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Buffertanks.
Industrial guideline is that a buffertank has at least 5 times the volume of the used volume per action. But that would make it very large for our purposes, so I give myself the guideline of 3 times used volume.
In a low pressure setup, the buffertank doesn't do a lot to combat freezing as it has the be in between the regulator and valve.
Ram stroke and bore.
A long narrow ram or a short fat one deliver the same amount of power, if the volume is the same.
Problem is, commercial long narrow rams have smaller inletports, and those restrict flow.
As you remark, long narrow rams are more vurnable to bending forces.
I myself try to keep stroke to a minimum, with stroke up to twice the bore (a 50mm ram will have 100mm stroke or less.)
On the other hand, that's not commercial stuff.
Amount of force on the tip of the arm.
Hannibalito 3 does about 200 kg. Hannibalito 4 goes over 400 kg. But those are Full Pressure setups.
I have seen robots with linaks (electric "rams") pushing 25 kg on the tip and win fights. Not fast, nor powerfull, but very controlable and easier than pneumatics.
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1 Attachment(s)
Ok, I think I have a basic design figured.
It's inspired by American middleweight T-minus, and I think it should provide a relatively compact shape capable of both running inverted and self-righting.
The whole machine should be about 35-40cm long, with a 50mm bore, 100mm stroke ram powering the weapon. According to my calculations, a 10bar system should deliver about 60kg of force at the tip of the arm.
Attachment 4356
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I think, if I follow the drawing, that it will be more force on the tip.
How high goes the tip according your plan?
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I'm building a lin-ac flipper! It's quite easy although how much flip it will have is debatable!
It's worth noting that Trev from Mighty Mouse Team runs a featherweight on low pressure I think and can also make you a lot of the hard to find bits.
To build a leccy flipper we're having a go with a half ton lin-ac placed right next to the arm pivot. The maths say it should still have 30-40kg of lift at the tip and will hopefully be quite quick when going off.
It may also be worth mentioning that a lot of the big flippers use the ram right by the pivot to make it deliberately mechanically inefficient.
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Ok, here are the components I've managed to source out so far.
2 x 12v Gimson GR02 motors
12v 3700mAh NiMH battery
Transmitter and receiver package from Scot-Bots (the people who supplied my current bot)
50mm bore, 100mm stroke ram
2 x 12oz paintball CO2 tanks
125mm Banebots wheels
There are, however, a few things I still need. If anyone can point me toward some good, low-cost ESCs it would be much appreciated. Also, would 5mm aluminium be sufficient enough armour for non-spinner battles?
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Why 2 12 oz tanks in a LP machine?
24Oz is 380 liters of CO2 @1 bar. Each action of your flipper uses 4 liters , max.
The cheapest useable escs are third hand electronises.
Best bet, the BotBitz 30A.
Then you can look at IBF 30A 2 channel speedo, a very nice piece of kit, but with £100 I guess above your budget. Also, not available second hand. The teams using those swear by it.
But best Bang for the Buck, TZ85's. Less cheap, but there isn't a featherweight brushed motor that can't be controlled, inside the voltage limits.
5mm ali.... depends on quality. If it's 2000 T1, that's just a tad tougher than cold butter, 7075T6 is almost as strong as steel.
But for most purposes in non spinner combat, yes, it will do. On the other hand, 10mm HDPE does the job as well, and weights half of 5mm ali.
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I should have probably mentioned about the tanks. I was planning to use a 12oz as the main tank anyway, but I also calculated that a 12oz tank is the perfect volume to use as a buffer tank for the ram I'm using. Can I get away with a smaller main tank?
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A paintball bottle as low pressure buffertank is pure waste of weight. For that there are better solutions.
And, if we keep the 4 liter per action, A 12 oz bottle contains 190 liter of gas @1 bar. 47 actions @10bar, lets say 35 real life.
A 9 oz bottle contains 138 liter of gas. Thats 34 actions op paper. 25 real life.
Lower the pressure to 6 bar, and the equation changes equaly.
