Dynamax fans
#3
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RE: Dynamax fans
Thanks for the info...
I was told that they produce around 15 lbs of thrust, is that true?
Seems like a lot of force for such a small size, not that I am complaining. I was expecting them to be around 10 or 12 inches in diameter.
I was told that they produce around 15 lbs of thrust, is that true?
Seems like a lot of force for such a small size, not that I am complaining. I was expecting them to be around 10 or 12 inches in diameter.
#6
RE: Dynamax fans
ORIGINAL: FalconWings
I'm more inclined to say perhaps 10~11.5 lbs on a good day, less on a hot summer Texas day. Don't ask me how I know.
I'm more inclined to say perhaps 10~11.5 lbs on a good day, less on a hot summer Texas day. Don't ask me how I know.
kc
#7
RE: Dynamax fans
Hi,
Depending on how you measure it, you're going to be doing well to get 11 pounds of static thrust with a Dynamax and O.S. 91. If your setup is in a model with a poor ducting design or small inlets, you can expect even less.
Depending on how you measure it, you're going to be doing well to get 11 pounds of static thrust with a Dynamax and O.S. 91. If your setup is in a model with a poor ducting design or small inlets, you can expect even less.
#8
My Feedback: (57)
RE: Dynamax fans
I never used more than 5% nitro on ym Dyanamax/OS .91's. I asked around to the local ex-DF addicts and it turns out costly to get just a little bit more of performacne out of an OS .91. There were guys out there that would sell aftermarket parts for the OS to "upgrade it" and we had a local guy (Mickey Edmunds) who could take a Dynamax and re-pitch the blades to get optimum performance.
A BVM .91/.96 would proably fall on the higher 11.5~12 lbs. For the Viofan is not so much about thrust but about holding 23K RPM for 10 minutes without a single hick-up.
You could take off full power and remain full-power all thoughtout your 4 minute flight.
A BVM .91/.96 would proably fall on the higher 11.5~12 lbs. For the Viofan is not so much about thrust but about holding 23K RPM for 10 minutes without a single hick-up.
You could take off full power and remain full-power all thoughtout your 4 minute flight.
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RE: Dynamax fans
Thanks to all who have taken the time to reply!
I have no knowledge at all of the function or setup of ducted fans and you replies have been very informative.
One thing I have garnered is that having the setup of the intake and ducting is an important consideration.
Are there any rules of thumb as far as the setup of ducted fans that you can give me.
I have no knowledge at all of the function or setup of ducted fans and you replies have been very informative.
One thing I have garnered is that having the setup of the intake and ducting is an important consideration.
Are there any rules of thumb as far as the setup of ducted fans that you can give me.
#10
RE: Dynamax fans
keep the intake clean and smooth to air flow and of sufficient size to not starve the fan, on the exhaust side the same goes for keeping it as clean to airflow as you can, it needs to be of sufficient size to not restrict the airflow excessively. tweaking the exhaust exit in relation to the fan size tweaks thrust to an extent.
kc
kc
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RE: Dynamax fans
Back in the day, we removed half of the stator vanes in the dynamax. This has a significant effect on thrust with a minimum amount of exhaust 'swirl'.
Although I never measured it, 13# of thrust might be a little optimistic. Although static thrust can be altered with exhaust diameter, 3 3/4 " seemed to be a real good compromise between static thrust and exhaust velocity.
DC
Although I never measured it, 13# of thrust might be a little optimistic. Although static thrust can be altered with exhaust diameter, 3 3/4 " seemed to be a real good compromise between static thrust and exhaust velocity.
DC
#12
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RE: Dynamax fans
when making your ducting it will depend on your flying field, concrete or grass as to the diameter of exaust outlet. if you are on strictly concrete you can make the outlet a little smaller than if you were on grass.
#14
RE: Dynamax fans
ORIGINAL: YellowAircraft
Mr. Crooks,
What effect did removing those vanes have, exactly? Thanks in advance for your reply.
Mr. Crooks,
What effect did removing those vanes have, exactly? Thanks in advance for your reply.
i never tried it on a nitro fan, but on a brushless 6 blade EDF I've taken 3 blades off and it dramatically increases speed.
kc
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RE: Dynamax fans
ORIGINAL: KC36330
keep the intake clean and smooth to air flow and of sufficient size to not starve the fan, on the exhaust side the same goes for keeping it as clean to airflow as you can, it needs to be of sufficient size to not restrict the airflow excessively. tweaking the exhaust exit in relation to the fan size tweaks thrust to an extent.
kc
keep the intake clean and smooth to air flow and of sufficient size to not starve the fan, on the exhaust side the same goes for keeping it as clean to airflow as you can, it needs to be of sufficient size to not restrict the airflow excessively. tweaking the exhaust exit in relation to the fan size tweaks thrust to an extent.
kc
For my application I know I may lose a lot of you jet guys here: max speed is not the issue (at least not with the design I am working on) thrust is the primary consideration.
Now the duct might be on the order of 5 feet long now I know this is going to cause a drop in velocity? Would it be better to have a longer intake of a large diameter tapering down to the DF unit? And a short duct to the exhaust, I really have no clue here, that much should be obvious to you guys. I am trying to learn on the fly, as I design my first airplane that uses ducted fan for power.
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RE: Dynamax fans
Point taken.
How much is it safe to funnel into the compressor?
Say the wide portion of the funnel is 3-5X the DF unit intake?
Again thanks for all the info...
If you are curious as to what all the questions are about check out "oddball design 101:name thruster", in the scratch build / design forum...
How much is it safe to funnel into the compressor?
Say the wide portion of the funnel is 3-5X the DF unit intake?
Again thanks for all the info...
If you are curious as to what all the questions are about check out "oddball design 101:name thruster", in the scratch build / design forum...
#20
RE: Dynamax fans
a ducted fan is not a compressor, you only need 'enough' air to be feed to the fan so that you don't starve it of incoming air, if you try to ram air the intake you'll have all sorts of efficiency and mixture problems from the constant loading and unloading of the fan as air is forces into the duct, this is why ducted fans loose efficiency the faster they go, if they had a compressor stage that wouldn't be an issue.
kc
kc