Constructing The Josslin NYC Hudson Lead Truck

[Carrdo]

Swaging the ends of the equalizers. This operation is an exact repeat of what I did with the Langworthy/Yankee Shop Hudson lead truck equalizers so one can see the procedure and detailed photos there also.

It is important to have the 1/16" offset layout lines on the ends of each equalizer square with the bottom surface of the equalizer. See the first photo. Then, an equalizer is aligned in the pressing fixture as shown in the second and third photos and held in place with some masking tape.

Then press away with whatever is most convenient or at hand to use.

[Carrdo]

Proceeding with the modification of the outside equalizers so they clear the lead truck frame brake lugs. Just some belt sanding and some extra milling with a ball nosed end mill are involved here.

When holding the outer equalizers in the mill's vise, one will either have to add a 1/16" (or thicker spacer) at the rear of the equalizer or one at the front so that the offset ends of the equalizer are not crushed against a vise jaw when the vise jaws are clamped tight. It just depends upon whether the swaged ends of the equalizer face inwards or outwards.

After that the equalizer assemblies were fitted into the truck frame. They look very good and everything moves as it should.

I now just have to do a little extra filing on the truck frame so the axleboxes have full vertical movement and cross drill the leaf spring hanger pins.

I still have to make the leaf springs themselves though.

[Carrdo]

Instead of cross drilling the ends of the hanger pins I decided instead to install miniature circlips to on the ends of the pins to retain the pins as I had done it this way before on another lead truck.

Well, this started another day of machining adventure.

For the size of circlip used on the 1/8" dia. pin shank, the circlips were only .016" (1/64") thick so how does one accurately machine such a narrow groove? I had come to the answer before as I had used a hollow ground Xacto blade as a very narrow grooving tool and it had worked very well for this purpose. The Xacto blade material is fine for grooving any type of mild steel (which the pins are made out of) but probably is less suitable for anything more difficult to machine such as 01, drill rod or case hardened material. Can't say as I never tried it on such materials.

Only problem, I could find the blade I made previously but not any suitable holder, so then spent a half day making a proper tool holder for the SB lathe. Then, one had to make a special split bushing to clamp down on the shank of the pin as the shank of the hanger pin is not long enough to be held directly in a collet without the 1/4" diameter head of the hanger pin fouling the back of the collet. Also, the shank of the hanger pin had to project out at least 5/16" from the face of the collet so as to be able to cut the groove on the end of the pin with the made up holder. See the second photo for how tight things were here.

The split bushing took all of another half day to make as it has to be made accurately as it really is a collet within a collet.

And after that, it took all of 10 seconds to make the groove in the pin for the circlip. Ironic...

[Carrdo]

Drilling and tapping the lead truck frame brake lugs for the brake shoe hangers.

The setup to do this was exactly the same as was done with the Langworthy truck frame. However, as the slots in the brake lugs were machined correctly this time, having the correct offset from the frame so that the centre line of the brake lug slots aligned with the wheel tread centre line, no offset brake shoe hangers were needed.

As the drilling and tapping of the brake lugs was also done correctly (the rear brake lug wall was tap drilled and threaded while the front brake lug wall was clearance drilled), step bolts were used to hold the brake shoe hangers in the brake lugs so the hangers would rotate on the smooth machined bolt diameters rather than on the threaded section of the bolt.

Little details...

The new 5/16" wide blue spring steel coil (0.015" thick), recently received, as seen in the last photo will be used for the truck leaf springs.

[Carrdo]

Back to the production of leaf springs.

The starting sequence.

As I have said before, the way one does this is often according to the equipment one does or doesn't have.

For the cutoff operation, as seen in photo 714, one needs to have a controlled/firm grip on the material but do not push the cutoff wheel as you do not want to draw the temper of the blue tempered spring steel. The same goes for the end squaring operation. Protect your eyes with safety glasses.

[Carrdo]

After slicing and grinding square the ends of all the leaf springs (17 in total), the next operation was to roll the curvature into the leaf springs (which was 3/16" setup on the bottom longest tripled leaves). Each subsequent leaf was then rolled slightly shallower until the next leaf became flat. I aimed to have a gap of one leaf spring thickness at the end of each shallower leaf when two adjacent leaves were pressed together at their centre (progressive spring design). Without having made the G. Thomas special bending rolls (which allow for a very fine control over the bending radius produced), the above would have been impossible.

Note that on the engine main leaf springs, the longest leaves are on the top and are curved upwards while on the four wheel leading truck the longest leaves are on the bottom and are curved downwards.

In both the Langworthy and the Josslin drawings, the leaf springs are all bent and have spacers between the leaves. I know why it was done this way as historically, in the 1930's - 50's when these designs first appeared, no one had the equipment to be able to roll the curvature into hardened spring steel. One was very lucky just to be able to afford a small (used) metal lathe or a drill press. Even today, such special bending rolls are not all that common. So one does things with the equipment one has or doesn't have.

Don't ask me how the total number of leaves and the 3/16" leaf spring setup (curvature) was arrived at. I just looked at a number of 3/4" scale model designs and picked one that looked good and performed well. Every reference which I have on model locomotive leaf spring design (starting with LBSC and Henry Coventry in the 1930's right up to the present) makes assumptions and uses numbers derived from who knows what (as they don't really say). And they all use different formulae, a different number of spring leaves, different leaf thickness' and leaf curvature, single, double or triple leaves on the top and bottom etc. etc. Then, there is the scale effect which means that what is used in 1.5" scale locomotives cannot be applied to 3/4" scale locomotives and vice versa. Then, one has to measure, experiment with (or assume correctly) the model weight distribution between the leading truck, the main drivers and the trailing truck... it just goes on and on.

