New pneumatics: tests, comparisons

[Sariel]

I couldn't quite figure which thread add it to, so perhaps it deserves a new one. I hope somebody can come up with alternative, perhaps more accurate tests.

And a short version :)

[Freekysch]

As soon as I saw this new pneumatic cylinders I thought of one thing: making 8043 fully pneumatic. Are the new cylinders the same dimension as the LAs ?

[captainmib]

So, the system has the same power output, only the lengths are different.

Still, nice to see an update on this. I think with the extended range of movement a lot of new possibilities wil come.

Somehow with the old style I always had the problem of not having enough range.

[Sariel]

Are the new cylinders the same dimension as the LAs ?

No, they're shorter.

[JopieK]

Nice comparison Sariel! Thanks for that. Lot of people will appreciate it. I think you method is scientific enough for a toy :)

[DrJB]

... the system has the same power output ...

I think so. Remember that the max force is the product of max pressure times cross section area (Force = Pressure × Area). Since the max pressure is lmited by the 'casping' power of the hoses onto the plastic connections, it 'makes sense' that the max lifting force will not change much. The only way to increase lifting/pushing force is to increase the cross section, or using a tighter plastic-to-rubber connection.

One thing I did not see in the review is whether the cross section of the cylinder's connections are the same as before. That determines how fast you can retract/expand the cylinder. In the LPE pneumatic engines, the cyliders had to be 're-drilled' to ease the air flow. That re-drilling makes the cylinders more fragile as the plastic 'wall-thickness' gets smaller, as if those bits are not already fragile to begin with.

[allanp]

Nice video, thanks for all the hard work Sariel . It does strike me as a little weird how all the cylinders have the exact same max int pressure values, give or take 1 psi. Could it be that's the max pressure of your pump/valve? I'm just wondering because the guy in the toy fair video said these new cylinders are smoother in operation. This got me thinking that they upgraded the seal material. Did you also test the new pump to see what pressure that could make?

[Sariel]

I suppose it may be the pump's limitation. The new 6L pump appears to perform just like the Unimog's one.

The cross section of cylinder's ports appears unchanged.

[efferman]

thank you very much Pawel. With these cylinders ther is it much easier to build a fully foldable knuckleboomcrane in 19 wide scale with a good lifting power .

Edited July 3, 2015 by efferman

[darsedz]

That determines how fast you can retract/expand the cylinder. In the LPE pneumatic engines, the cyliders had to be 're-drilled' to ease the air flow.

what you meen redriling in case of LPE - cylinder or conectors? For me a flow is limited by all this pneumatic conectors, and a cylinder is not a problem. Redriling cylinder diameter increases a flow consumption and reduces a rod velocity (Flow = Area * velocity).

[jorgeopesi]

This is an epic year for machinery builders like me, at last we can build better machines. My first problem is that I don´t know what I will build first.

[darksheep]

Thanks for the review really well done and helpfully.

I ma shocked the new small cylinder is weaker , that is disappointing , I hoped it would be stronger .

[D3K]

Really looking forward to getting my hands on these pieces!

Thought I'd just mention that the really old long cylinders have a 9/15 length (retracted/extended), so the stroke is the same as the new long ones, but the pieces are actually 2 studs shorter, so it's not exactly a drop-in-replacement.

I am almost certain we'll see a pneumatic excavator in 2016

[gti180]

Hi Sariel, yet another great review !

Are they more controllable? or is it quite hard to quantify

[MajklSpajkl]

Thanks for the report. Too bad that the brackets are not fully compatible, it seems as the two combined cylinders are not perfectly aligned. But I understand, that TLG didn't bother to make them compatible to a piece that has been discontinued years ago...

[captainmib]

Can't we just make connection ourselves?

The cylinder connection is 2 by 1 by 1, above and beneath is room for bracing?

[DrJB]

what you meen redriling in case of LPE - cylinder or conectors? For me a flow is limited by all this pneumatic conectors, and a cylinder is not a problem. Redriling cylinder diameter increases a flow consumption and reduces a rod velocity (Flow = Area * velocity).

Good catch, and I should have been more careful in my wording. The max flow rate through a pneumatic line is controlled by the smallest cross section (as you said, of course). In this case, I meant the ID (internal diameter) of the cylinder's connectors. I believe I saw a video where LPE_power shows how he drills the connectors, but can't find it now.

I am almost certain we'll see a pneumatic excavator in 2016

I like this. We 'bitched' so much about Lego not having LA's ... we got them, and now we're moving back to full pneumatics. I'd love to see a remake of 8455 (or other construction machine) with a LARGE number of cylinders. One can only dream (and wait).

[Blakbird]

I think so. Remember that the max force is the product of max pressure times cross section area (Force = Pressure × Area). Since the max pressure is lmited by the 'casping' power of the hoses onto the plastic connections, it 'makes sense' that the max lifting force will not change much. The only way to increase lifting/pushing force is to increase the cross section, or using a tighter plastic-to-rubber connection.

The limiting factor on pressure is not the hose connection. If it was, we would have seen the hoses pop off in the video. The limiting factor is the piston seal on either the cylinders or the pump. I expect it was the pump because we saw about the same max pressure in every case. Based on ninjasno's tests, we know pressure can sometimes be as high as 40 psi before hoses come off. When depressing the pump against high pressure, you can feel when it starts to slip. So you would get slightly higher output force by using an external compressor instead of the Lego pump. I expect that they intentionally made the pump an effective pressure limiter.

[allanp]

Some pumps are stronger than others. My most worn one only reaches 14 psi but most of them reach well over 40 psi, some near 60 psi.

[DrJB]

@Blakbird: You and I may be saying the same thing. From experiments I conducted myself, I thought the clasping /grip between hose/connector was the weakest link. What I did was simply this: keep on pushing air inside the piston with a hand pump (while holding the piston firmly halfway through stroke) until hoses pop-off. If the seal inside were the weakest link, I'd expect to hear some whistling sound (when air bypasses the seal) BEFORE the hose pops off. Then again, all of this depends on how old the tubing is and on whether the hoses were put on dry or wetted (with saliva?) ... for ease of insertion.

Edited July 3, 2015 by DrJB

[allanp]

Well like I say, some pumps are stronger than others. One of my motor pumps is very well used and you will hear air leak past the seals before hoses pop off. It also really depends on the exact composition of the hose material. Some older ones blow off very easily but the modern ones stay on tight.

[Daniel-Technic]

Where did that long one come from? What new set? Sorry to ask.

Daniel.

[Milan]

Funny how you got different results on regular cylinders then me.

I did the same testing, with both 6L pump (LBG) and big hand pump:

I used brand new, never used cylinders and pump.

Small Cylinder:

Results:

Powered by compressor/6L pump/M motor: 435 grams.

Powered by large hand pump: 570 grams......Your results with same pump: 690

Big Cylinder:

Results:

Powered by compressor/6L pump/M Motor: 1810 grams.

Powered by large hand pump: 2450 grams.....Your results with same pump: 2880

Edited July 4, 2015 by Milan

[Sariel]

I'd say we have a different pumping performance ;)

[MaxSupercars]

Hmm interesting...

Max...