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Old 09-12-2017, 02:25 PM   #1
Rosstnfound
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Inverted roller conversion for Aluminum barrel railgun?

Hey Guys,

I have a 101 cm PLOP (pathos laser open pro) with aluminum barrel and I would like to convert it to an Inverted Roller. I have seen a few railgun conversions but most guys are using carbon tubes.

I was wondering if I should be concerned about the aluminum barrel strength. I will have the bottom bands be 18mm and 16mm with a 14mm kicker driving a 130cm, 7.5mm or 8mm shaft. I will aim for 350-360% ish band stretch.

I am just trying to see what it is capable of. It has lived its life as a standard 130, 120 and now as a 101.


Thanks,

Ross
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Old 09-12-2017, 10:46 PM   #2
Diver278
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Re: Inverted roller conversion for Aluminum barrel railgun?

Hey Ross I converted my HammerHead 90 cm to a roller and it is a aluminum barrel. So far no problems. Also mine is not a inverted roller it has two bands connected together at each end. One on the shaft and the other one one the bottom.
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Old 09-15-2017, 11:01 AM   #3
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Re: Inverted roller conversion for Aluminum barrel railgun?

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Originally Posted by Diver278 View Post
Hey Ross I converted my HammerHead 90 cm to a roller and it is a aluminum barrel. So far no problems. Also mine is not a inverted roller it has two bands connected together at each end. One on the shaft and the other one one the bottom.
Thanks. I am more concerned about the addition of kicker band to two already powerful bands on the underside. That is quite a bit of load on the barrel and I just don't want any parts coming back at me.

My friend Josh helped me turn some new rollers to convert my Mantis roller head to an inverted head.

The Harken 16mm Fork Head Air Block looks like a good block to use.
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Old 09-15-2017, 09:58 PM   #4
Diving Gecko
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Re: Inverted roller conversion for Aluminum barrel railgun?

That's the block Roisb uses, I think. Also, I have seen a few guys use a small pulley from Ronstan. It might be called the "kite block". Dunno if it is as strong, though.
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Old 09-16-2017, 02:49 AM   #5
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Re: Inverted roller conversion for Aluminum barrel railgun?

You can reinforce the tube by adding a Carbon Fiber sleeve. I would acetone the aluminium and maybe sand it a little first. For a tube you could probably get by with using only a heat shrink sleeve ... no need for a vacuum pump. Check out sollercomposites as they have the info and the products you need.

For a roller setup, I would look at something that would keep the wishbones from flipping the back of the shaft. The Roisub seems to have a system that stops the wishbones parallel to the shaft. I haven't tried it but my guess is that would send the shaft out straight and stable. Using an extra conventional booster band might actually benefit more than you think. Of course it adds energy, but I think it could also tone down the effect of the wishbones lifting the shaft tail up on exit.

Last edited by spearq8; 09-16-2017 at 05:02 AM.
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Old 09-16-2017, 02:59 PM   #6
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Re: Inverted roller conversion for Aluminum barrel railgun?

Quote:
Originally Posted by Diving Gecko View Post
That's the block Roisb uses, I think. Also, I have seen a few guys use a small pulley from Ronstan. It might be called the "kite block". Dunno if it is as strong, though.
I was looking at those kite blocks as well and I like the fact that they are not metal and may not scratch up the gun. Plus, they are super light weight are 1/2 the price or the Harken blocks.

The cool thing about the forkhead blocks is that you can thread the your wishbone loops over the removable post on the the forkhead block. So, no need for extra knots or hardware.

Last edited by Rosstnfound; 09-16-2017 at 03:25 PM.
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Old 09-16-2017, 03:17 PM   #7
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Re: Inverted roller conversion for Aluminum barrel railgun?

Quote:
Originally Posted by spearq8 View Post
You can reinforce the tube by adding a Carbon Fiber sleeve. I would acetone the aluminium and maybe sand it a little first. For a tube you could probably get by with using only a heat shrink sleeve ... no need for a vacuum pump. Check out sollercomposites as they have the info and the products you need.

For a roller setup, I would look at something that would keep the wishbones from flipping the back of the shaft. The Roisub seems to have a system that stops the wishbones parallel to the shaft. I haven't tried it but my guess is that would send the shaft out straight and stable. Using an extra conventional booster band might actually benefit more than you think. Of course it adds energy, but I think it could also tone down the effect of the wishbones lifting the shaft tail up on exit.
I will look into the carbon sleeve but it is not a material I have worked with before. If it is a big expense, I may look into upgrading the barrel to carbon. It would be lighter and would allow me to use a heavier shaft than aluminum. Or I may just use a 7mm shaft and skip the Kicker band.

I spent a few hours yesterday looking at the Roisub website and videos. I really do like the idea of the stops that they use. I have seen this stop system on Andres inverted rollers and it made a lot of sense to me.

I wanted to keep my costs down this time, but if the concept works well for me, I will probably get the Roisub head with the torlon bearings. Not sure which of the two stop version are best, the delrin stops or the dyneema loop stops?

Majd, why do you think the addition of kicker would tone down the effect of the wishbone lifting the shaft? I am curios about that.

Thanks!
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Old 09-16-2017, 08:28 PM   #8
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Re: Inverted roller conversion for Aluminum barrel railgun?

As for the lifting of the wishbones, would there even be any with soft dyneema? I thought it was a band thing, not a dyneema thing since the bands don't like tight turns around the front roller?
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Old 09-25-2017, 06:59 AM   #9
Azure Recluse
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Re: Inverted roller conversion for Aluminum barrel railgun?

Haha I have a 90cm aluminium Pathos I am also considering turning into an invert roller. Please update this thread if you do end up converting the gun over, I'd be interested to see the results. I am not interested in a roller conversion, only an invert so I was glad to see this thread!
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