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Post by the light works on Oct 19, 2013 1:03:35 GMT
No but your taking the comparatively gentle force of a V8 off and putting a bloody canon in its place.............. Have to agree with Paddy on this one*. The force an airboat hull has to withstand from the weight of the engine and the thrust are fairly minor, and spread over a long period of time. The force it would have to withstand from a cannon is considerably larger and almost instantaneous. An analogy would be a car roof. I could stand on a car roof without causing any real damage to it, I can even walk on it or push down in it without doing anything notable. If however I fall on the car from two stories up there is going to be a mess. (*Try not to look surprised) the difference being that a car roof, for the most part, is not designed to have you flogging the car around through the everglades on its roof. remember: the airboat travels ON its hull, at speeds, if youtube is to be believed, up to 80 MPH. remember, you arenot shooting the cannon AT the airboat, and you are not using the airboat to stop the recoil of the cannon. the cannon is taking the airboat along for the ride. remember: your cannon is free to do this: and they are not trying to do this:
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Post by privatepaddy on Oct 19, 2013 2:33:01 GMT
Have to agree with Paddy on this one*. The force an airboat hull has to withstand from the weight of the engine and the thrust are fairly minor, and spread over a long period of time. The force it would have to withstand from a cannon is considerably larger and almost instantaneous. An analogy would be a car roof. I could stand on a car roof without causing any real damage to it, I can even walk on it or push down in it without doing anything notable. If however I fall on the car from two stories up there is going to be a mess. (*Try not to look surprised) the difference being that a car roof, for the most part, is not designed to have you flogging the car around through the everglades on its roof. remember: the airboat travels ON its hull, at speeds, if youtube is to be believed, up to 80 MPH. remember, you arenot shooting the cannon AT the airboat, and you are not using the airboat to stop the recoil of the cannon. the cannon is taking the airboat along for the ride. remember: your cannon is free to do this: snip and they are not trying to do this: snip no your not you want to harvest as much recoil as possible zero movement in the gun mounting with respect to the hull of the boat.
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Post by User Unavailable on Oct 19, 2013 4:02:16 GMT
the difference being that a car roof, for the most part, is not designed to have you flogging the car around through the everglades on its roof. remember: the airboat travels ON its hull, at speeds, if youtube is to be believed, up to 80 MPH. remember, you arenot shooting the cannon AT the airboat, and you are not using the airboat to stop the recoil of the cannon. the cannon is taking the airboat along for the ride. remember: your cannon is free to do this: snip and they are not trying to do this: snip no your not you want to harvest as much recoil as possible zero movement in the gun mounting with respect to the hull of the boat. I believe what TLW means is, the air boat becomes the cannons carriage. The airboat slides back on the water, just as if it were the wheels of the carriage on land.
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Post by the light works on Oct 19, 2013 5:22:19 GMT
the difference being that a car roof, for the most part, is not designed to have you flogging the car around through the everglades on its roof. remember: the airboat travels ON its hull, at speeds, if youtube is to be believed, up to 80 MPH. remember, you arenot shooting the cannon AT the airboat, and you are not using the airboat to stop the recoil of the cannon. the cannon is taking the airboat along for the ride. remember: your cannon is free to do this: snip and they are not trying to do this: snip no your not you want to harvest as much recoil as possible zero movement in the gun mounting with respect to the hull of the boat. so I'm not allowing the gun to travel freely? I need to anchor the airboat securely to the sides ot fhe trench to restrain it from moving? doesn't that kind of defeat the test?
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Post by privatepaddy on Oct 19, 2013 6:01:37 GMT
no your not you want to harvest as much recoil as possible zero movement in the gun mounting with respect to the hull of the boat. I believe what TLW means is, the air boat becomes the cannons carriage. The airboat slides back on the water, just as if it were the wheels of the carriage on land. I think your correct, but his explanation is ambiguous where his video clearly shows the period guns recoiling several feet on their carriage. With no clarification on how they are to be mounted on his air-boat it leads one to think that the cannon will be mounted wheels and all.
