StRaNgEdAyS
Well-Known Member
Time has come for me to start workig on some of the minor details.
One of these details is the method by which I will secure the engine inside the fuselage of the plane.
"Why not just bolt it up ?" you ask?
Here's why...
The means by which the pulsejet engine operatres gives it both its unique (and LOUD!) sound, and also a LOT of vibration.
The only first hand experience I have of this is with smaller engines operating at fairly high frequencies, of 150Hz and above, which would not pose such a problem. However, the operating frequency drops as the size increases and the engine I want to use will have an operating frequency of around 42Hz.
Just a small idea of how this will feel, think of a LARGE single cylinder reciprocating engine ohhh lets say of about 80ci (since this engine will have a combustion chamber of 800ci I don't think that is a bad guess), and add 42 detonations per second, so that would be about a vibrational equivalent of say 42 Revolutions per second, say roughly 2500RPM and you will get an idea of the vibration that will have to be managed if the airframe is to hold up.
Think of the vibration you'd get from a big 500CC single swinger dirt bike, and then triple it in intensity!
My intial ideas are to bolt the engine and heatsheild front up to the duct and support via a large rubber ring and use some sort of heat resistant flexible material possibly high temp resistant rubber of some sort to hold the engine/heatsheild combo steady along the length.
This is something that will keep me thinking for a while anyway....
:whistle:
One of these details is the method by which I will secure the engine inside the fuselage of the plane.
"Why not just bolt it up ?" you ask?
Here's why...
The means by which the pulsejet engine operatres gives it both its unique (and LOUD!) sound, and also a LOT of vibration.
The only first hand experience I have of this is with smaller engines operating at fairly high frequencies, of 150Hz and above, which would not pose such a problem. However, the operating frequency drops as the size increases and the engine I want to use will have an operating frequency of around 42Hz.
Just a small idea of how this will feel, think of a LARGE single cylinder reciprocating engine ohhh lets say of about 80ci (since this engine will have a combustion chamber of 800ci I don't think that is a bad guess), and add 42 detonations per second, so that would be about a vibrational equivalent of say 42 Revolutions per second, say roughly 2500RPM and you will get an idea of the vibration that will have to be managed if the airframe is to hold up.
Think of the vibration you'd get from a big 500CC single swinger dirt bike, and then triple it in intensity!
My intial ideas are to bolt the engine and heatsheild front up to the duct and support via a large rubber ring and use some sort of heat resistant flexible material possibly high temp resistant rubber of some sort to hold the engine/heatsheild combo steady along the length.
This is something that will keep me thinking for a while anyway....
:whistle:
