Thinking things throu, carronade carriages

[dafi]

While building I found some of my usual questions about the carriages of carronades with sliding upper parts as seen on HMS Victory:-)

 

Carriages:

In the drawings that I know, the upper sliding part is linked by a round bolt to the lower part. This bolt moves backwards in a long slot of the lower part.

 

In the front the forward position of the movement is limited by the eyebolts ...

 

 

... and drawings show a quite spectacular overhang in the backward position, that - seen the slot - could be even more than 50 %.

 

 

 

How much did the breech line allow?

 

As the wheels already allow a sideways movement ...

 

 

... it is intersting, that with the round bolt, the sled with the barrel would allow a turn too.

 

 

Could this be?

 

Coin:

In drawings or models in NMM the guns are displayed without coin if a threaded rod for height adjustment is used.

But seen the turning radius around the low situated trunnions would transfer all energy onto the threaded rod, and therefor on the point on the bottom of the rod where it meets the carriage. Would a coin relieve the rod in this situation?

 

Questions over questions,

 

Daniel

Edited March 16, 2015 by dafi

[jbshan]

I believe, without checking my sources, that there would be, in addition to the bolt, a block of wood also sliding in the slot.

The traverse of the slide, by way of its wheels, would be enough for aiming, and, as you suggest, the carronade would be unstable and not function well if the carriage could pivot as you have shown on the slide.  The elevation screw would remain in a position where it would function as well.

[jud]

Suspect there is more than a round bolt in the slot. Would expect to see a traveling "T" arrangement. That would do two things, one to hold the slide in alignment and the other to keep the upper and lower part of the recoil system attached in case of an upset.

jud 

[druxey]

The development of carronade slides is an avenue of research all its own. I recently needed to find details of an early form of slide and found a plethora of different design variations as the Admiralty and Woolwich Arsenal (not the football team!) tried to work out the snags. One of the best sources (you may need to get this through library loan, as copies are rare) is Adrian Caruana's  The History of English Sea Ordnance, 1523-1875, Volume II, The Age of the System, 1715-1815.

[dafi]

Here a bit of NMM NMM

 

Description and illustrations of a 24-Pounder Carronade on a Carriage etc with key) (Misc 60A)

 

Possibly a early model, with round bolt but second guide for the slide.. 

 

http://collections.rmg.co.uk/collections/objects/147421.html PAH7474 

 

Helena (1804)

Plan showing the elevation of a 32-pounder carronade as fitted to Helena (1804), a 16-gun Ship Sloop. A letter dated 12 August 1804 to Sir William Rule from Robert Seppings at Chatham Dockyard explains the reasons for the plan.

 

Is this thing underneath a stop?

 

http://collections.rmg.co.uk/collections/objects/83650.html zaz3859

 

 

32 pounder carronade (1796)

Plan showing the elevation, carriage plan, and deck plate plan for a 32 pounder carronade, fitting agreeable to General Bentham's directions, on board a river barge at Woolwich.

Date made Circa July 1796

 

http://collections.rmg.co.uk/collections/objects/85086.html ZAZ5295

 

 

18 pounder Joint Carronade

Plan showing the port profile for a 18 pounder Joint Carronade on its Slide Mounting. Joint Carronades had a metal loop on the bottom instead of trunnions to fix it to the slide mounting. Note: The date is taken from B. Lavery, "Arming and Fitting of English Ships of War", page 131.

http://collections.rmg.co.uk/collections/objects/86780.htmlZAZ6989

 

18 pounder Trunnion Carronade

Plan showing the port profile for a 18 pounder Trunnion Carronade on its Slide Mounting. A trunnion Carronade was fixed by the trunnions either side of the gun to the slide mounting. Note: The date is taken from B. Lavery, "Arming and Fitting of English Ships of War", page 131.

 

http://collections.rmg.co.uk/collections/objects/86779.htmlZAZ6988

 

... and one more :-)

 ZAZ6989

 

 

 

Interresting:

- All carriages have a round bolt with a coin to adjust the friction and no second guide at the slot

- Is the thing underneath the carriage a stop? But I know at least one carriage where the bolt is behind the "stop"

- If this is the stop, a pivoting around the bolt would be beneficial to load the guns, especially seen by the weight of heavy shop. 

