After numerous failures of my "made of junk stuff" lockwood. I've moved onto a FWE styled engine.
After reading a couple hours of this forum I've decided that almost everyone has problems with just jumping into this wild and crazy "mad scientist" hobby except those of you who seem to take it more serious than the hobby level. As a result, making us ametuers want to try it anyway.(After all, who doesn't like to make things glow red and go boom. Other than my neighbors! Hee.. Hee... )
BACK to my question(s).... My FWE is also built from "junk laying around". I have attempted to build up my engine using Larry's scaling chart as a reference. My chamber is 121mm dia(big end) x50mm (small end) X280mm in length. It has a 50mm dia. tailpipe and overall I THINK it should be between 865mm-915mm long. The material for the intake I have is 35mm dia. with the 106 degree bend, it will be flared of course. But I could use some expert advice on an overall length of the intake to start with. Any advice from the forum to get me on the right track? SECONDLY, I gave the variation in overall length in case I need to cut it down some, is this a good idea or should I just start with the 865mm I came up with?
FWE intake length for a 2x sized engine ????
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madmike
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FWE intake length for a 2x sized engine ????
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larry cottrill
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re: FWE intake length for a 2x sized engine ????
mike -
Sounds like a good start. The 35mm pipe would be about right for a 50mm tailpipe, I think. The main chamber cone will be broader than the recommended angle for a true FWE, but it certainly should work. I would design for your 865 dimension, but start out with the 915, as you've proposed. Your elliptical hole for the intake would then be at 865/8 = 108mm aft of the large end of the cone (reduce this a few mm if you use a 'domed' front end as in the original FWE). Make the total length of the intake about 170mm - and, I would follow Eric's advice and just make it connect to the hole in the cone rather than penetrate down into the center. So, the bent part will be a very small part of the whole length.
This should start and run easily at the longer length, and with luck, you'll be able to shorten it to L=865mm with no trouble.
L Cottrill
Sounds like a good start. The 35mm pipe would be about right for a 50mm tailpipe, I think. The main chamber cone will be broader than the recommended angle for a true FWE, but it certainly should work. I would design for your 865 dimension, but start out with the 915, as you've proposed. Your elliptical hole for the intake would then be at 865/8 = 108mm aft of the large end of the cone (reduce this a few mm if you use a 'domed' front end as in the original FWE). Make the total length of the intake about 170mm - and, I would follow Eric's advice and just make it connect to the hole in the cone rather than penetrate down into the center. So, the bent part will be a very small part of the whole length.
This should start and run easily at the longer length, and with luck, you'll be able to shorten it to L=865mm with no trouble.
L Cottrill
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larry cottrill
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re: FWE intake length for a 2x sized engine ????
mike -
I set this up in UFLOW1D by swinging the intake around the front of the cone and ran it using Graham's method (initiated at low pressure part of the cycle). It looks like it resonates really well. I assumed a dome about 45mm deep added onto the front end of the chamber, just a moderately large intake flare and a fairly small tail flare. I used L = 865mm from front of dome to tailpipe end.
L Cottrill
I set this up in UFLOW1D by swinging the intake around the front of the cone and ran it using Graham's method (initiated at low pressure part of the cycle). It looks like it resonates really well. I assumed a dome about 45mm deep added onto the front end of the chamber, just a moderately large intake flare and a fairly small tail flare. I used L = 865mm from front of dome to tailpipe end.
L Cottrill