Is it possible to fix a cracked gear?

[mecgp7]

Just wondering if it is possible to fix a cracked axle gear? I have a brand new Doodlebug with one. Manufacturer not to receptive and claims that I will need to replace the whole truck. I was instructed to purchase one from their parts dept. I reminded them of the "lifetime warranty" and that is was a defect and not damage. They are now requiring proof of purchase which I'm not sure I have anymore. Not sure why they need it given the warranty.

So, can it be fixed or is there another source for replacement gears?

[mmagliaro]

In general, no, it's not possible.  Depending on just where and how it's cracked, you can sometimes pull
the axles out (if it's an plastic tube with the gear molded on to it), then press a little piece of brass tubing over
the cracked plastic tube, like a collar, to close the crack and hold it.  Or wrap a piece of wire around it and twist,
like a cheapie hose clamp.
But if the gear itself is cracked, it's darn impossible to close that crack so the teeth will really run past that spot
smoothly.
If you can show some super close-up photos, count how many teeth, somebody on here (myself included) might be able to spy a suitable replacement.  Kato and Atlas both sets geared axle wheelsets and maybe one of those has the right
type of center tube/axle to fit your case.  Need photos and measurements, though.

[narrowminded]

How much is the truck?  Or can you get just the axle with gear? 

I'm going to say that they can't be fixed.  The problem starts with either a bad material, bad processing (mold heat, etc), or a bad fit that overstressed the part.  Whichever of those it was, it doesn't really matter at this point because the crack showed up where it did but the part is flawed at a fundamental level.  So even if you could effect a repair to the immediate crack and as strong or stronger than the original part (which might be a first in all of repairland), the problem will just surface again elsewhere.  It's a shame and as one who knows at least a little about these processes, failures of this type and with the decades of history with this same problem, I find it's beyond inexcusable.  But I wasn't invited to any of those meetings so...

[rrjim1]

Yes,   you can. I have done this before a couple times and it works pretty well. I have a big advantage as I own a lathe/milling machine. You need something to go over the gear to keep it together. Then drill the gear out so it just fits over the shaft. Use Loctite retaining compound 680 to glue the gear to the shaft. Make sure you have it in the correct place as you won't be able to move it after the 680 sets up.     

[mecgp7]

The whole truck is $15.00 plus shipping so over $20.00. A big steep for a gear and, as others have said, it will most likely happen again. I will tinker trying to fix it and with replacing it with spare gears. I may be able to simply drop in a geared axle and wheels. I also thought about removing the teeth from the gear and making the a loco two wheel drive with the good axle driving the wheels with the traction tires. The rear truck is not geared. It's not like a doodlebug really pulls anything.

[JMaurer1]

Even if you can, it most likely will eventually fail again. The 'slippery plastic' they use for gears doesn't play well with most adhesives and eventually the crack will win. Odds are better on a Doodlebug since it won't be pulling long trains, but eventually it will fail again. If only you had a computer that you could use to create a receipt and print it out... Just scan a full page receipt from...anyone and 'update' the info on it and send it all in to them. It's easy to say 'buy the part' when the engine is still sitting on your table and not theirs. 

[Big Train]

As stated elsewhere here...you can, but don't be disappointed if it splits again. I have ACC'ed the split then slightly reamed the centre bore of the gear to prevent splitting again when sliding on the axle then ACC'ed the gear to the axle as a fix. But the stresses applied during operation caused it to fail again. If done carefully, the gears will mesh fine, but if not careful, you're no better off.

There needs to be a special place in hell for the people that continue to use this same technique, with the same material to result in the same failure over and over. Especially if replacements aren't easily available and the manufacturers are aware of this kind of failure. Maybe 3D printing will supply a reasonable solution, if not now, than in the foreseeable future the way this technology is developing.

Hop this helps.

[C855B]

The whole truck is $15.00 plus shipping so over $20.00. ...

I realize you're feeling cheated, but count your blessings that they're making a spare [something] available at all. B'mann isn't exactly reknown for their parts support.

