WBB Berkshire - Stripped Motor Mounting Screw

I takes it you have concluded that it is the die casting, not the screw that is stripped.  First thing would be to identify the screw, diameter and pitch, then you can determine your options.  Best possible solution would be a Helicoil. If the loco is new, maybe the maker would cover it up under warrantee. Zinc can be diffcult to tap, if you go that route, you might want to get some help.  It might be that a new screw of the same size will hold.  Some times you can get a screw of the same pitch,but larger diameter.  You could check into the Locktite products that are available and see if something like 242 would work.  Good luck.

Thanks David!  Yeah, trying a new screw first probably makes the most sense.  I think I was kinda dismissing that option given how hard it might be to find one at the local ACE hardware...it's so small, I have to wear my cheaters just to take the screws out and put them back.

Looking at the parts list though, Bachmann does have the part number, but does not have the size or thread pitch listed for 1-26080DPM unless it's imbedded in that part no.

It is a new engine, so maybe I can get them to waive the $5.00 minimum shipping charge for the $.50 pair of screws, and try that first.

Robert

But that's a good question about what material the threads are tapped into...I'm assuming it's die cast, but thought some of the engine chassis were still stamped steel

I just checked mine. The screw is a 3mm x .5 x 12mm. If the thread was coarser I would fill the hole with JB Weld, coat the screw with silicone and screw it in. Given the thread is so fine this is unlikely to work. You could either drill and tap it for a 4mm screw (or 3.5mm if you can find screws and a tap). Or, what I would do, counter bore the hole from the bottom to accept a 3mm nut. That would be the cheapest fix but require care in drilling making sure the body is well clamped in a vise using a drill press. The nut has to be recessed or it will hit the trailing truck.

Pete

JB Weld is good....as is a automotive thread restore that is strong enough to take 20 pounds of re-torque , plenty for a model train motor.

Thanks for the ideas Pete and Dave!  I've seen the thread repair stuff, it sounds similar to what Pete was describing epoxy/jbweld to restore the threads and a release agent applied to the screw to prevent bonding.

I've never tried anything like that on something this small, but it's probably worth a shot especially if I can attempt it with a new screw.  I know I need some glasses, but I can't even fathom a helicoil on this scale.

Pete, many, many thanks for the screw size!  That's a huge help to know where I'm starting.  Figure I might try to chase the threads with the correct tap as currently sized, follow up with a thread repair if necessary or for insurance...and if all else fails try something more permanent like tapping for the next size up screw.  Your idea about recessing a nut to grab from the bottom gave me the thought that maybe I could convert the screw to a stud...maybe.  Just not sure what thickness or type of material the screw threads into currently (die cast, steel, etc).

Thanks again,

Robert

Robert, the frame is diecast. If you plan to chase threads you will obviously have the tap. In that case if chasing doesn't help you could simply fill the hole with JB Weld ( forget generic epoxy) and then drill and tap the threads. I have tried Loctite's thread repair compound without much luck. JB Weld is much stronger. Maybe Loctite has a newer product that works better than the stuff I tried though. The stud trick should work as well also as there is room above the motor mount for a nut. 

Pete

Possibly the following thread has some similarities !

https://ogrforum.com/t...80#17479526133573080

Thanks for confirming that Pete!  That does make me a little more concerned that the die cast would damage before the screw threads.  I'm guessing the die cast is softer  , but I will try a replacement screw first...crossing my fingers. 

If not, I hope to find the right size tap, and the fill & drill does sound like a more straight forward approach.  Hopefully the tap could grab a 'good' portion of original threads, and the JB weld left behind will fill in the bad spot.

Thanks for the reply TGP.  Glad to hear Bachmann service took care of you.  I'm guessing the motor retaining screw on those GP-30's is like the other diesels (motor is vertical and screw threads into motor shaft).  That's how my F7 & FA-1 are.

On this steam loco these two screws don't seem to keep the motor in place as much as they cover the gear box.  I could be wrong, but it seems like the motor is held in place by the angle it sits at along with the mesh/cut of the axle gear...I am speculating.

If this were a stripped motor mount screw on a diesel I would probably just send it back to WBB (guessing they would just change out the motor).  I'm hoping to avoid sending it back, but it does make me wonder if they would just replace the whole engine in this case or just the chassis frame.  I can't imagine they would spend the time to repair the threads.

Robert

If it is a new or relatively new loco, particularly if it is under warranty, send it back.  Why play with it just to save a few weeks of downtime?  It's good to be handy and creative, but that should be a fallback when there aren't better options.  Here there clearly is, in terms of rectifying the problem and making sure that the locomotive is useful for the long-term.

RL NYC, you might be psychic!

Worsening development...

After running for about 10 minutes, the engine starts coming to a halt...practically a dead stop, and won't respond to more power from the throttle (just hums loudly).

I assumed initially it might be the z750, being a 75w transformer, was a bit under powered, but when I remove the engine from the track and turn the flywheel by hand it is noticeably stiff, difficult to turn.

I cannot feel any clicking, clunking or grinding like you would expect from debris or damage to the gears.  I also could not see any binding in the side rods.

My guess is the stripped screw is loose or coming loose after running a brief period, allowing the motor to move some amount causing binding in the gears.  Carefully turning the flywheel back and forth it will loosen up again.  So it appears the "gear box cover" (as wbb refers to it in one part of the manual), does have something to do with keeping the motor seated and the gears properly meshed.

