Engines | Development | Primer | Supplies | Constructopedia | Control |Compressors | Tester | Build | Bibliography | Miscell
Large Pump Compressors |
|
| Why
Use the Large Pump? There are many air compressors using the large pump around and new designs still keep cropping up. This page is for those who still believe in using the large hand pump (with or without the spring) as a motorized compressor. For some people, using the large pump as a compressor is a necessity as they do not as yet own one or two of the small pumps. |
|
| Springless Pneumatic Pump | |
| JP Brown wrote: I have long been an admirer of your Pneumatics web page; it is now almost a daily event to refer people to it when they get stuck with LEGO pneumatics. | |
| I read your remarks in lugnet.robotics about the inefficiency of the springless large LEGO pneumatic pump with some surprise, however. I do not know that this is necessarily the case. I attach a DAT of a design which I have found quite efficient (largepump.zip). | |
| CS: I have built your large pump
design (see pictures). It looks kinda like a piece of sculpture :-) I used the large pump with the spring. Not unexpectedly it performed poorly. When I tried to measure the pressure with the tire pressure gauge, the motor could hardly move. JPB: Well, having the spring on does make a significant difference. BTW, I entirely agree that the large pump design is not so efficient as the revised Hempel design, but many people do not have access to two of the small compressor pumps. CS: It may have worked a little better without the spring. But then, I have fixed back all the springs and I didn't fancy prying them off again! |
 |
 |
 |
| JPB: I sympathize. I have three large pumps with the spring removed, and two with the springs still in place. However, have you tried *tying* the spring down? This technique was developed (so far as I know) by Chris Smith, and provides a way of controlling the spring without removing it. To do this you take a needle and thread (or light fishing line), and lace the thread in and out of the coils of the spring. You must do this with at least three threads. Then you tighten each thread and knot it to hold the spring in the compressed position. | |
| I would be delighted for you to post the design. I attach a 24t variant which has better torque, but slower pump rate. Note that this alternate design requires *20* links of LEGO chain -- in the DAT there are 20 links but they do not join up. In the real model, the double-bend liftarms bend slightly towards the motor and allow the chain loop to close (largepump1.zip). | |
| A Two-Motor Design | |
| John
Doe wrote: I have an extremely simple compressor design that can out pump the double-mini pump using a single large pump. It would be cool if you could put it on your website, because I feel that it is an excellent compressor. It is really good for those who only have a large pump. I'm not bragging or anything, its just that I lost my mini-pump and thought of a way to make a good compressor with my large ones. It works good, because unlike conventional compressors, this one takes a complete stroke, and spins at an extraordinary velocity. In the picture, it has two motors because I had an extra one lying around. It works really good with just one as well. |
 |
| One thing is that I was a little bit off with the gearing, if you want more pressure, then use lower gears, but it works good for getting pressure into the tank quickly | |
| CS: I have built and tried it out to drive my 2-cylinder engine. I used a springless pump and one motor with 1:1 gear as in your picture. | |
 |
 |
| It does not work as well as you claim. The pump works slowly even without any load. When I connected it to drive my 2-cylinder engine, the motor stalled right away.
I changed the gearing to 3:1, with 8T gear on the motor. The pump works a little better. But still not enough power to drive my 2-cylinder engine. |
 |
| JD: I realized that--when
I tried it out--so to solve the problem, I used the 40t and the smallest gear--it didn't pump as fast, but it was able to pop the hose on 33 strokes when connected to the Lego air tank. I think it took about 1 min but I'm not sure. |
|
| I admit that it is not as good as
I first claimed--after I applied it to a load, but I know for sure if you use the same gearing as the large-pump compressor in your website, it does far better than that one. |
|
