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Topic review - Hotchkiss 6 pounder QF in Rhino3D
Author Message
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
A fascinating project!

Someone mentioned earlier in the thread about RCN Saluting guns.

Here are some photos of current service RCN Saluting guns - these appear to be WW2 6 Pd AT guns mounted on modified original 3Pd QF mounts from VS&M in some cases dated 1901.

IMG_7800.JPG [ 278.86 KiB | Viewed 120 times ]
IMG_7804.JPG [ 183.06 KiB | Viewed 120 times ]
IMG_7805.JPG [ 142.94 KiB | Viewed 120 times ]
Post Posted: Fri Nov 19, 2021 12:06 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Excellent! A search for the cruiser Cosmao turned up a photo linked here: ... entier.jpg

Would love to see more images of your model of this ship. The tumblehome hull and especially the bow are exotic. Michael

Ah. Found your build thread:


Beautiful work.
Post Posted: Tue Feb 16, 2021 8:35 am
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Very interesting post with an amazing amount of detail I wish I had seen this before I modeled my Hotchkiss for my virtual model of the French cruiser Cosmao (1889). It's not that detailed as it's part of a much larger model and the file size is already quite large. Here is what I came up with.

Hoch-1.jpg [ 392.67 KiB | Viewed 353 times ]

Hoch-3.jpg [ 394.34 KiB | Viewed 353 times ]
Post Posted: Sat Feb 13, 2021 10:39 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
WWI tank version SIDE.jpg
WWI tank version SIDE.jpg [ 201.34 KiB | Viewed 455 times ]
Thank you Cliff. This shows a WWI version of a Hotchkiss 47 mm. The recoil mechanisms we have been discussing are more highly evolved, or maybe adapted to work inside of a tank. The designer has separated the springs and the shock absorber. The shock, now identified as a "counter recoil" is mounted above the gun tube. The springs, two of them, go below. In this system the cylinders are fixed in position and the piston moves with the gun tube.

In the early 57 mm I am modeling, the whole system, spring plus shock, is designed within a single long cylinder. The handbook makes it easier to understand the variety of recoil systems that turn up in photos taken across the years. And it is great to see some 3-view machine drawings, rather than perspectives! Michael
Post Posted: Fri Nov 20, 2020 12:37 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Is the following relevant? It's an Army application, but perhaps there are similarities?

Handbook for the Q.F. Hotchkiss 2.244-inch, 6-pdr., 6-cwt. Mark II gun with tank mounting. ... ll9/id/943
Post Posted: Wed Nov 18, 2020 9:02 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Many thanks wefalck. I will assume the displacement of the barrel is a reasonable approximation and proceed to the next step — probably the pintel.

Keen observation about the exaggerated recoils depicted in movies. Michael
Post Posted: Fri Aug 28, 2020 8:47 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
If the 80 mm is what you measured, then this is likely to be true. I have never seen any such gun been fired, but have been surprised to see in drawing over how short distance the recoil was stopped. I think we are often mislead by cinema films, where guns either don’t show any recoil or jump madly. I think on youtube you can see some late 19th/early 20th century guns being fired.

A major concern would be the heat dissipation from the recoil brake. The glycerine would heat up fast after a few shots, the kinetic energie being converted into heat. In some guns this seems to have limited the rate of fire, rather than the level of training of the gun crew.
Post Posted: Thu Aug 27, 2020 12:42 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
recoil -- max piston travel.jpg
recoil -- max piston travel.jpg [ 95.22 KiB | Viewed 563 times ]

With the brake cylinder mounted, it is now possible to make some basic measurments of the maximum possible travel associated with a recoil. The travel is limited absolutely by the distance that can be moved by the piston inside the shock absorber.

This turned out to be 80 mm, as shown. Not sure this is a realistic value and would welcome comment. It implies that in a single cycle, the piston (actually the cylinder) traverses about 6 inches altogether through the glycerine fluid -- 3 inches aft and then 3 inches forward.
recoil slides aft & brake cylinder.jpg
recoil slides aft & brake cylinder.jpg [ 236.16 KiB | Viewed 563 times ]

Shown from below at the full extent of a recoil. The slides, their mounting ring, the gun tube and the brake cylinder all shift aft as an integral unit with the recoil. Note the slides protruding aft from the guides. Inside the brake cylinder can be seen a fixed disk and retainer that provide the base for the internal springs. The cylinder freely slides past this disk as the gun recoils.
Post Posted: Thu Aug 27, 2020 11:37 am
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
USS Maine & Cradle assy.jpg
USS Maine & Cradle assy.jpg [ 208.71 KiB | Viewed 622 times ]

Found a photo of a Hotchkiss 6 pdr recovered from the USS Maine. There are a few other photos that show the cradle assembly, but this is the most helpful I have come across. This Hotchkiss is in South Carolina, here: ... -uss-maine

The cradle consists of the two guide plates united by a bridge. The whole assembly appears to be a single casting, subsequently machined.

