Small yet powerful compressor needed!

[trinitechnic]

Hello all!

I realise 8455 has quite a following on this forum, and I agree its one of the best technic sets of all time. However, I do want to do a hybrid mod/moc and add 4wd, a side shift backhoe and a motorised pump with tanks and an autovalve to shut off the pumps.

So far, I've tried a couple of compressor designs but they are either not powerful enough or too large, my most recent attempt was a copy of a allanp(radbot) design with eight compressors, but using the new 6l pumps I can only generate 35-40 psi and it does not make enough pressure as fast as I'd hoped it would. It's also a large design, to big to fit into the size of the original 8455.

I would really appreciate some ideas from any one on this!

[DrJB]

I have not done a compressor in a while but there are many options out there. Now, one feat need (IMHO) is an air tank, so that when you actuate any of the cylinders, the pressure does not drop too much, and you do not need to wait for the compressors to 'recover'. I've seen some that are connected in parallel and, from experience, you got to be careful so that while one is pulling air, it is not taking it from the one charging. Maybe a setup with one-way valves could be used, and here they sell those for air-pumps for aquariums.

Edited April 23, 2016 by DrJB

[radafuk]

Hi,

I'm using a 3 minipumped compressor, that originally was designed to fit into 8455 (only 3 wide to fit into the nose). On the below image you can see it in a quite different setup (including control valves, bicycle pump extension, tank extension), but the concept remained the same. Simple, quite continous.

The current stuff it drives (quite slowly):

And the control valves (it's just being disassembled, that's why it's missing gears and motor already):

[trinitechnic]

Thank you DrJB and radafuk, unfortunately what i really need is something with a high output to be able to actuate up to four large cylinders simultaneously (as in using the loader arm), at a decent speed and with good force. Radafuk, your design looks ingenious however! I appreciate the photos!

I really am keen to use an 8 pump design, however i am either not getting the output i want or the vibration is too much or the compressor itself is a little too large. Yes I am being very picky! But I realise this would be the best place to ask for advice.

As a side note, DrJB, I myself am also a doctor and my senior's initials are also JB... go figure!

[allanp]

It is strange that you are only getting 40 psi with my compressor. Might sound weird but have you tried running it the other direction? For whatever reason some individual pumps don't seem to work so well when the crank is turned one way but work fine when turned the other. Make sure the compression stroke of each pump is on the outside of the pump (right crank turns counter clockwise, left crank turns clockwise) and that the hoses are not trying to bend the pump. I have got over 60 psi with this compressor with very little waiting times. Though I don't yet own enough of the newer slightly longer pumps to try it with those, only the older ones.

[trinitechnic]

Hello allanp!

I will have to rebuild your compressor. As I used longer pumps, I needed a slightly bigger frame. I cannot recall exactly which direction the banks of pumps ran, but I did orient all of them upside down, with the outlets all oriented outwards. It did take a little while to achieve 40 psi, and thats without a tank. Your design had the best balance and very minimal vibration, I ran it with an xl motor. Just needed to get the pressure up to 60 psi, and perhaps make the frame smaller but not really seeing how thats possible.