Constructing the Josslin Hudson
Moderator: Harold_V
Re: Constructing the Josslin Hudson
Some of the misc. parts associated with the side rods which needed to be made. These are all "straightforward" lathe turning operations.
I put the term "straightforward" in quotation marks as the bronze bushings were anything but that. The bushing ID had to be drilled and then precision bored to a dead close running fit (tenths) on the steel crankpin while the bushing OD had to be a press fit in the rod (more tenths). As well, the surface finish and geometry on the ID and the OD of the bushings had to be dead smooth and straight. Everything on these bushings has to be turned at one setting. Lose one's concentration for a second and you can start over again.
I put the term "straightforward" in quotation marks as the bronze bushings were anything but that. The bushing ID had to be drilled and then precision bored to a dead close running fit (tenths) on the steel crankpin while the bushing OD had to be a press fit in the rod (more tenths). As well, the surface finish and geometry on the ID and the OD of the bushings had to be dead smooth and straight. Everything on these bushings has to be turned at one setting. Lose one's concentration for a second and you can start over again.
Re: Constructing the Josslin Hudson
Continuing with the front side rods where I left off 4 years ago. I previously described how I got to this point.
The first operation was to rough down the tongue ends of these rods. It is very important that the tongue of the front side rod does not end up being canted with the rest of the rod (it has to be square, parallel and closely on size but it is also offset) so the setup to make and keep it this way has to right. I don't claim to have the perfect setup but with care, the one shown in the first photo worked. I don't need to repeat that it is very important to have all of the rod blanks as rectangular as possible to start with as this and all of the other rod setups depend upon this initial machining being correct.
But first numerous measurements and a lot of calculations (see the last photo - ignore the numbers as it is the methodology which is important) are needed here as with the rear side rods, the front side rod ends are also offset 1/32" from each other and the rods are asymmetrical about their centre lines.
One has to first establish where the two centre lines are on the rod blank and then work from there. Also, in my case, the layout process included marking the rods LH and RH as well as the inside face and the outside face and the top and the bottom of the rod blanks.
As with the rear side rods, I feared that I had not left enough blank thickness on the front side rods to achieve the above (as I came to the realization that the rod ends were offset 1/32" quite late). The first calculations indicated nearly .030" to the good on one blank but only .007" with the second blank so I escaped again this time.
The first operation was to rough down the tongue ends of these rods. It is very important that the tongue of the front side rod does not end up being canted with the rest of the rod (it has to be square, parallel and closely on size but it is also offset) so the setup to make and keep it this way has to right. I don't claim to have the perfect setup but with care, the one shown in the first photo worked. I don't need to repeat that it is very important to have all of the rod blanks as rectangular as possible to start with as this and all of the other rod setups depend upon this initial machining being correct.
But first numerous measurements and a lot of calculations (see the last photo - ignore the numbers as it is the methodology which is important) are needed here as with the rear side rods, the front side rod ends are also offset 1/32" from each other and the rods are asymmetrical about their centre lines.
One has to first establish where the two centre lines are on the rod blank and then work from there. Also, in my case, the layout process included marking the rods LH and RH as well as the inside face and the outside face and the top and the bottom of the rod blanks.
As with the rear side rods, I feared that I had not left enough blank thickness on the front side rods to achieve the above (as I came to the realization that the rod ends were offset 1/32" quite late). The first calculations indicated nearly .030" to the good on one blank but only .007" with the second blank so I escaped again this time.
Re: Constructing the Josslin Hudson
Some quick and dirty ways I scribe all of the partial intersecting arcs and half round ends, etc. on the front rod blanks prior to generating them with the rotary table setup(s).
Just to make things interesting, every partial arc on these Hudson rods has a different radius.
Just to make things interesting, every partial arc on these Hudson rods has a different radius.
- Bill Shields
- Posts: 10557
- Joined: Fri Dec 21, 2007 4:57 am
- Location: 39.367, -75.765
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Re: Constructing the Josslin Hudson
So cool....
Makes my method of drilling holes at each of the curve tangent points seem positively Byzantine in comparison
Makes my method of drilling holes at each of the curve tangent points seem positively Byzantine in comparison
Too many things going on to bother listing them.
Re: Constructing the Josslin Hudson
Hi,
As I said elsewhere, Don is meticulous in his work. Everything has to be just right.
