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Bachmann Spectrum Shay NWSL gear replacement issues

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Bachmann Spectrum Shay NWSL gear replacement issues
Posted by Lastspikemike on Sunday, February 21, 2021 9:41 AM

This ambitious production by Bachmann is well worth acquiring if you like these weird geared locomotives. Unfortunately, the driven gears on the driveshafts were incorrectly manufactured and they split. Unlike the Proto diesels, replacing these driven gears is very difficult. The truck assembly does not come apart as easily as it needs to.  Originally, Bachmann supplied complete drive assemblies that replaced the driver side of the trucks. Those are of course NLA.

 

http://gearedsteam.blogspot.com/2012/06/repairing-bachmann-shay-line-shaft.html

 

In the case of gear splitting on the Spectrum Shay you get no symptoms until the traction from trucks with functioning gears is insufficient. There is no differential gear action, the drivers are all linked to the one worm gear.

Usually, the split causes the gear to lose grip on the axle. Turning the locomotive upside down you will be able to move the driven wheels that have the split axle with just your finger. Certainly for the Shay you can do this. 

 You can also test with one of those brass wire power units applied to the drive wheels when upside down (or just wires if you don't want to clean the wheels). The wire brush should develop enough resistance to stall the slipping axle.

Just a note on the NWSL gear kit for the Shay:

The replacement gears are beautifully cast and, I suspect, a perfect copy of the original plastic gears, too perfect maybe.

NWSL instructions are not easy (probably impossible) to follow with any chance of success. The interference fit of the metal gears is far too tight to get the new gears on using needle nosed pliers. By now the plastic bits used to clip the drive shafts to the trucks are so old they have little to no flexibility and are secured by tiny plastic moulded in projecting pins less than 3/64" in diameter that actually hold on the driveshafts. These old plastic bits are in the way and cannot withstand much force. Not a design to emulate in future. The truck frames are metal.

NWSL method involves pressing the gears onto the drive shaft using needle nose pliers against what they say is not plastic (but half of it is) and forcing the new gear against the driven crown gear on the wheel, which is plastic. Not a good method.

I ran into trouble also when trying another method shown on a very complete video of the process involving prying out aforesaid plastic clips and using a gear press fabricated for purpose into a modelling vice (a very good quality vice, btw). The presenter used brass tubing as a sleeve over the shaft to press the two gears into position. I managed to bend the 3/64" shaft, twice....

 

https://m.youtube.com/watch?v=mspLRpXIlYI

 

Not an easy task imho.

Also, imho the interference fit of the NWSL gears is far tighter than required. Metal gears will grip those driveshafts adequately with a much less tight clearance. My guess is NWSL cast these gears from a plastic original. Plastic stretches much more easily than metal, which is of course why they split in the first place.  My plan is to ream out the center hole just a tiny amount, assuming my LHS can't press on the gears with a proper gear press. 

Alyth Yard

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Posted by Lastspikemike on Saturday, March 13, 2021 8:57 AM

"The Guy" at my LHS pressed the two gears onto the front truck driveshaft for me. 

While following NWSL printed instructions (do NOT do it their way, it cannot possibly work as described) I broke off the vital driveshaft retaining clip which is plastic and a press fit into two +/- 1mm blind holes in the otherwise lovely brass cast truck frame. 

Two different videos explain that you should VERY carefully pry up and remove these two plastic retaining pieces, remove the driveshaft, press on the new gears and then pin the driveshaft back by VERY carefully pressing these plastic retaining pieces back onto the truck frame. 

The plastic retainers each have two plastic projecting pins. These are what snap off if you try the NWSL installation method. I now need to recreate these securing pins on one of the two retainers in order to press on the one plastic retainer and refit the truck. The other retainer remained in place. It is possible to just remove the one front retainer and still get the two gears on and refit the driveshaft into the second retainer before pressing the first retainer back on. Mind you I did not see how The Guy actually did that. 

Solutions please? 

Any and all ideas and comments welcome no matter how outlandish they may seem to you.

My current plan is to buy Kadee #1059 tap and drill set for 00-90 threads. This is 1.1mm. The blind holes are just a nano tighter than 3/64" which is pretty close to 00-90. If I tap those holes the Woodland Scenics' tiny screws would thread in. I'd cut those off leaving two mounting studs. I'd then drill tiny holes in the plastic retainer. I'd thread those holes and gently press fit those threaded holes onto the threaded "studs" I created in the truck frame.

A touch of J B Weld into the plastic holes should key to the stud threads and to the threads in the plastic by enough to hold it all together. I'd oil the driveshaft where it passes through in order that no J B Weld could epoxy the driveshaft stuck.

