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Old Oct 09, 2006, 10:34 PM
Durability test pilot
Clovis, CA
Joined Sep 2005
323 Posts
Help!
Wemo Minifan 480 rubbing HET F-18

Need some help here.

Building a HET F-18 that has been laying around for a long time.

When I installed the motor in the fan (HET 2w-20) it was slightly rubbing on the "bottom" of the fan shroud. While there is side to side adjustability with the slotted mounting holes, there is none for vertical adjustment.

I slid the fan into the intake duct (tight fit) and the rubbing is much worse now.

If I flip the fan unit upside down and try to install it, it will not fit (just in case anyone asks)

How can I stop this from happening?

My first thought was to remove the stabilizing ring from the back side of the motor and see if I could "shim" it more on one side vs the other to get some movement. I could stabilize it around the whole motor using 4-6 shims so I still lock it in place but use different sizes (toothpicks?) to get the adjustment.

Any better ideas?

Thanks.

Rob
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Old Oct 09, 2006, 10:38 PM
EDF all the way!
bruff's Avatar
Gilbert, Az
Joined Jun 1999
7,939 Posts
I alway wrap my motor with tape to provide a snug fit at the back side of the fan. This should also help in the centering.
Bob
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Old Oct 09, 2006, 11:05 PM
Durability test pilot
Clovis, CA
Joined Sep 2005
323 Posts
The ring that was included should be more accurate than tape, but less adjustable....
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Old Oct 10, 2006, 09:33 PM
Durability test pilot
Clovis, CA
Joined Sep 2005
323 Posts
fan rubbing

Ok, so I pulled the fan out and disassembled/reassembled it. Ran it out of the bird and it does not rub (on 2s). Put it in the bird and it rubbed again. Pulled it out and rotated it 20 degrees or so - so that it is not using the mounting blocks (see pic) and it does not rub in the plane. So, it is a misalignment of the blocks.

I could secure the fan with zip ties through the mounting tabs to keep it from moving and just leave it as is or I could try shaving down the mounting blocks but if I dont get it right, then I would have to shim back up.

Opinions?
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Old Oct 10, 2006, 09:45 PM
AKA Terry Till
ex-racr's Avatar
Alexandria, VA
Joined Apr 2002
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If the blocks are twisted, you could grind them down a little, vaseline the body of the fan and use epoxy/microballons to re-seat the fan on the blocks.

just a thought.

Terry
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Last edited by ex-racr; Oct 10, 2006 at 09:58 PM.
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Old Oct 10, 2006, 10:13 PM
Durability test pilot
Clovis, CA
Joined Sep 2005
323 Posts
Thanks Terry.
That is a viable option. It would automatically give me the spacing I need.

The fan as it sits is a very tight fit. When running I am sure that the vibration would still allow it to move but I don't think it would take much to secure the fan.

I may even be able to cut the blocks down a bit and put the screws through there with a thread locker and not lock them down all the way. But it would be nice to be able to lock it down and have it right on the money.
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Old Oct 10, 2006, 11:38 PM
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United States, CA, North Highlands
Joined Sep 2004
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Quote:
Originally Posted by ex-racr
If the blocks are twisted
You can see the twist pretty clearly in the pic.

You have a good view of it in the fuse. Why don't you set the fan in the correct position and use a shim or washers in the gap?
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Old Oct 11, 2006, 12:07 AM
turbonut's Avatar
upland CA
Joined Dec 2004
7,266 Posts
If the fan is a tight fit in the air frame that is why it rubbs! you cant squeeze the shroud. I agree with ex racr his Idea should work very well.
Scott
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Old Oct 11, 2006, 09:04 AM
Look out! The lever!
bobthenuke's Avatar
United States, AZ, Peoria
Joined Feb 2005
2,601 Posts
Any amount of twist or torque applied to the fan shroud will distort it. If you really need to use the mounts I'd *very* carefully shim one side or both until it's perfectly square to the tabs on the shroud. As Punkindrublic mentioned, the twist in the wooden mounts are obvious and this is what's causing your problem.

bob
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Old Oct 11, 2006, 09:34 AM
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dave morris's Avatar
orlando fl
Joined Oct 2000
5,713 Posts
best way to do it is to mount the fan to the mounting blocks, then glue the fan/mounting blocks into the fuse while appling no stress to the fan at all. some gap filling glue for the mounting block to fuse joint would be best
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Old Oct 11, 2006, 10:59 AM
Durability test pilot
Clovis, CA
Joined Sep 2005
323 Posts
Well, I'll have to decide which would be easier - removing the blocks and mounting fan then regluing or cutting them down and shimming. I am leaning towards the removal and regluing.

Thanks! I didnt even notice the twist until you mentioned it. Gotta love the Groups!!!
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Old Oct 11, 2006, 10:54 PM
Flying Fatboy
Gordito Volador's Avatar
Tampa, FL
Joined Apr 2003
1,295 Posts
Also be sure that in regard to the tight fan fit, that the seam of the cardboard intake tube is not compressing the fan shroud. That combined with a slight twist in the mounts will give you lots of rubs and vibrations at different speeds.

Regards, Bill
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Old Oct 11, 2006, 11:03 PM
Durability test pilot
Clovis, CA
Joined Sep 2005
323 Posts
seems clear without the mounting blocks. I have only run it up on 2s though so far.

Thanks.
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Old Oct 12, 2006, 03:37 AM
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United States, CA, North Highlands
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Quote:
Originally Posted by dirtypool
seems clear without the mounting blocks. I have only run it up on 2s though so far.

Thanks.
3s is gonna make a difference. The blades are gonna stretch as the RPMs go up. A lot of times you won't get any contact till you run it up to higher rpms.

Good luck,

Brian
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Old Oct 12, 2006, 09:42 AM
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Joined Jun 2005
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The HET F-18 fan doesn't need much to hold it in place. I just positioned the fan in mine and put a small dab of 5 minute epoxy on each fan flange that flowed to the mounting block. It's really easy to pop the glue loose if you have to remove the fan at some point but clamps it just fine for flight and this method doesn't put ANY tension on the fan housing.

Gordito mentioned the seam on the intake duct; I took an x-acto and shaved the seam down as well to achieve a snug but smooth fit.

All this goes without saying that the fan MUST not vibrate/rub before install.
Cheers,
-Mike
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