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Post by the light works on Oct 19, 2013 7:49:27 GMT
I believe what TLW means is, the air boat becomes the cannons carriage. The airboat slides back on the water, just as if it were the wheels of the carriage on land. I think your correct, but his explanation is ambiguous where his video clearly shows the period guns recoiling several feet on their carriage. With no clarification on how they are to be mounted on his air-boat it leads one to think that the cannon will be mounted wheels and all. No, you are just trying to dig up some way for me to be wrong. in fact, it would probably work well to just secure the carriage to the airboat, like putting it on a sled. the carriage is already demonstrated to be able to keep the barrel of the cannon from leaving the area.
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Post by privatepaddy on Oct 19, 2013 8:11:16 GMT
I think your correct, but his explanation is ambiguous where his video clearly shows the period guns recoiling several feet on their carriage. With no clarification on how they are to be mounted on his air-boat it leads one to think that the cannon will be mounted wheels and all. No, you are just trying to dig up some way for me to be wrong. in fact, it would probably work well to just secure the carriage to the airboat, like putting it on a sled. the carriage is already demonstrated to be able to keep the barrel of the cannon from leaving the area. So when the black powder burns what torque are you placing where the draw bar meets the deck? Edit just to recap, you have a 300 kg cannon + carriage weight where a 150 kg motor used to be (good luck getting the mountings to line up) You have the wheels locked so the carriage cannot move relative to the boat.So the axles points now act as a pivot, a meter above the deck (where wheel meets the deck) a 3 meter draw bar on which the cannon is mounted. When the gun is fired?
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Post by silverdragon on Oct 19, 2013 11:02:58 GMT
The cannon shot back eight feet?... One of the silly buggers was stood at the side of the muzzle as it fired. As in almost touching the damn thing. WTF?.... Just WHY stand there?.... From what I know of history, the "Loader", as in the one in that video playing that part, holding the Ram-Rod, did NOT stand at the side of the muzzle as it was fired....?... He, like everyone else, stood where they could be most help putting the [heavy] thing back in place after it had fired......
As in mounting the thing.
I have mentioned the "Glassing in" of framework to Fibreglass hulls.
This is much stronger than glue. Dare I say it, its even stronger that Duck-Tape......
A properly glassed in bit of four-by-two is a bloody strong bond..... Several together would hold the weight, and provide excellent anchor points for "Weaponry"....
Would it be too much to mock up a fibreglass base and frame that could hold a cannon's weight and test fire it for strength testing?.... I think it may surprise you.
Several layers may be required, of course. We aint building a canoe here, but if I can build a hull that can withstand dropping of 20-30ft waives at speed repeatedly, a small cannon shouldnt cause too much distress....
For consideration, we had under-deck fuel tanks in a four ton boat that had fractured and needed replacement. We cut off the half-inch thick deck, but we had glassed-in the tanks for stability on the move....
We tried craning out the tank, all we did was lift the boat off the cradle?... Eventually we freed the sides of the tanks with crowbar and sledgehammer.
(Replacement tanks fitted were of honeycomb nature and less liable to fracture... we ratchet strapped them in on top of foam rubber matting, and made them as stable as the last, we thought indestructible, although they did try, dropping of 30ft waives around north Scotland...)
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Post by the light works on Oct 19, 2013 11:06:55 GMT
No, you are just trying to dig up some way for me to be wrong. in fact, it would probably work well to just secure the carriage to the airboat, like putting it on a sled. the carriage is already demonstrated to be able to keep the barrel of the cannon from leaving the area. So when the black powder burns what torque are you placing where the draw bar meets the deck? Edit just to recap, you have a 300 kg cannon + carriage weight where a 150 kg motor used to be (good luck getting the mountings to line up) You have the wheels locked so the carriage cannot move relative to the boat.So the axles points now act as a pivot, a meter above the deck (where wheel meets the deck) a 3 meter draw bar on which the cannon is mounted. When the gun is fired? I thought we established a Chevy 350 (a representative motor) weighed about the same as a 6 pounder - and perhaps I was wrong in assuming that meant the entire gun, not just the barrel. that means we either have a 150Kg cannon, or are replacing a 300Kg motor with it. we are also removing the superstructure used to elevate the motor far enough to keep it from breaking off the prop on the hull of the boat; just in case you wanted to claim I was overlooking that. so the gun carriage sits on the floor of the hull, with the drawbar, as you have elected to call it, secured in a bracket built to adapt from the existing mounting points to transfer the recoil from the cannon to the hull of the airboat. if the axle points act as a pivot on the boat, they will also act as a pivot on the ground, because in essence, all you have done is convert the gun carriage into a sled. but of course, it is me saying that, so you will not listen
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Post by silverdragon on Oct 19, 2013 11:22:51 GMT
Well, on that score, I was already thinking a thick transom.... I have built craft to withstand an outboard that requires two people and a crane to lift into place, for a water ski boat... But no transom I have handled would take the power of a small cannon without some risk of damage?... I was thinking more along the lines of the muzzle being just above deck height, but hanging out over any decking, to prevent muzzle flash damage?... Yes partly affixed to Transom, but also to floor, sides, bulkheads, ..... This would have to be some framework. That framework its self would have to be test-fire before fixing to boat?... Metal work with Bolts, or Wooden?....
