What does a QEPH do?
QEPH = Quick Exhaust Piston Housing
A QEPH is designed to vent the pressure in front of the piston during the piston stroke and behind the piston on the back stoke. Venting the air in front of the piston during the front stroke means that you won't need as much presssure to advance the piston. By venting the air behind the piston you allow it to return faster. This yields a higher Rate of Fire. The o-ring keeps junk(dirt, paint, water, etc.) out of the Piston Housing. The groove that I show you how to cut will keep the o-ring in place so that it doesn't move during play.
I was cleaning out my gear box the other day, and noticed that I had two spare Piston Housings. I was deeply infected with modding syndrom, so I decided to attempt a vented piston housing with an o-ring covering the holes just like the Lapco QEPH has. I noticed right off, that a tank o-ring was almost a perfect size to fit around the stock piston housing. This is great because anyone that is really into paintball has at least 2 unopened bags of these.
I would like to thank sect8echo for his help on getting some pictures for me.
What I used:
- Stock Piston Housing
- Standard Tank O-ring
- Pipe Cutter
- Small Grinder
- Small File
- Drill Press
- Wooden Dowel
- Time, Patience, and preferably warm hands...(it was -4F when I made mine.)
I started out by marking the Piston Housing(PH) at 1 7/8ths inch from the cyclone end. This is were the venting in on the Lapco QEPH.
Next I took pipe cutters and made a scribe mark on the PH. This will ensure that you have a perfectly straight line. Be careful not to make this cut to deep. It just needs to be deep enough that the grinder can follow the mark.
Time to grind away! I am using a little bench to grinder. It is perfect for these little mods.
Start out nice and slow. There is no need to rush this step. The more time you take, and less pressure you use, the more even your groove will be.
Once you have a groove that looks pretty close to the above picture, take a small file, and file off any burs that may be on the PH. This will make drilling a little easier.
If you have a drill press you're all set. If not, you will need to take extra care in ensuring that you drill nice and straight holes.
The drill bit I used was a 3/32 inch bit. I based the size off my RAP4 QEPH which has 3/32 inch holes. I think this is a little bit bigger than the holes on the Lapco QEPH, but I didn't have the Lapco QEPH in my posetion.
I found a wood dowel that was just the right size to fit inside the PH. This helpped keep burs out of the inside of the PH. If you don't have a dowel, it shouldn't be to big of a sweat. You will just need to spend a little more time sanding the inside.
To drill, just start out slow and even. The bit should slide into the metal without to much effort. I went all the way through the dowel and the other side of the PH. This way you get two perfectly striaght holes.
I used a nail to ensure that my second set of holes were perfectly centered.
NOTICE: REMOVE THE NAIL BEFORE DRILLING!
You will drill 4 times total. This will get you 8 holes on your PH. Drill the first set. Rotate the PH 90 degree, and drill the second set of holes. Rotate the PH 45 degrees so that you are drilling between your first and second set of holes. Then rotate it 90 degrees and drill the last hole in the last spot.
After you are finished drilling, you should have something like this:
If you used a dowel, you should have almost no burs on the inside:
Here is the time consuming task; Sanding it smooth. I started by sanding out what little burs there were on the inside. I wanted to get it nice and smooth, so I used 600, 800, 1000, 1500, & 2000 grit sand paper. You probably don't need to use quite this many grits. I would think using just 800 & 1000 will get you decent results. Of course you will get better results the more grits you use, and the fewer sizes that you skip.
Once I was finished with the inside, I took the file and removed as many of the burs that I could on the out side. Once I had the bulk of the burs cut out I took the sandpaper and repeated the same process in the little groove. I used a bent paper clip to get a rounded curface for the groove.
Once you have it sanded down it should look like this:
This post has been edited by KRA SHARPSHOOTER: 13 March 2009 - 08:05 AM