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Unnamed - Team Ellis - QLD
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Philip
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Joined: 18 Jun 2004
Posts: 3842
Location: Queensland near Brisbane


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Beautiful.

Why did you choose a straight spring rather than a conical one? Have you determined your valve's Cv? What is the thickness of your piston?
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Post Sun May 10, 2009 12:08 pm 
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assassin



Joined: 27 Jun 2004
Posts: 1105
Location: SunshineCoast


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Its a XU1 spring. No less than 10 CV. Which part of the piston?

I quickly designed a valve that would suit your ram today. But would your ram handle it and could you make your bot handle it? Shocked
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Post Sun May 10, 2009 12:31 pm 
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Philip
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Joined: 18 Jun 2004
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Location: Queensland near Brisbane


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I was wondering how thick the UHMW (?) is. Actually, I would be interested to see the dimensions of all of the parts of the piston valve and four bar mechanism.

I would like to put an enormous Trent valve in Marauder and if it dies, it dies. Woody's Flipper Calc for Flow and Throw says a CV of up to 18.65 would suit the ram. http://www.teamonslaught.fsnet.co.uk/pneumatics.htm

I would like to build me an entire Trent valve and ram combination at 60 * 60 mm. This would be the basis of a complete new bot. I will need to be more financial before I do anything new.
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So even the rain that falls isn't actually going to fill our dams and our river systems

Post Sun May 10, 2009 1:58 pm 
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assassin



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Location: SunshineCoast


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15mm

A new valve could be done cheaply. Your piping is 1/2 inch? That's like 12 CV, so a valve designed around 1/2 inch piping would be the go. Which is the same as the ram on these pages.
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Post Sun May 10, 2009 2:11 pm 
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Philip
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Location: Queensland near Brisbane


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Yes I have 1/2" BSP piping. My current CV is only 2.2, IIRC. 12 would be a huge improvement.
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So even the rain that falls isn't actually going to fill our dams and our river systems

Post Sun May 10, 2009 3:37 pm 
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Philip
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This is the sort of thing I had in mind. Not to scale. http://robowars.org/forum/album_pic.php?pic_id=1504
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So even the rain that falls isn't actually going to fill our dams and our river systems

Post Sun May 10, 2009 4:14 pm 
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assassin



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I could do this with my lathe and drill press.
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Post Sun May 10, 2009 5:24 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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Any reason for choosing UMHW for he piston over stronger plastics like Nylon or Delrin? After having machined all three, I am not nearly as impressed with UMHW as I used to be.

Post Sun May 10, 2009 7:01 pm 
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maddox



Joined: 21 Dec 2006
Posts: 786
Location: Belgium


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The softness of UMHW is a good way to assure a seal.
Also, I tried nylon for the piston itself in a few rams, and it did break,I replaced those with UMHW pistons, No more problems.

Post Sun May 10, 2009 7:11 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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Fair enough. I thought the O ring did all the sealing?

Post Sun May 10, 2009 7:15 pm 
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assassin



Joined: 27 Jun 2004
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The shuttle seals with aluminum to UHWM-PE. Nylon is too brittle Nick, as Mario stated and has tested.

Nylon is a lot better to machine and has it place, but not here.

thanks for the interest Nick and G'day Mario I've been away for a while, thanks for your help I'll be testing @ FP soon.
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Post Sun May 10, 2009 8:48 pm 
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maddox



Joined: 21 Dec 2006
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Location: Belgium


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I mean for the shuttle. On a HDPE piston I use nothing or Viton Orings.

The shuttle in my version of the QEV ram seals directly on the ali body. And with harder plastics the seal is difficult to achive.
In the Burkert it's solved with a PTFE ring in the bronze shuttle. Just to give another example.

Post Mon May 11, 2009 9:57 am 
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Woody



Joined: 07 Oct 2004
Posts: 202
Location: UK


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quote:
Fair enough. I thought the O ring did all the sealing?



I think you'll find that Trent's design is a face seal....could be wrong.
There will be however an O ring in the shuttle body.

So..... inlet port in the side ...outlet port at the top and bolted to the ram base via the staggered bolt hole pattern.

UHWM-PE shuttle ... probably stepped to give an annulus at the inlet port...with small bleed hole drilled thru it ...is pressed against the outlet by pressure of gas that bleeds thru the small hole...a NOS valve or similar actuates the valve by dropping the pressure below the shuttle.

This would be at the small end ( bottom ) of the pic.

Post Mon May 11, 2009 7:26 pm 
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Nick
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Joined: 16 Jun 2004
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Location: Sydney, NSW


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Thanks Woody. I was just looking at the ram seal. The shuttle valve still mystifies me, even though I have read several explanations; guess I'm a noob with gas weapons Embarassed.

Post Mon May 11, 2009 8:12 pm 
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Glen
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its exactly the same as the plan c ram, except the shuttle valves are smaller in these designs Smile same concepts anyway.

fantastic work Trent. nothing short of perfect Surprised

i think with the design the pressure holds the shuttle valve up against the bottom of the ram sealing it off. then the pressure under it is vented allowing it to drop down and the gas to flow around it into the ram.

all of these super flow valves are spin offs from spud guns. theres tons of websites on the majority of the designs Smile AFAIK anyway Razz
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Last edited by Glen on Mon May 11, 2009 8:20 pm; edited 2 times in total

Post Mon May 11, 2009 8:18 pm 
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