FP ram size?

[Max]

Hi,
What sort of bore/ capacity full pressure rams do people use in heavyweights? And what leverage ratio for the flipper arm?
I've tried looking through old threads but what I read seeme to suggest a 6 bore which by my calculations would give 12 tonnes of force, sounds wrong to me

[terry]

Re: FP ram size?

100mm bore maximum, I have 160mm stroke.

[typhoon_driver]

Re: FP ram size?

Why 100mm bore max? Some feathers are using similar rams these days. If you can crank it up then I say go for it!

[terry]

Re: FP ram size?

I think jonno is 80 or 100, iron awes are 80 I think kronic is 100 or 120 plenty of power, just get less flips the bigger you go.

[typhoon_driver]

Re: FP ram size?

Increase the bore to say 150mm and decrease the stroke accordingly to get the same volume. Same pressure, same volume of gas used, huge increase in the force applied to the flipping arm. Where is the down side?

[Max]

Re: FP ram size?

Where is the down side?

Where is the advantage if you just have to use a large lever ratio to get the same movement at the tip of ye flipper arm?

[typhoon_driver]

Re: FP ram size?

Why move it back along the arm? Just keep it in the same position and have a short sharp smack to flip the opponent over. Where is the need to accelerate the opponent throughout the movement?

[Max]

Re: FP ram size?

That's a good point. I may mount it so it is adjustable to find tye best solution.

On a different note- does anyone know the Rpm of the Iskra 1.2kw motors or the 0.8Kw motors

[Shakey]

Re: FP ram size?

If the volume of 2 rams is the same but one is a shorter but higher bore than there is little difference between the two if the throw of the flipper remains the same by adjusting the lever ratio. A short powerful flip can be achieved through a longer stroke arm simply by moving it down the ram.

You can't magic up more energy for the same volume of gas expanding, so don't fall into the normal trap of thinking a huge bore is the be all and end all. A longer ram with the same volume mounted further down the flipper arm for an equal flipper throw will kick out the exact same force on the point of the ram. The trick is getting the right balance of stroke, bore and the lever ratio.

[maddox10]

Re: FP ram size?

Ok.

Project One was my first FP heavy. Ram used 70mm bore, 125mm stroke. (the twin of that ram went into Sater 2)
In the same time, Tough As Nails and Gravity3 were build, and those machines use 100mm bore rams. Gravity 180mm stroke, TAN 356mm.

Later I made 2 70mm bore 200mm stroke rams. One of those 2 briefly resided in Dantomkia.(Chatham grammar school for girls event), as they were build to be direct replacements to the 50mm bore 150mm stroke hydraulic ram , as used in Bigger Brother and Dantomkia.

After series 7, a group of 140mm bore rams was made. Stroke around 150mm. One is in Hammerhead 3(that machine should still excist in a shed somewere). Another one is in the Swedish machine Mitril.(now a pile of parts). One is in Bullfrog. That ram is severely shortened to 80mm stroke. Yielding a short, fat ram.

Between that group 140mm bore rams, and now, a series of ali 100 bore rams is made, stroke varying between 120 and 180mm. A few 70mm bore rams for the less powerhungry people...

But ramsize ain't everything. If you can't feed it properly, it's waste of space and weight.

My personal guidelines.
Rams op to 70mm bore work fine with a 1/2 BSP valve. 100mm requires 2. 120mm is the cut-off for 3. 140mm bore needs 4.(or a 1 BSP valve)

Buffertank needs to be 3 times the volume of the ram at minimum.

[typhoon_driver]

Re: FP ram size?

the flipper remains the same by adjusting the lever ratio

This was the point I was getting at though. If you are increasing the diameter of the ram where is the need to adjust the lever point?

For how long is the other robot actually in contact with the arm as it's being flipped? I would hazard a guess that for the most powerful flippers, not that long is the answer.

[team_mute]

Re: FP ram size?

Mute has 2 off 38mm bore for the front flipper and 2 off 38mm bore for the rear one.

Our new hammer bot Bonk uses a single 63mm bore ram.

[Max]

Re: FP ram size?

this is off topic but hardly worth a new thread-
does anyone know if you could make your own gears ,for gearing down a heavyweight drive motor, using steel plate and a cnc plasma cutter?
All the gears I've looked at online cost a fortune and I might be able to get access to a cnc plasma cutter.

[typhoon_driver]

Re: FP ram size?

I would be surprised if you got the accuracy required from a plasma cutter.

Cheap gears here

http://www.technobotsonline.com/index.p ... ory_id=189

[daliad100]

Re: FP ram size?

Gears for chain, pretty easily but unless you're making large, low tooth count gears you probably won't get nice meshing gears. Might be able to do a cycloidal drive as it's less sharp and has less teeth.