Greg's French 75 Mm Field Artillery Model

[gjmontll]

Status Update: Wooden Wheels in progress
For the past few months I've been working on the cannon's wooden wheels. As the image in my prior message showed, these are fairly complex assemblies and I've been feeling my way through the process.
I need to produce 42 wooden pieces, the 14 spokes and 7 fellows for each wheel. ( A "fellow" is a segment of a wooden wheel's rim.) I have finished the basic shaping of the fellows.
Each spoke fastens to the fellow with a small steel spoke-shoe. I just finished the milling of these 30+ shoes (I have a few spares.), each requiring about 12 milling operations (plus hacksawing and hand filing). I quickly recognized the productivity value of a vise work stop, and took a break from the wheel work to make one that proved very useful. Below is the work stop in action as I machine a spoke shoe (center drilling for the 0.063 hole used to bolt the shoe to the fellow.)


So far, I have done one prototype spoke. Each spoke will be formed from a 0.5" x 0.36" x 2.8" piece of oak and requires about 12 machining operations. Because of the small size and odd angles, ordinary woodworking tools (sander, router, jigsaw) don't seem to work well enough. Given that I need to make about 30 spokes, I need to get a more productive process going. Based on my prototype, the first step will be on the metal lathe, the rest on my mini-mill/drill, several cuts using a router bit. The oak machines nicely, except for the sawdust. Because each of the four long faces have two different angles, I plan to make a set of fixtures that will position the spoke in the mill vise in all the needed positions. (Or maybe use my sine-vise.)

Below is another image showing a wheel mockup with a set of fellows temporarily held in place with a hose clamp, and the pile of spoke shoes. One shoe is assembled on the prototype spoke which sits in place in the wheel hub. The bottom four shoes, adjacent to the dime, show the shoe from top, bottom, left and right side views.



Not yet started are small steel joining plates that connect the fellows together. And I haven't yet figured how I will weld a strip of 14 gauge steel to form the tire.

From the gun on display at Orange County, here is the real-world object showing spokes, shoe, plate, fellows, and fasteners. As you see, this gun is painted gray and black. I haven't yet decided on the finish for mine. To be historically-correct, it should be a green/brown/white/black camouflage pattern. But I don't want to obscure the mechanical details.

This week I hope to finish the spokes! I'll be glad to get the woodworking out of the way.
Greg

 

[gjmontll]

Making the Wooden Wheels
For 4 months now, I've been building the cannon's wooden wheels. Not quite done, but yesterday was a milestone: a success test fitting of the spokes, shoes, and fellows that I've been working on.

Fellows:
Each wheel's rim is made from seven fellows (aka "felloes"). They were cut from 1/2' oak and sanded to match the template of my CAD drawing. Each fellow connects to two spokes using steel spoke shoes. Rabbets for the spoke shoes were done on the mill, using a router bit and hand holding/guiding the pieces.

Fellows1 The oak pieces after cutting on Rockwell BladeRunner table-jig saw.


Fellows2 And after cutting/sanding the curved faces.


Spoke Shoes
The wooden spokes connect to the fellows by use of a steel spoke shoe, bolted to the fellow.
These shoes were machined from 3/8 x 3/8" steel key stock. Making 28 of them, plus some extras was tedious, with about 20 machining operations to do on each shoe.
I improved my process by spending two days to make a mill vise work stop with plans from a great website I'd not known about, see http://www.homemadetools.net/
Still tedious in the multitude of openings and closing of the mill vise, but then doing the work in an assembly line fashion greatly improved my speed and accuracy.

Spoke Shoes 1

Mill work stop: built from plans on HomemadeTools.net, but to half-size.

Spoke shoes 2

Spoke Shoes 3

Machining Spoke Shoes Workstop


Spokes
The 28 oak spokes were the toughest part yet to make.
Each one has a 3/16" stud or boss on the end to fit into the shoe. This stud is on-center radially, but off-center axially, to implement the outward dishing of the rim from the hub. These oak studs were turned on my metal lathe, using a 4-jaw chuck and metal cutting lathe tools.
Then the mill was used to cut several different tapers on the radial and axial faces. A sine vice was used for the angles, but as the photos show, because of the small size of the pieces, I clamped them in a small vise, held in the sine vise. These cuts were made with a router bit in the mill, running at my mini-mill's 4300 rpm top speed. (I have Little Machine Shop's Belt Drive Mod kit.)
After milling (routing) all the tapers, I made a fixture to hold the spoke for the cutting of two arcs into each of the axial faces. My normal mill vises don't open wide enough to hold the fixture, so I again used my sine vise, just because it opens wider.One arc is to start the tapering after the spoke leaves the hub. The other is for the #2 bolts that holds the hub and spokes together.
:
Spokes 1 The first of nine routing operations was a rabbet, sine vise not needed.