Long story shorter (again), this may need to go back to Bachmann after all since it is a new engine, and I've had it less than a week at this point.  At any rate I'm not as concerned about being without the engine for a period of time (although I have enjoyed running it), I'm more concerned about them fixing it correctly for the long run...at this point that may be better left to the professionals.

Thanks,

Robert

Just wanted to update this regarding the 'dead stop development'.  The engine did this another time or two after I last posted, and I was preparing to just send it back; then it spit a traction tire loose.

It didn't damage the tire that I could tell, so I put it back in place, checking closely to see it was seated in the groove properly.  I expected it might come right back off from stretching or the engine locking up, but I have run it several times since and it's running fine...no more lock up.

It even seems a bit smoother, which makes me wonder if the tire was mounted right in the first place.

So I guess I'm back to just having the stripped motor mount screw, but even that seems okay at the moment.  The Teflon tape on the threads must be keeping it in place at least.  I've flipped the engine over a couple times to see if the screw backed out, but so far so good.  I think I might put the ball in Bachmann's court and see what they suggest...see if they want to send me a replacement screw, or if they want me to send the engine in for repair.

I know I probably should just jump at the option of warranty coverage, but I guess I'm hoping for an easy fix (like a replacement screw).  I also can't help but be aware of the potential for more damage during roundtrip shipping plus the cost (at the $191 all in price I paid, that can easily increase 10%), and time involved.  Maybe I'm waiting or wanting a more cataclysmic failure  ...I know, careful what you wish for, and I admit my indecision here seems down right silly.

Sorry for another long post, but thanks!

Robert

A new screw wont help if the female threads are wasted. But while under warranty, Bachmann has sent me small low buck items to me on occasion free of charges to see if we could skip the shipping. Bachmann's service impressed me, e-mail them, they often respond very quickly. Calls can be made too, but the email response time was great (48hr longest wait) and the stuff was in the snail mail on its way here a day before they e-mailed back. I was down a full 5 days, how awful. If you send it out let us know if they repair it. My guess is they send you a new one. Maybe right away too. A few months is the norm on an actual repair but warranties often seem to be handled much sooner. 

Thanks for the suggestion Adriatic!  I'm still hoping a new screw will fix it, providing the female threads are not shot.  If I can't reach them by phone tomorrow, then I'll drop them an email as you suggest.

Main aversion to sending the whole thing back is still just anxiety over a proper long term fix.  If a replacement of the engine was definite possibility, then it would be a no brainer, but this engine was not in the 2013 line-up.  Bachmann doesn't list a chassis available for this engine, yet I have heard they re-purpose parts from other returns.  I'm fairly mechanically inclined, so thinking I may be able to provide as good a fix as Bachmann can offer...maybe. 

Additionally, I found a couple threads that were not reassuring.  One where the buyer sent the engine back to Bachmann only for them to send it right back to them saying they couldn't fix it.  Then there was another where someone had a very similar issue, and Bachmann apparently replaced two stripped screws with larger ones and cracked the casting   That owner went back and forth with WBB for weeks.

Hopefully those were exceptions and not the rule.  At least for the moment the screw with Teflon tape seems to be holding, and in the meantime I found the source of the "dead stop" or lock-up.  The engine eventually threw it's traction tires (could be due to over lubricating on my part).  Initially they were binding against the un-flanged wheels in the driver set as they were 'buckling' or becoming unseated from their grooves, causing the engine to slow down dramatically or just come to a dead stop at points.

Thanks,

Robert

Why not let WBB worry about making it right?  Do you really think they have no way of fixing or replacing that part?  Moreover, your original post was over a week ago.  Had you just shipped it, the loco would be back with them already.  They are not going to do anything without your permission . . . .

As a car guy, I am very familiar with JB Weld.  It is a great product, but it is largely a "kludge" fix.  No need for that here, and teflon tape is not a permanent fix for bad threads, it is also basically a patch repair.  If it were an older loco, I would get it but not here.

Sometimes a longer screw can be used to get past the bad threads in the diecast part. It might be necessary to drill and tap the hole a bit deeper.

Otherwise: according to a conversion program I found on the web, your 3 mm screw should be .125 inches in diameter. You could use an SAE #6 machine screw, which is .138 inches in diameter. These screws are available in many hardware stores as self threading . You would need to enlarge the hole, but could skip the tapping.

Self threading screws are not the same as self-tapping (sheet metal) screws. They will create a standard machine thread.

why  not just  return the engine under warranty?

quote:

why  not just  return the engine under warranty?

Earlier in the thread, the idea was discussed, and the owner wrote that he didn't want to go that route.

If that engine is not repairable and not replaceable, an upgraded alternate just might be offered. Actually I think I've read of an incident like that before, but I cant remember the source, or if the offer was accepted. I think the guy wanted a cash refund but the store refused because of time gone to manufacturer, and the manufacturer would replace it with an alternate +upgrade, but would not refund the cash.  Moral? If its brand new, the place of purchase is the best place to get your satisfaction. Warranties are for when those purchase liabilities expire. Legally, its the way to go to cover your butt 100%. Even the best customer service fails on occasion.

 If you do the repair yourself, the length is a great thing to consider. A longer screw alone may find some clean threads. Going for a new oversized screw would be my choice if there is room. If T.Tape is holding it the JB would likely need the hole enlarged to work best anyhow. Bearing retainer? Maybe, but I would likely try the tap first, JB if I failed that. Its plenty strong for that. For some I prefer to use coarse thread stainless screws coated in release agent embedded into curing but wet JB weld, other really small stuff I tap.