 

 

Funny:

The mount for the back ring of the breeching rope shows on the Vic in P. and in McKay on the top backwards, on all the drawings it is pointing foreward, which makes more sense.

 

Stupid me, I followed McKay and the Vic. in P. (no bashing as I like his work!!!)

 

 

Cheers, Daniel

Edited March 18, 2015 by dafi

[dafi]

Possibly need to rename the thread: Tinkering things throu ;-)

 

Just for the model, I used a second guide ...

 

 

... and a breeching rope of 20 feet as this was indicated for 32 pounders.

 

 

Fixed it gives a realistic looking overhang ...

 

 

... while in the front ...

 

 

... the radius is surprisingly limited.

 

 

Cheers, Daniel

[mtaylor]

 

... the radius is surprisingly limited.

 

 

 

At that extreme, you'll be blowing off parts of your railing and bulwark....  I think the front of the carriage was actually at the port/bulwark and not set back as far as you have it.  Still... radius is limited by the port opening.

[dafi]

Thank you for all the hints. Some more NMM!

 

Royal William

 

Sectional design model depicting midship gun deck of the 'Royal William' (1719). Shows corronade. Model is decked, equipped and working. Model inscribed "Royal William 2nd rate lower. deck. port.".

Date made circa 1800

 

 

 

http://collections.rmg.co.uk/collections/objects/68882.htmlSLR2927

 

Muzzle loading carronade

 

Model of a carronade (about 1830) on a non-recoil carriage made entirely in wood with a metal swivelling retention bar. The gun is turned from a single piece of wood, painted black, and pivots on trunnions fixed to the bottom of the gun. The carriage is also made in wood and painted black. The bottom of the carriage has a metal rail running its entire length and extending from the front through which two securing holes are bored. Beneath the rail at the mid point of the carriage is a single transverse mounted wooden truck.

 

http://collections.rmg.co.uk/collections/objects/68940.htmlSLR2985

 

Gun carriage for a 32 pounder

 

Model of a wooden gun carriage for a 32 pounder. It has a raised flatbed on which the gun supports slide along for running in and out when firing and loading. The whole model is finished and varnished in natural wood and is complete with various fittings for mounting and working the gun, such as a pair of trunnion clamps, eyes for the rigging to work the gun and the brass edged track to work the slide mechanism. On the underside of the truck between the sets of wheels is inscribed "32 pounder by one inch scale.".

 

http://collections.rmg.co.uk/collections/objects/68886.htmlSLR2931

 

Carronade model

 

Wooden carronade model and mounting with brass fittings on swivelling slide. Mahogany slide.

Date made circa 1840?

 

http://collections.rmg.co.uk/collections/objects/43126.htmlNAV0914

 

Sea service carronade

 

Instructional model of a sea service carronade on a sliding and pivoting wooden carriage. The gun has been cast and includes a sight, a prickhole and the mechanism for raising and lowering its elevation. It is mounted on a mahogany slide and the slide is mounted on a swivelling mahogany carriage. Both slide and carriage contain ring bolts for working the gun. The swivelling mechanism is pivoted on a rectangular piece of mahogany. At the back of the carriage, two sea service trucks allow the carriage to swivel in an arc.

 

http://collections.rmg.co.uk/collections/objects/68878.htmlSLR2923

 

Carronade, 24pdr

 

A model of a carronade on a pivoting sea-service sliding carriage (early 19th century) made in metal and wood, possibly walnut. The gun is patinated a dark bronze finish, has a number of reinforcing rings and has an integral front sight, aft sight, pommel and vent. The elevation thread, ring bolts, trucks and the curved edging strip around the front of the mobile pedestal are brass. The mobile pedestal and the housing for the horizontal rotation axis are made in a light-coloured wood. The sliding carriage is made in a dark wood, possibly stained or patinated.

 

 

 

http://collections.rmg.co.uk/collections/objects/68873.htmlSLR2918

 

The last picture is quite interesting as it shows the sled pivoted by 180 degrees!