At the center of the bridge is the retaining nut for the brake. The large disk visible below the bridge in the CAD sketch is the piston of the shock absorber. The piston is fixed in position -- the cylinder slides back and forth with the gun tube.
Post Posted: Tue Aug 25, 2020 6:12 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Welcome to the forum.

Some observations and possibilites:

No pintel.

The base and perhaps the trunnion bearings look as though they might have been improvised. Are these film can bearing housings waterproofiing?

The brake unit may be broken or opened or corroded away in such a way that the springs have expanded and, in effect, lengthened or telescoped the brake assembly.

About as close as I can get is this drawing of a Mark IV, which was specialized for anti-aircraft in WWI.

WNBR_6pounder_m1_sketch_pic.jpg [ 70.38 KiB | Viewed 938 times ]

It has a rotating base instead of a pintel, a broomstick instead of a shoulder-fitted traversing arm, and two recoil brake components mounted above the tube. Might be a cousin of your antique Mark X cum Mark II.

Root and VavDervoort has an interesting history, here: ... dnance.htm

Root & VanDervoort may also be a key to researching this find. Bridgeport manufactured commonplace Hotchkiss 6 pounders under license. But all the unusual components in your example are R & V and date from the WWI epoch. We can speculate that these components upgraded and specialized the already archaic Mark II design, in 1917, for some specific purpose: AA, coastal defense, maybe the deck of a submarine.

Might try searching the National Archives for ordinance made by Root & VanDervoort.
Post Posted: Mon Jul 06, 2020 8:44 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Hi, New here. I'm very glad I found this site. I recently obtained a 6 pdr gun. Yes, the real deal. In brief, from the markings, it has a Mark X Mod slide on top of the gun. It is from the Root and VanDervort Eng company 1917. The gun is a 57mm and breech markings: 6 pdr Br. Mech Mk II Mod. Gun no: 293 A 26245-1 Stamp is from Bridgeport Conn and I cannot see the other part of it.
There are more markings on the slide.
Your diagram of the breech has helped immensely to understand it and it is slowly opening up.
I have attached a picture of it. I have found many sites and cannot find one just like it. That is, with the rather large slide on top. I'm cleaning the sight (a lot of brass and only use a brass brush of course). and hope to get it working soon.
I'm trying to find out where it came from and if it was a working gun on a ship or somewhere.
Is there such a site to put in the SN or other information to find this out?

Thanks for any help.

File comment: Rear View
IMG_1155.jpg [ 176.77 KiB | Viewed 981 times ]
File comment: Good side view
IMG_1156.jpg [ 173.3 KiB | Viewed 981 times ]
Post Posted: Mon Jul 06, 2020 12:56 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Many thanks, wefalck. This makes it perfectly clear how the energy of the recoil is dissipated in two strokes, aft and foreword.

I notice the piston and cylinder dimensions set logical limits on how far the gun tube can move. Michael
Post Posted: Thu Jan 30, 2020 8:04 am
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Normally, the piston has various small holes in it through which the fluid (e.g. glycerine) is pressed from one side to the other. The number and size of holes is adapted to the viscosity of the break-fluid used. The spring then moves the gun forward again into the firing position, squeezing the fluid through the holes in the opposite direction. The break-fluid has to have a fairly high boiling point, as a considerable amount of heat is generated by the movement. This limited also the number of shots that could be fired per hour in order to dissipate that heat.
Post Posted: Wed Jan 29, 2020 12:59 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Hello wefalk,
Yes, the brake contains a piston and cylinder for the hydraulic shock absorber. This is a Hotchkiss drawing for the 3 pounder, but we can probably assume a similar brake was used on the 6 pounder.
hydraulic brake.jpg
hydraulic brake.jpg [ 79.99 KiB | Viewed 1163 times ]

