Bouch's workbench - 7mm Jinty

[PAD]

Hi Mike,

Following your question on Jazz's thread regarding springing the centre axle, here's my twopeneth on the subject.

 

This is the method on my L1. First the spring without the bearing.

 

And with the bearing in place.

 

It's very simple, and easy to do and only involves two parts. It allows the axle to move up over humps in the track, avoiding the front or rear axle loosing contact with the rail, and let's it drop in the dips to maintain contact. It works very well and I have used it on small 0 6 0s up to Pacifics, and they all run very well even on poorly laid track. It strikes me that it you need anything more complex than this to achieve good performance, then it's the track the needs addressing.

 

I don't understand why 3Link added the extra rod to control the ride height, and perhaps he could explain that.

 

Cheers,

Peter

[Mike Boucher]

Hi Mike,

Following your question on Jazz's thread regarding springing the centre axle, here's my twopeneth on the subject.

 

This is the method on my L1. First the spring without the bearing.

post-13414-0-87739000-1495571001.jpg

 

And with the bearing in place.

post-13414-0-07902700-1495570954_thumb.jpg

 

It's very simple, and easy to do and only involves two parts. It allows the axle to move up over humps in the track, avoiding the front or rear axle loosing contact with the rail, and let's it drop in the dips to maintain contact. It works very well and I have used it on small 0 6 0s up to Pacifics, and they all run very well even on poorly laid track. It strikes me that it you need anything more complex than this to achieve good performance, then it's the track the needs addressing.

 

I don't understand why 3Link added the extra rod to control the ride height, and perhaps he could explain that.

 

Cheers,

Peter

 

Hi Peter,

 

Thanx for the pictures.  I figured that the wire acted as the thrust bearing, but wanted to make sure that I hadn't missed something.

 

Mike

[Mike Boucher]

Even with 2 weeks of vacation time around the holidays, I've made little to no progress on the Jinty.  I have managed to make the 2nd set of connecting rods, but that's about it for the engine proper.

 

However, I have made a set of "bearing alignment rods", based on a few photos I've seen on other build threads.

 

If you've never seen them, you put the rods thru the bearings before you solder the bearings to the assembled chassis, and the connecting rods on the ends.  Make sure everything is square, and your bearings should be at the same centers as the connecting rods, which should mean no binds when the wheels and rods are assembled in the chassis.  (when I actually get to it, I'll have photos of the process.)

 

 

 

I started with some 13" long pieces of 3/16" rod.  (why 13"?  I had a piece about 40" long kicking around, left over from another project, so I cut it in thirds, put them in the lathe and made them a consistent length, and 13" was the closest "nice round number")

 

I turned 1/2" on the end to .125" diameter.  I then set the compound in the lathe to 5 degrees, and turned the taper.  Turned out that that made a very sharp point, so I shortened the 1/2" to 3/8", which made the overall length of the rods 12 3/4".  I probably should have used a smaller angle.  I can always cut these ends off and re-do it if the taper is too much.

 

We'll see how well they work.

[Mike Boucher]

Hi Mike,

Following your question on Jazz's thread regarding springing the centre axle, here's my twopeneth on the subject.

 

This is the method on my L1. First the spring without the bearing.

post-13414-0-87739000-1495571001.jpg

 

And with the bearing in place.

post-13414-0-07902700-1495570954_thumb.jpg

 

It's very simple, and easy to do and only involves two parts. It allows the axle to move up over humps in the track, avoiding the front or rear axle loosing contact with the rail, and let's it drop in the dips to maintain contact. It works very well and I have used it on small 0 6 0s up to Pacifics, and they all run very well even on poorly laid track. It strikes me that it you need anything more complex than this to achieve good performance, then it's the track the needs addressing.

 

I don't understand why 3Link added the extra rod to control the ride height, and perhaps he could explain that.

 

Cheers,

Peter

Hi Peter,

 

Quick question:  From my initial reading of the technique, it seems that some people only allow upwards movement of the axle.  Reading your reply, it seems that you lengthen the slot both directions.  My thinking is that If you don't allow downward movement, it won't "drop into dips", only "go over humps", to use your description.

