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Sabot, has anyone tried it yet?

Post about things you have launched or thought about launching. Also post about various materials used for building cannons. No posts about explosive projectiles!
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Unread postAuthor: SpudFarm » Wed Mar 28, 2012 6:05 am

The design looks solid and good, i will see if I find some of the nails when I get home and give you the dimentions :)

Thanks
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Unread postAuthor: jackssmirkingrevenge » Wed Mar 28, 2012 7:16 am

I'm going to make myself a 6mm one to try it out first :)
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Unread postAuthor: SpudFarm » Wed Mar 28, 2012 7:42 am

That would be nice, document it properly :wink:
If possible, could you first test it at low velocity and try to capture the moment of separation? Might reveal ways of improving the design :)
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Unread postAuthor: POLAND_SPUD » Wed Mar 28, 2012 8:41 am

If possible, could you first test it at low velocity and try to capture the moment of separation? Might reveal ways of improving the design
ohh yeah do get it filmed in slowmo
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Unread postAuthor: jackssmirkingrevenge » Wed Mar 28, 2012 12:39 pm

Well, capturing the separation is going to be a bit tricky with the EX-FC100. I didn't get any useful results, fired at just 10 bar. Still, it worked! Good penetration even at low pressure. I think the best way to evaluate separation would be to have some light paper screens at various distances ahead of the muzzle.

One issue I'm seeing with this is that you can't simply make the sabot then cut it up into "petals" because that would leave gaps, you would have to machine each one individually, with a lot of precision, so it would be quite time consuming. Another vote in favour of fullbore fins...
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Unread postAuthor: al-xg » Wed Mar 28, 2012 2:06 pm

Cut them first then machine them, maybe keep a bit of extra length when you can keep them together and then part off.
I've done this to drill out a split cylinder on the lathe. It was a bigger part though so I actually bolted the parts together. Still wouldn't want to do very many like that though... You could cut multiple sections from the same cylinder I guess, some sort of ring jig could hold the end together, you could also use the tailstock that way...


Although, does the sabot even need to close up fully ?
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Unread postAuthor: dewey-1 » Wed Mar 28, 2012 2:33 pm

jackssmirkingrevenge wrote:One issue I'm seeing with this is that you can't simply make the sabot then cut it up into "petals" because that would leave gaps, you would have to machine each one individually, with a lot of precision, so it would be quite time consuming.


JSR
Don't you remember this conservation in the machinist thread?
I think it applies to sabots also. :D

Do you understand when you cut the block in half, your mold will not be a "round" diameter bullet but elliptical shaped.

Two piece molds are not made the way some of you think.
Stop and think about it for a few minutes before you make such simple assumptions.

If you cut a solid ball in half then glue it back together again, it will not be a true ball shape again.
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Unread postAuthor: jackssmirkingrevenge » Thu Mar 29, 2012 12:56 am

al-xg wrote:Although, does the sabot even need to close up fully ?


Yes, because there's no sealing plate, any gap between the petals is a space where air can leak through, not very efficient.

This is definitely something that is best cast if you're going to do it in quantity.

Don't you remember this conservation in the machinist thread?


The problem here isn't about fit - since the two halves are clamping on the projectile, they still form the correct OD and keep the projectile centred. The issue is that propelling gas can seep past the gaps.
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Unread postAuthor: Crna Legija » Thu Mar 29, 2012 5:32 am

What if you cut with a razor blade they don't remove much if any? it will only work for plastic sabot or epoxy in the gaps to fill them up again if you lube it up it shouldn't stick.
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Unread postAuthor: al-xg » Thu Mar 29, 2012 7:22 am

Oh, yeah didn't see the threads, though it was just to keep it centered. :oops:

For small quantity testing the cutting in half then turning down and tapping should be fine then.


