Large Scale Central

Bachman 45 Ton surging problem

Problem Solving
#1

One of my two Bachman 45 ton locos has a surging problem that has gotten much worse lately. At first it was noticeable only on steep down-grade runs. It was bad enough to bang the couplers on a 4 car train. Lately it has gotten worse showing up even on level track. Yesterday one of the two trucks repeatedly stalled at slow speeds causing the wheels to skid.

I’m going to open up the truck and take a look for a foreign object in the gear grease, a loose motor mount or broken gear. Anything else I should be looking for?

BTW - This particular 45T has added weight over the problem truck. Most of the weight that came out of my Porter ended up being hot-glued into the rear hood looking for better traction. I wonder if I over did it.

My other 45T runs pretty smooth, even on the down grade with a train.

#2

I should mention that I have hard-wired the motors eliminating the spring contacts, so it shouldn’t be a power issue.

I went to drop the bottom off the offending truck; I forgot they need to be removed from the loco then opened from the top :frowning: I’m really not wanting to tear down the whole loco again.

So inspected through the lube holes and added some grease. Ran it on battery while upside down and it seemed OK. I put it back on the track and so far on level track it is running fine.

Go figure :smiley:

#3

Good to know. I noticed dad’s center cab (which rides on 45-tonner trucks) surging a bit on his 4%+ grades. I thought about adding copious amounts of grease to the gears, but got busy with other things and the thought escaped me. I’ll definitely pass that along to him as a thing to try if it gets obnoxious. Those trucks do run pretty darned smoothly. I’m keeping my eyes out for another pair for a future project.

Later,

K

#4

Kevin - I’m not sure the lube did anything. It was running OK upside down before I added lube.

What I did do before powering it was to remove all 6 screws and lifted the case bottom just enough to disengage the gears. With them disengaged I moved the wheels by hand to feel for any binding and found none. Since I realized the truck needed to be off the loco to open it completely I just closed it back up.

After that I powered it directly from an 11.4V pack and let it run a while. It seemed fine, so I lubed it and put it back on the track.

#5

Jon, what you did was to let the Gremlin out by lifting the case and disengaging the gears. He shouldn’t bother you any more. :stuck_out_tongue:

#6

Sometimes opening it up DOES release the evil spirits. A club member told me his ten wheeler had burned up the motor and it needed to replaced.

I turned it upside down and attached a couple of leads to the pilot truck. It immediately sprang to life, but wouldn’t when i attached the leads to the engine drivers.

I reattached the leads to the pilot truck, then ran a few drops of Dexron III on the rear driver and ran the engine rubbing those wheels with a coarse cloth. After a few minutes, I attached the leads to the track cleaning brush, and that to the drivers I’d put the Dexron III on.

It began to run hesitantly, so I opened the bottom of the engine. I began to run better, and I didn’t smell a burned motor. There was a LOT of white grease in there, and I removed a bunch of it, leaving a thin film on the axles.

Now it runs much better, no smell or smoke. With power at the pilot and the rear wheels, it runs fine. Forward drivers don’t seem to be electrically attached. I thought they were.

Will investigate further!

#7

I know that the Bachmann Davenport has surging problems on a down grade. I was told that Barry, Barry’s Big Trains, was looking into the issue. However, I believe he is not doing any work at this time. Adding large amounts of grease dimishes the surge slightly. The surging has something to do with the worm gear design. Not being an engineer, I cannot say why.

#8

Yes the Davenport problem seems to be the combination of the gear design and excessive end play… I think a possible solution being considered was a double lead worm, but that changes the gear ratio and you would have to make up for that elsewhere.

(Dunno what greasing a 10 wheeler has to do with the Davenport surging problem from last August)

Greg

#9

I have converted a number of 45 tonners to battery power for owners because of surging problems.

What I did notice on all of them before conversion was the spring contacts on the wheel pick ups were very often suffering from a decided lack of spring. Because there are no suitable spares available here in OZ the locos had to be converted.
If you can actually find suitable springs I would try replacing them. Otherwise you might be faced with doing what other owners have had to do.

