Bachmann Big Hauler Modeling Tips

Bachmann produces a low-cost 4-6-0 that comes in many road names and with a good bit of variety in the details. These engines are also packaged in sets with a few cars, some track suitable only for indoor use, and a small power supply. You can sometimes find bargains on these sets, and we picked up a couple of sets for $100 each after Christmas of 1998. Almost all the parts are plastic, but the engines look very good for the cost and run fairly well. George Schreyer has an excellent Web site on maintaining and improving these engines. 

Power Pickup Modification for Tender

I found the power pickup on the Big Haulers to be a bit unreliable. We also have one of Bachmann's new 4-4-0s, and its power pickup through the drivers and the eight wheels on the tender is outstanding. I decided to modify the front truck on the Big Hauler tender so that it also picks up power. George Schreyer used LGB spring-loaded contacts for this, but here's a way to do it using a little brass, styrene, and shrink tubing.

I used the trucks that came with the tender and replaced the plastic wheels with a pair of Bachmann metal replacement wheels, but another brand could probably be used just as well. Begin by cutting some scrap styrene to fill the openings in the cross piece of the Bachmann truck. This is clearly visible in the photo as the white area under the brass strips. I was using scrap and I'm not sure of the dimensions, but I think I used two pieces from an .050 styrene sheet for each opening. Cut the pieces large enough so they require pressure to fit them in the openings, then glue them in with CA.

Next, modify the wheels. Both wheels are electrically isolated from the axel by a plastic bushing. One of the wheel/bushing assemblies moves on the axel to allow adjustment of the gauge. The wheels are coated with a dark material to make them less shiny. Chuck each end of each axel in a power drill and use a file to remove this coating from the rims of the wheels to insure good power pickup. If your drill chuck will not close down tight enough for this, you may need to get a micro-chuck. The last time I bought a power drill, I picked a model with this particularly in mind and got one with a chuck that will close down on a needle.

Remove one wheel and set it aside. A bit of solder bridges the plastic bushing, connecting the remaining wheel to the axel. You can see this on the upper right wheel in the photo. Use a continuity tester to make sure current will pass between the wheel and the axel.

If you solder the other wheel directly to the axel, you will just short your track when you place the wheels on the rails. The solution is a piece of shrink tubing and a piece of brass tubing. The shrink tubing I used is the largest size that comes in an bag of assorted sizes sold at Radio Shack. The blue tubing and it is clearly visible in the photo. Of course, part of the shrink tubing is under the brass tubing; it goes flush against the plastic bushing in the wheel. It's just the right size to fit over the axel. Cut a piece a bit less than half the length of the axel between the wheels, slip it over the axel, and shrink it with a hair dryer. Next, take a piece of 9/32 brass tubing, cut a long slot in the side with a Dremel tool using a fine cutoff wheel, and cut two short lengths off the slotted part of the tubing. (I had to split the tubing because the 9/32 brass tubing was too tight to fit over the shrink tubing. A piece of 5/16 brass tubing might fit, but the local shop was out and I was afraid it might be too loose anyway.) Pry the pieces of brass tubing open along the cut and slide them over the shrink tubing on the axel. Replace the other wheel, adjust the gauge of the wheel set, slide both shrink and brass tubing to that end of the axel, and tighten the brass tubing around the shrink tubing with pliers. Solder this second wheel to the brass tubing and check for continuity between the wheel and the brass tubing. The wheel sets are done.

The axel and the brass tubing are electrically isolated by the shrink tubing. One wheel on each axel set is connected to the axel and the other is connected to the brass tubing. Do a continuity check to make sure that current can not pass from wheel to wheel. I installed the axels with the brass tubing on opposite sides of the train to balance the overall weight of the truck.

Construct and install a set of wipers from brass. Drill and tap holes for 2-56 screws through the brass wipers and the styrene inserts in the trucks. Then attach the wipers to the trucks with 1/4" 2-56 screws. The wipers ride above the axels to reduce the chance that they might catch on small debris on the rails. Solder two wires to the tops of the wipers, drill a hole in the bottom of the tender, and pass the wires through. I used 22 gauge red and black wires that can be seen in the photo.

All that's left is to run a set of wires between engine and tender to connect the power pickups. Details on how are did that are in the section below on installing a sound-only decoder. The improvement in the performance of the Big Hauler with the power-pickup in the tender is remarkable. I planned to modify both tender trucks, but the improvement was so great with one truck modified that I haven't felt compelled to modify the other yet.