Anyone see any pitfalls there? Not feasible? 

Another way to proceed?

Alyth Yard

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Posted by Overmod on Saturday, March 13, 2021 12:19 PM

You'd accomplish much the same thing without the risk of breaking tiny taps by drilling the 'matching' holes in the retainer, putting small circumferential grooves in a piece of plain wire or stock (36-grit paper might give adequate 'tooth') and then cut to "stud" length with the touch of adhesive.

I confess I can't think of a better way to mechanically key the holes you're drilling in the retainer than to tap them, and if the retainer is a low-surface-activity plastic like acetal your successful adhesive bond may depend on mechanical keying.  There are very good etchants and  surface adhesion promoters for Delrin but I suspect actually getting them, even in the tiny quantity necessary, might not be worth it.  I'd just thread a slightly oversized screw into the drilled hole in the plastic, hold a hot soldering iron on the screw head for a few moments, then thread it out again.

Have you considered using a cheap and less effective 'glue' that will hold resiliently but let go without damage if you need to go in and do something later?  I'd use one of the 'glorified rubber cements' for that purpose...

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Posted by Lastspikemike on Sunday, March 14, 2021 9:33 AM

I had thought about possible future access but my conclusion was that if those metal NWSL gears ever needed replacing ......

So, some sort of threaded or ringed metal stud* and JB Weld it is.

* I am familiar with boat nails and I used very expensive silicon bronze ring nails actually still made in the USA by Swan to fasten my vertical T&G red cedar siding to my house. Why? Silicon bronze does not corrode (the exposed nail heads just go greenish black and remain that way indefinitely)  nor react with the cedar so there are no fastener stains. For the same reason I used even more expensive Swan stainless steel screws around the sealed unit window areas to prevent hammering vibrations from damaging the seals.  Also, ring nails aren't coming out whereas stainless screws can be easily removed and reused if windows have to be replaced for any reason. My little tract bungalow has 7" thick walls after I retrofit 2" extruded styrofoam under 1" (nominal) solid cedar planking. Nice and warm and sound resistant. 

Alyth Yard

Canada

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Posted by snjroy on Sunday, March 14, 2021 11:10 AM

Overmod

You'd accomplish much the same thing without the risk of breaking tiny taps by drilling the 'matching' holes in the retainer, putting small circumferential grooves in a piece of plain wire or stock (36-grit paper might give adequate 'tooth') and then cut to "stud" length with the touch of adhesive.

I confess I can't think of a better way to mechanically key the holes you're drilling in the retainer than to tap them, and if the retainer is a low-surface-activity plastic like acetal your successful adhesive bond may depend on mechanical keying.  There are very good etchants and  surface adhesion promoters for Delrin but I suspect actually getting them, even in the tiny quantity necessary, might not be worth it.  I'd just thread a slightly oversized screw into the drilled hole in the plastic, hold a hot soldering iron on the screw head for a few moments, then thread it out again.

Have you considered using a cheap and less effective 'glue' that will hold resiliently but let go without damage if you need to go in and do something later?  I'd use one of the 'glorified rubber cements' for that purpose...

 

For Delrin, I like using 5 minute epoxy. It's solid enough for our purposes, and parts can be twisted off if you need to re-do something. 

I do sympathize. My Bachmann Climax B broke after less than one hour of operation (over a long period - I don't run these engines that long on my pike). I bought the NWSL gears, but have not been successful installing them after two tries. I still have the parts. I'm hoping that the next attempt will be the right one.

Simon

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Posted by Lastspikemike on Sunday, March 14, 2021 1:47 PM

https://m.youtube.com/watch?v=mspLRpXIlYI&ebc=ANyPxKrkldP_CjgXTrfMKGELFOaCvNdTDx1E_xsyjI1t5kxI1LNIAExOk-uUBEs-9lWl84c5nDtvaFgLxiljOfWJp02maOy0-Q&feature=emb_title

 

https://m.youtube.com/watch?v=8l6kLkCEnUo

 

I found the two methods of pressing or tapping gears onto shafts useful although neither method worked for me. I lack the tools and the skills. My Guy at my LHS said it took him only a few minutes. !!!!!!

The key is to press the gear onto the shaft with NO bending force acting on the shaft. It's mild steel and bends easily at 3/64 diameter. Those knurled sections intended to hold the gear in place are serious overkill but that's the main issue. As for Churchill's description of golf... a small ball into an even smaller hole...

Alyth Yard

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Posted by Lastspikemike on Monday, March 15, 2021 7:41 PM

Well that was interesting. Despite (because of?) the two espresso doppio I consumed after lunch I decided to tackle drilling and tapping the truck frame and retainer cap, one brass the other plastic (probably delrin as it seems to be very tough). 