 

Do you lengthen the slot in both directions?  Thanx!

[PAD]

Hi Mike,

Yes, I lengthen both ways so the  axle  can move down as well as up from the  center line.  On my recent  Duchess build I only allowed upwards movement at first to see if  it  could be simplified further.  It seemed to work OK but  that was only on my brother's layout where the  track is  pretty well laid. As a belt and braces approach I decided to allow  downwards movement also to allow the  wheels to stay in contact with the  rail in any dips. 0.5 mm to 1 mm should  suffice and  if  you  need more  then the  track needs fixing!

 

Good luck with whatever you  decide  to go with, but  as far  as I'm concerned the  wheel has  already been invented.

 

Cheers,

Peter

[Mike Boucher]

On a brutally cold Saturday (high temperature was 7* F with 30 mph winds), I did a little more work on the Jinty.

First was to use taper reamers to open up the holes in the connecting rods to fit the Slaters top hat bearings. Based on Jim McGeown's suggestion in one of his downloadable PDF "hints and tricks" documents, I used the reamer to open the hole a little from from each side until the bearing fit smoothly but with no slop.  To aid with this, I used my gauge pins, measuring the hole size so I knew how much more I had to open it up to get to the right dimension.

If you're unfamiliar with gauge pins, its a set of precision ground pins which increase in diameter .001" at a time.

 

This is a set of .062" to .250". I also have from .250 to .500.  (the advantages of also having model engineering as a hobby!)  Note: I got these 2nd hand, so there are a few I'm missing. I have enough for my current purposes, and if I need to fill a "gap" you can buy individual ones (but they're not cheap!)

As I started opening up the hole, I would use the gauge pins to determine the current hole size. Repeat until I got close to the target dimension (.095", measured using my micrometer, for reference), I would take smaller, lighter cuts. Eventually, I got the point where I could put the .095" gauge pin easily, but not the .096" one.  The bearing would fit in easily, but there was no horizontal play between the bearing and rods.  (for the record, that makes the diameter of the hole about 2.43mm)

 

Over on the Gauge O Guild forum (where I'm also documenting this build), several people have suggested that the alignment rods I made are too long and will be unwieldy, and the tapers on the end aren't necessary. So, I made shorter ones with straight ends. These are 2.5" long with 1/2" on each end turned to a hair under .095". (I made 4, rejected one as I made a mistake and one side was .092", fit was too sloppy) Still longer than the width of a chassis, but not by much.



And with the rods on them...

 

We'll see which ones work better, or if I use both of them at different stages of the build.

And I started working on the chassis itself. I removed the sides and the spacers from the etches and cleaned up the kerf on the edges.

 

For the chassis sides, the rivets were pushed out, and I opened up the axle holes to fit the provided bearings. Once again, I used the gauge pins to constantly measure the hole size so I knew when to take lighter cuts. I was able to creep up so the bearing fits right up against the sides with no slop at all.

Next it to open up the center bearing hole for a little vertical movement. Pondering how I'm going to ensure there no horizontal play and the vertical play is consistent between the two sides.

[JeffP]

I like those gauging rods. Are they size-marked?

 

It would be my luck to knock the lot over........

[david.hill64]

I like those gauging rods. Are they size-marked?

 

It would be my luck to knock the lot over........

That's why there is a micrometer in your toolbox!

[Mike Boucher]

I like those gauging rods. Are they size-marked?

 

It would be my luck to knock the lot over........

The larger, good quality ones, usually.  I do have a few that aren't marked.  When you get to the smaller ones, there's not a big enough surface for a mark so you need to take out the micrometer.  (similar to # sized drills.  The #20 will usually be marked, the #60 won't be)

[Mike Boucher]

And away we go...

Tonight, I decided to file the center axle holes into a slot instead of a circle.  I came up with a unique way to do it, I suspect, but it seemed to work for me.

 

First, was to mark the upper and lower limit of travel.  I decided to extend the hole .032" (.8 mm) in each direction.    So, first step was to determine the dimension from the top of the frame to the bottom of the axle hole (The top of the frame is the only flat surface, so everything was done "upside down", if that makes any sense.)  The setup I used is probably easier to see than describe...