Installing a SoundTraxx DSX sound-only decoder

I replaced the original sound system with a SoundTraxx DSX sound-only decoder for a K-36. I put the decoder in the tender following the very clear instructions that came with the decoder and using the speaker that came with the Big Hauler. I filled stray openings in the bottom of the tender with silicone cement to make the sound chamber as tight as possible. I removed the wires and switch for the original Bachmann sound system from both the engine and the tender using the opening left by removal of the wiring for the original sound system. Then I installed a three-wire cable with a mini-connector between the engine and tender. One the engine, the first wire goes to the right-hand pickup, the middle wire goes to the left-hand pickup, and the third wire goes to the chuff switch. One the tender, the first wire goes to the right-hand pickup (see section above on adding power pickup to the tender, and to one of the power leads on the decoder, the middle wire goes to the left-hand pickup and the other decoder power lead, and the third wire goes to the brown lead on the decoder.

Experiences with Barry's Big Trains 4-6-0 drive for the Big Hauler

While pulling half a dozen cars up a grade of about 4%, my Bachmann 4-6-0 stopped. The engine was running, but all that it produced was a clicking sound. The Big Hauler curse: stripped or slipping gears. 

I ordered a BBT 460 kit from Barry's Big Trains. Installation instructions were clear and the job was relatively fast and painless. The motor is electrically isolated from the chassis and I had no problems with reinstalling the DCC decoder. The motor is much larger than the original Bachmann motor and the chassis is both sturdier and heavier. The worm gear on the motor shaft is brass; the gear on the axel is plastic like the original Bachmann drive gear, but it is heavier and should hold up better. The engine runs smoothly. I haven't increased the weight yet, but I plan to add at least another pound or two. I had added this much weight to the engine originally to improve traction and this probably contributed to the gear slippage.

The BBT chassis is very rigid and fits tightly into the Bachmann boiler shell. There is essentially no play in the drivers, that is, they cannot move up and down at all. In the original Bachmann configuration, the front truck was attached to a slot in the chassis with a screw and wide washer. As the train rounded a curve, the truck pivot (the screw holding it to the engine) slid from side to side in the slot. The configuration is completely different with the BBT chassis. The truck is mounted to a metal tongue that connects to the chassis a few inches behind the truck. The mounting screw acts as a pivot and the truck at the end of its tongue swings left and right to follow the track. The part of the Bachmann chassis that held the truck was made of plastic and I found this to be one of the weaknesses of the engine. Due to the wear from the truck sliding in the slot and the stress from disassembling the engine several times during painting and installation of the decoder and sound system, the plastic cracked on one of my two Big Haulers around the slot where the truck mounts.

The BBT configuration makes a stronger engine, but it also results in some characteristics which are not altogether desirable. As the engine runs along the track the leading truck appears to be able to swing much wider than before, nearly out from under the engine. So the front of the engine swings very wide in curves. I could be wrong, but I think the original Bachmann configuration caused the front truck to pull the engine tighter into the curves. I watched with some concern as the modified engine took the turn going into my truss bridge. It looked like the front might swing wide enough to hit the side of the bridge, but fortunately it did not. I'd like to compare an original Big Hauler with a BBT-modified Big Hauler on the same track to see if the BBT-modified engine really needs wider clearances in curves as I suspect it does, but I no longer have an original Big Hauler for the comparison.

The new front truck configuration may need somewhat greater clearances in curves, but the truck tracks as well or better than it did on the original. I cannot say the same for the drivers. First, I should note that these are the original Bachmann drivers that were sent to Barry's Big Trains for installation in his chassis. The drivers seemed to move up and down just a bit in the Bachmann chassis, allowing the engine to handle some roughness in the track. The BBT chassis is far more rigid. If the track is a bit uneven in a curve, one of the drivers may lift off and ride over the rail. It looks like it will take a bit more track maintenance to keep the renovated engine on the rails. The rear drivers also want to climb the frogs when taking the curve on Aristocraft switches even when I can detect no uneveness in the track. I haven't figured out a solution to that problem yet.

So my perception is that the BBT-modifed 4-6-0 runs much smoother and stronger than the original, but the front of the engine swings wider in curves and the rigid chassis is less forgiving of unevenness in the track and of tight switches. I must note, though, that these perceptions are not based on a side by side comparison but rather on my recollections of how the original engine performed. We had several heavy rains while I waited to receive my BBT 460 kit. The more frequent derailments could be the result of deterioration of the roadbed caused by these rains.

All things considered, I'm pleased with the BBT 460-modified Big Hauler. After all, the original engine was dead.