The existing holes in the brass frame are just slightly oversize the tap drill so all I needed to do was tap the holes. Then ran in Woodland 00-90 brass screws to clean up the tapped threads. So far so good.

Then the plastic.  Man that is a tiny bit of plastic. The cast on pins snapped off clean. I was able to find the centres of each pin fairly easily but unfortunately not precisely enough. I drilled and tapped the pin locations for a threaded fastener. There's only about a mm of depth available. I had to drill right through. The lower hole is ever so slightly off line relative to the upper hole. Drat.  

However, the one upper hole lines up perfectly and one screw holds the retaining cap precisely in place. The other screw hole is a nanometer off and will not thread. 

Here's my current thinking. J B Weld is going to be pretty strong in this application. I have in mind to "cast in place" threaded "rods" of pure JB Weld by filling the now threaded holes in the truck frames and plastic retainers with the JB Weld instead of relying on any mechanical fastener at all.  The key aspect is the one screw will hold the plastic retainer precisely in place until the other hole is filled and has fully set. Then I can withdraw that screw and fill that hole. Because the faces of the plastic and brass will be pressed together throughout there is no danger of epoxy leaking onto the driveshaft.  I'll put just a dab of oil on the shaft just in case.

Maybe inserting a piece of very thin wire into the hole as the JB Weld sets up might be wise. I've used this version of "fibre" reinforcement before, borrowing the idea of stitch and glue from wooden boat building. The idea is to relieve any cracking forces exerted on the JB Weld by transferring those to the wire. Composites like fibreglass or carbon fibre  rely on this effect: the fibre matrix holds the resin firmly. Well, also,  rebar in concrete serves the same purpose.

Or, just leave the one screw in place in the upper hole and cut off the head flush with the back of the frame. One mechanical fastener and one JB Weld fastener.  Hmmmm. 

This joint just has to be very low stress because the drive forces themselves are tiny. The outward thrust on this joint will be a fraction of that tiny drive force.  Any thrust force is absorbed by the universal joint at the rear end of this driveshaft. I'm working on the front truck. The drive gears are to the front of these plastic retainers so they exert no linear thrust forces on those retainers (which would be a sheer force relative to the joint). The only possible force is in line with the driven axle, trying to push the plastic retainer horizontally outward and off the frame. No doubt that's why the original cast-in pins don't routinely break in operation, no sheer forces.

Alyth Yard

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Posted by Lastspikemike on Monday, March 22, 2021 6:22 PM

Done and dusted. Replaced the plastic drive shaft retainer cap that I snapped the pins off.

Changed my mind a little. Decided to secure one broken pin location with a tiny brass screw but driven from the outside so that I could cut off the head and excess thread and still get a file on it to flatten it into the surface of the retainer. You can reach the back of the lower hole with "spruce cutters" but you cannot do the same for the upper hole. 

Using that screw to secure the retainer firmly onto the truck I threaded part (3 or 4 strands fit) of 22 gauge wire into the other broken pin location. I left the insulation on the end to use as a handle while I worked the JB Weld into the hole surrounding the bared wire strands and totally filling the hole. Together with the threads tapped into the hole the idea was to create a cast in place JB Weld "screw" reinforced with copper wire strands.

Left to cure for 24 hours. Then worked the screw back and forth in the other threaded hole with JB Weld on the screw threads. Left that for 24 hours to cure.

Clipped off the wire stubs flush with the retainer and the truck frame, using what look like sprue cutters but are actually designed for trimming through hole components for ICB being hand repaired due to manufacturing errors. Used the same tool to cut the brass screw head off flush with the retainer. I made sure the inner end of the screw did not protrude past the end of the hole.  There's very little clearance betweeen the inside of the side frame and the crown gear on the wheel face. 

Filed the protruding copper and brass flat against the plastic surface and painted the bright spots with flat black acrylic.

Reassembled the frame (which requires four hands or a lot of patience). Tips for that include starting the side frame retaining screw before you introduce the electrical contact and the metal and plastic bolster to the mounting pin. Assemble the one side first. When I took it apart originally I only took off the drive gear side. I also left the tiny assembly screw in place in the bolster in order not to lose it. That is also a good way to handle the reassembly.

Place the axles into the partially assembled left side frame, gear wheel up. Insert one end of each of the end frames (also plastic and each consisting of three parts)  into the side frame (each has two projections which insert into matching holes).

Then holding your facial expression just so, holding the rickety partial assembly in one hand (your non-dominant hand)  carefully and simultaneously place the gear side frame onto the axle ends, the two pins on each end frame and the locating pin holding the electrical contact, using your other three hands.