 

Now that you've seen it, let me explain a bit...  The vernier height gauge is designed that the scribing edge can't go much lower than 3/4" inch, so in order to scribe a line lower than that, you have to put a 1" ground steel bar under the part you're dealing with.  That's why the frame is up off the surface plate.  Secondly, to both hold the frame piece steady and make sure its vertical, I clamped it to a 123 block, which is sitting on top of another 123 block.  Then I put a .266" diameter gauge pin through the axle hole (smooth fit, but a .267" won't fit in the hole!) and the picture shows me measuring to the top of the pin.  This finds the bottom of the axle hole.

 

I read the height gauge, and did 2 equations.  Current height + .032 (to get the "lower edge" of travel") and Current height - .266 pin diameter - .032 (to get the "top edge" of travel)  Remember, everything is upside down, and scribed two lines at those dimensions.

 

I then held both frame pieces together, took 2 hardened machinists clamps and used 123 blocks to make them square to the top edge of the frame, and pushed them right up against the gauge pin through the hole.  Now I had both frame pieces together, with two "stops" on either side of the axle hole to make sure I couldn't make it any wider, only longer.  And I put everything in a vise.

 

 

Then I used a 7/32" (.218") diameter fine round file (intended to sharpen chain saw blades) to extend the axle hole in each direction to the scribed line.  And I got two nice oval holes.

 

 

The "fixturing" may have been unorthodox, kludgy, unintentionally complex and convoluted, but it worked.  Due to the angle of the camera, they may not look it, but they are both the same size.  If you look through when they're held together, you can see this...

 

No going back now!

This weekend, we have a 3 day weekend here in the states to celebrate Dr. Martin Luther King, Jr.  Hopefully I'll get some time in those 3 days to tack the frame pieces together.

 

 

[PAD]

Hi Mike,

Excellent. As you  say the  method is a bit complex but sound in principal, and I like the idea of the stops to ensure you elongate only vertically. I scribe vertical lines either side of  the hole and add masking tape to act as a guide, but  you  method is better.

Cheers,

Peter 

[Mike Boucher]

Hi folks,

 

One more question...  For those of you who use the "springy wire" compensation, what size piano wire do you use?  I have some .015 which seems way too flimsy.

 

Thanx!

 

Mike

[PAD]

Hi Mike,

I use 0.7mm nickel silver rod and it works ok. I don't think it's critical as long as the wire used has enough spring to push the axle and wheels to the lowest part of the slot with the frames inverted. That's my rule of thumb any way.You don't want the spring to be so strong that the wheels cannot raise over any humps in the track.

Cheers,

Peter

[Mike Boucher]

Well, I was going to work on the chassis itself over the weekend, but I didn't have the piano wire I needed.  So, I decided to work on the wheels themselves.

 

First, Slaters wheelsets are notorious for coming out of the package rusty.  Fortunately, mine weren't too bad, just a few spots (not bad considering I bought them about 15 years ago when I got the kit) but the axles were horrendous.

 

 

A quick spin in the lathe with a shot of WD-40 and some fine steel wook made short work of that.

 

Then, I sanded down the backs of the wheels themselves.  But I wonder why the "countersunk" hole for the crankpin is a) so big and b) off center to the crankpin itself?

 

 

Next, I put the threaded crankpins in.  Connoisseur suggests countersinking a little to make sure the head is below the surface, but after doing the first one, I found it wasn't really necessary.  On two of the wheels, I overtightened and seemed to strip the hole, even though I never felt any real resistance. The other 4, there was a definite "bottoming out" feel, so I'm not sure how I overtightened.  Connoisseur suggests filling the "countersink" with epoxy to lock the crankpin in, so I had been planning on doing that anyway, but with the 2 stripped wheels it seemed necessary.  The screw is pretty well encased in epoxy.  After re-sanding, here's what one looks like...