In the old days (before CNC), the rod outside profile would have been done by filing to shape since the outline was for appearance only.
Now you simply draw the rod outline in CAD to tenths, do an offset on the part outline which is the same as the radius of the cutter you plan to use then write the G code to follow that offset path. Before writing the code, you make a simple fixture to hold the part by the rod centers, decide where home is going to be and then write the code (you have to determine "home" before you can write the code and "home" needs to be some feature that will allow you to accurately position the cutter if you make a mess of things).
Finally, you accurately fasten the fixture to the CNC mill table, put the part in the fixture, move the cutter to the "home" position and start the mill. You wind up with a part profile which is accurate to tenths and you can do as many parts as you need with the same profile. Accurate mass production!
From my point of view, the world has changed for the better (I built my own CNC), but you have to admire Don for the quality of his work and not everyone has CNC.
Richard Trounce.
As I said elsewhere, Don is meticulous in his work. Everything has to be just right.
In the old days (before CNC), the rod outside profile would have been done by filing to shape since the outline was for appearance only.
Now you simply draw the rod outline in CAD to tenths, do an offset on the part outline which is the same as the radius of the cutter you plan to use then write the G code to follow that offset path. Before writing the code, you make a simple fixture to hold the part by the rod centers, decide where home is going to be and then write the code (you have to determine "home" before you can write the code and "home" needs to be some feature that will allow you to accurately position the cutter if you make a mess of things).
Finally, you accurately fasten the fixture to the CNC mill table, put the part in the fixture, move the cutter to the "home" position and start the mill. You wind up with a part profile which is accurate to tenths and you can do as many parts as you need with the same profile. Accurate mass production!
From my point of view, the world has changed for the better (I built my own CNC), but you have to admire Don for the quality of his work and not everyone has CNC.
Richard Trounce.
- Bill Shields
- Posts: 10557
- Joined: Fri Dec 21, 2007 4:57 am
- Location: 39.367, -75.765
- Contact:
Re: Constructing the Josslin Hudson
I also have a CNC mill and love the capabilities....but like being manual creative.
Too many things going on to bother listing them.
Re: Constructing the Josslin Hudson
Back to finish profiling the pair of front side rods.
This time I tackled the upper rod profile between the main crank pin bore and the tongue. This involves no less than four intersecting radii which all have to blend in perfectly to look right.
But first I had to half end round the end of the tongue using the rotary table. I took no photos of this as you have already seen a lot of similar setup's and photos of such operations on the rear side rods.
I use plunge milling for this operation using 1/4" dia. 3/8" dia., 5/8" dia and 3/4' dia. end mills not caring much what they were (i.e. two or four flute, HSS or carbide, a regular end mill or a fine rougher. Just use very small in feed increments a moderate speed and a slow down feed and I can't see much difference in the profile finish as long as all of the end mills are very sharp.
This is just slow careful work starting the cutter away from the partly finished rod and then slowly moving it in up to the layout line, checking after each cut that the partial curve is forming where it should be. Good lighting and being able to see what is going on from any angle is essential.
After completing all of the plunge milling operations, the profile was given a final lick using a 1/4 " dia. drum sander which was held in my bench drill press and run at high speed (3000 rpm).
I know everyone will say this is the perfect application for CNC profiling and it is but I like the final result achieved here also.
This time I tackled the upper rod profile between the main crank pin bore and the tongue. This involves no less than four intersecting radii which all have to blend in perfectly to look right.
But first I had to half end round the end of the tongue using the rotary table. I took no photos of this as you have already seen a lot of similar setup's and photos of such operations on the rear side rods.
I use plunge milling for this operation using 1/4" dia. 3/8" dia., 5/8" dia and 3/4' dia. end mills not caring much what they were (i.e. two or four flute, HSS or carbide, a regular end mill or a fine rougher. Just use very small in feed increments a moderate speed and a slow down feed and I can't see much difference in the profile finish as long as all of the end mills are very sharp.
This is just slow careful work starting the cutter away from the partly finished rod and then slowly moving it in up to the layout line, checking after each cut that the partial curve is forming where it should be. Good lighting and being able to see what is going on from any angle is essential.
After completing all of the plunge milling operations, the profile was given a final lick using a 1/4 " dia. drum sander which was held in my bench drill press and run at high speed (3000 rpm).
I know everyone will say this is the perfect application for CNC profiling and it is but I like the final result achieved here also.
