15 replies to this topic

[Karl]

Hi All,

I've been trying to get my lift cups as close to the factory ones as possible without much joy. Does anyone have a tutorial to make a proper lift 'bag' rather than the cup or cone types? Also the lift cups on factory shells appear to 'blend' into the shell pasting, how do they achieve this?

Thanks in advance!

[a_bab]

Liftcups are boring to make indeed. That's one of the main reasons I went to rockets: basically you double the amount of lift and get a more dramatic effect. No flowerpots, no heavy mortars to carry, just a nice "fire and forget" item.

The best liftcups are the papercups you can find in the stores: paper cups

[Karl Mitchell-Shead]

I designed a template using some CAD software and plotted the design onto heavy craft paper, alas I no longer have the file

[martyn]

I designed a template using some CAD software and plotted the design onto heavy craft paper, alas I no longer have the file

I have though!

I saved it when you posted it on 'the other place' - thought it would come in handy one day

I hope you don't mind but I had to put it up somewhere to link to here - so pyrobin.

I'll take it down if you'd rather it was not available publicly

Cheers

Martyn

Edit: - actually, looking at it I think something has gone wrong with the scaling - it is obviously too small as it is at the moment - sorry.

Edited by martyn, 07 April 2011 - 09:19 AM.

[MDH]

I hope I am not derailing this but does anybody remember how the Maltese produce their lift cups?

[Karl Mitchell-Shead]

Ha well done Martyn, yes that's the design I created! Once blown up to the correct size they work well, you just need to add a paper or card disc to the bottom.

MDH, dont they just wrap it into the shell with Kraft then draw it tight with flax twine?

[Karl]

Thanks for the replies guys, they've given me a few ideas. Ill have a fiddle with the template and create some master copies :-)

[megabusa]

Depends what size you're making.

Most of my stuff is for 2" mortars, I use the disposable sauce pots from McDonalds - the kids keep collecting them !!

1 pot full holds about 12g of slow BP roughly made with BBQ charcoal. This will send a 70g shell to a good height - about 150 feet I would estimate.

[MDH]

Ha well done Martyn, yes that's the design I created! Once blown up to the correct size they work well, you just need to add a paper or card disc to the bottom.

MDH, dont they just wrap it into the shell with Kraft then draw it tight with flax twine?

Yes, but it is well known that the Maltese lift shells with a relatively low grade of black powder. It seems to me that it has more to do with harnessing potential energy than anything.

[dan100]

for ball shells i use toilet roll tubes cut in half/thirds and a disc on the bottom this is then pasted over for security and a nice finish
for canister shells i put the lift in a bag with the leader fix it to the shell and wrap in kraft tied off with clove hitch knots above and below the lift and on top at the leader our american friends like this method for top fusing
the maltese top fuse the larger shells as they wouldn't survive any other way they also like to use h3 as lift, top fused shells can take it with a compression buffer
the lift bag is normally spiked to the shell to increase the speed the energy is released onto the shell increasing its overall velocity to nearly terminal [going up anyway]

spiking the lift whatever its quality will increase its perfomance
dan

[pyrotrev]

Yes, but it is well known that the Maltese lift shells with a relatively low grade of black powder. It seems to me that it has more to do with harnessing potential energy than anything.

Wrapping the lift into an extension of the outer wrap of the shell is more an Italian thing than Maltese - nice quick way of making high firing bag mines too if you get some perforated cups - they use powder which although quite coarse seems to burn pretty fast. The traditional way of lifting the big Maltese cylinders is to use a low grade BP in a little container (think of a short cardboard tube with end caps the same sort of dimensions as a tin of tuna) which is well spiked to increase the burning rate. Also unlike typical ball shells theirs make a relatively good seal in the mortar.

[phildunford]

Also unlike typical ball shells theirs make a relatively good seal in the mortar.

I believe they include a compressable newspaper/cardboard washer between the lift and the shell which seals tight to the mortar like an artillery shell driving band - but then they are barmy!

[pyrotrev]

Yes, sometimes even a polystyrene foam disc to help seal - and maybe cushion that 300g chlorate flash bottom shot . Barmy maybe, but great pyro!!

Edited by pyrotrev, 12 April 2011 - 12:41 PM.

[dan100]

agreed the shells need to be a tight fit some weigh 80k and need alot of push.and from what ive seen corrugated card discs are used as the "compression buffer" to cushion the lift with newspaper sandwiches between the breaks to help stack them straight. coarser powders are used for gentler lifts on bigger salami shells from what i understand is to still have some burning as the shell leaves for a more progressive less explosive lift
dan

Edited by dan100, 12 April 2011 - 07:55 PM.

[Vic]

Hi All,I've been trying to get my lift cups as close to the factory ones as possible without much joy. Does anyone have a tutorial to make a proper lift 'bag' rather than the cup or cone types? Also the lift cups on factory shells appear to 'blend' into the shell pasting, how do they achieve this?Thanks in advance!

You can of course just use a bag for your lift, don't tie the bag too tight you can then mould it to the shape of the bottom of the shell, then paste your strips to blend in, but it can be a fiddle to do without damaging the cross match.
There are some that say you get more lift from cups with the shell being that bit higher in the mortar, I tend to agree.