Constructing The Josslin NYC Hudson Lead Truck

[Carrdo]

The lathe setup for drilling and boring the bolster for the king pin.

After marking out and centre punching the hole location on the top face of the bolster, the bolster was setup on the lathe faceplate as shown for drilling, boring and final reaming.

Note the fancy "wiggler" at the rear of the cross slide which was used to exactly centre the centre punch mark.

To get everything into the correct position is quite fiddly so try to alter one part at a time by light clamping and then by tapping as things can move all over the place very easily. It is best to use a centre in the lathe's tailstock to initially align the centre punched hole in the part, otherwise one will be fiddling forever with the wiggler.

Once everything is aligned, final tighten all clamps and then check again that nothing has shifted. You do not want anything to move during this machining operation.

[Carrdo]

After weeks and weeks of machining, the bolster fitted to the heart shaped swing links and the entire bolster/swing link assembly assembly fitted down between the truck cross beams. Everything has to be dead square, parallel, straight and on size for this to happen with only about 0.001" clearance everywhere. What would I do without the surface grinder.

I am not finished yet. Still have to end round the ends of the bolster legs where the swing link pins are fitted.

The entire bolster assembly has to be completely free to swing side to side in the truck frame without any shake and for this to happen, there is one last operation necessary to do on the heart shaped swing links.

[Carrdo]

More end rounding to finally complete the bolster.

After a final bit of fiddling with the bolster swing link pins and collars to cut them exactly to length but still have them free to rotate between the bolster legs, everything works as it should.

[Carrdo]

Finally got around to finishing the heart shaped rockers.

The final operation was to cut away the shark's tooth bridges between the upper two 1/8" dia. drilled holes in all of the heart shaped rockers and then die file the bridge contours so the rockers/bolster could swing freely from side to side on the truck frame cross beams.

I used a fine jewellers coping saw to cut through the bridges. The jewellers saw wasn't meant for cutting through steel but with care the miniature blades did the job. They did twist, jam and break but with care and a light hand the job was accomplished.

Each rough sawn bridge was then die filed to its finished contour by careful die filing. The semi circular bridge shape (5/32" radius) was first laid out from a plastic circle (drafting) template laid over the parts and held there with a small toolmakers clamp. Fiddly, but it worked.

I am very happy with the final result as the bolster now swings freely from side to side between the truck frame crossbeams (as it should) without any shake or twist.

[Carrdo]

The bolster plate machining.

For this operation, I choose a miserable block of flame cut HR steel that had been sitting in the shop since my student days. Torch cutting of the steel alters the machining properties of the steel in the heat affected zone, (not for the better) and leaves rock hard surface ridges which can be up to 1/8" deep.

In the General Discussion section of Chaski, I recently added a thread on how the block was initially dealt with ( "rectangularized") using my 7" bench shaper and a C5 brazed carbide tool bit.

Since one is taking a lot of interrupted cuts here turning the corners down on this block of steel, keep your HSS tool bit well sharpened and take light cuts to prevent destructive chatter as you will still be cutting through the heat affected zones of the steel block. Everything is turned at one setting to keep things dead concentric.

To return to what I have said several times before, in the last photo, one can see how little clearance there is for the Josslin lead truck to translate from side to side and/or to rotate before the lead truck wheels rub (and wear grooves into) the cylinder covers, the crosshead guides or whatever else is there to obstruct their movement. The more detail one adds to the lead truck, the worse this situation becomes.

I have added 1/16" to the axle centre line to the truck centre line spacing on each axle opening in the lead truck frame (from the print dimensions) to allow for more lead truck rotation but there is a limit (as the rear set of lead truck wheels get dangerously close to the front set of drive wheels if more than this is attempted) and still you can see how little clearance there is.

The Hoffman Hudson design has the same problem and so does the Langworthy/Yankee Shop Hudson. People swear up and down that this doesn't happen but the next time you are out at the track, when they are not looking, just run your finger up on the inside of their cylinders and feel the lead truck wheel wear grooves on their cylinder covers.

The only other solution would be (in conjunction with the above) to turn a second set of undersize lead truck wheels for track running. One would also need to add a spacer on the bolster king pin to compensate for the loss of wheel diameter.

[FKreider]

Any detail pictures of the steel boiler?

[Carrdo]

It is an all welded steel boiler. I did not make it. It was made to the original Canadian Carl Hoffman boiler design which was all copper but about half or more of all the existing Hoffman Hudson boilers are these steel boilers.

It was made by Reg. Miller of St. Thomas, Ontario when he was working for the Clark Forklift Company. He told me that he welded up over 20 of these boilers and did all of the welding himself during his lunch breaks at the factory.

I think Reg. Miller is still with us but he is long retired.

[Carrdo]

The nearly finished and the finished bolster plate and how it is attached to the bolster. The truck looks pretty complete now externally but...

Still have to make the (modified) drop equalizers, the leaf spring assemblies, hangers and retainers, and if I feel like it, all of the brake parts, the brake cylinder, the brake cylinder frame support and fulcrum and... all of the things which will make the lead truck inoperable on the track.

Oh, as an afterthought, from the dim dark past, as I just found it, my additional drawing to the Josslin lead truck drawings showing the brake lugs as the Josslin design never had them.

[FKreider]

Thanks for the history on the boiler, interesting!

[Carrdo]

The start on the machining of all of the remaining lead truck parts.

The cycle seems to repeat itself over and over again. Begin by "rectangularizing" the HR steel blank parts, in this case they are the leaf spring end hangers (4), the leaf spring central hangers (2), the leaf spring hanger pins (4), the new CI brake shoe blanks for the Langworthy (4) which I previously messed up and the 1/16" thick HR steel drop equalizer blanks (4). The outer two drop equalizers have to be modified from what is shown on the Josslin prints for reasons which I have outlined before.

Also, seen is the special 1/8" wide by 1-1/2" diameter Woodruff cutter which will be used to slot the brake shoe blanks on the rotary table in an operation very similar to the one I used previously. One cannot use a normal saw type cutter with this setup.

It is a lot of careful, basic "squaring" operations to even get to this stage.

[Carrdo]

The machining of the leaf spring centre and end hangers. These are small but important parts which have to be machined correctly.

The hanger blanks were left about 1/32" oversize on width and thickness as the rule is do all of the internal machining first as it is much easier to machine things externally if the central slots have to be centred rather than to try and machine the slots perfectly centred when the external dimensions of the parts are the finished size - at least if one is doing this via manual machining without any digital aids.

The hanger blanks were also made 1/4" longer than the finished hanger length so that there was something for the mill's vise to hold on to when the internal slots were being milled to the finished size.

I have probably described the following operations elsewhere before but for completeness I will repeat the procedures.

When making long narrow slots do not attempt to mill them out directly, rather remove as much slot metal first by other means leaving only light finishing cuts to be made with the milling cutter. I initially used the bandsaw followed by chain drilling small holes along the bottom of the slots then cutting through the remaining bridges with a jewellers fret saw to first remove the bulk of the metal internal to the slot. See the attached photos.

[Carrdo]

The leaf spring end hanger slots were then held in the mill's vise by the extra length tabs and finish milled as shown in the first photo.

I finish a slot by milling to its full depth first, then moving the end mill side to side to shave down each slot side wall. Measure each side wall thickness as you proceed to keep both slot side walls the same thickness. This is easy to do if you have left extra metal on the blank as explained previously. The ground rod seen in the photos was used to determine the finished slot width which was 5/16" in this case. The rod just slips down into the slot when
a slot is at finished size and all of the slot size walls are exactly the same thickness.

I have done slots like this many times before and the method will work to the limit of your measuring equipment.