Delrin is quite hard, so might be a bit of a pain to slice in half, worth a try though, would be a much easier solution.
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Unread postAuthor: DYI » Thu Mar 29, 2012 1:33 pm

If you used a simpler external profile than a thread to hold the sabot on in the barrel, you could simply produce two sabot blanks, then mill off half of each one. It's wasteful, but these aren't exactly time consuming, high precision parts you're making. Threads could still be used, but you'd either have to be very precise, or tolerate a bit of mismatch between where each sabot half sits along the length of the dart, which could decrease accuracy. If you don't care about accuracy, it's probably the easiest method - just make the second half longer than it needs to be, and cut off based on where the threads match up.
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Unread postAuthor: jackssmirkingrevenge » Fri Mar 30, 2012 12:48 am

Crna Legija wrote:What if you cut with a razor blade they don't remove much if any?


As al-xg mentioned Delrin is pretty hard to cut with a razor blade.

If you used a simpler external profile than a thread to hold the sabot on in the barrel, you could simply produce two sabot blanks, then mill off half of each one. It's wasteful, but these aren't exactly time consuming, high precision parts you're making. Threads could still be used, but you'd either have to be very precise, or tolerate a bit of mismatch between where each sabot half sits along the length of the dart, which could decrease accuracy. If you don't care about accuracy, it's probably the easiest method - just make the second half longer than it needs to be, and cut off based on where the threads match up.


True, you could have no threads at all, just a shoulder on the sub-projectile on which the sabot halves can push, something like the attached. I still prefer the fullbore fin idea though.
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Unread postAuthor: SpudFarm » Fri Mar 30, 2012 1:16 pm

Good test, I was worried about the gaps created by cutting, that`s why I thought about casting when I was going to do it full scale. I have to use threads as that is the best solution that is readily available IMO.

This pretty much proved the thread part to be sound and that is really all I wanted to know.
To eliminate leakage you have to create two pairs of shorter petals and have them turned 90 degrees on the axis of the penetrator. They should adequately seal.

I will not push you to make any sabots for now, as I see it`s working as planned I will rather come back to you when its time to fire my hybrid again. Hope to get a chance to fire at some range with it for that test.

Anyways, thank you for now :)
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Unread postAuthor: jackssmirkingrevenge » Fri Mar 30, 2012 3:01 pm

SpudFarm wrote:Good test, I was worried about the gaps created by cutting, that`s why I thought about casting when I was going to do it full scale. I have to use threads as that is the best solution that is readily available IMO.


Casting is definitely a better way of doing it in relative quantity - however by the same logic, you can also cast fullbore fin units.

This pretty much proved the thread part to be sound and that is really all I wanted to know.


Given how similar it is to how actual tank rounds work, I had little doubt this was the case. The shoulder design I posted last would eliminate the need for threads completely, making it even simpler.

To eliminate leakage you have to create two pairs of shorter petals and have them turned 90 degrees on the axis of the penetrator. They should adequately seal.


Good idea! That certainly would simplify the manufactuing process, and smaller multiple petals make them less likely to interfere with accuracy.



I will not push you to make any sabots for now, as I see it`s working as planned I will rather come back to you when its time to fire my hybrid again. Hope to get a chance to fire at some range with it for that test.


I'll be happy to contribute to testing by those with more acres to shoot over than I do, such is the spirit of this forum.
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Unread postAuthor: SpudFarm » Fri Mar 30, 2012 4:40 pm

cast fullbore fin units.

I actually doubt it would be strong enough if I don`t reinforce it with a steel plate or something.
There is easier ways to make this work but I want to make it like this because it looks good, is solid and should be fool proof if made correctly.

Good idea! That certainly would simplify the manufactuing process, and smaller multiple petals make them less likely to interfere with accuracy.

There will probably be made more changes with time. I am trying to think out a way to make this as simple as possible for you but still meet my "demands" .

I'll be happy to contribute to testing by those with more acres to shoot over than I do, such is the spirit of this forum.

That makes you a true Spudder :wink:
I wish I could help out with anything in return but you seem to be able to make whatever you want after you got your machinery :D

Sidenote; The only computer I have access to now is a non-admin school computer so I sadly can`t install my drawing programs to give you designs eigther. I will have to MSpaint it!
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