I am finally succeeded to make my variant of the LPEpower 3 cylinder inline LEGO Pneumatic Engine, a Scoctch yoke engine. Rebuilding the engine was very difficult. Many people try to build LPE's and they share their contributions in forums like Nicjasno. To let an engine run, is very difficult, but to let it run fast, by modifying the cylinders and switches, is even more difficult.
Alex Zorko and Ivan Franciskovic, the owners of LPEpower.com, offer LPE's for sale in their store. They build incredible constructions, like automatic gearboxes and 2, 3 and 4 inline and v4, v6 and v8 custum engines. I am now convinced that the amount of money they ask for their engines is not much (in fact very little!) in relation to the effort it takes to build an engine. At Nicjasno's forum (owned by Alex) they say that many people can't build a LPE, even with a building instruction. I now believe that is true.
As I said, I reconstructed the engine, but it is not identical. The original LPEpower Inline 3 cylinder 2.0 SYS is a speed monster. All parts are optimized for speed, even the tubing. I have rebuild the engine with my own view and I made several changes, sometimes dune to the unavailablity of particular parts and sometime because I though it was a smart thing to do. I made photos of my construction which can be used as a building instruction. It starts with this:
In the following picture you can see how the switches are mounted:
But before mounting them you must modify the technic pneumatic switches (part no: 4694). To ensure that the air can flow easily through the switch, the nozzles (inlet and outlet) are drilled up to 2mm in diameter. First open the switch by cutting the back plane from the switch body with a very sharp knife. Don't drill the holes without opening the switch. You will damage the inside and you can't remove the drilling dust. Also, the pins at the bottom of the switch (that defined positions of the switch) must be cut way, so that the switch can easily move back and forward. And remove some plastic on the black part that obstructed quick release of "used" air.
After drilling and cutting you must clean the parts that otherwise can damage your switch. A good way to clean the switch is to blow with compressed air from a compressor. Use some silicone spray for lubrication into the switch before you reseal it with epoxy glue. Don't press the back plane to strong to the switch, otherwise your switch will move with to must friction. Check Nicjasno's forum for more info.
I damaged several switches before I successfully modified one. Removing the back plane without permanent damage is very diffecult. Glueing it all back together also awkward. I can't describe how to do it. It takes some practice to do it. Take some old switches to practise before you use good switches.
The difference between the original inlet and the 2mm drilled inlet doesn't looks so much, but in performance it really makes a difference. In this video you can see that a modified cylinder respond directly and an original cylinder moves quite slow:
To open the cylinder I used a screwdriver. I pressed it between the edge of the black cylinder cover and the yellow cylinder body. Ones it opens on one site I moved the screwdriver to the other site of the cylinder.
Before the cylinders are placed into the engine, the crankshaft is made. This is how the crankshaft finally looks like:
The tubing must be connected to the switch before placing the cylinders. Otherwise it is not possible to connect the hose at all. I used blue pneumatic hose which I bought at www.BlokBricks.com. LPEpower uses tubing made of special plastic tube, also used in the pneumatic industry. It is stiff and it has a bigger diameter then the orginal LEGO pneumatic hose. The tube they use give a better air flow and can run engines up to 6 Bar.
The axle at the down side of the engine has a important function. If the two black 36 tooth gears are not adjust is the right way to each other the engine wouldn't run. After I had constructed the LPE I tried to run it, but it didn't work. Ones I removed one of the 8 tooth gears and placed the crankshaft in the correct shape and then put back the 8 tooth gear, the engine start running.
But at the fist test run this LPE didn't break any speed record, although I used a 6 bar (87 PSI) compressor. I didn't modified the switches and cylinders jet. In fact engine run rather slow. And lubricate with silicone spay didn't help:
I knew what I had to do. I had read about it in the forums. It is a absolute requirement for performance: Modify the switches and cylinders to improve the air flow. Do apply both improvements (the switches and the cylinders), because the air flow is dependents on smallest passage!
Despite its in size a small engine, its made of many parts. Altogether, including the expensive pneumatics components, it will still cost you quite a lot money. If you don't have extreme much perseverance (I give up many times) and a lot of time to spend on building and modifying, you are probably cheaper and much quicker ready when you buy an engine in the LPEpower.com shop.