Are the trunnions on the centerline of the barrel or are they below it? Some pictures look like they are below center.
Sorry, I forgot. English late 18th century
Sorry, I forgot. English late 18th century
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Most canons I've seen have the trunnions below center.
I'm sure someone on here has the definitive answer.
The trunnions were / are under the centerline of the muzzle
Here you can see it on original naval guns
Here you can see it on original naval guns
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Right is real the observation of Uwek, see how many guns on the models are wrong of that position of the mumps
Yes - it is easier to drill the hole in the centerline, but technically incorrect
Thank you.
A good question from Don. Admittedly I hadn't paid any thought to this before and took it as given that the trunnion is on the centre line of the barrel.
Most manufacturers of kit models I have seen drill the hole for the trunnions through the centre of the barrel. This applies also to cast cannons, which also have the trunnions on the centre line.
Most manufacturers of kit models I have seen drill the hole for the trunnions through the centre of the barrel. This applies also to cast cannons, which also have the trunnions on the centre line.
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they have to be off center
OK now we've decided that they are off center(below the center line of the barrel). Now, why?? I'm thinkin' it's to make the barrel slightly unstable so it's easier to move. What other guesses do we have? Must be an engineer on here.
No I'm not an engineer but I would be surprised if Archimedes and levers aren't involved. Lower centre of gravity for pivot point might also be considered.
Geoff Smith, MSc FIMF Scientist, Ordnance Society. Gunpowder researcher. Says on Quora:
Now that makes sense to me.
I am pretty sure, that this has something to do caused by the forces on the muzzle / barrel during the firing. For this the center of mass, the pivot point and the forces would be necessary to find out.......
not that the end of the muzzle is moving downwards before the ball is leaving the gun ...... but I can be wrong
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On most guns, the top of the trunnion is on the centreline of the bore. This might be used for sighting in combination with a witness mark on the muzzle bell (although it is no more inherently accurate that sighting along the top of the barrel if one allows for the taper of the tube), except that the top of the trunnion is almost entirely covered by the capsquare fastening the gun to the carriage and so hardly visible in use.
The shot leaves the muzzle before any parts of the tube or carriage start to move significantly, so trunnion placement probably does not affect accuracy in a significant way, although early modern gunners had no way to observe this directly. Placing the trunnion below the bore axis does offset the recoil force from the pivot point of the tube, so the recoil tends to push the breech down onto the carriage. We could see this in the high-speed video of the tests we made with a full-scale copy of a Vasa 24-pounder in 2014, with service load and shot. It may have been felt that forcing the breech down onto the quoin would make the gun more stable during firing or improve accuracy.
In terms of location along the length of the barrel, the trunnions are usually placed just in front of the balance point of the gun, so that the tube is slightly breech-heavy, but elevation can still be adjusted. On the Vasa 24, the tube weighs 1250 kg, but I can lift the breech by myself, or depress the muzzle by leaning my weight on it.
The shot leaves the muzzle before any parts of the tube or carriage start to move significantly, so trunnion placement probably does not affect accuracy in a significant way, although early modern gunners had no way to observe this directly. Placing the trunnion below the bore axis does offset the recoil force from the pivot point of the tube, so the recoil tends to push the breech down onto the carriage. We could see this in the high-speed video of the tests we made with a full-scale copy of a Vasa 24-pounder in 2014, with service load and shot. It may have been felt that forcing the breech down onto the quoin would make the gun more stable during firing or improve accuracy.
In terms of location along the length of the barrel, the trunnions are usually placed just in front of the balance point of the gun, so that the tube is slightly breech-heavy, but elevation can still be adjusted. On the Vasa 24, the tube weighs 1250 kg, but I can lift the breech by myself, or depress the muzzle by leaning my weight on it.
Thank you Fred, that makes sense. Since the barrel is supported by the trunnions and the quoin the muzzle is free to move down. Putting the trunnion below center ensures that the recoil tries to raise the muzzle. Am I understanding it right?
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Yes Don, that is essentially it. The combination of the trunnions below center and in front of the balance point means that the natural position of the barrel is with the breech resting on the quoin. When the gun fires, the recoil force is above the pivot point of the trunnions, which in engineering terms is a couple, which causes the barrel to try to rotate, pushing the breech down and the muzzle up, although the gun should not actually rotate if the breech is already on the quoin. Most of the force effectively pushes the gun backwards, but it can cause the muzzle to jump (this was noted by gunners as more common once the gun got hot). The recoil can cause the breech to bounce off the quoin, so that the muzzle tips down towards the end of the recoil, and then settles back once the gun comes to rest - our gun did this fairly often, at certain angles of elevation, probably because the trunnions were very close to the balance point.
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then we have the carronade where the trunnions are under the gun, but maybe that is not considered a trunnion
That has actually bothered me since I first saw one. So many "why" questions