It appears to me the central shaft is anchored at the forward end by a bolt to the cradle. The cylindrical housing recoils with the gun tube while the shaft remains fixed. I am looking for some means for the fluid in the shock absorber to circulate as the piston moves, but not seeing it.

edit: Actually in this design the piston is fixed, and the cylinder oscillates back and then forward. mcg

It would be very helpful if you could explain how this brake worked. Many thanks. Michael
Post Posted: Wed Jan 29, 2020 11:58 am
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Inside the recoil-spring there is no hydraulic shock absorber ? They became quite common on larger guns at least from the early 1870s on.
Post Posted: Wed Jan 29, 2020 11:12 am
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Slides integral w Ring.jpg
Slides integral w Ring.jpg [ 66.24 KiB | Viewed 1169 times ]

The slides are secured to barrel's jacket with a ring mount, probably shrunk into place. The ring and the slides are modeled as an integral casting.

In order to mount the ring and slides the original casting had to be modified. Here is the original Mark I version with trunions mounted directly to the barrel.
trunion.jpg [ 40.19 KiB | Viewed 1169 times ]

Below is the modernized version, with the trunion deleted. Note that the aft section of the jacket is now perfectly cylindrical.
Jacket w trunions deleted.jpg
Jacket w trunions deleted.jpg [ 19.47 KiB | Viewed 1169 times ]

Finally, here is tha jacket with the ring and its integral slides mounted.
Jacked w slides mounted.jpg
Jacked w slides mounted.jpg [ 20.42 KiB | Viewed 1169 times ]

This entire recoiling mass, maybe about 600 lbs, slides aft freely and suddenly against a spring when the QF is fired.
Post Posted: Wed Jan 29, 2020 10:33 am
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
57_45Br.jpg [ 207.7 KiB | Viewed 1216 times ]

This version of the Hotchkiss 6-pounder is fitted with a recoil brake, noticeable underneath the gun tube. It is also fitted with two side plates. These support parts of the recoil mechanism, but it is difficult to guess how they work, exactly, from most photos.

In 2017 I found some fairly good 3-view drawings of the recoil mechanism for a Hotchkiss 3-pounder. Here is a side view:
3 pdr side view.jpg
3 pdr side view.jpg [ 55.96 KiB | Viewed 1194 times ]

The basic components include the brake cylinder, a U-shaped cradle with a front bridge arcing beneath the barrel, and the gun tube suspended on slides within the cradle. The slide and guide rails are more evident in a view from behind:
3 pdr guides & slides.jpg
3 pdr guides & slides.jpg [ 19.63 KiB | Viewed 1194 times ]

The 3-pdr drawings show what elements to look for but do not directly apply to the 6-pounder.

Finally I came across a photo snapped of a 6-pdr on the USS Olympia that is a great help. It was taken from behind and the traversing arm has been removed, so there is an unobstructed view.
USSOlympia hotchkiss brake.jpg
USSOlympia hotchkiss brake.jpg [ 85.51 KiB | Viewed 1216 times ]

The photo clearly shows the thickness of the plate, and since it has not been painted over, it is possible to see the merest outline of the slide it contains and guides. Here is a CAD sketch of the two plates with the slides extended to the rear, as they would be in operation.
Guides & Slides.jpg
Guides & Slides.jpg [ 34.17 KiB | Viewed 1216 times ]

The CAD image and file are labelled "Guides & Slides." Note that the slides are beveled top and bottom to lock them into the guides. The gun tube is attached to the slides, and the guide plates carry "new" outboard trunnions. These replace the trunnion that was solidly molded into the barrel in the earlier Hotchkiss 6-pounders, which had no recoil brake save the crinoline mount.

Not shown is a front bridge that arcs under the barrel and connects the two side plates to form a typical U-shaped gun cradle.
Post Posted: Thu Jan 23, 2020 12:55 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Many thanks, Alexey -- this is very helpful. Michael
Post Posted: Sun Mar 13, 2016 5:13 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote

Post Posted: Sat Mar 12, 2016 3:18 pm
  Post subject:  Re: Hotchkiss 6 pounder QF in Rhino3D  Reply with quote
Thank you Alexey. Do you know what type of wood was used? Michael
Post Posted: Sat Mar 12, 2016 11:49 am

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