do it. Mark off the remaining bends and make all the bends that are left. Make all 8 bars the same. The middle bar is the 13 inch long one. Using the same procedure I described above bend all 4 bars. Now if you'd like, lay the bars into position on your bench. I know, most of you say "the ends aren't even". Well, I don't worry too much about that because later I'll just trim them off until they are even.

The next parts are the pedestals. I've made a pattern that is about 4-1/4 inch long with the same profile as the drawing, and have castings made. Two castings are needed for one set of (2) rucks. I cut up the castings in 4 pieces, then dress them off with a disk sander till they are about 1 inch thick (try to make all of them the same thickness). If you don't have the castings you can use 1 inch by 3/8 inch steel bar stock cut to length (2-3/8 inch).

Next you'll need some 1 inch by 2 inch tube for the bolster. Cut off two pieces 12-1/16 inch long, and one 2-3/8 inch long. Set the two long pieces aside for now.

Using the 2-3/8 inch long piece of tube laying on the 2 inch side, position the pedestals and the upper, middle and lower bars in place. I slip in a piece of 0.020 inch tape between the tube and a pedestal then clamp all the pieces in place. Mark the center of the upper bar pedestal bolts, center punch and drill 1/2 inch deep with #21 drill to accept a 10-32 tap. Do the same of the lower/middle bar set. Now you've got four holes drilled. Remove the clamps and drill out the bars with a #10 drill. Tap the holes in the pedestals with a 10-32 tap, the threads should go as deep as possible, so you'll need to use a bottoming tap. Temporarily bolt the upper, middle and lower bar to the pedestals, then go on and repeat the process on the remaining 3 side frames. Things are beginning to shape up now, all those pieces you had are beginning to look like truck side frames.

Pick up those nicely machined journal boxes and group then in twos. Lay the blocks on their faces so the bores face up then clamp two blocks together. Mark off the center (5/8 inch from the bore side) across both blocks, punch and drill (#10) on the intersection of the two blocks and the center line (so when you finish and unclamp the blocks you have one half a hole in each block). Rearrange the blocks so that you drill another hole along the side opposite of the half hole you drilled before. When you finish the drilling you have two blocks with bores and two half holes on the sides at 90 degrees to the bores. Repeat the drilling so that all 8 journal blocks are the same. Position the blocks in place between the lower and middle/upper bars, so that the half holes are on center line of the bars and block bores centers are 9 inches apart. Refer to the drawing. Clamp in place, mark and drill (#10) the bars (make sure the blocks are flat/square on the bore face). The drill should follow the half hole of the journal while drilling through the bars. Now temporarily bolt the journals to the bars using 10-32 by 2-1/8 inch long bolts and nuts. Do the same for all 8 journals. Then guess what? We've got some side frames now! Remove all the bolts and deburr all the holes and reassemble the side frames. Now is when I trim off the ends of the bars so that they're all even (I know I should have bent the bars so the ends are flush, it's cheating but it works). Place the bearings on your wheel sets and slide the side frames in place, one on each end of both axles. Now slide the piece of 1x2 inch tubing (you've cut before) between the pedestals and carefully turn the assembly upside down. Measure off the distance across the outside of the side frames. Using the dimension cut two pieces of 1/8 by 1 inch steel strap (these are bottom braces). Position these two braces inside the bolster opening on the bottom side, and clamp both side frames and braces together, keeping the side frames and axles square (allow about 1/32 inch axle end play in the bearing bores). Mark centers, punch and drill (#10) bottom, middle and braces. Deburr holes and bolt bottom braces and side frames together.

Position the 1x2 inch tubing so the ends stick outside the side frames equal distance and mark off the inside face of the pedestal on the tube. Do this on both sides. Remove the tube from the side frame assemblies. Mark the center of the tube on its 2 inch face 6-1/32 inch from the end. Punch and drill (0.375) through (truck pivot pin bores). The bolster retainers need to be made next. But sixteen 1 inch pieces from 1/8 by 1/2 inch steel strap. Half of these will be used on the outside of the side frames and other half of the inside of the side frames. Lay the bolster tube (1x2) on its side and position two just inside (0.020) of the marks you made before and clamp in place. Now the torch comes into play. Braze the inner retainers to the bolster. Repeat until all 8 inner retainers are in place. Remove two side frame and bottom brace bolts and slide side frame off axles. Slide in the bolster and reassemble side frame and bottom brace. The bolster should slide freely up and down inside the pedestals. Position outer retainers and clamp in place. Drill retainers and bolster for 5-40 bolts (two per retainer). Deburr and assemble retainers to bolster (again check bolster for free movement).

Springs? Well, we need them! There's all kinds of strength of springs, but I've been trying to keep this easy as I can. So let's check the local gas station or car repair shop. We're looking for automotive valve springs. They seem to work okay and the price is usually right. The only thing that needs to be done to the springs is that they need to be cut down to a length that just fits between the bolster and the bottom braces. Turn the truck over and tack weld the two bottom braces together (tack weld should be about an inch from the outside ends). Once the spring are installed, the trucks need to be check for flexibility. The best way I've found is to set the truck on the bench and put a finger under one wheel so it is lifted (3/8 inch or so) and the remaining three wheels stay on the bench. This should be the same for all four wheels. If any of the other three wheels lift off the bench then you need to loosen up the clearances on the bolster, bearings or bolster retainers.

All that's left is the painting. I guess I'll leave that up to you.

Happy Railroading Chuck