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Post by the light works on Oct 19, 2013 11:26:15 GMT
oh, sorry, no. I intended to take the wheels off so the barrel of the cannon was laying against the transom below the waterline, because I am stoopid. You really don't leave much room for others to comment do you. not when it is you making knee jerk attacks, no.
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Post by the light works on Oct 19, 2013 11:29:41 GMT
Well, on that score, I was already thinking a thick transom.... I have built craft to withstand an outboard that requires two people and a crane to lift into place, for a water ski boat... But no transom I have handled would take the power of a small cannon without some risk of damage?... I was thinking more along the lines of the muzzle being just above deck height, but hanging out over any decking, to prevent muzzle flash damage?... Yes partly affixed to Transom, but also to floor, sides, bulkheads, ..... This would have to be some framework. That framework its self would have to be test-fire before fixing to boat?... Metal work with Bolts, or Wooden?.... well, yes, someone less sarcastic than I am would certainly have a mounting system built to adapt the existing hardpoints on the hull to whatever was necessary to insure that the gun wasn't going to wander off in some random direction. since the hull of the airboat is Aluminum, it only makes sense to make the mounting system out of aluminum as well. it is light, and ductile enough to take the abuse you are going to be subjecting it to.
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Post by Cybermortis on Oct 19, 2013 11:32:58 GMT
I think your correct, but his explanation is ambiguous where his video clearly shows the period guns recoiling several feet on their carriage. With no clarification on how they are to be mounted on his air-boat it leads one to think that the cannon will be mounted wheels and all. No, you are just trying to dig up some way for me to be wrong. in fact, it would probably work well to just secure the carriage to the airboat, like putting it on a sled. the carriage is already demonstrated to be able to keep the barrel of the cannon from leaving the area. There is a very big difference between the carriage used for a cannon on land and one used on a ship or boat. On land the recoil can be dealt with by allowing the gun and its carriage to move backwards, since space is not usually a factor. Even the huge artillery guns used during World War 1 allowed the guns to recoil backwards. When you mount guns in a vehicle, ship or fortification however you can't allow guns to recoil in the same way simply because there is not enough room for them to do so. With ship mounted cannon the recoil was used to bring the gun back inboard for easy reloading*. Beyond this, or for breach loading guns, recoil has to be dealt with in various ways. For cannon this was thick - three to five inch thick - ropes attached to the hull and frame. For the lighter carronades, which also used a LOT less powder than a cannon of comparable calibre, the gun carriage was designed to absorb some of the recoil. In both cases it was not unusual for guns to recoil so strongly that they snapped either the ropes or ripped the bolts out of the frame. In this case we are also looking to see if the recoil can move the boat, which means that the recoil has to be absorbed by the hull. Otherwise the gun is just going to roll back and exit through the stern of the ship. The carriage designs used for, say, their six pounder cannon (Old Moses, although its not owned by MB) is totally unsuitable for this as there are no attachment points to allow it to be secured to the boat - or at least not without risking damage to the carriage. Besides, a typical airboat has a hull 1/8th of an inch thick and its frame is 1/4tr thick steel bars in a 'T' shape to resist flexing of the hull as it moves through the water. Old Moses and its carriage masses some 850 lbs**, and using a full charge of powder an airboat's hull and frame is simply not capable of handling that much force without major modification. This is why I'm starting to think that it may be cheaper and more practical for MB to build their own airboat hull. They can not only use much thicker material but custom design the internal frame to handle the forces involved. Yes, a thicker hull and stronger frame would mean more weight which would reduce the effects of recoil on the boat. But it would allow them to use much larger and more powerful guns than they could otherwise manage. I'm also starting to think that they might have to build their own cannon, if they decide to go down that route for supersizing the testing. This, like custom building a hull, might be more practical since they can design a central 'carriage' that is part of the boats frame and then design their guns to fit that regardless of calibre. Although a homemade cannon is much more likely to fail in a spectacular way if given a full load of powder, the dangers are likely to be minor as they are not going to be anywhere near the gun when it is fired. (*Early ship mounted guns did not utilize the recoil, and had to be reloaded by a man who was hanging over the side of the ship. Little wonder that the rate of fire of such guns was around three shots per hour, with presumably as many changes of underwear.) (**My earlier figures of 600-700 lbs for the weight of the gun were for the gun without its carriage. Total weight with the carriage is 850lbs.)