There's enough sideplay in the side frames to allow a little rejigging as you try to line up all seven "pins" into their respective sockets all at the same time.

Once you succeed do not let go. Use your non-dominant hand as a clamp and your dominant hand to pick up the tiny Phillips jewellers screwdriver you thoughtfully left just out of reach and screw in the single remaining retaining screw. That's when you'll realize you needed to start that screw before you began.

And yes you do have to remove the front coupler to reinstall the front truck just as NWSL advises because the coupler  cover acts as a sliding  restraint on the front edge of the truck (the rear truck is clear of the coupler cover there). The electrical contacts slightly spring the trucks. 

You can just wiggle the front truck out from under the coupler cover but there's no point to doing so because you cannot get it back in. Go figure. 

Alyth Yard

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Posted by Lastspikemike on Sunday, May 2, 2021 1:30 PM

Center truck now done. New NWSL gears installed with the help of the friendly staff at my LHS.

This job requires a proper gear press capable of handing the small diameter drive shaft without putting any bending force on it.

Also, here's an important tip (EDIT, Maybe!!): you don't need to pry out both plastic axle retaining clips. Remove the "front" one only and slide the axle out from the rear clip. It may take a little wiggling but it will come out. Be VERY careful maneuvering the axle with gears installed so as not to put any prying force on that remaining clip. The tiny plastic cast in pins break off VERY easily now the models are so old. 

EDIT Caution: I have just discovered the upper pin on the rear clip on the centre truck broke off. The lower pin held. I used a 00-90 tap and drill to very carefully drill through the broken stub left in the metal side frame and right through the clip and tap threads from the outside or plastic side. From the plastic side (outside)  I installed a 00-90 brass flat head 3/8" machine screw from WS Hob-Bits inserted with white glue to stop it backing out. After the glue sets up hard I will clip off the head of the screw and file the stub flush  as I did for the front truck where I broke off both clip pins. For the upper pin you cannot screw the screw on from the insude of the frame be ause there is no room to clip and fine the stub flush and all the clearance is needed for the driven crown gear on the wheelface. 

The gear shrouds can be carefully bent upwards if need be. These sheet metal gear guards clip into the inside face of the metal sideframes.  Although a bit fragile the shroud is metal and so is the nub cast into the frane that holds it on. Just don't bend it more than you need to and avoid distorting the very short section that clips onto the frame. 

Reason you don't want to pry the plastic clips out if you don't need to is they will break. It is virtually impossible to pry the clips out without breaking off one or both securing pins. The videos I've seen show this being done but one video is old enough the plastic in those clips may have retained some flexibility. The guy was VERY careful prying out the clips but so was I. In the other video the clip is shown after removal...with one pin snapped off. 

I did  effect repairs on the one I broke both pins off (front truck)  but it was far from easy. Avoid breaking the pins if you can. The one pin I broke on the center truck clip I "repaired" by drilling and tapping (threading) the remaining hole, reinserting the clip to be held on by the one remaining pin and filling the threaded hole with white glue. Reasoning that if any glue adheres to the tiny bit of the clip where the pin broke off it should be enough. There's not much outward pressure on this clip. If this repair fails then I can attempt the tricky repair with JB Weld that I effected on the front truck. 

With more conductalube on the axles this locomotive now runs very well. 

I have yet to replace the unbroken plastic gears currently driving the rear  truck. If it ain't broke then don't fix it. Each truck is a separate project and there are no economies of scale available by doing more than you need to. The risk of breaking the plastic axle retaining clips is very high, virtually inevitable at this age of model. Best to leave well enough alone is my opinion.

Alyth Yard

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Posted by SeeYou190 on Monday, May 3, 2021 12:27 AM

Some pictures would be nice of a project like this.

A simple picture like this of a project in progress helps a lot more than all these confusing descriptions.

-Kevin

Wink Happily modeling my STRATTON & GILLETTE RAILROAD. A Class A line located in a personal fantasy world of semi-plausible nonsense on Tuesday, August 3rd, 1954.

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Posted by snjroy on Monday, May 3, 2021 11:33 AM

I agree. I have this model and there are some things I don't catch from your description. Posting pictures is not that hard, and a cell phone picture usually does the job (remove the flash and rest the camera on something when taking the picture to avoid the fuzzy look). 

Simon

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Posted by Lastspikemike on Monday, May 3, 2021 2:22 PM

As soon as the website accommodates my posting skillset I'll put up the video and photo evidence. Until then, not happening. Not intending to brush you off but I just dont want to bother.

Alyth Yard

Canada

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