 

 

So, with the wheels taken care of, I just had to test fit the rods.  They might be a little tight, but its usually easier to loosen something up than it is to make something tighter.

 

 

The next photo was the obvious next step... 

 

 

I've made the trip to the nearest hobby shop (30 minute drive), as it is on the way to my parents house (needed my father's Bridgeport mill for the stationary steam engine I'm working on) and I now have some .025" diameter piano wire, so I'm ready to work on the chassis itself.  (a bundle of 5 pieces of piano wire, 3 feet long each, for under $2.  I now have more than I'll ever use...)

 

[PAD]

Hi Mike,

I spoke to Slaters on the phone recently about the possibility of exchanging some of their standard bogie and tender wheels for the Finney variety with the smaller 5/32 axles. They told me they would do it for a small handling charge, as long as the packs were sealed and the wheels were not rusty. They mentioned that if they are not stored in damp free condition moisture gets in through the cardboard backing. You would think that they would look at improving the packing to avoid moisture ingress, bearing in mind that many contributors on here have mentioned receiving wheels from them with rust present.

 

Long story short, I have

made some modification to the kit so I can use the wheels with the 3/16 axles.

 

The Jinty is looking good especial the invisible frames!

 

Cheers,

Peter

[Mike Boucher]

The invisible frames hopefully won't be invisible much longer.  Over the past few days, I've done some work on them.

 

First was to install the springing for the center axle.  I used my Foredom tool to drill a .028" hole in the top of two of the bearings.  I put them in the vise, and used a piece of scrap etch as a spacer to make sure the hole was the proper distance from the outer lip of the bearing.  Then I took a short length of .025" piano wire and bent one end 90 degrees.  I then used a grind wheel in the Foredom to trim the bent end so it was shorter than the thickness of the bearing, so the wire wouldn't foul the axle.  Then I put the bearing in the frame, put the wire in the hole, and clamped the wire to the frames where I thought was a reasonable tension.  Using my 80W iron, I attached the piano wire to the frame.  I used standard 60-40 solder so reduce the chance I would accidentally un-solder it while assembling the frames.

 

 

After taking the photo, I used the grind wheel in the Foredom to trim the end, so the wire doesn't extend any further than the solder point.

 

Next was to tack the frame spacers to one side.

 

 

Note that there's a 3rd frame spacer "D" which isn't tacked in place.  This is because there's no 90 degree bend in it, so I left it out for now until tacking both halves together.

 

Now is where I go a little bonkers and over-engineer what needs to be done.  When attaching the 2nd frame side to the spacers, I wanted to make sure that it was nice and square.  I let the picture speak first, then try to explain what's going on there...

 

 

The working surface is an 18" square steel surface plate.  On this, I placed 4 1-2-3 blocks.  Using the long alignment rods I made and described in an earlier post, I assembled the frame, inculding the axle bearings.  I placed the rods on the 1-2-3 blocks, so all 3 axles would be perfectly level.  Because of the springing on the center axle, I put a small piece of scrap there to weigh the frames down.  I then put the side rods on the end of the alignment rods to maintain the spacing.  Finally, I used a machinists square against the alignment rod and the frame side to make sure the axles were square to the frame sides.  Once I was satisfied everything was aligned correctly and square, I tacked the frame together in a few places.  I then flipped the frame upside down and tacked in frame spacer "D".

 

And now I have a frame.

 

 

 

Next step is to tack the remaining 4 bearings in place and try to get the wheels rolling smoothly with the rods on.  I suspect I'll have to do some fiddling there.  Once I have a free rolling chassis, I'll finish the soldering of the frame spacers and make a nice solid frame.

 

[JeffP]

Googled Foredom tools, interesting.

[Mike Boucher]

Googled Foredom tools, interesting.

Hi folks,

 

For those of you unfamiliar with Foredom, its fundamentally an "industrial quality" Dremel.  Variable speed motor which hangs off a hook attached to the workbench, approx 3 foot long flexible shaft, a handset, and foot pedal control.  Goes from a few hundred to about 5000 RPM. My father was a machinist (toolmaker, actually) and he's had one for years.  I had the opportunity to buy a used one 10+ years ago, and I'm glad I did, its a marvelous tool.  Brand new they're quite expensive, but they're worth it.

[PAD]

Hi Mike,

The frames are looking good.

 

When you come to solder the front and rear bearings in place, put the wheels and axles on. Then centre the wheels with some suitable packing either side (I use old business cards) and slide the bearings out until they just touch the backs of the wheels. Finally solder the bearings and remove the packing. Now you won't need any washers on the axles, which makes it easier to fit and remove the wheels when needed. The middle axle will need washers as appropriate to reduce side play depending on how tight your curves are.

 

I like your home made chassis jig. My brother has an Avonside jig which I use for assembling the frames on my locos. It's a nice tool and although I could get by without it, it does make the process easier. It is particularly useful when converting coupling rods from articulating on the centre crankpin, to articulating on the actual joint as in the prototype. I have found that pivoting the rods on the crankpin tends to wear grooves in the brass bush.

Cheers,

Peter

[Mike Boucher]

I had some time to install the axle bearings into the chassis, and the results are basically what I expected...

 

As suggested, I didn't solder the bearings for the leading and trailing axles tight up against the chassis sides.  I measured the difference between the witch of bearings tight against the frame and the back-to-back of the wheelsets, and found it to be about .058" (1.5 mm)  I used some .025" thick shim stock to hold the bearing out from the chassis and soldered them in place.  I used the same setup I used when assembling the two halves of the frames to keep the bearings inline, perpendicular to the frame, and on the correct centerlines.

 

I had some difficulty here initially, as I tried to use my 25W iron, as it was smaller and easier to maneuver.  However, it didn't have enough power to heat up the bearings, so I got a cold joint on the first axle bearings.  I didn't discover this until I took it out of the fixture.  When I tried to use my 80W iron to just tack the other side, the whole bearing heated up and shifted out of alignment.  I had to remove the bearing completely (with my butane torch) and re-do it using the fixture and the 80W iron.

 

Here's a close up of the front axle, so you can see the spacing.  There's still a small amount of side to side play, but not much, and the wheels spin smoothly in the bearings with no drag from the bearings themselves.

 

 

Back to the fixture and solder in the rear axles, and now the drivers can be assembled in the chassis for the first time.

 

 

Now for the moment of truth, how well does it roll?

 

 

As you can see, there's tight spots at both front and rear dead centers on one side.  I pretty much expected tight spots, as I've been building this to some pretty tight tolerances.  As I've said, its a lot easier to loosen up tight spots than it is to make a loose chassis tighter.

 

The first thing I looked at was if the axle bearings aren't quite on the right centers.  I took the wheels out, and used the homemade shorter axle alignment rods, and the side rods are definitely tighter than with the longer rods.  It was hard to get the rods on between the center and rear axles.  It looks like the long rods are good for making sure the chassis sides are square, but not so great for installing the bearings (as others correctly suggested, which is why I went and made the shorter ones!).  With the shorter rods in place, I gave the rear axles bearings a quick shot with my butane torch, once the solder went liquid, the bearings were pushed back a small amount, and the rods no longer as tight.

 

After reassembling the chassis/wheels/rods there's still a slight tight spot, but once the body is put on the chassis (at about 25 seconds into the video) it rolls pretty well.  Might do some more tweaking of the holes in the rods, but I think its time to start working on the gearbox/motor.

 

 

I also tested the springing on the center axle.  I took a dull X-Acto knife and put the blade on top of the rail.  I slowly ran the loco over the blade, watching the center axle.  When the front/rear wheels were lifted on the blade, the center axle stayed on the rail.  Similarly, when the center axle was lifted on the blade, the other two axles stayed on the rail, no "rocking".  So, I'm satisfied with the compensation.

 

 

One thing I have to start pondering is electrical pickup.  The kit comes with some PC board and instructions on making phosphor bronze wire pickups.  I also have a set of Slaters plunger pickups, and Jim has designed the chassis such that there are holes for these already in the frame sides, but I had some passenger cars with plunger pickups and they increased the drag on the cars "exponentially".  However, the springs on the Slaters pickups seem pretty "weak", so I don't think there will be a lot of drag.  Which to use...