Spokes 2 The 28 spokes, shoes, and one spare. I ended up having to make more blanks and take them through the lathe and milling/routing process.


Spokes 3 Note the small vise being held in the sine vise for routing one of the six taper cuts.

Spokes 4 Spokes, shoes, fellows and hub laid out on the CAD drawing, showing both axial and radial faces of the spokes and shoes.

Spokes 5 This is the fixture to hold the spokes for more routing operations

Spokes 6 Fixture in use for routing arcs in the axial faces of the spokes.


Wheel Progress and Test Fittings
The first test fitting showed the spoke were interfering with each other inside the hub flange, thus the circumference was too large, causing the gaps between some of the fellows. Today I sanded the spokes' hub taper and retried it. Much better, although I need to fix the angle on one of the fellows, or use a spare.

Wheel Progress 08 Nov: Fellows have not yet been rabbeted to accept the shoes.


Wheel Progress 22 Nov Testing the fit with a rabbeted fellow and two spokes


Wheel Test Fit 1a 28 Nov Now with rabbeted fellows, a full fitting. Note the gaps between some fellows. The spokes are not fully seating into the hub...

Wheel Test Fit 1b 28 Nov With the hub's outer flange removed, the cause of the fellow gaps is seen, need to adjust the tapers where the fellows abut against each other.

Wheel Test Fit 2 29 Nov After sanding the spoke tapers, now it fits! But still more to do, as listed below.



Remaining wheel work
Fellow splice plates: I've only completed the CAD. Need to make 14 plates out of 26 gauge steel. See photo of real wheel fellow with its plates and shoes.


Fellows: drill the holes for the spoke shoe bolts, rabbet for the fellow splice plates, and drill holes for the tire and splice plate bolts.

Spoke shoes: round the corners with a file or grinder.

Spokes: Mill (or sand) a chamfer on each of the spoke edges. Some final finishing sanding and they will be done.

Tire: A steel hoop of 14 gauge steel needs to be made, probably by brazing. After heating and shrinking it onto the fellows, holes for #0 flat head bolts need to be drilled (and countersunk) through the tire and the fellows matching up with the fellow splice plate holes. I'm worried about getting just the right circumference for a proper fit.

Finishing: I am undecided on the color scheme. It will probably follow my grandfather's historic "First Shot" gun which is now at West Point''s museum. This is a camouflage pattern of browns, greens, and black. From the online photos I see, it looks like the wheels are just painted a solid brown.

Question to the Forum: Is anyone close enough to West Point that they could get me some really good photos of the actual coloring? And of mechanical details when I need more info. That Orange County Courthouse gun is 1) not camo painted, and 2) is missing some pieces.

right side view wheel at the Old Orange County Courthouse, Santa Ana, California


That's all for now. I hope to complete the wheels this month.
Greg

 

[CNCMAN]

looks great.

 

[Rick Berk]

OUTSTANDING. When I made a set of tires for a cannon I made, I used a piece of 5/8 plate and hole sawed the middle out then back to the lathe for boring. My final width was .400 so my tire material being .625 I tapered one ID leading edge about .200 deep and bored the tire .020 undersized. When assembling I made a jig and pressed the felloes and and spokes into the tire, the results were worth the effort on tightening everything up. Then back to the lathe to final trim to width and removed the taper used for assembly. I then made another jig to sandwich the hole wheel in the lathe and turned to OD. Hope this gives you an idea as I spent 6 months figuring this out 40 years ago.

 

[gjmontll]

Rick,
That taper is a great idea. I have been considering a similar "saw/turn/bore it out of 3/8 plate" but hadn't considered the taper. At first reading, I didn't quite understand you, but now I think I do -- basically you included a temporary funnel to guide the pieces together, then machined it off once the parts were mated, right?

I did look at my favorite local scrapyard for some appropriate raw material for this approach but found nothing. At home the other day, I saw a small barbell weight plate, but it was not quite the necessary 6.525" OD. (And it was cast iron; it would be messy machining, but that's not a showstopper.) Since I already have the 14 gauge steel ready, I may first try the more traditional method this week, bending and brazing. Even this approach could make use of the "temporary guide funnel" approach.