 

 

XXXDAn

Edited March 20, 2015 by dafi

[Izzy Madd]

Hi,

 

Not wishing to hijack you other thread. I'll cont here but I realise that there is a metal plate for the screw to slide on but with several tons of recoil that would be like putting a biscuit under a wobbly table leg. The bar would still bend if not embedding in the wrought iron plate... At least digging into the wood at one side or the other. And if not in the plans surely a Wiley old sea dog would have realised this drawback and used something in his own redesigned version..

 

Being unable at the moment to actually read the entire thread due to my condition. But having spotted several words on the issue I feel that the gun be mounted I such a way that the pivot was able to slide but not able to rise. Either a removable spike through the pivot making it simpler to transport around deck if needed. Or a fixed system of some kind. Or else the same force that drives the back down would flip the barrel over. Unless you can find a loop hole in all three of newtons laws of motion.

Edited March 21, 2015 by Izzy Madd

[jud]

Izzy; Have been wondering about the early elevation screws that are not hinged at the breach and base. Have came to the conclusion that the lower end slid in or on a well greased table or the gun was lifted with bars and the screw then turned into place to hold the tube at the desired elevation, no bending moment that way.

jud

[dafi]

Hello Izzy and Jud,

 

not sure if I got you a 100% ...

 

Jud: I believe the elevation screw was actually used to adapt the height, as all carriages using wedges and therefor bars have the sides of the carriage made of wood and with those typical steps as silhouette. Those steps served for the bars to have a leverage point. If those side parts are missing, it is rather difficult to work the bars properly ...

 

Izzy: As I mentioned before, me too I wonder, if the screw was eased by a wedge while shooting or being lashed for sailing. Fact is, as long as the screw is used, I just discovered the wedges only in 19th century replicas so far, and not in contemporary sources. Not being a physicist, I do not know enough about the stability of 18th century iron rod srews of about 2" (guessed by the proportion; about 6 cm) and the forces of the shot pressing onto them. 

 

XXXDan

Edited March 21, 2015 by dafi

[Izzy Madd]

Hello Izzy and Jud,

 

not sure if I got you a 100% ...

 

Jud: I believe the elevation screw was actually used to adapt the height, as all carriages using wedges and therefor bars have the sides of the carriage made of wood and with those typical steps as silhouette. Those steps served for the bars to have a leverage point. If those side parts are missing, it is rather difficult to work the bars properly ...

 

Izzy: As I mentioned before, me too I wonder, if the screw was eased by a wedge while shooting or being lashed for sailing. Fact is, as long as the screw is used, I just discovered the wedges only in 19th century replicas so far, and not in contemporary sources. Not being a physicist, I do not know enough about the stability of 18th century iron rod srews of about 2" (guessed by the proportion; about 6 cm) and the forces of the shot pressing onto them. 

 

XXXDan

I'm no physicist but I do know that an iron bar of even two inches 60 mm. Would bend like toffee when faced withe the weight of the barrel flying back at at least ten tons of force. Look at cars and they are only one maybe two tons. I once snapped an axel going at ten miles an hour because the verge I hit was solid ice. Very little impact. Yet snapped a 100mm bar designed for the job. Wrought iron is renowned for being flexible that it's main benefit over cast.

 

But you say you've only seen wedges in 19th century replicas. I assume you mean 1900-2000(20th century) otherwise they would the same era as Victory. But how many times have old timers said. "I used to use something like that when I was a lad"

 

While it may not be documented until much later it may well be like the story of eating carrots during WWII. To prevent the enemy suspecting we had a secret weapon, radar, the rumours went around that carrots were good for your eyesight. The same with the guns. It could and probably was common practice to use a wedge just not put down in the instructions. the same as devinci did with his plans. There was always a fault to prevent others just copying it.

 

There is no way a small screw or even a large one. Not bending under the strain. I've seen modern bolts 150mm snapped like twigs when the force was in the wrong direction. Even a foot bridge collapsed under the weight of people because the builder moved two bolts. The designers of the guns probably never even saw one up close.and just thought that looks better without the wedge.

