A Real Dirty Job

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Thu Nov 08, 2018 6:19 pm

No new incidents to report.

The first leaf spring bundle assemblies. They are not finished yet but I am getting there.

I don't know if I like the leaf springs with the spacers or not. Will at least try it out and see how it works.

I do know that without the very fine control on the bench rollers, this would not have been possible as each leaf except the shortest two (top) spring leaves are curved slightly more than an adjacent leaf. I tried to make the curvature on each leaf such that when two leaves were set together without a spacer, if one pinched the two leaves at one end, the gap at the other end was equal to a leaf thickness (0.015").

You really can't see this feature with the spacers in place.

I also noticed another issue coming up with the Langworthy design regarding the above but I will deal with it shortly.
Attachments
201 The Leaf Springs First Assembly into a Leaf Spring Bundle.jpg

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NP317
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Re: A Real Dirty Job

Post by NP317 » Thu Nov 08, 2018 8:14 pm

I do not understad how that spaced leaf spring would work.
Normally, the spring functions by adding each leaf force as the spring is compressed.
Those spacers prevent leaf interaction, leaving the longest leaf to do all the work.
~RN

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Thu Nov 08, 2018 9:27 pm

NP317,

Yes, you are correct.

As I mentioned, this was the first setup.

There was a reason for doing it this way. I needed to know if I hit or missed another required dimension which was shown on the Langworthy drawings and this was the setup which would tell me. Yes, I did hit it or am very close.

The final result (most likely) will be the metal spacers will be replaced with a lot of dummy plastic leaves (to keep the dimension which I was trying to hit) or I am going to have to make a lot of additional curved spring leaves. The spring leaves were made curved, one slightly more curved than the one above, to try and make them "progressive". If I put in all those additional metal leaf springs, over what Langworthy specified, there will be no spring at all.

I simply don't know at this point as I really need to find a practical way of determining the actual weight which is on the locomotive lead truck, the drivers and on the trailing truck (and I don't have such a method). I suspect that virtually 100% of the locomotive dead weight (in 3/4" scale) is on the drivers and that the lead truck and trailing trucks are just going along for the ride but I can't prove it. The Langworthy lead truck dead weight is only 5 lbs.(and add another 15% for vertical impact loads - my guess) and if that is all the weight the lead truck springs will see then yes, the first two leaves are all that one needs to be working.

Otherwise, it is all just so much trial and error (so one needs to find a very flexible spring design/arrangement).

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NP317
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Re: A Real Dirty Job

Post by NP317 » Fri Nov 09, 2018 12:31 am

Now I understand what you were doing.
Thanks.
~RN

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Thu Nov 15, 2018 11:42 pm

Back to the Josslin lead truck for the moment to eliminate the problem I noticed with the outer equalizers fouling the inner curved surfaces on the frame brake lugs which prevented full vertical travel of the axleboxes in the truck frame. On the Josslin lead truck, the axleboxes should be able to move more than 1/4" vertically and they weren't moving anywhere near that amount.

That is when Murphy threw everything at me including the kitchen sink.

I had first to take the entire truck apart to be able to mill out much more clearance on the central upper equalizer surface of the outer equalizer than was shown on the Josslin drawings. See the first photo. Actually, in the end, much more relief was needed than what is shown in the photo.

Then I found that some of the leaf springs had jammed on the end hanger pins and would not lay flat on in the bottom of the hanger. OK, shave down some of the sticking leaf springs (on width) about 0.003" to give a little more clearance on the hanger pin.

Then, now that the ends of the leaf springs weren't jammed, they wouldn't stay on the pin in the end hanger. Now I had to cross drill a 3/32"" dia. pin with a #60 drill 4 times with the pin in place in the hanger. Bad move. Two I managed to do and with the other two the drill ran off the pin even though I had carefully aligned the drill and started the cross hole with a miniature center drill.

Pull the bad pins out and they refused to move. Get out the propane torch, heat everything up to a sub red heat, let it cool and try again as they may have been Loctited in - I don't remember (this time with a miniature made up tapered knockout punch - and with one bad blow I would be making a new hanger as well).