So when faced with all of the above, one is left to make the design as flexible as possible so one can add or subtract leaves, use dummy leaves if needed and experiment until the locomotive and/or the locomotive trucks do not derail, the engine can pull without the drivers slipping excessively and the locomotive ride is stable (and to your liking) under the varying model track conditions one will encounter.

[Jerry_H]

Where could one find the drawings for the G. Thomas bending rolls?

Jerry

[BAdams]

Model Engineer magazine, October 1976 issue.

[Carrdo]

The critical drilling of the spring steel leaf springs.

Nowhere does C 1095 blue tempered spring steel show its nasty nature than when trying to drill it in a home shop environment. So, preparation is everything and even with the best preparation, things can and do go wrong.

The problem. I needed to drill a 1/16" diameter centre hole (actually, using a #52 drill which is 0.0635" - 0.001 larger than 1/16") in each of the leaf springs as each leaf spring has to be free to slide, without shake, on the leaf spring centre hanger leaf spring post which is made from 1/16" drill rod.

All of the holes have to be exactly on centre width wise and to a slightly less degree length wise on each leaf spring.

As well, the operation has to be cost effective.

There are many ways of doing this as shown on the net but there is nothing shown for such a small size and requiring such precision.

Commercially, one can bite the bullet and use HI-ROC drills or carbide stub drills but be prepared to spend the $$$ and then there is the problem as to how to re-sharpen them as you will need to with the number of leaves needing to be drilled.

For the critical first drilling operation, I used a solid carbide miniature spade drill (the Supplier's information says it is normally used for sheet metal drilling) which is considerably cheaper than any of the above types of drills and then did everything possible to preserve its integrity. But sooner or later, it will fail also as home shop conditions are far from ideal.

To be continued.

[NP317]

That's basically the same method I used to drill all the leaves for the springs on my Mikado.
'Made a fixture to hold the leaves during drilling.
I consumed several carbide drills in the process, and learned that lubrication, lower rpm, and steady aggressive drilling pressure made the job far easier.
RussN

[Carrdo]

To summarize the critical drilling process, the following procedure was used. As I do not have anything digital, only old fashioned mechanical methods were employed.

To accurately centre the drill, width wise, on a spring leaf, a single use 1/16" dia. centre hole drill bushing made from mild steel was employed.

The spring steel leaf to be drilled is bedded on a flat spacer in the vise. Make certain that there is no interference from the vise mounting bolts or other obstruction to the spacer laying flat and square in the vise jaws. I used two of them as shown in the previous post (first photo) as the top one is sacrificial.

A 1/16" dia. HSS drill or a piece of straight 1/16" dia. drill rod is held in the drill chuck and used to locate and align the drill bushing on the leaf spring width wise. The OD of the bushing was made 0.001" smaller than the width of each leaf. Using commercially slit spring steel, the width on the coil is usually uniform but it may not be exactly to width (5/16" or 0.3125") as I found out!

The leaf spring is then aligned lengthwise under the drill bushing as shown in the second photo of the previous post. My drill press has a provision to lock the quill in any "down" position which makes shifting the leaf spring/drill bushing easy.

With everything now aligned replace the HSS twist drill with the carbide spade drill and carefully remove the drill bushing making certain that nothing shifts out of position in the process.

Set the drill press to a very slow speed for the small size carbide drill now employed. I used 900 rpm.

To be continued.

[Carrdo]

Sorry for the choppy messaging. I had all of this in one post earlier but it all disappeared when I hit "submit".

The reason one cannot use the drill bushing with the carbide spade drill is a spade drill functions differently to a regular jobbers twist drill. They do not drill the same size holes and the drill bushing would be damaged by the spade drill.

The job of the carbide spade drill is to penetrate through the spring steel and not necessarily to drill a round hole. First, bring the point of the carbide spade drill to just above the surface of the spring steel and then with a slow but firm downward movement of the quill drill through the spring steel until the tip of the spade drill has penetrated through the leaf thickness and slightly into the underneath supporting mild steel sacrificial spacer. The aim is to have about 3/4 of the full diameter of the hole on the bottom surface of the spring steel leaf. No lubricant. Then switch to a sharp # 52 HSS jobbers drill to complete the drilling of the hole. Use lubricant here. The result was a nice round hole in the spring steel with minimal burring.The HSS jobbers drill survived quite nicely.

Why the above?

If the carbide spade drill were to fully drill through the spring steel, the cutting edges of the spade drill will experience breakthrough shock and vibration resulting in microchipping of the drill's cutting edges. Remember, we are not drilling under ideal conditions at all here and the aim is to preserve the carbide spade drill for as long as possible. A # 52 HSS jobbers drill is 0.0635" dia. which is 0.001" larger than the drill rod upper spring hanger centre post(s) and the aim is to have a shake free sliding fit of all of the leaf springs on the leaf spring hanger centre post(s).

Of course, the better your drill chuck, vise and drill press is, the better the results. Also, keep everything square and rigid.

That's it. Since I have done all of this before, you now have all of my experience and I can't offer anything better.

Your experience may vary.

Stay tuned as we are not out of the woods yet.