Constructing the Josslin Hudson
Moderator: Harold_V
Re: Constructing the Josslin Hudson
Getting ahead of myself but here is my handy dandy rod holding and fluting fixture made to fit all of the various NYC Hudsons in 3/4" scale. It was made many decades ago.
Re: Constructing the Josslin Hudson
More work on the rear side rods.
This time it is forming all of the external rod radii. A lot of slow careful work here as there are multiple radii to form and few of them are the same size.
This involved using some standard size end mills, the boring head and a small fly cutter as one type of cutting tool was not able to form all of the required radii. Also, the different type of tools were needed to get into some of the tight corners on the rod.
Be certain to hold the rod blank securely and have it lay flat on the supporting parallel for these operations. The radii formed with standard end mills were formed through careful plunge milling up to the layout line.
This time it is forming all of the external rod radii. A lot of slow careful work here as there are multiple radii to form and few of them are the same size.
This involved using some standard size end mills, the boring head and a small fly cutter as one type of cutting tool was not able to form all of the required radii. Also, the different type of tools were needed to get into some of the tight corners on the rod.
Be certain to hold the rod blank securely and have it lay flat on the supporting parallel for these operations. The radii formed with standard end mills were formed through careful plunge milling up to the layout line.
Last edited by Carrdo on Mon Jun 06, 2022 4:30 pm, edited 1 time in total.
Re: Constructing the Josslin Hudson
When all of the above operations have been completed, the rod will now look like this.
Re: Constructing the Josslin Hudson
That's a lot of work!
I was fortunate to have a 2-axis CNC mill available to profile the rods on my Mikado.
SO much less effort, with excellent repeatability.
Your results look good.
RussN
I was fortunate to have a 2-axis CNC mill available to profile the rods on my Mikado.
SO much less effort, with excellent repeatability.
Your results look good.
RussN
Re: Constructing the Josslin Hudson
ya it seems side rods are one of the prime applications of CNC to even one off builds, there's just so much setup and various operations on prototypical profiled and radiused rods.
Re: Constructing the Josslin Hudson
Further machining operations on the rear side rods.
As stated, there are a lot of different setup and operations involved.
From this point on, all of the operations are going to be controlled by the two rod centres and the rods are going to be machined as a matched pair.
If I had to do this again, I probably would do the end rounding as a first operation and then machine the various radii to blend in with the rounded rod ends.
As stated, there are a lot of different setup and operations involved.
From this point on, all of the operations are going to be controlled by the two rod centres and the rods are going to be machined as a matched pair.
If I had to do this again, I probably would do the end rounding as a first operation and then machine the various radii to blend in with the rounded rod ends.
Re: Constructing the Josslin Hudson
Slotting the forked end of a side rod with a side tooth HSS saw cutter.
I did this in three stages all with side tooth cutters. First, with a 1/16" thick saw followed by a 3/32" thick saw and finally with the print 1/8" wide saw. Since I want the slot to be on size or as near as possible, I used the thinner saws to remove the bulk of the material first so there was minimal cutting force on the final cut.
One other important point is to have the rod bedded square on the support spacer or parallel in the vise and ensure that it stays that way (square and bedded) when all of the other spacers have been added and the vise is tightened up. One does not want to have an on size slot that is tilted in any way.
I did this in three stages all with side tooth cutters. First, with a 1/16" thick saw followed by a 3/32" thick saw and finally with the print 1/8" wide saw. Since I want the slot to be on size or as near as possible, I used the thinner saws to remove the bulk of the material first so there was minimal cutting force on the final cut.
One other important point is to have the rod bedded square on the support spacer or parallel in the vise and ensure that it stays that way (square and bedded) when all of the other spacers have been added and the vise is tightened up. One does not want to have an on size slot that is tilted in any way.
Re: Constructing the Josslin Hudson
Fluting the inner and outer face on a rear side rod using my handy dandy fluting fixture. Just slow careful milling work here utilizing a freshly sharpened end mill. The pile of of my dull cutters is growing rapidly.
Note that the fluting is not symmetrical about the centreline of the rod so one has to keep track of and mark each rod face on all of these rods.
Use the mill's table stops to regulate the length of a flute. Also, as the cut gets deeper, the stops have to be adjusted slightly so as the end mill does not cut past the layout lines.
Note that the fluting is not symmetrical about the centreline of the rod so one has to keep track of and mark each rod face on all of these rods.
Use the mill's table stops to regulate the length of a flute. Also, as the cut gets deeper, the stops have to be adjusted slightly so as the end mill does not cut past the layout lines.
