Naval four truck gun carriage features

[Cannoneer]

A few members have recently been asking for suggestions on how to make more realistic looking naval carriages, and I started to think about these two features again. This photo is of a "Steen Cannons" reproduction US Navy four truck carriage, and I believe this is the last model of this type carriage used by our Navy (these carriages were still in use in the Civil War). I picked this photo because it shows the two features that I'm asking about to good advantage.

Is there a practical reason for the wheel lynchpins being raked back at an angle?

Each cheek is made of two pieces of wood, and the top piece isn't resting evenly on the bottom piece, they're constructed with a zig-zag pattern that I've seen called a "jog".  What is the purpose of the uneven joining of the two cheek pieces?



We may have covered this here before (I can't remember), but what the heck, we've got a bunch of new members.

[BoomLover]

Just a guess, but would the "jog" have something to do with lessening the effects of recoil on the wood of the cheek? Help absorb the sudden kick backwards? The design and placement may suggest that...like I say, just a guess...BoomLover

[Zulu]

Certainly the "jog" is to add strength to the joining of the upper and lower pieces of the cheek.
It was also used to good advantage in the garrison carriage in the top picture.
 

 
The lower picture has the rake of the lynch pins but in the opposite direction.  I see no purpose for it myself.
This picture is from "Round Shot and Rammers".
Zulu

[Max Caliber]

The "jog" is to lock the two pieces of the cheeks together in recoil. The linch pins at an angle are so handspikes can be worked against the ends of the axles.

[Zulu]

The "jog" is to lock the two pieces of the cheeks together. The linch pins at an angle are so handspikes can be worked against the ends of the axles.

Handspikes!!  Way to go Max!  Of course that's it.  You would think I could have figured that out.
Zulu

[Cannoneer]

Well, leave it to Max to set me back on my heels! I've never seen that photo before, and it had never even occured to me to think that the pins were set at angles to facilitate levering the axle arms with handspikes; but even though Zulu is already thoroughly convinced, let's not be too hasty to accept this explanation as fact, not just yet anyway. I"ll get back to this one.

I guess that the reason for the "jog" in the cheek pieces is a little more obvious, but I haven't found it explained in any of the naval literature that I've read so far. I agree with BoomLover, Zulu, and Max on the reason for this construction, it's got to be to stop the rearward movement of the top cheek piece caused by the force of recoil, and thus prevent, or at least greatly reduce the pressure placed on the through bolts that hold the two pieces together.

[Frank46]

Think of it as a recoil shoulder somewhat similar to that of a modern rifle with the mortise for the recoil lug. Nice looking carriage. Frank

[Double D]

As much as I like Max Calibers thought, I don't think its right, because the linch pin would be in the way if you have use the handspike in the opposite direction.    Besides in the offered photo the linch pins are inside the lever.

Here is the repro carriage on the U.S.S. Cairo.  Vertical linch pins

 

here is the original.

[GGaskill]

Assuming the vertical bolts through the cheeks were kept tight, the induced friction between upper and lower pieces should be transferring most of the load from upper to lower.

[Cannoneer]

As much as I like Max Calibers thought, I don't think its right, because the linch pin would be in the way if you have use the handspike in the opposite direction.    Besides in the offered photo the linch pins are inside the lever.

Here is the repro carriage on the U.S.S. Cairo.  Vertical linch pins

 

here is the original.

Excellent observations, Douglas, and you also saved me from having to search my photo files for USS Cairo cannon carriage pics. The repro carriage with the lynchpin straight up and down could be in error in this case, but it doesn't really matter, because there are historic examples of pins placed this way on earlier carriage models. The photo of one of the real surviving carriages shows an angled lynchpin, but I think I can demonstrate that these more modern US ship carriage models would not have been maneuvered on any gun deck by using handspikes on the axle arms. If you look at DD's first pic you can see brackets on the inside plane of the cheek by the bottom step, and these brackets fit the ends of handspikes made specifically for these carriages. The crewmen working these handspikes easily ran these guns out into battery, and traversed them left or right. So I'll ask the question again, but this time just concerning this model U.S. carriage. Why are the lynchpins placed at an angle through the axle arms?   

[Double D]

Here's what I think, the angle is meaning less...

[Cannoneer]

The earliest known naval truck carriages (Mary Rose, northern European, etc.) had perpendicular pins holding the wheels on the axles, so we know that a carriage maker/designer somewhere along the line of the truck carriage’s evolution decided to change things, and place the linchpins at angles on the axle arms; but why? I find it impossible to believe that there was no rationale behind this development, even if the reason turns out to be that someone thought they’d look cool that way, which by the way, I think is an extremely far-fetched notion.
I’ve been curious about this for years, and I haven’t found an answer in any of the artillery literature that I’ve read so far. My humble opinion is that they were angled simply to make it easier to remove them. The trucks would have had to have been removed on a regular basis to grease the arms, check for and repair any damage, replace trucks, etc., so having the linchpins placed at angles through the axle arms would have eased the task of tapping them out from the bottom. 

U.S. Marsilly carriage mid 1800's