Make up a miniature steel drill bushing and cross drill a piece of 3/32" dia. rod by itself in the mill vise twice. Press fit or Loctite in the new pins and soft wire lock the pins so the leaf spring ends are free to slide on the pins but are captive. See the second photo.

Put everything back together (which is a big fiddly job) and the axleboxes hardly moved any more than before!

Now I noticed that the inner equalizers were jammed up against the two central cross beams of the frame which carry the 4 swing links and the truck bolster. The Josslin drawings showed the ends of the cross beams relieved but not to the degree needed to solve this new problem.

Take the lead truck completely apart again and set it up on the table of the mill to mill away the interfering frame material. Not an easy setup so in the end it was partially milled/filed with hours of work involved. See the third photo.

Put the truck pieces all back together again and see that the outer equalizers still need to have more metal removed so...

Finally, the latest (last photo). It just looks like the any of the photos of the truck taken previously but it isn't.
Attachments
678 A Relieved Outer Equalizer Needed to Clear the Truck Frame Brake Hanger Lugs.jpg
679 The Wire Locked Leaf Spring Ends on the Leaf Spring Hanger Pins.jpg
680 The Highly Relieved Bolster Cross Beam Ends To Clear the Inner Truck Equalizer.jpg
681 The Josslin Hudson Lead Truck with All of the Latest Changes.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Fri Nov 16, 2018 3:57 pm

Back to the Langworthy lead truck.

Fully disassemble it to clean it thoroughly as it was absolutely filthy.

Install the leaf spring bundles between the side equalizers and set the ends of the bottom leaf springs (the longest ones) in the bottom "vee" of the spring hangers. The Langworthy has exactly the same problem as found on the Josslin lead truck. The spring bundles will just flip out of the spring hangers as there is no cross drilled locating pin in the end of the spring hangers to locate and hold captive the ends of the leaf springs. Maybe that is why I found the lead truck with the crude coil spring arrangement it came with.

And guess what. Despite everyone saying that the leaf spring bundle shown previously can't/doesn't work that way, this spring arrangement flexes beautifully in a truly progressive manner (despite the spacer washers being there) when I press down on the spring bundle. So I am going to leave it this way for the moment and see, when the truck is fully reassembled, if I still have the same effect.
Attachments
202 The Langworthy Lead Truck Fully Disassembled.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Thu Nov 22, 2018 5:29 pm

Machining a new lead truck bolster base plate and kingpin.

I certainly wasn't impressed with the existing arrangement. Did the lead truck have a terrific whack at some point as the 5/16" dia pin was slightly bent or was it just poor construction...?

The existing base plate seemed to be made out of bronze (don't know if this was an original part or a replacement). Then it seems someone tried to silver solder the king pin into the baseplate which didn't work either (see the second and fourth photos). And once assembled, that was it the way it was.

I went for a new all steel base plate which was bronze bushed.

The Langworthy drawing notes said rivet the top of the king pin into the bolster plate. Right - a terrible detail. Not going to happen as I changed the design. You can see the original riveting mess in the third photo.

The top of the kingpin now has a steel collar which fits flush into a recess on the underside of the base plate.It is pressed into the top of the king pin to retain it rather than the permanent riveting (to keep the lead truck from falling off when lifting the locomotive).

The new design is a bit more more complicated but now everything can be easily disassembled if ever the bronze bushing has to be replaced or a new king pin installed.
Attachments
203 Machining a New Bolster Base Plate and King Pin.jpg
204 New Bolster Plate and King Pin.jpg
205 New Bolster Plate and King Pin.jpg
206 New Bolster Plate and King Pin.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Sat Nov 24, 2018 2:42 pm

Finishing the bolster plate by drilling the cylinder holes to exactly match the existing hole pattern on the bottom of the cylinders where the old plate was attached.

The old plate had cap screws but since no steam locomotive ever used this, only high strength hex bolts, rivets and studs, 6-32 NC studs were made to fit the existing holes.

I have a method for picking up totally unseen/not accessible existing hole patterns. And I did not use the old plate as a drill template as the old and new bolster plates are different sizes.

I shouldn't be giving away all of my secrets on how to do this but I will give a big clue. I use socket head set screws screwed into the existing holes so that the recessed socket hex end stands just proud of the hole surface. There is a reason for inserting the set screws this way and not the other way around with the cone end or pointed end facing up (other than this being the normal way to insert a socket head set screw).

