Split gears, a never ending story

To close this chapter of the never ending story, I finally succeeded in taking apart the power truck (thanks to the advice of Frank/zstripe). I thoroughly cleaned all the gears and wirth a magnifying inspected them for every possible flaw. Found none. Put the truck together and tested the doodlebug. Same thumping noise as before. So maybe it is a characteristic of the bug and I shall have to live with it. I think I’ll call it the galloping bug since the noise reminds me of a galloping horse.

Hans

They don’t have traction tires on a Doodlebug…

Cheers,

Frank

I went to the HO Seeker website and found this instruction sheet & diagram

http://www.hoseeker.net/assemblyexplosionbachmann/bachmanemcgaselectricdoodlebugpg1.jpg

http://www.hoseeker.net/assemblyexplosionbachmann/bachmanemcgaselectricdoodlebugpg2.jpg

After looking this over, consider holding the unpowered truck on the track for power and the powered truck up off of the rails to see if it makes a noise and if the noise changes as you rotate/move the powered truck. If there is a change, then you may have interference elsewhere such as in the driveline.

Finding the source of the thump is just a matter of trial &error/elimination.

Richard

The easiest way I’ve found to find a bad gear is to turn the locomotive on its back and run it at about 10 volts. Feel each wheel lightly with your fingertip. The bad gear will thump badly while the others run much smoother.

When examining those gears, did you check them w/ the axles installed? A few of the cracked P2Ks showed nothing even under close inspection, however, when flexing the axle shafts the hairline crack became evident. You still could have a gear issue, If doesn’t need much especially under load to affect the mesh and cause the gear thump. Easiest sign of a proble is as Jeff noted, that the axle will spin within the gear.

I had a Doodlebug with the thumping cracked gear syndrome and called Bachmann to find out about replacement gears/axles. They don’t stock them nor the truck assembly. He told me to check Ebay for used/parts models that could be used as a ‘donor’ for mine. I was also informed that they are not the same gear as on the FA, GP, and SD models, so the Athearn ones wouldn’t work either. Then I put my thumping doodlebug on Ebay and sold it with the explanation that it had cracked/thumping gears. I then bought a new one and it is as smooth as all my other Spectrum and P2K locos.

-Bob

Split & cracked gears are a huge problem in Bachmann’s On30 line. The message boards have been full of complaints for years. Bachmann refuses to even acknowledge the problem much to the frustration of us all.

My Bachmann Doodlebug has been sidetracked because of this cracked gear problem for several months. The Bachmann website lists a replacement power truck, but it has been out of stock for several months. Wheel sets are not available either. The company deserves a poor grade for product support in my opinion.

NWSL sells gears, and I might be able to get suitable replacement gears from them. However, they are selling a good quality replacement drive for the doodlebug. I have decided to order it although it is a bit expensive. I plan to install it in the next few weeks.

It’s just so astonishing to me that a company so large as Bachmann has just disregarded this KNOWN problem for literally years!!! Complaints number in the many many hundreds if not thousands. Still…there’s been no attempt to satisfy the consumer with more robust engineering. I find it incredible.

how long has this been going on? a couple of decades at least, right? at the risk of sounding like a ranting radical, i just accept the fact that most manufacturers have one primary goal. separating you from your money.

at least these are not critical things we need in our everyday lives but they sure do spoil the fun for some of us

. oh well, some automobile companies made a living selling junk for years. now i will duck my head down and see what you guys think.

Charlie

The P2K gear problem goes back to the early 1990’s so it is about 20 years ago that the units have experienced this problem. It started to show up a few years after the product was on the market. I recently decided to dig out a PA-1 Union Pacific unit to check it out after twenty years in the box new. Guess what?? The lights are working fine but no movement now what so ever. This unit had never been run but the gears just broke away from the axles. I had replaced a bunch of those on Geeps but did not realize the PA’s had the same problem. They are hard to fix, but this should have never happened. The P2K model line was purchased by Walthers and they will not fix them.

CZ

As far as the P2K gear problem, keep in mind that most of the diesels affected were produced in the 90s. After acquiring Life Like, Walthers offered complete assemblies with wheels, bearings and axles free of charge. Many of these engines are still new, never sold. The gears split while the units sat on the shelf. One upside, secondary sellers that aren’t modelers don’t know how easy they are to fix and will sell them cheap. For a few dollars and a few minutes time anyone that knows which end of a screw driver to hold can get a bargain.

In one of the umpteen other threads on this topic, someone made a reference to the fact that the problem was due to the fact that uncured teflon (if that’s what the gears are made of) was used during the manufacture of the gears. Over time, after the gears were machined/installed, the material “cured” which caused it to shrink. This resulted in a tightening of the bore around the shaft, and led to the cracking.

Concerning the issue that some are finding the gears cracked after years of the models sitting on a shelf, while I’m somewhat sympathetic because I have some models on the same shelf, I think that it is ridiculous for folks to expect the manufacturers to have an “evergreen” warranty that will rectify a consumer’s complaint 10 or 15 years after the fact.

I doubt “uncured” Teflon is the problem. Teflon is pretty stable, IMHO, which leads to a story.

While in high School I worked at a company that made Teflon high pressure oil seals. They extruded a tube of Teflon and then used a lathe to machine off each ring. One of the slide rule engineers showed me what happened when they cut one ring, and tied it in knots and heated back to the same temperature as when extruded. Before our very eyes the oil ring untied itself and went back to it’s original shape. When it cooled it was back in the tolerance required for it to pass inspection, except the cut did not “Heal” itself.

Dick Haave

It was my understanding that the “uncured” teflon would shrink, causing the gear to tighten on the gearshaft. Here is a link to a discussion that discusses this: http://railroadfan.com/phpbb/viewtopic.php?f=16&t=22346. I believe that the second poster, fmilhaupt, is a memeber of this forum. Maybe he can chime in and tell us how he arrived at the shrinking bore size idea.

Look at the sleeve part of the gear that the axel pushes into. If it has a line on it, that is the crack.

Getting anything out of Northwest Shortline is like pulling teeth…Since January I have been waiting for replacement gears for the Walthers doodlebug…I might cancel the order and do something else.

Just to put matters right, my doodlebug doesn’t have the Athearn type axle gears. It has a white plastic (probably delrin) gearwheel on a metal axle.These gearwheels are flawless as far as I could see with a magnifying glass. The thumping noise must therefore originate in one of the gears inside the powertruck, a broken tooth maybe. Anyway I didn’t have the guts to pry the gearhousing open and look for the flaw fearing that I couldn’t put it together again correctly.

Hans

Just give them time. NWSL is less than half a dozen people, and they have over 2,000 different products they manufacture themselves. I was recently asking Dave about progress on the development of the new Flea drive units and other products, and things are slow right now for reasons beyond their control. The old aluminum molds for many of their plastic parts are wearing out beyond use, and funds to repair or replace them are very tight. They’re doing what they can, but the wait on some of their stuff is very long. I’m also waiting for some 42" wheels and steel worms, but I’m sure they’ll have them done and sent out eventually.

When they tell me that it will be 3 to 4 weeks for the gears I was fine with that…

…but when it becomes 3 to 4 months…I kind of have a problem with that.