[jud]

Think that the screw has plenty of compression strength to withstand the forces of recoil; the force vector on the screw would be only a very small part of the whole. The weakness I have been wondering about is the bending moment, caused from the long screw on the breach holding that screw in alignment with great force. As the gun tube rotates around the trunion or pivot, that screw will move with it. That rotation of the gun would cause the bottom of the screw to move parallel to the tube. Something has to give or the design changed. The quick and easy way to relieve that bending moment would be to break contact between the bottom of the screw and its resting place on the slide. Could do that with lifting bars just as guns using wedges were, with the weight supported by the bars, spinning the screw into place would be quick and easy and when set the bars were removed, viola, no bending moment and only compression forces acting on that screw. Windy old Fart ain't I.

jud

[davyboy]

Interesting article,I may well be wrong but it seems the gun barrel attached with a whacking big bolt to the sliding carriage and elevating screw are in effect a single unit. On discharge of the gun everything moves rearwards simultaneously. Cant see the elevating screw being bent bent by this although there may be a slight downward force caused by the muzzle tending to rise on firing. Of course a wedge if inserted before firing would alleviate this.

 

Funnily enough Lavery mentions in his `Arming and Fitting' that the screw thread through the button allowed elevation/depression without the use of quoins and wedges. This happened when trunnions were superceded on carronades by the loop under the barrel. Can't see them using both. 

 

We really need a time machine     

 

Dave 

[dafi]

Here is just a copy of my building report, that shows, how some minor changes effect quite heavily the usage:

 

 

After the rounds in the NMM, beyond all the different shapes and systems, I did find some similarities.

 

- The bolt of the lower part as near to the wall as possible, gives 2mm

- Shortened the front of the sled gives 1,5 mm

- makes 3,5 mm closer to the edge :-)

- no feed for higher flor plate as it was apparently in use for smaller calibers.

 

Ok let´s go for the infamous Texas carronades massacre ...

 

... new hole in the floor plate, new bolt on the lower part and shortened sled ...

 

 

... pushed back ... 

 

 

... and now fits in the front ... 

 

 

... also the radius fits much better :-)

 

 

Have to admid the timberheads being quite close to each other.

 

Now still is the mystery of the turning sled ...

 

 

... but I am sure we will find that out ;-)

 

XXXDAn

[jbshan]

I haven't been able to find any drawing showing other than just the big pivot under the barrel, no block to keep it aligned in the slot.  Since this has a large washer or retaining ring, and the slide has a slot for the ring, I can only assume this would be enough to keep the barrel from rising.

They made a replica of one of Vasa's long guns and fired it, first with no recoil lines, breeching or tackle, and then hooked it up to the normal lines.  Without breeching or tackle it was a wild ride!  With them the gun was very tame and mannerly.  Remember, the breeching only serves as an ultimate stop, most of the recoil is taken up by pulling the tackle through the blocks.  I wonder if the carronade likewise would be 'tamed' and it could recoil with only slight ('slight' being a relative term here) pull up on the muzzle, just enough to keep it in contact with the slide at the rear.

Edited March 21, 2015 by jbshan

[jud]

Elevation screw movement.

ELEVATION SCREW.pdf

[lehmann]

I looked at the drawings for the carronades provided on the CD from the USS Constitution Museum.  They provide two designs, one from the 1927-31 rebuild and another that is "1812 Era" (1985 drawing).  The first drawing shows two wooden "t-nuts" that fit in the slot in the skid and hook under the skid.  Each t-nut is attached to the slide with four 1.25" bolts. There is 1/2" clearance between the bottom of the skid and the hook edge on the t-nut.

 

The 1812 design just shows a 3.75" fighting bolt that runs in the slot and goes through a large (8" diameter) ring that runs under the base. There is no other block in the slot to stop the slide from rotating on the skid shown on the drawings.  

 

I did some engineering calculations to estimate the forces on the various components of the 1812 design. (I'll post them later).  Assuming the thrust force from the barrel is 1000 lbs, then:

     Compression force on the elevation screw: 350 lbs

     Tension (lifting) force on the fighting bolt:  260 lbs

     Force of the back edge of the slide on the skid:  540 lbs

 

There's a lot of friction between 1) the end of the slide and between the skid and 2) the fighting bolt ring that slows the recoil: assuming a friction coefficient of 0.5 (wood on wood and metal on wood), then the friction force is (0.5)(540+260) = 400 lbs.  Most, if not all, of this force will be transferred to the pivot pin next to the gun port.  (I wonder if this means more energy goes to the ball since the barrel recoil velocity must be smaller.  Also, since the recoil is absorbed over a period of time, it should mean less impact on the hull when the breech cable tightens up.)