Re: Constructing the Josslin Hudson
When I began building my CPR Hudson, 'ol 2888, in 1985, I had neither milling machine nor band saw.
My machine inventory was a 6" Atlas lathe, Delta bench drill press, and a 6" Atlas shaper which I still have. Hmmm, any customers out there for one?
I layed out the rods and drilled the perimeter with 3/16" drills because I had a number of them.
Fortunately i inherited some bastard files from my father, to bring the contours close to size. The circular ends were done by means of filing buttons.
Many year later when my younger son came across the scalloped edge cut offs from the side rods, he quipped: "Pop, you must have been really hungry in those days!"
Patience was certainly a virtue in those days.
Re: Constructing the Josslin Hudson
Three fluted rear side rods. The two new and one saved from the two original ones machined at Richard's. I guess I will have a spare LHS rear side rod now.
One more fluting operation to go and then I can de-burr and polish all the rear side rods if I feel like it which I don't.
One more fluting operation to go and then I can de-burr and polish all the rear side rods if I feel like it which I don't.
Re: Constructing the Josslin Hudson
Finishing the rear side rod inner fluting.
Again, just careful work with the appropriate sharp cutter. Ensure that the rods are set in the rod holding fixture so that the inner fluting is centred and leaves parallel (with the same thickness) the two outer ribs as the eye can see the slightest mistakes here. Also, check the fluting depth and don't be aggressive with the DOC (depth of cut).
Not quite finished yet, there is one last critical operation left to do. These Hudson side rods are filled with all sorts of little offsets here there and everywhere.
Again, just careful work with the appropriate sharp cutter. Ensure that the rods are set in the rod holding fixture so that the inner fluting is centred and leaves parallel (with the same thickness) the two outer ribs as the eye can see the slightest mistakes here. Also, check the fluting depth and don't be aggressive with the DOC (depth of cut).
Not quite finished yet, there is one last critical operation left to do. These Hudson side rods are filled with all sorts of little offsets here there and everywhere.
Re: Constructing the Josslin Hudson
Finishing the rear side rods.
This is a lot more tricky than it appears as the side rod ends (both the rear and the front ones) are offset by 1/32" one to the other (as well as the rods being asymmetrical with all of the fluting). One has to study the Josslin drawings very closely to notice this.
Many, many measurements/calculations had to be made (and checking) to establish both end centrelines from which the amount of material to be removed from each face of the big end could then be determined. And this amount, in my case, was quite different with the inner big end face needing about 0.020" to be removed and the outside face needing about 1/16" to be removed. I was just in dread that I had not left enough material on the rod blanks to accommodate these offsets along with the asymmetrical fluting but yes I had (more by luck than anything).
The inner big end rod faces could be finished directly on the grinder magnetic chuck as seen in the first photo as the rods still had the same thickness at both ends at this point and there was not a lot of material to remove. But then to finish the outer face, the rods had to be shimmed to replace the lost thickness when the rod was flipped over and where a lot of material had to be removed. This was done by first setting up a rod in the mill as seen in the second photo to mill away the bulk of the material before finish grinding.
The second finish grinding operation on the front face of the big end needed the same shimming as with the milling operation. In addition, the rod had to be blocked in all around to prevent the big end from shifting as the magnetic chuck held the shims in place firmly but not the shimmed end of the rod.
This is a lot more tricky than it appears as the side rod ends (both the rear and the front ones) are offset by 1/32" one to the other (as well as the rods being asymmetrical with all of the fluting). One has to study the Josslin drawings very closely to notice this.
Many, many measurements/calculations had to be made (and checking) to establish both end centrelines from which the amount of material to be removed from each face of the big end could then be determined. And this amount, in my case, was quite different with the inner big end face needing about 0.020" to be removed and the outside face needing about 1/16" to be removed. I was just in dread that I had not left enough material on the rod blanks to accommodate these offsets along with the asymmetrical fluting but yes I had (more by luck than anything).
The inner big end rod faces could be finished directly on the grinder magnetic chuck as seen in the first photo as the rods still had the same thickness at both ends at this point and there was not a lot of material to remove. But then to finish the outer face, the rods had to be shimmed to replace the lost thickness when the rod was flipped over and where a lot of material had to be removed. This was done by first setting up a rod in the mill as seen in the second photo to mill away the bulk of the material before finish grinding.
The second finish grinding operation on the front face of the big end needed the same shimming as with the milling operation. In addition, the rod had to be blocked in all around to prevent the big end from shifting as the magnetic chuck held the shims in place firmly but not the shimmed end of the rod.