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Old Nov 21, 2010, 11:06 AM
DELTAS RULE
corsair nut's Avatar
tehachapi, CA
Joined Jan 2006
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3" is way too small for this fan. this fan is barely smaller than the turbax, maybe 1/4" less dia. its not a true 110mm, its 114. the turbax is about 120. 3.5" is about the smallest pipe you can run on a turbax


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Originally Posted by rvincent View Post
sure you can Only thing that matters is exit size and thrust. Now if he can maintain 14.5 lbs and a 3" exit he would have 242.7 Mph
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Old Nov 21, 2010, 11:07 AM
Renegade Fun Forever!!
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Fontana, California, United States
Joined Jul 2004
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Hi Eric, FSA doesn't matter just exit size. If the rear of that fan is 5" then thaty is the exit diameter. I used Stu's calc to get those numbers The great thing about his calc is it is not any specific fan. All that matters is the exit size and thrust at that size. Makes no difference how long the inlets or their size or the length of the thrust tube. Just plain old exit diameter and thrust.
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Old Nov 21, 2010, 11:09 AM
DELTAS RULE
corsair nut's Avatar
tehachapi, CA
Joined Jan 2006
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no bob, that is not true. if your trying to get numbers without a tail pipe, you need to account for the motor tube area....there isnt any thrust beeing made from the motor tube right?????? eric is right on this one. lets just wait to see what he gets with a tail pipe
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Old Nov 21, 2010, 11:11 AM
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No its not Brent. The best size for the Dynamax is 3.380 and it's a 5 1/4" fan. So remove .250 from that equation and it would be 3.13". Don't under estimate this fan! If you can get past the sound it is a really a great performer
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Old Nov 21, 2010, 11:13 AM
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Brent it does not matter If you extend that fan with mylar at the same 5" diameter it will not change. It doesn't matter what fan it is.
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Old Nov 21, 2010, 11:21 AM
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You are not calculating FSA. This is straight up fluid dynamics 101 No different than the hydraulics on our cranes. A certain size tube line moving a certain GPM is going to equate to a specific pressure.
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Old Nov 21, 2010, 11:23 AM
DELTAS RULE
corsair nut's Avatar
tehachapi, CA
Joined Jan 2006
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yes, but it doesnt have the blade coverage the dynamax has. difernt fan designs. just because the dynamax can run a small pipe, doesnt mean the turbax can.

if your reading the eflux from right behind where the air accualy comes out, you would need to take in account for the motor tube. if you put 4.5" dia into the calc, your going to get bad readings. its not a 4.5" pipe. i dont know bob, what your saying doesnt make much sense. now, if you were to make a straight tail pipe off the fan at 4.5"....then yes, you can put in 4.5" on the calc. but you cant say 4.5" if you dont have a pipe on it.




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Originally Posted by rvincent View Post
No its not Brent. The best size for the Dynamax is 3.380 and it's a 5 1/4" fan. So remove .250 from that equation and it would be 3.13". Don't under estimate this fan! If you can get past the sound it is a really a great performer
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Old Nov 21, 2010, 11:24 AM
DELTAS RULE
corsair nut's Avatar
tehachapi, CA
Joined Jan 2006
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yes bob...but that certain size tube happens to have a tube in the middle not making any thrust...so....


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Originally Posted by rvincent View Post
You are not calculating FSA. This is straight up fluid dynamics 101 No different than the hydraulics on our cranes. A certain size tube line moving a certain GPM is going to equate to a specific pressure.
once again...if you made a straight 4.5" pipe off the back of the fan, then yes, that rule applies. but in the case of not using a tail pipe, this simply isnt true. go ask stu himself. then tell me im wrong.
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Old Nov 21, 2010, 11:33 AM
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It doesn't matter Brent exit size is exit size. Also doesn't matter what fan. It's a simple math equation. If the fan is making thrust, measure it and calculate it against the exit diameter. It makes NO DIFFERENCE what is inside that fan at all. If you were to extend that pipe at the same diameter it's still just a tube. Don't believe me, try it Has nothing to do with Turbax, Dynamax, Hoaye, Stumax, Midi, you name all have to use the same laws of physics
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Old Nov 21, 2010, 11:50 AM
EDF rules... :)
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Quote:
Originally Posted by rvincent View Post
Hi Eric, FSA doesn't matter just exit size. If the rear of that fan is 5" then thaty is the exit diameter. I used Stu's calc to get those numbers The great thing about his calc is it is not any specific fan. All that matters is the exit size and thrust at that size. Makes no difference how long the inlets or their size or the length of the thrust tube. Just plain old exit diameter and thrust.
I know Bob, but if there is no exit pipe then the fans annulus exit is equal to the FSA.

Eric B.

I was under the impression that the test had no exit tube.
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Last edited by AirX; Nov 21, 2010 at 11:52 AM. Reason: Added information
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Old Nov 21, 2010, 11:56 AM
EDF rules... :)
AirX's Avatar
Joined Nov 1999
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One other thing if you want to see how much power that equates out to, all you need to do is multiply the force by the velocity again and you will get power. Mind you it is easier if you use the metric force and velocity as it will then equal watts.

Eric B.
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Old Nov 21, 2010, 11:59 AM
Renegade Fun Forever!!
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Fontana, California, United States
Joined Jul 2004
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Yep And with our hydraulics we can do the same figuring out how many horse power it takes to move the oil at a specific pressure and pipe diameter. then that can be converted into watts as well 746 watts = 1 horsepower.
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Old Nov 21, 2010, 12:08 PM
Lee Liddle
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Carrollton, Tx
Joined Dec 2006
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Wow, a guy goes out to eat breakfast and comes back to an exploded thread, glad everyone`s playing nice and having fun. I`ll catch up some questions and then do a tailpipe and get those numbers for us to hash about.
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Old Nov 21, 2010, 12:13 PM
DELTAS RULE
corsair nut's Avatar
tehachapi, CA
Joined Jan 2006
20,860 Posts
i understand about the eflux and diameter and trust thing bob...but thats if your using a pipe....if its just the fan unit, you cant run those numbers in the calc. since you dont believe eric or me, just ask stu.

but for now, your not making sense to me.

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Originally Posted by rvincent View Post
It doesn't matter Brent exit size is exit size. Also doesn't matter what fan. It's a simple math equation. If the fan is making thrust, measure it and calculate it against the exit diameter. It makes NO DIFFERENCE what is inside that fan at all. If you were to extend that pipe at the same diameter it's still just a tube. Don't believe me, try it Has nothing to do with Turbax, Dynamax, Hoaye, Stumax, Midi, you name all have to use the same laws of physics
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Old Nov 21, 2010, 12:13 PM
Renegade Fun Forever!!
rvincent's Avatar
Fontana, California, United States
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Make a couple pipe sizes Lee Then we can see the relationship for thrust to exit with the same rpms and what it does to your amps and watts
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