 

As Jud showed in his drawing, the elevation screw is threaded into the cascabel, so when the screw is not 90 deg to the top of the sled then there is a bending torque on the screw.  However, since the bottom of the screw is just sitting on the surface, there is some friction involved, which reduces the bending forces by about 60%.

 

Going back to the original question of why there there is only one pin in the slot.  If the fighting bolt (pin) is not exactly under the bore then there will be torque that will twist the barrel sideways (looking from above).  This will happen also if the blast force is not symmetric to the bore or the friction between the underside of the slide and the top of the skid were not the same on either side of the slot (actually, this would be outright unstable), so I would think it would be a good idea to have a second slide in the slot.  

 

There are, however, several reasons why the slide will recoil straight back:

1. that the moment of inertia of the barrel is so large that it would take a lot of torque to make it turn as it recoils.
2. there is a lot of friction between the breech end of the slide and the skid, which will limit rotation of the slide.
3. the force of the explosion acts on the breech, so as long as the fighting bolt (pin) is out-board of the breech, then this force will push the barrel straight back.  

These factors also apply to army artillery mounted on two wheels - they recoil straight back.

 

I have to think this out some more, but I think it's important that the center of mass of the barrel is inboard of the fighting bolt.  Overall, it looks like getting the geometry right does most of work, and friction helps to take care of the imperfections.

 

 

Bruce

[dafi]

Thank you all for your research :-)

 

Another good hint came from Jörg/Chapman in our german forum:

 

He quotes Caruana´s Sea Ordonance saying, that the wedge was necessary for shooting as the spindle for height adjustment would be destroyed after some shots. It looks like there was even a square surface on the bottom of the barrel to properly fit the wedge. This small surface was also used for the serial number. 

 

He also claims that when the low trunnions were introduced, the side parts of the carriage had to be left off on the new carriage, thus resulting in the introduction of the elevation screw as handbars could not be used any more efficiently because of the missing leverage points. As the spindle was too weak, the wedge was placed just before the shot.

 

Chers, Daniel

Edited March 22, 2015 by dafi

[dafi]

Double check - the small surface for the wedge, if one knows where to look, one can find ;-)

 

XXXDAn

 

 

 

 

 

 

[mtaylor]

I don't know about that wedge, Daniel.  Here's two life fire vids and I'm not seeing a wedge.  I would think these guys would use one if for no other reason than safety.

 

https://www.youtube.com/watch?v=XfsuIaTU92Y

 

https://www.youtube.com/watch?v=aVRh6O-8rGg

[Izzy Madd]

Thank you all for your research :-)

 

Another good hint came from Jörg/Chapman in our german forum:

 

He quotes Caruana´s Sea Ordonance saying, that the wedge was necessary for shooting as the spindle for height adjustment would be destroyed after some shots. It looks like there was even a square surface on the bottom of the barrel to properly fit the wedge. This small surface was also used for the serial number. 

 

He also claims that when the low trunnions were introduced, the side parts of the carriage had to be left off on the new carriage, thus resulting in the introduction of the elevation screw as handbars could not be used any more efficiently because of the missing leverage points. As the spindle was too weak, the wedge was placed just before the shot.

 

Chers, Daniel

Pleading thIs while not conclusive seem to indicate I'm not the only person with doubts as to the strength of the screw. And a wedge may have been used.

 

As for the quote about every recoil forces I recall reading that the 68 pounders had a recoil force well over ten tons. Which would bend all but the thickest screws as shown in your inmates.

[Izzy Madd]

I don't know about that wedge, Daniel. Here's two life fire vids and I'm not seeing a wedge. I would think these guys would use one if for no other reason than safety.

 

 

I've not looked at the image but from personal experiments. misspent youth. The recoil on a gunpouder load only is proportional to the weight of the pouder only. Where as the real load force has the force required to move both the explosive forces and the mass of the ball which would be multiplied by each other. Resulting in the recoil force of over ten tons.

 

Having just watched the first vid the screw is some five time more substantional than that which raised my doubt in the beginning. Dafi's recreation. Which are little more than 1" across when scaled up. So the real question becomes not "did they use wedges?"

But "when did they increase the diameter of the support bolt enough to do away with the wedge?" Even then I would imaging some old timers still putting in a wedge as the "didn't trust this new fangled technology"

 

And judging by the prancing around done with the second vid there was only enough powder in it to go bang . As the recoil should have sent the whole thing a good 18' backwards. If the idiot lighting it was lucky.

Edited March 22, 2015 by Izzy Madd

[mtaylor]

Good questions, Izzy.

 

I would think that if the "wedge" or quoin were used it would have shown up on the plans and drawings for these guns.  Or in the list of equipment as quoins do show up for cannon.   They do show in the drawings/lists for gunnades which were cannonades on the wheeled carriages.   Most puzzling.

[dafi]

Also could be a question of how much powder and shot was used. Apart from Niagara all life fire seems to be without shot and reduced charge. 

 

To my rendition: Even though the screw is 0,4 mm (means 4 cm in real life) I already prepared a 0,6 replacement.

 

Cheers and thanks, Daniel

[dafi]

Just by luck discovered this small detail on the Vic replica ...

 

 

... just a small twist for the story ...

 

XXXDAn

Edited March 22, 2015 by dafi

[lehmann]

More engineering calculations:

 

Based on the data in http://www.thenrg.org/resources/articles/The%20carronade.pdf, the muzzle velocity of a 32 lb carronade is 750 ft/sec.  Assuming that the explosive force, and therefore the acceleration, is constant, then the average muzzle force is 70,000 lbs.   A lot of this force will go to accelerating the mass of the barrel, but for the moment assume all of this force has to be counter-acted by the elevation screw (which would happen is the slide stuck, or the breech rope were too long and the fighting pin hits the end of the slot).   From the geometry of the 1812 design I described above, then the load on the elevation screw is about 25,500 lbs.  The drawings specify a root diameter of the screw as 1.25" (outside diameter = 2.125"), resulting in a stress of 20,000 psi.  The yield strength of wrought iron is in the range of 23,000 to 32,000 psi. It they used a heat treatable (hardenable) or cold worked steel, which was available, the the yield strength is in the 60,000 psi range.  

 

Since I've greatly over-estimated the load, a screw could survive with a good safety margin in "regular" use.  

 

Bruce

Edited March 22, 2015 by lehmann

[amateur]

Just silly me asking again.

As the gun is fixed to the upper carriage, and the elevation screw is rsting on a metal plate fixed on this same upper carriage, where does this enormous lateral force on the screw come from? I would understand if gun and screw were not fised to the same carriage, but like it is...?

 

Could the wedge be someting like a convenience article? There is quite a load on the screw, which makes it difficult (and slow) in turning. Getting of part of the load would make it easier to lower the elevation.

 

 

Jan

[mtaylor]

Daniel,

I don't know how much faith I'd put in that since it's a replica.  Also,there's no screw fitted.

 

Jan,

I'm kind of like you on this.  There's questions....  we know that much was never recorded as being "known knowledge". And then there's areas of meticulous record keeping. 

 

All,

If we look to the newer, in the American Civil War (aka "The recent unpleasantness"), the pivot guns only had the screw.  These were sometimes huge guns firing large caliber shells and the carriages were made from a variety of materials.   Still,  I wonder if we're missing something obvious, or reading too much into this.

[Izzy Madd]

Also could be a question of how much powder and shot was used. Apart from Niagara all life fire seems to be without shot and reduced charge. 

 

To my rendition: Even though the screw is 0,4 mm (means 4 cm in real life) I already prepared a 0,6 replacement.

 

Cheers and thanks, Daniel

Sorry for getting the wrong size guess but I've seen bars of silver steel 50mm bent like butter but if you look at the plans the issue of friction on the pin was noticed as the pin comes to a rounded point to reduce this. So there must have been some issues regarding the pin bending at some point.

 

I may have asked erroneously but it seems that it's a salient point especially when done to scale. As this emphasises the issue.

 

It may well be one of those things that it's better to look right that be right. As in have an over sized pin that when scaled up would be too big but at scale looks right?