 

[PAD]

Hi Mike,

Before you put the motor in you need to get the chassis running smooth, so that when you raise one end of the track, it rolls freely.

 

Ream the holes in the rods slightly, the put back on and check. Put it on a 3 foot length of track and push it back and forth to run it in.

Cheers,

Peter

[3 link]

Hi Mike,

 

I'm also not a great fan of plunger pick ups, looking at the height of the footplate and the tops of the wheels hidden by the splashers, I would use wiper pick ups resting on top of the wheel treads where they won't be seen.

 

Martyn.

[Mike Boucher]

Yesterday, while watching Arsenal eviscerate Everton, I did a little work on the side rods of the Jinty.  As stated in my previous post, there are still some tight spots, so enlarged the holes in the rods to loosen it up.

The holes were reamed out to be a snug fit on the Slaters crank bearings, measured to be .095".   I had used my gauge pins to verify that dimension.  Using the gauge pins again, I slowly reamed out the rods, one thou at a time, and then re-assemble the chassis and re-test.

 

At this point, most of the holes in the side rods are .097" diameter, with one or two reamed out to .098".  The chassis runs much more free now, especially when the body is on.  There still one point where there's a very slight bind when there isn't any weight on the chassis, but I suspect that's because the center axles aren't at the same center line as the front and rear.  As soon as a little weight gets added, the bind disappears.  I think this is good enough.

Here's the latest video of testing the rods.

 

 

This is without any lubrication on the axles/rods, so its pretty free rolling.  If I put the body on, as soon as I lift the track, it starts rolling.  Time to finish soldering the chassis together and start working on the motor mount.

[PAD]

Yesterday, while watching Arsenal eviscerate Everton, I did a little work on the side rods of the Jinty.  As stated in my previous post, there are still some tight spots, so enlarged the holes in the rods to loosen it up.

 

The holes were reamed out to be a snug fit on the Slaters crank bearings, measured to be .095".   I had used my gauge pins to verify that dimension.  Using the gauge pins again, I slowly reamed out the rods, one thou at a time, and then re-assemble the chassis and re-test.

 

At this point, most of the holes in the side rods are .097" diameter, with one or two reamed out to .098".  The chassis runs much more free now, especially when the body is on.  There still one point where there's a very slight bind when there isn't any weight on the chassis, but I suspect that's because the center axles aren't at the same center line as the front and rear.  As soon as a little weight gets added, the bind disappears.  I think this is good enough.

 

Here's the latest video of testing the rods.

 

 

This is without any lubrication on the axles/rods, so its pretty free rolling.  If I put the body on, as soon as I lift the track, it starts rolling.  Time to finish soldering the chassis together and start working on the motor mount.

 

Hi Mike,

Sorry to disagree but  you  need to free it up before  proceeding. It's better but  not good enough, and is easy to remedy.

 

I suggest you "run in the chassis" by repeatedly pushing it  back and  forth on the  length of  straight  track, applying pressure by hand. I do about  50 cycles at a time and  check. Repeat until it  will roll down the  straight when raised, under its own weight.​  No point  in putting the  motor in until it  will do that. 

 

Regarding  pick ups, I don't think you  can put  them on the  top of  the  wheels as mentioned earlier. On the  one  I built, the  pick ups are fixed to the  outside  of  the  frames with wipers acting  on the  back of  the  wheels. They are not  visible from normal viewing angles.

 

 

 

Here are some  prototype pics of 47279 on the  Worth Valley Railway that you  might  find useful.

 

 

 

 

 

 

 

 

 

 

 

Cheers,

Peter

[Mike Boucher]

I haven't done much work on the Jinty for the past few weeks.  I was  focusing on working on my stationary engine for my model engineering club's show.  That was last Saturday, and here's a picture of my son sitting behind my display just before the show started.  The engine in progress is on the far left.