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Post by the light works on Oct 19, 2013 11:39:44 GMT
No, you are just trying to dig up some way for me to be wrong. in fact, it would probably work well to just secure the carriage to the airboat, like putting it on a sled. the carriage is already demonstrated to be able to keep the barrel of the cannon from leaving the area. There is a very big difference between the carriage used for a cannon on land and one used on a ship or boat. On land the recoil can be dealt with by allowing the gun and its carriage to move backwards, since space is not usually a factor. Even the huge artillery guns used during World War 1 allowed the guns to recoil backwards. When you mount guns in a vehicle, ship or fortification however you can't allow guns to recoil in the same way simply because there is not enough room for them to do so. With ship mounted cannon the recoil was used to bring the gun back inboard for easy reloading*. Beyond this, or for breach loading guns, recoil has to be dealt with in various ways. For cannon this was thick - three to five inch thick - ropes attached to the hull and frame. For the lighter carronades, which also used a LOT less powder than a cannon of comparable calibre, the gun carriage was designed to absorb some of the recoil. In both cases it was not unusual for guns to recoil so strongly that they snapped either the ropes or ripped the bolts out of the frame. In this case we are also looking to see if the recoil can move the boat, which means that the recoil has to be absorbed by the hull. Otherwise the gun is just going to roll back and exit through the stern of the ship. The carriage designs used for, say, their six pounder cannon (Old Moses, although its not owned by MB) is totally unsuitable for this as there are no attachment points to allow it to be secured to the boat - or at least not without risking damage to the carriage. Besides, a typical airboat has a hull 1/8th of an inch thick and its frame is 1/4tr thick steel bars in a 'T' shape to resist flexing of the hull as it moves through the water. Old Moses and its carriage masses some 850 lbs**, and using a full charge of powder an airboat's hull and frame is simply not capable of handling that much force without major modification. This is why I'm starting to think that it may be cheaper and more practical for MB to build their own airboat hull. They can not only use much thicker material but custom design the internal frame to handle the forces involved. Yes, a thicker hull and stronger frame would mean more weight which would reduce the effects of recoil on the boat. But it would allow them to use much larger and more powerful guns than they could otherwise manage. I'm also starting to think that they might have to build their own cannon, if they decide to go down that route for supersizing the testing. This, like custom building a hull, might be more practical since they can design a central 'carriage' that is part of the boats frame and then design their guns to fit that regardless of calibre. Although a homemade cannon is much more likely to fail in a spectacular way if given a full load of powder, the dangers are likely to be minor as they are not going to be anywhere near the gun when it is fired. (*Early ship mounted guns did not utilize the recoil, and had to be reloaded by a man who was hanging over the side of the ship. Little wonder that the rate of fire of such guns was around three shots per hour, with presumably as many changes of underwear.) (**My earlier figures of 600-700 lbs for the weight of the gun were for the gun without its carriage. Total weight with the carriage is 850lbs.) so you have an 850# gun imposing recoil on a 300# hull... which you want to increase to a 600# hull that rides lower in the water, so you can be sure there is as much energy imparted to the hull material as possible? I say again, you are not using the airboat to resist the gun's movement - you are using the gun to impart movement to the airboat.
