Formost 150 & XPS Dynamax fan system - RC Groups
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Jan 02, 2010, 05:29 PM
EDF all the way!
bruff's Avatar

Formost 150 & XPS Dynamax fan system

Flew the Formost 150 today with the XPS Dynamax fan system installed.
Looking at the pictures below you can see it is smaller than the Hoaye 5" fan. So basically it has no inlet on the fan. Fan sounds great. Flew it 3 times this morning. Here are the numbers from the Hacker/Spin 200 ESC. They were consistent between the flights. See here for the video.

Voltage 39.7
Amps 74.8
RPM 22,300
Timing 0
RTF weight 18 lbs
Exhaust dia. 4.25

Last edited by bruff; Jan 03, 2010 at 02:12 AM. Reason: correct voltage callout
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Jan 02, 2010, 07:35 PM
Don't believe the SPIN 200 numbers. If you are flying with 10S then there is no way that you are seeing only 29.7 volts - that is only 2.97v per cell!

Also, since the fan housing is smaller (weird?), you should use an inlet ring if you can fit it... you will gain at least one more pound of static thrust.

Your exhaust cone is almost 1 full inch to large! You need shrink that to 3 3/8th (3.375"). Your top end speed is really suffering.

If you make these changes, you will find a totally new plane!
Jan 02, 2010, 09:26 PM
corsair nut's Avatar
i was going to say the same jim. i saw the id before i saw this post, and i said to, that tail pipe must be REALLY big! and it is! i agree bob, shrink that puppy down to atleast 3.5". and a simple foam lip for the upper portion of the fan wouldnt hurt either.
Jan 02, 2010, 09:39 PM
5kW Club
racer1's Avatar
Bob may have the same problem I did when I first set up the Dyanmax on the Falcon. I only had a 6 inch thrust tube and when I had a 3.5 diamater it choke the thrust down and the plane did not perform.

Later testing I did using the T-jet was the tail cone needed to be at least 12 inches long before I could use the 3.5 exit.

Using a 6 inch exhaust I had to use about 3.75 for the exit.

Jan 02, 2010, 09:49 PM
corsair nut's Avatar
that lip is probably really hurting it too.
Jan 02, 2010, 09:57 PM
5kW Club
racer1's Avatar
At least I had an intake ring to help the Falcon work really well.

Jan 02, 2010, 10:43 PM
Registered User
mpope1's Avatar
It seems to perform much better then the hoaye did!
Jan 03, 2010, 12:12 AM
Average Joe 2 Semi-Pro n Back!
I might have a special NACA 96005 inlet bowl around still that should fit the Dynamax fan - I just need to clean the cheerios out of it!
Jan 03, 2010, 12:15 AM
Registered User
mpope1's Avatar
That is a very aerodynamic bowl, I think NASA uses them!
Jan 03, 2010, 01:46 AM
Renegade Fun Forever!!
rvincent's Avatar
I can hear the video but can't see it Sounds good though
Jan 03, 2010, 02:15 AM
EDF all the way!
bruff's Avatar
I'm, going to put the fan in the Venture (improved Formost 150) it has a full inlet ducting. I will reduce the exit diameter down also. You need a Divx codex for the video.
Jan 03, 2010, 12:36 PM
Air Sally's ring is PERFECT for the Dynamax. Slips on and just works... and it looks good too!

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