Yet another idea just occurred to me: that large hoseclamp I showed in my last posting, holding everything together in a test fitting .. I think I could overtighten it a bit (flexing the spokes) to shrink the wood OD enough to get it started into the tire, even without a taper. And heating the tire will help a bit too. I need to do the math on that to see how much expansion I can get.

Or I may just enlist a professional welder for advice / assistance.
Thanks,
Greg

 

[Rick Berk]

First paragraph is correct, Second paragraph don't use cast iron it will break and barbells are made from CI that cant be used for anywhere else. Last paragraph Shrink fit will not work for this thin material. Brazing or tig welding will greatly soften the metal at the joint leading to all kinds of alignment and diameter control. Look forward to the rest of you build.

 

[gjmontll]

Rick
Okay, I will defer to your experience and recommendations on this and very thankfully forget about the "bend it and braze it" method.
For my project, the tires will be much easier, they are almost a standard off-the-shelf size.

My cannon's steel tires need OD/ID of 6.52/6.43.
Luckily, Schedule 40 6" pipe OD/ID is 6.625/6.065.
... so no massive metal removal is needed.​

I've just ordered 4 slices of 1/2" thick pipe from SpeedyMetals.com.
Why 4 slices? If everything goes well, I'll have two tires for the cannon and two for its companion limber, if I decide to built it. (I already have some spare spokes, spoke shoes, and fellows in various stages of completeness.)
More likely, the extra slices will be expended in making two good tires. I am concerned about holding the piece tightly enough in my 4-jaw to prevent slipping but not too tight that it deforms the radius. . Too bad my faceplate is only 6" OD, but I'm sure I can figure some sort of fixture to assist in this. (And take very light cuts.)
Greg

 

[gjmontll]

Wheel Assembly - End of Year Status
I wanted to get the wheels done by the end of the year. Didn't quite make it!
Today I began the trial assembly, bolting the spokes into the hub and fellows for the first wheel. This is just an initial assembly to check the fit and get a final reading on the critical outside diameter prior to making the tires. Those are #0 nuts and bolts on the shoes and #2s through the hub. Again, 7" hose clamps are in use to hold the fellows in place during assembly.

After my request for some Forum member near West Point, Tino volunteered to visit the Museum for me and get some good photos, concentrating on the color scheme. I called the Museum before Christmas and spoke with the Arms Curator to arrange VIP access for Tino. He was very receptive to my request. On the colors topic, he told me the guns came from the factory with the camo already done, I had assumed it was done in the field by the soldiers,
So far, my parts have had initial primer coats.. When completely assembled, I'll top coat with the correct shade(s) of camouflage paint.

Not shown in this picture - the fellow splice plates that will be bolted at each fellow-fellow joint. I've already drilled their holes through the fellows. Once the tires are on, I then need to remove the spokes in order to get drill access to continue the splice bolt holes out through the tire. Then countersink for 14 #0 flat head bolts that will go thru the tire, fellows, and splice plates.

For the tires, per Rick Berk's suggest (see the 13, 14 December postings), I have my 1/2" slices of 6" Schedule 40 steel pipe ready to go, this week I'll put them in the lathe and turn* them into tires. (*Pun intended).

Happy New Year
Greg

 

[gjmontll]

Wheel Construction Finished
The woodworking is now done and the wheels (hubs, spokes, shoes, and fellows) have been assembled.
I set them up in the mill on a pivot to true the outside diameter (first photo). In this configuration the fellows and spokes are not fully-constrained. It took an elaborate setup (1-2-3 blocks to either side of the cutter and the arm of my mill work stop on the left side of the mill) to adequately stabilize the fellows for the cutting with a 1/4" router bit.

Then I put the hose clamps back and tightened down. As shown in the second photo below, as it's compressed, the spokes tilt outward and the gaps between the fellows come together as the wheel assumes its final shape. Now I can measure the final OD, 6.50". This will be the inside diameter for the steel tires, which I will make today,
Below are the two wheels, on their axle. You see the positive camber since the axle ends bend downward. The rabbets, slots and holes at the fellow joints will be filled with splice plates and #0 flat head bolts.

In the foreground are the 1/2" slices of 6" Schedule 40 pipe that will become the tires.They already have an almost perfect OD, just a light finishing cut should be needed, then I'll bore it 0.148 and cut the guide ramp, following the technique Rick Berk mentioned here 3 weeks ago.
Greg

 

[wrmiller]

Cool stuff.