Re: Constructing the Josslin Hudson
Before I could proceed any further with the profiling of the front side rods, I discovered a problem which needed to be corrected. It developed from the time I was in Richards shop and used his Bridgeport milling machine and super accurate digital readout to layout, drill and finish bore/ream the three holes in the front side rods (1/4", 1/2" and 13/16" dia. as per the Josslin prints). I know that the three holes were accurately spaced, on size and in line but for whatever reason, I did this operation on each rod individually and not as a matched pair.
Somehow and somewhere something moved slightly (I don't know how) on one of the rod blanks so when the two partially machined rods were set together on their bores (which aligned perfectly) they (the partially machined blanks) were canted slightly one to the other. Fortunately, there was enough material left on the rod blanks so this problem could be corrected. But this involved having to make a new alignment setup based on the rod bores and not the original machined reference surfaces.
To do this I used two 1/2" dia. dowel pins and a new precision bushing to sleeve down the main 13/16" diameter main bore. By precision bushing, I mean one made to tenths both OD and ID and dead straight and concentric. This was all collet work carried out in the old WWII 13" SB toolroom lathe here which I had my doubts but it turned out fine - the dowel pins are a totally shakeless hard sliding fit fit in the bushing bore and the bushing itself is a hard sliding shakeless fit in the main rod bores so the "fit" has to be less than 0.0005". See the first photos.
This new assembly then became part of the new setup (based now only on the rod bores when the two front side rods were set together) so everything now could be machined from them as needed to have a matched set of rods. See the remaining photos. And it worked! - but just another unanticipated work detour.
Somehow and somewhere something moved slightly (I don't know how) on one of the rod blanks so when the two partially machined rods were set together on their bores (which aligned perfectly) they (the partially machined blanks) were canted slightly one to the other. Fortunately, there was enough material left on the rod blanks so this problem could be corrected. But this involved having to make a new alignment setup based on the rod bores and not the original machined reference surfaces.
To do this I used two 1/2" dia. dowel pins and a new precision bushing to sleeve down the main 13/16" diameter main bore. By precision bushing, I mean one made to tenths both OD and ID and dead straight and concentric. This was all collet work carried out in the old WWII 13" SB toolroom lathe here which I had my doubts but it turned out fine - the dowel pins are a totally shakeless hard sliding fit fit in the bushing bore and the bushing itself is a hard sliding shakeless fit in the main rod bores so the "fit" has to be less than 0.0005". See the first photos.
This new assembly then became part of the new setup (based now only on the rod bores when the two front side rods were set together) so everything now could be machined from them as needed to have a matched set of rods. See the remaining photos. And it worked! - but just another unanticipated work detour.
Re: Constructing the Josslin Hudson
The finish profiling of the top half of the front side rods.
It is the same operations and setups done over and over again. It probably has involved at least 15 additional operations and 5 different setups as the resultant profile involves producing several compound curves although it doesn't look that way in the photos but it is.
I have included some sample photos of the additional operations undertaken but without any description.
As stated previously, I don't know how to program these operations in CNC and due to the fact that it involves many compound curves, it is not a simple deal to first draw the part in CAD and then write the program for it. And since nobody is going to do this for me for only two parts, then I guess I will have to stick with the devil I know.
It is the same operations and setups done over and over again. It probably has involved at least 15 additional operations and 5 different setups as the resultant profile involves producing several compound curves although it doesn't look that way in the photos but it is.
I have included some sample photos of the additional operations undertaken but without any description.
As stated previously, I don't know how to program these operations in CNC and due to the fact that it involves many compound curves, it is not a simple deal to first draw the part in CAD and then write the program for it. And since nobody is going to do this for me for only two parts, then I guess I will have to stick with the devil I know.
Last edited by Carrdo on Wed Nov 23, 2022 12:02 pm, edited 1 time in total.
Re: Constructing the Josslin Hudson
Slowly working my way around the rod profile. It is just more of the same with virtually each radii requiring a different setup.
One also has to slowly cut away at the reference surface to provide clearance for the cutting tools. But do not eliminate it entirely at this point as the remaining reference surface is still needed to align the rod blank dead parallel to the rods big and small end bores.
One also has to slowly cut away at the reference surface to provide clearance for the cutting tools. But do not eliminate it entirely at this point as the remaining reference surface is still needed to align the rod blank dead parallel to the rods big and small end bores.