#10

Tony, you have me confused. The surging I think we’re talking about is caused by the motors and gears, having nothing to do with power pick-up. The 5% grade on my dad’s railroad is notorious for inducing surging on almost anything that rolls down it with more than a few cars behind it. (I’ve often thought of putting a retainer on the caboose wheels to stretch out the train.

Later,

K

#11

Kevin.
In the very first post Jon described the loco as:

“Lately it has gotten worse showing up even on level track. Yesterday one of the two trucks repeatedly stalled at slow speeds causing the wheels to skid”

That sounds like lack of power to me.

#12

Saw that, but he also mentioned the connections are hardwired, so that would (hopefully) eliminate connection problems between the truck and the locomotive. Speaking from my own experience, I hardwired the trucks I used, and have surging problems going down the 5%, though on the level it’s very smooth. Dunno…

Later,

K

#13

Kevin.

You cannot hardwire the springs in the pick ups. It is those springs that fail regularly.

Granted that hardwiring should mean that just one truck will power the other. But not always.

If the motor blocks have single start worms they will surge down grade. Twin start worms fix that but halve the gear ratio doubling the track speed. Ala the problem with the K-27 which goes too fast at a given voltage, lugs down upgrade and will runaway down hill.

#14

Tony Walsham said:

Kevin.
In the very first post Jon described the loco as:

“Lately it has gotten worse showing up even on level track. Yesterday one of the two trucks repeatedly stalled at slow speeds causing the wheels to skid”

That sounds like lack of power to me.

This is a battery R/C powered loco with hard wired trucks/motors. The problem truck likely has some kind of a drag issue that causes it to stop moving before the other one. I still have the pick-up springs in place because I kept the track-power option with a DPDT switch. Could theses springs be giving me trouble too?

I really think the issue is more likely the worm gear. I just wonder why one suffers more than the other.

#15

OK Jon. My mistake.

The DPDT switch would isolate the track pick ups and would affect both trucks if that was part of the problem.

Sounds like a dud motor to me.

#16

Yup, possibly. I added a lot of weight to the end that stalls, that might be part of the problem.

In any case, this is an old thread from last August that somehow came back to life. This issue has moved way to the back burner for now.

#17

Tony, getting back to the Davenport for just a moment. I had converted the one I had to battery power. I removed the wheel contacts and hardwired the motor to the battery system. No difference in the surging.

By the way, the wiring used by bachmann in the Davenport is about the lightest gauge I have ever run across. I think they may have had some left over wires from their N gauge line.

#18

Ran into this problem personally about 12 years ago. Found the problem to be the single thread worm I was using. Changed to a double thread worm with a countershaft to regain the correct gear ratio and the surging was gone - forever.

I happen to have a 45 tonner truck torn down and can confirm that the worm in that gear box is a single thread worm, without rebuilding the box the best you can do is keep it well lubed.

I have a couple of the Davenports and like them very much, but only run them on level track.

What is said here makes me think the same problem exists in it.

The single thread worm and worm gear have a gear ratio determined by the number of teeth in the worm gear, i.e., 30 teeth equals 30:1. A double thread is similar, but half the number of teeth indicates the gear ratio, i.e., 15:1. That is not a good ration for what we do, so I add a 16 tooth gear on the same shaft as the worm gear and from that gear drive the 30 tooth axle gear at about 29 to one. Now it works perfectly without surging. It is what I do today in every gear train I build.

Barry

#19

Interesting information Bary. Thanks!

If I am understanding the mechanics here, the single thread worm introduces some gear lash. When going down hill, the weight of the cars push against the gear lash; then the worm catches up and cycle repeats. Am I close ?

My Shay doesn’t seem to suffer from this problem, or if it does it’s not noticeable. Could be because there are more gears in the train ?

Keven mention adding drag at the end of the train to keep the loco working. I tried this using my hand on the caboose and it does work. Now all I need is a working set of brakes complete with brake wheel on my caboose and problem is solved :]

#20

The Shay doesn’t have a double thread worm, but I think the slow speed and High motor RPM of the Shay helps prevent the surging becoming an issue. Also the shay would have to be on a steep down hill with a heavy train being pulled (pushing behind).

I think Keven’s suggestion might work (adding drag at the end of the train) but I don’t know how we could control it. Squeeze the freight wheels?

Barry