The usual clearance drill size given for a 6-32 NC screw is a # 27 drill (0.144" dia.) but I used a # 29 drill (0.136"). In your thread tables, the major dia. on a 6-32 NC thread is given as 0.138" but I file the OD of the thread slightly after threading to remove any residual burrs. But, essentially, I am using a "0" clearance drill. Not possible - yes it is but one needs to take great care with the procedure and a little luck always helps.

All of the four corner holes lined up perfectly to the existing previously drilled hole spacing.

When final positioning the new bolster base plate to the underside of the cylinders, one has to check out numerous things before starting to drill the plate stud holes.

Carefully roll the engine onto its side. Put the bolster base plate in its "final" position, assemble the lead truck completely and slide it up on the king pin. Are the lead truck wheels now level with the drive wheels in this free position or does one have to add a spacer or machine something off to achieve this condition?

How close are the rear set of lead truck wheels to the first set of drivers? As per the prints or something else?

Can the truck now move sideways (in a straight line back to front position) the design amount without hitting or fouling something?

When all of the above issues have been resolved now,

Try and rotate the truck about the king pin and note how much can it rotate without the front and rear wheel flanges rubbing against the cylinder covers or cylinder bolts ? Or something else? This can be a real problem which I have seen on many operating model steam locomotives.

On the Langworthy engine, the front truck wheel flanges rub up against the front cylinder covers first, and when rotated the other way, the truck rear wheel flanges touch the crosshead guides first. The truck has to rotate quite a bit before this happens but it could become a problem on tight curves.

On the Josslin lead truck, the axle spacing (and frame) was increased 1/8" over what was given on the Josslin prints to help address some of the above issues. Another example of where one has to modify the model design to accomodate what is found under actual operating track conditions. But one has to be very careful, as can only go so far without creating other (interference) problems.

Finally, the above also revealed another big problem with the Langworthy. The bolster itself was now seen to have been butchered which left the lead truck far to high on the king pin making it impossible for the truck to move sideways or to rotate to any degree. Fortunately, I had a quick fix which was to make up a spacer to lower the truck on the king pin to what the prints show but at some point, I will now be making a new bolster.

The photo shows the base plate with the new spacer added.

What else is there yet to discover wrong!!
Attachments
207 Cylinder Studs Located and Drilled (to match existing holes on bottom of cylinders) with New Spacer.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Mon Nov 26, 2018 8:21 pm

Back to the leaf springs installation on the Langworthy lead truck.

The leaf spring end hangers on the Langworthy lead truck drawings may closely follow the prototype, but they don't work on the model as they do not hold the ends of the leaf spring bundles captive for all of the reasons I have elicited previously. So I am replacing them with the Josslin designed leaf spring end hangers.

The start of the machining operations to produce the "U shaped cutouts from the 1/4" by 1/2" cold rolled steel blank pieces.

The solid bottom sections on the hanger blanks are there to provide a holding tab for the milling operations which are to follow.
Attachments
209 Making New Josslin Type Leaf Spring End Hangers for the Langworthy Lead Truck.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Thu Nov 29, 2018 7:21 pm

Further along.
Attachments
210 Further Along.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Fri Nov 30, 2018 2:59 pm

An interesting setup to drill and ream the leaf spring hanger pegs exactly in the center of the end hangers in two directions by purely mechanical methods.
Attachments
211 Drilling and Reaming the Leaf Spring End Hanger Peg Holes.jpg
212 An Interesting Setup.jpg
213 The Setup Broken Down.jpg

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Carrdo
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Re: A Real Dirty Job

Post by Carrdo » Sun Dec 02, 2018 10:01 pm

A leaf spring assembly nearly finished.

These assemblies are pretty much bullet proof now .

The second photo shows the miniature (1/32") cotter pin locking detail which captures the ends of the bottom spring leaves on the spring hanger pins while still allowing the bottom leaves some free movement on the pins. The spring hanger pins are 3/32" dia with a #60 drilled cross hole at one end for the locking cotter pin.
Attachments
216 A Nearly Finished Leaf Spring Assembly.jpg
217 The Cotter Pin Detail.jpg

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