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Post by privatepaddy on Oct 19, 2013 11:40:08 GMT
So when the black powder burns what torque are you placing where the draw bar meets the deck? Edit just to recap, you have a 300 kg cannon + carriage weight where a 150 kg motor used to be (good luck getting the mountings to line up) You have the wheels locked so the carriage cannot move relative to the boat.So the axles points now act as a pivot, a meter above the deck (where wheel meets the deck) a 3 meter draw bar on which the cannon is mounted. When the gun is fired? I thought we established a Chevy 350 (a representative motor) weighed about the same as a 6 pounder - and perhaps I was wrong in assuming that meant the entire gun, not just the barrel. that means we either have a 150Kg cannon, or are replacing a 300Kg motor with it. we are also removing the superstructure used to elevate the motor far enough to keep it from breaking off the prop on the hull of the boat; just in case you wanted to claim I was overlooking that. so the gun carriage sits on the floor of the hull, with the drawbar, as you have elected to call it, secured in a bracket built to adapt from the existing mounting points to transfer the recoil from the cannon to the hull of the airboat. if the axle points act as a pivot on the boat, they will also act as a pivot on the ground, because in essence, all you have done is convert the gun carriage into a sled. but of course, it is me saying that, so you will not listen I am going off cybers and yours for the weight of the cannon 600+pounds motor 350 pounds & converted them into something more recognisable to me. You have not addressed the torque issue. I can conclude from previous experience that you have not considered it relevant if at all. Your gun carriage is not on a sled it is on a boat and from your videos not a large boat. The axles will act as a pivot as they do on the ground but there the "draw bar"/limber cannot penetrate the ground, it just runs over the surface. You have still to evaluate the shear forces involved and where stress is involved it is common for faults to occur where welds stop.
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Post by the light works on Oct 19, 2013 11:42:27 GMT
mounting a cannon in an airboat does NOT compare to mounting a cannon on a large sailing vessel. mounting a cannon on an airboat compares to using a sled as a carriage for a land based gun.
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Post by Cybermortis on Oct 19, 2013 11:49:27 GMT
{Mod hat on - Lets please try to keep things civil thank you. - CM}
Someone had to aim the gun, which required looking down the barrel. At sea the gun captain could do this by leaning over the gun from the side, as the carriage would not hit him on the recoil.
You couldn't do that with a field gun, as the wheels would catch anyone trying the same trick, so you'd have to do it from in front of the gun.
It is also possible that the sponger helped show where the gun needed to be returned to. You'd think this would be a simple thing to work out without someone standing there. But then we are not used to the idea of there being very thick white smoke obscuring everything.
And I noted that fibreglass is time consuming and unforgiving of errors, meaning that it isn't really suitable for such builds on the show. They should be able to put together their own boat from wood or metal in a day and a half at most. It would take then at least a week to make something similar from fibreglass, and if they messed up they'd have to start again.
A gun on a sled is firmly attached to the sled, which in turn had to be physically strong enough not to be damaged by the recoil.
My comments about mounting guns on ships IS relevant because they deal with things that you have to consider. No matter how you design the boat the energy from the gun is going to try to move the gun backwards before that energy bleeds into the boat as a whole. If we were talking about a gun that was also a boat* then there would be no problem. But the gun and the boat are two different objects, and the recoil will affect and start to move the gun before it moves the boat.
You would argue that this is no different to using a engine. But the engine is applying much less force and over a longer period than a recoiling gun does.
(*Humm, a literal 'gun-boat'...interesting idea there.)
