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        Discussion Whats the deal with these blade balancers?

#1 BowerR64 Jul 05, 2007 10:48 PM

Whats the deal with these blade balancers?
 
I dont get it, why cant i find a blade balancer that will do CP blades AND FP blades in one unit? Both have pins that arnt small enough to mount CP blades on.

The K&S balancer only has 3 pins now the helimax has about 5 and it cant do both either.

What are you guys using?

#2 raz Jul 05, 2007 11:14 PM

I spent $25.00 on a balancer that doesn't work half as good as a bolt, 3 nuts and 2 drinking glasses. That's what I use now and it cost less than a buck to make.

#3 BowerR64 Jul 05, 2007 11:17 PM

Its the CP blades that im having problems with. The hole in them is so tiny and i thought the helimax balancer would work. The FPs dont seem as critical as the CPs and i cant get anything to work. Maybe ill just use the helimax and just balance the whole head with the blades and everything on it.

#4 osterizer Jul 06, 2007 01:15 AM

Hey, Bower. For the CP blades I used appropriately sized finishing nails to locate the blades on the tray of the HMX balancer, then clamped them to the surface using (iirc) the 2.5mm clamp on top of them. However, I got tired of that balancer-- it's finicky and easy to get a bad reading from --and started doing what raz suggests; nice long bolt and a couple of nuts/washers to hold the blades out, and you can get very accurate.

You still need something else for spanwise CG, but a razor blade, or just setting the blades together in opposite directions in the HMX balancer will work for that usually.

#5 raz Jul 06, 2007 07:39 AM

My home made bolt balancer is way more accurate than the store bought one. Like osterizer said, it was always giving false readings. For CG I use a razor blade (like osterizer said) in a small vise which also works much better than the one that came with the balancer.

#6 Roish Jul 06, 2007 08:20 AM

Quote:

Originally Posted by raz
I spent $25.00 on a balancer that doesn't work half as good as a bolt, 3 nuts and 2 drinking glasses. That's what I use now and it cost less than a buck to make.

Raz,

Can you post a picture of your balancing jig?

#7 gravydrive Jul 06, 2007 08:35 AM

Quote:

Originally Posted by BowerR64
Maybe ill just use the helimax and just balance the whole head with the blades and everything on it.

Bingo! Balance the main blades as best you can - you may try raz's method with the bold and nuts, or you could just mass them with a scale, then balance the whole head (I balance with the main gear attached, as well, but it's really personal preference).

After all, that's what you're really working for (getting the whole head balanced). Having two balance blades on an unbalanced head will still give you weird vibes. I usually add tape to the paddles, rather than the blades to get it to balance level.

#8 raz Jul 06, 2007 09:02 AM

Quote:

Originally Posted by Roish
Raz,

Can you post a picture of your balancing jig?




As you can see the store bought balancer won't set level so the readings aren't as accurate. (It doesn't set level even with blades on it) After I get the 2 blades to set level I use a small scale to make sure they weigh the same.

#9 Santini Jul 06, 2007 09:55 AM

IMO, Id rather invest in an electronic scale (.01). At that level of resolution, you get extremely consistent results as far as matching blade weight (even a very small sliver of tape will register).

From there, I use a razor blade as a teeter toter to find the cog of the heavier blade, then transfer the mark to the lighter blade, and then place the tape on it to achieve desired cog mark on the lighter blade.

I know some people think you dont have to get that exact, but IMO if you are trying to ferret out those last bits of vibs/shakes, this allows you to eliminate the rotor head as a source and you can focus on other possibilities like the shaft, paddles/flybar, tail.

#10 raz Jul 06, 2007 10:07 AM

I use an electronic scale too so I can make both blades weigh the same.

#11 rocknbil Jul 06, 2007 12:23 PM

At the end of the day it's the whole head balance that is important, I use a home-made balancing jig used for both the heli and just the head.

#12 BowerR64 Jul 06, 2007 02:35 PM

Quote:

Originally Posted by rocknbil
At the end of the day it's the whole head balance that is important, I use a home-made balancing jig used for both the heli and just the head.

How do you balance the head? i wanted to see your jig for that.

I remember seeing a post some one used the helimax balancer to balance the head. Using the bearings and the side supports or somthing but these bearings look a little big, i dont think the main shaft will just fit right in there like it looked on the other guys jig. The inside hole looks larger then the CP main shaft.

#13 osterizer Jul 06, 2007 11:46 PM

I just take the spur gear off so the mainshaft turns freely and prop the heli on its side.

Doesn't work if the mainshaft is bent :).

#14 zen@lanset.com Jul 07, 2007 10:56 AM

I use an old CP Pro frame with a couple of old bearings to hold and balance the head on the mainshaft. When neither flybar paddle moves lower than the other one the head is balanced. I carefully move the flybar a milimeter or so to get it to this state.

#15 Santini Jul 07, 2007 03:56 PM

Quote:

Originally Posted by zen@lanset.com
I use an old CP Pro frame with a couple of old bearings to hold and balance the head on the mainshaft. When neither flybar paddle moves lower than the other one the head is balanced. I carefully move the flybar a milimeter or so to get it to this state.

I've done it that way, but then I've also considered where error might creep in. For example, it may appear the paddles "balance" (no bias to either paddle) when in fact one is slightly heavier and has been offset by moving the flybar, which results in the the cog of the whole flybar+paddle set up being off (like having blades with matching weights but the cog's dont match), follow? Vibes or wobble is imparted to the head because the set up does not want to spin perfectly around the focal point.

What Ive been doing is start by weighting the paddles (get them identical, .01), then mount them so that they are dead-on equidistant from the head, then spin it up without the blades as a final check for any vibes (because that is where the rubber meets the road so to speak). (To me, dead-on means use a caliper or a good measuring tool such that there appears to be no perceptable difference). Then, when you slap on a perfectly balanced set of blades (weight and cog), you should be good to go. Anyway, this is another reason I perfer a good scale versus a teeting method :)


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