Team MedBots

[Max]

I'll have a look at the electronizes this evening, I've had a rethink on the layout for the heavyweight, I've dropped one of the main tanks and replaced the other with a longer thinner bottle.

I have lost the 'ideal' flow setup from the buffer like I had before but this way is much more compact so can be better armoured. I'll make the pipes from the buffer to the ram 3/4" rather than 1/2" to increase flow around the bends. Is it true that a 90 degree bend halves the flow, I find that hard to believe

[maddox10]

For practical purposes, you can say that a 90° corner halves the flow.

[Max]

Is there any way of reducing that loss, like swept elbows?

[Danjr1]

Here's a video of the problem:
http://youtu.be/yuxFTgrWts8
Just to explain what's going on- to begin with I have to motors going full speed forward, then after looking at both wheels I put it into full reverse then back into full speed forward, during the jittering I am holding the stick on the transmitter in one position never changing speed or direction, the wheels just stop.
At the end I quickly how the insides trying to show the flashing/sparking inside the motors caused by the starting and stopping.

I had the exact same problem, which I sorted by changing the motors but it was a trial and error fix. I never worked out why it was actually happening but electronize said it wasn't the ESCs. I've never had the problem again after switching to hacked tz-85s.

[maddox10]

yes, large radiï bends are one solution. Another , and that one I prefer, is to eleminate any corner.

Now, from main tank to buffer isn't the issue, from buffer to valve, and from valve to ram, that's the part you need to look after.

[Max]

Is it safe to drill into the side of my (empty!) fire extinguisher bottle and tap a hole to have my outlet in the middle of the bottle? Not sure if there is enough wall thickness or if it makes it lose a lot of the strengh?

[Liftoff]

I wouldn't risk doing that Max. More so if the extinguisher you have is a low press type (water, powder, foam)

[Max]

Its a co2 fire extinguisher, I've seen people drill and tap in the end of the extinguisher before for pressure gauges, dump valves etc.
But I Think your right about drilling in the side

[Eventorizon]

Taping it wouldn't be enough. I can't see a problem with a welding it if its a low pressure system. Ask the Beauty guys, they weld up their own buffer tanks.

[Liftoff]

I can't see a problem with a welding it if its a low pressure system.

As long as its LP you could do that and then pressure test it...although I really doubt anyone will certify it, but at least you'll know its safe. I don't know how strict are the rules regarding alteration/modification of pressure vessels.

[Max]

Ok new idea- if I just use larger piping for the elbows then even with only half the flow I still get the maximum amount the burkert can take. Does anyone know what size pipe you need to supply a burkert with the maximum flow it can handle?

[Ellis]

I have no experience with robot pneumatics systems, but I have built many air guns that I'll typically fill to 17 bar (limits of a cheap bike pump!), and I'd never trust a vessel with a large diametre like that, and just a tapped hole or something in one side. In the end of the bottle is different, the weakness is even, but in the side sounds like a disaster waiting to happen. Unless it's an entirely custom setup, welded into place, properly pressure tested, etc, I'd give the idea a wide berth.

In fact, unless it is common practice in the hobby, I'd avoid drilling into the bottom of the bottle too.

[maddox10]

Is it safe to drill into the side of my (empty!) fire extinguisher bottle and tap a hole to have my outlet in the middle of the bottle?

As long it's empty , you can drill and tap to you hearts content.

Not sure if there is enough wall thickness or if it makes it lose a lot of the strengh?

If you ask that, you learned something. NO that wall ain't thick enough to do what you suggest.
For 1/8 or 1/4 bsp you can do so in the bottom - as it is about 3 times thicker than the wall, but even then you'll need to have it retested.

If you want a 1/2 BSP or bigger in the sidewall, you'll need a welded in/on piece. Most ali CO2 bottles are from a weldable kind of ali. And with the advent of cheap AC/DC TIG welders, more and more people can do so.

The main problem here is to get a firm retesting and certify adapted bottles.

[Max]

So that's not an option, am I right in thinking that by using 1.5" BSP fittings and tubes then even with 3 bends in it I get the same flow through to the ram as using 1/2" BSP fittings and tubes?

[maddox10]

Just build the damn thing, that spike won't do any damage, so whatever flow you give it, it won't matter.