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Post by the light works on Oct 19, 2013 11:51:30 GMT
I thought we established a Chevy 350 (a representative motor) weighed about the same as a 6 pounder - and perhaps I was wrong in assuming that meant the entire gun, not just the barrel. that means we either have a 150Kg cannon, or are replacing a 300Kg motor with it. we are also removing the superstructure used to elevate the motor far enough to keep it from breaking off the prop on the hull of the boat; just in case you wanted to claim I was overlooking that. so the gun carriage sits on the floor of the hull, with the drawbar, as you have elected to call it, secured in a bracket built to adapt from the existing mounting points to transfer the recoil from the cannon to the hull of the airboat. if the axle points act as a pivot on the boat, they will also act as a pivot on the ground, because in essence, all you have done is convert the gun carriage into a sled. but of course, it is me saying that, so you will not listen I am going off cybers and yours for the weight of the cannon 600+pounds motor 350 pounds & converted them into something more recognisable to me. You have not addressed the torque issue. I can conclude from previous experience that you have not considered it relevant if at all. Your gun carriage is not on a sled it is on a boat and from your videos not a large boat. The axles will act as a pivot as they do on the ground but there the "draw bar"/limber cannot penetrate the ground, it just runs over the surface. You have still to evaluate the shear forces involved and where stress is involved it is common for faults to occur where welds stop. let me repeat the weight of the motor: "keep in mind a stock Chevy 350 V-8 weighs around 575 pounds. Read more: citadelofmyths.freeforums.net/thread/775?page=4&scrollTo=27631#ixzz2iARQINNK" so in Australia a pivot defined as a point that moves while the rest of the structure remains in the same alignment around it. in America a pivot is defined as a point that remains stationary while the rest of the structure rotates around it. that must be the source of the misunderstanding. and no, it is not a sled, it is a boat that happens to float on whatever surface it happens to be on whether it is water, dirt, mud, rocks, tree trunks, or asphalt; because it runs over the surface. and yes, it is small, it is only big enough to carry 18 people plus the motor and propeller.
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Post by the light works on Oct 19, 2013 11:53:15 GMT
Someone had to aim the gun, which required looking down the barrel. At sea the gun captain could do this by leaning over the gun from the side, as the carriage would not hit him on the recoil. You couldn't do that with a field gun, as the wheels would catch anyone trying the same trick, so you'd have to do it from in front of the gun. It is also possible that the sponger helped show where the gun needed to be returned to. You'd think this would be a simple thing to work out without someone standing there. But then we are not used to the idea of there being very thick white smoke obscuring everything. And I noted that fibreglass is time consuming and unforgiving of errors, meaning that it isn't really suitable for such builds on the show. They should be able to put together their own boat from wood or metal in a day and a half at most. It would take then at least a week to make something similar from fibreglass, and if they messed up they'd have to start again. fiberglass and wood are also much less ductile than aluminum; which makes them much less suitable for such an abrupt method of propulsion.
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Post by privatepaddy on Oct 19, 2013 12:13:25 GMT
I am going off cybers and yours for the weight of the cannon 600+pounds motor 350 pounds & converted them into something more recognisable to me. You have not addressed the torque issue. I can conclude from previous experience that you have not considered it relevant if at all. Your gun carriage is not on a sled it is on a boat and from your videos not a large boat. The axles will act as a pivot as they do on the ground but there the "draw bar"/limber cannot penetrate the ground, it just runs over the surface. You have still to evaluate the shear forces involved and where stress is involved it is common for faults to occur where welds stop. let me repeat the weight of the motor: "keep in mind a stock Chevy 350 V-8 weighs around 575 pounds. Read more: citadelofmyths.freeforums.net/thread/775?page=4&scrollTo=27631#ixzz2iARQINNK" so in Australia a pivot defined as a point that moves while the rest of the structure remains in the same alignment around it. in America a pivot is defined as a point that remains stationary while the rest of the structure rotates around it. that must be the source of the misunderstanding. and no, it is not a sled, it is a boat that happens to float on whatever surface it happens to be on whether it is water, dirt, mud, rocks, tree trunks, or asphalt; because it runs over the surface. and yes, it is small, it is only big enough to carry 18 people plus the motor and propeller. The figures you quote for the motor are those you quoted earlier. A pivot point, in the present case. The wheels support the cannon via the axles the limber supports the cannon to the rear at d distance above the plane of the deck. The force of the firing is in a parallel plane to the deck (for maximum transfer of energy) but the gun cannot move backward so all the force is transferred to the limber which will try to rotate about the axis of the axle.
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