 

today I decided to try to build a gearbox and test the chassis with a motor.  First, I spent another couple of hours fiddling with the rods until there were no binds whatsoever.  No more work with the gauge pins, only took a few twists of the reamer at a time and then reassemble and test.  Next, I finished soldering the chassis together.  It had just been tacked together, now its much more solid.  Finally, I finished the motion bracket and soldered that in place.

 

So, with a nicely running chassis, time to think about the gearbox/motor mount.

 

First, as I expected, the provided motor mount is designed to be soldered to the sides of the chassis.

 

 

With the added springing on the center axle, using that was out.  But, over the past years, I acquired a few other options.  First, a LONG time ago, when I bought the JM models kit for a new chassis for a Lima 4F ((from Home of O Gauge, tells you how long ago it was!), I also got this gearbox along with a Sagami motor.

 

 

Second option, a plastic shell, double reduction gearbox from North West Short Line (aka NSWL - a well known US supplier of gears, wheelsets, and other drive parts.)

 

The NSWL gearbox has two issues.

1) there's no way to attach the motor directly to the gearbox.  Many US models have the motor mounted on the chassis separate from the gearbox, with a rubber tube or some form of driveshaft connecting the motor and the gearbox.

2) The diameter of the hole in the 1st gear is significantly larger than the shaft on the motor, so I would need a sleeve somewhere along the line.

I wasn't terribly impressed with the HOG gearbox either.

1) There was supposed to be two triangular braces to solder on the inside, but the slots in the etches were about twice the width and significantly longer of the etch, all but useless.

2) The circular holes in the gearbox sides were etched oversize, the bearings flopped around.  The bearings themselves had issues, the hole for the axle was drilled undersize, the axles wouldn't fit through it.

3) The holes to mount the motor were positioned such that the axle would block access to one of the screws.  So, I had to tighten that before putting in the axle, which also limits being able to adjust the gear mesh.

But, I decided to go with the HOG gearbox since the issues seemed easier to deal with, so I soldered it up.

 

 

When I went to test fit it to the chassis, the problem was obvious.  No picture, but the width of the gearbox was significantly more than the distance between the axle bearings.  To get it to fit, I took the axle bearings, put them in the lathe, and reduced the width to 1/8" (taking about .045" off).  Then I filed down the outer lip of the bearings on the gearbox.  Had to take quite a bit off there, as evidenced by the pile of filing on the work surface after I was done

 

But it now fits, no side-to-side play, but its not tight either.

 

After getting the chassis back together, time for a bench test.  The first test there was a horrific bind.  It took me a minute to figure out that I flipped the axle around, the wheel that was on the right when I was fitting the rods was now on the left.  After fixing that, I was back to a free running chassis when the drive gear wasn't engaged.  I'm a bit worried as to how much of a difference it made, so I have to mark the wheels so that doesn't happen again. Then I powered it up...

 

It sounds pretty horrific, although it does sound worse on the video than in real life.

 

Clearly I don't have the mesh correct for the gears.  I fear that the gearbox isn't square, so the motor shaft isn't perpendicular to the axle, so the gears don't mesh correctly.  One other suspicion is that since this center axle has some side-to-side play, that once the motor starts spinning, it pushes the axle to one side or the other, which will force the gears out of mesh.  I'm now understanding why people spend so much extra $$$ on precision made gearboxes.

 

But, at least it runs without binding.  Note that as soon as the power is turned on, the wheels start to spin, that tells me that my controller doesn't really provide zero voltage when its at its lowest setting, but I'm also somewhat happy that the wheels start spinning with that little voltage. 

 

I also tried to test-fit the body on the chassis, and the Sagami motor might be too long.  I know the rear shaft of the motor is too long, it hits the firebox rear wall, so that needs to be shortened, but I'm worried there isn't a lot of room for the motor, and the electrical connectors will short on the inside of the body.  I need to do more test-fitting there.

 

But, since I have to take everything apart to add the chassis details, I'm not going to deal with this for now.  Since I have a machine shop. I might make my own gearbox and throw out the folded-up one, but I'll ponder that, and the motor size, for a while.
 

Next step is to put in the dummy inside motion provided with the kit.  I also might go back and start adding details to the body.