Weight of Full Pressure Rams for Flippers

[jeremy_cuss]

After watching Gravity on Sunday, I decided to do some research on full prssure systems as an alternative to the 100mm 16barg pneumatic cylinder that I had planned for my new robot. I was surprised by the weight of the equipment.

My new pneumatic cylinder and end fittings will weigh almost 8kg, and develop a force of 12.5KN at 16barg. An 80mm hydraulic cylinder (with the same 125mm stroke) and equivalent end fittings weighs over 24kg. It develops twice the force at 50barg (25KN), but weighs 3 times as much.

Unfortunately I dont have sufficient spare weight in the new design to even consider using hydraulic equipment.

Jeremy

PS. I believe that William Dijkstra used a 100mm ram on his machine, and is now reputedly going for a 150mm ram!

PPS. I would be interested to hear from any full pressure competitors whether they disregarded the limits on maximum piston speed on their hydraulic rams or whether they are all running one-off specials?

[blazerbotics]

we have a modified hydraulic ram in merlin, 40mm bore 200mm stroke. our pneumatics weigh no where near 24kg. by using full pressure dont expect the same results as gravity, he has that power due to the large buffer tanks, you will only get similar results by doing the same. were full pressure, and we dont have a spectacular flip, we us FP due to size restrictions.

[mute]

We have 4x 1.5 full pressure rams in Mute, 2 valve sets and with the pipes etc our system weighs no more than 10Kg (probably more like 8Kg).

If you know what you are doing and know how to correctly design/manufacture the things then weight isnt really an issue with this kind of stuff... but only if you know what you are doing.

Piston velocity is kind of a grey area. We thought about the problem and we didnt really know how to really work it out. From a pressure standpoint we were ok, but the shock loading is very hard to calculate. Mute can blow its front rams (2x 1.5 dia x200mm travel) out in about 0.01 seconds (by gas flow calcs, and no load) so as a guesstimate we made the end caps roughly 5-6 times thicker than what was needed to retain the pressure.

[maddox]

Gravities ram , a 100*180 weights in at about 6 kg.

The velocity is less crucial due the rod/arm non connection

Gravities arm weight and velocity is big enough to rip 5mm steel cable like a kotton tread. .WJ uses now Aramide ropes good enough to anchor large yachts with.

The speed in normal, non modified hydraulic rams isnt deadly for the rams, but the seals inside cant cope with those speeds.

[tunna]

Bulldogs new Ram is a specially constructed 100mm
bore, designed by Midland Pneumatics about 18 months ago it was too heavey for the old Bulldog,
but the new machine holds it well, its construction is very complex internally with multiple seal sets!! and rotating Rod,
but most importantly it now only weighs 7.6 kgs

[simon]

Sorry to hijack the thread but... simple question (i hope) how many lts of co2 do you get from 1kg at 50bar ?

[maddox]

I cant say how much CO2 you get from a liter, but a CO2 bottle is filled with 750gram per liter of bottlevolume.So, when using this , and the common accepted figure a kg CO2 gives us 512 liters of gas on 1 bar, at room temperature.I would say, about 384 liter.

[woody]

My guess is around 5 litres of gas @ 50 bar from 1kg of liquid co2.

[maddox]

Hoi Woody, 512L on 1 bar, is in gasform 512/50L=10.24l ramvolume on 50 bar.But thats also the liquifying point depending on temp.
So the 5L ballpark figure is correct, if you dont prevent liquid to be vented.
And the chilling effect doent make this less annoying.