This is the current Doodlebug? And it isn't new-to-you old stock? Two things I find odd... first, that we are discussing "Lifetime Warranty". AFAIK, Bachmann dropped this marketing program several years ago. Second thing is more of a disappointment, if this is current production... cracked tube-axle gears were notorious in B'mann product in the '80s and '90s. They could simply sit in the box unused (new old stock, again), and the gears would spontaneously crack. Later production I'm familiar with did not have the tube axles, but if they returned to this design, then frankly they're asking for it.

[rrjim1]

As stated elsewhere here...you can, but don't be disappointed if it splits again. I have ACC'ed the split then slightly reamed the centre bore of the gear to prevent splitting again when sliding on the axle then ACC'ed the gear to the axle as a fix. But the stresses applied during operation caused it to fail again. If done carefully, the gears will mesh fine, but if not careful, you're no better off.

There needs to be a special place in hell for the people that continue to use this same technique, with the same material to result in the same failure over and over. Especially if replacements aren't easily available and the manufacturers are aware of this kind of failure. Maybe 3D printing will supply a reasonable solution, if not now, than in the foreseeable future the way this technology is developing.

Hop this helps.

Your right ACC doesn't work very well, the 680 is not a super glue, it is a retaining compound. I have done this to gears and joints 15-20 years ago and they are still holding today.   

[randgust]

I guess it also depends on how much of a 'first line' piece of equipment it is.   I've got one and it's a novelty and shelf queen.  It's also incredibly noisy and the performance really isn't very good.  Like all other Bachmann first-runs, they've probably fixed it, but mine is kind of a POS.  Mine is most certainly the first run - see http://www.spookshow.net/loco/doodbug.html 

I've had the power truck out in mine and studied it for other critter applications and decided it was designed so oddly and poorly it wasn't worth it.  Nothing else like that was available when it came out.   Now, there's a whole series of Tomytec chassis out there in various types and lengths for Japanese MU cars that I seriously think I'd consider repowering the shell with one of those.   They are designed well, end-axle pickups for most of them, have a couple different wheelbases, removable truck sideframes, motors with flywheels, and 8-wheel or 4-wheel drive.    Search the Plaza Japan store and you can order them there.  They have plastic frames so chopping them up and modifying them is pretty easy.    Pretty much all of them are under $30.

Just mentioned it because every other solution still leaves you with a piece of equipment that was marginal as originally designed.   If I had one of these as a regularly-operated piece of equipment I'd change it all out.

[SkipGear]

If it has a cracked gear, and advertises "lifetime warranty" then it has to be from the original run 15+ years ago. The other indicator would be if the gear is white.

As mentioned above, just be happy you can get parts for it. If it wasn't for a recent re-run of the Doodles you would be out of luck. The new power truck is interchangeable with the old one but is improved in design and materials. Just bite the bullet and order the new power truck.

Even with the limited lifetime warranty, after one year on N scale spectrum items it still required a $20 fee and they would swap you for a new one. Free replacement only happened within the first year with a valid receipt. No receipt or proof of purchase and it defaulted to the $20 fee.

[mecgp7]

If it has a cracked gear, and advertises "lifetime warranty" then it has to be from the original run 15+ years ago. The other indicator would be if the gear is white.

As mentioned above, just be happy you can get parts for it. If it wasn't for a recent re-run of the Doodles you would be out of luck. The new power truck is interchangeable with the old one but is improved in design and materials. Just bite the bullet and order the new power truck.

Even with the limited lifetime warranty, after one year on N scale spectrum items it still required a $20 fee and they would swap you for a new one. Free replacement only happened within the first year with a valid receipt. No receipt or proof of purchase and it defaulted to the $20 fee.

Yep, white gear. If the new truck is improved, I may just bite the bullet. I got a great deal on it to begin with so it won't hurt too bad to go that route.

[brokemoto]

Yep, white gear.

Check your PM.