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Old 11-24-2008, 08:52 PM   #1
Finless
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Default Review - Heim Joint's "Tennis Racket Effect" mod for helis

OK as you all know way back Kevin (Fireup) decided to do a Chinese wight mod for the Trex 450. This helps keep the tail servo from working too hard. All up, I would never fly a 450 without the mod. YES it's that much better!

So Helifreak user Heim Joint went the extra mile and and with testing to the "NATS ARSE" level came up with a screw on device that works prefect and is easy to apply.

Here is his testing videos on YouTube:

Trex500:
http://www.youtube.com/watch?v=iiW7McBiN5s
http://www.youtube.com/watch?v=XWkQGFaArzg

Trex600:
http://www.youtube.com/watch?v=bkEX1QOLGjQ

OK so he sent me some to try. LOVED THEM on my Trex500 with Kasama tail grips! In this review because Heim Joint sent me a few other like for the STOCK Trex500 tail I let others try them.

Here is my review:

Video Link ->Heim Joint's Tail Weight Mod (17 Megs)

In the end this is a good product. I think heli manufacturers should start doing this in the design.

Bob
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Old 11-25-2008, 07:36 AM   #2
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Whoa! Those are some pretty compelling demonstrations!

First off, Heim Joint that was great! I can't believe I was staring so intently at someone sliding a force gauge, but damn, I was!

I've been following the C.W.M. threads on the forum since they started, and lots of folks have done some good work researching, experimenting, and developing. (Fireup's jig has been sweet). But this does a great job of quantifying the problem and a solution.

Of course it leads to some questions!

HJ mentioned that at the extremes he though the forces he measured with the CWM were actually aerodynamic. Is the mod taking out aerodynamic forces at smaller pitch angles? Or is the pivot axis of the tail rotor along the center of lift so that there aren't any aerodynamic forces at smaller angles? Or is it a cosine thing at smaller angles? Just curious as taking out too much of the aero forces could result in funny gyro performance between really hot and cold days. (i.e. tail goes from self centering or neutral to anti centering as it does with CWM without blades)

This also begs for some on-heli tests investigating what we think we know about tail servo size and tail performance. Is it time to fly 450's with micros on the tail? How 'bout a 600 with a 9257? All with no loss, or even an increase, in performance?

I'll leave the "OMG THIS IS AWESOME WHERE CAN I GET IT????!!" questions to others.

.......

The hell I will, THIS IS AWESOME WHERE CAN I GET IT??

Erik
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Old 11-25-2008, 02:00 PM   #3
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Quote:
Originally Posted by yellowbillycat View Post

I'll leave the "OMG THIS IS AWESOME WHERE CAN I GET IT????!!" questions to others.

.......

The hell I will, THIS IS AWESOME WHERE CAN I GET IT??

Erik
Eric PM me to purchase them.

The Trex 500 chinese weights are $16.50 a set plus $2.00 shipping & handling for up to 2 sets in USA (US postal letter) I need:
what type (kasama, Align metal or stock plastic)
quantity,
your name & shipping address
email address to send you a paypal invoice that can be paid with credit, debit, or paypal.

The Trex 600 chinese weights (nuts only) for stock plastic grips are $7.50 a set plus $2.00 shipping & handling for up to 2 sets in USA (US postal letter)


Thanks for your interest.

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Old 11-25-2008, 05:32 PM   #4
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Hello Heim Joint,

and what do you think of these ? :

http://flying-hobby.com/catalog/prod...oducts_id=2860

Can I use the mod for Kasama?

and do You send to europe?

Z
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Old 11-25-2008, 06:25 PM   #5
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Quote:
Originally Posted by Z900 View Post
Hello Heim Joint,

and what do you think of these ? :

http://flying-hobby.com/catalog/prod...oducts_id=2860

Can I use the mod for Kasama?

and do You send to europe?

Z
Yep i ordered two last week(holland) theyve not arrived yet though
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Old 11-25-2008, 07:57 PM   #6
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PM sent.
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Old 11-26-2008, 02:45 PM   #7
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I'm a dutchy too and mine arrived just fine.
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Old 11-26-2008, 06:46 PM   #8
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Quote:
Originally Posted by damige View Post
Yep i ordered two last week(holland) theyve not arrived yet though
yep, to both questions ?
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Old 11-28-2008, 03:38 PM   #9
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PM sent to Heim
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Old 11-29-2008, 09:34 PM   #10
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Default Tried my set out:thumbup:

I got to try a set that Bob got for the Trex 500 Kasama grips as well. Like Bob I previously used a longer bolt with extra nuts on the ends to help with the "tennis racket effect".
Heim Joint's Trex 500 chinese weights worked very well for me. I had to turn the gain down about 4%, but after that it held very steady. It even felt easier to turn my tail around. I think it is a perfect match for the Kasama grips I have.
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Old 11-29-2008, 09:35 PM   #11
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Default Tried my set out

oops double post
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Old 12-02-2008, 08:41 AM   #12
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This is probably a silly question.

Would this type of mod benifit basic flight, most people strive to do extreem 3D

and I could see that there would certainly be benifits in 3D

I am pretty new to all this and I'm like most blokes - want the latest gadget for their toy.
But in the real world if it has no real benifit to a novice, money would be better spent elsewhere ... like a spare set of rotor blades or carton of beer

Troy
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Old 12-02-2008, 09:35 AM   #13
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Quote:
Originally Posted by JetGSR View Post
This is probably a silly question.

Would this type of mod benifit basic flight, most people strive to do extreem 3D

and I could see that there would certainly be benifits in 3D

I am pretty new to all this and I'm like most blokes - want the latest gadget for their toy.
But in the real world if it has no real benifit to a novice, money would be better spent elsewhere ... like a spare set of rotor blades or carton of beer

Troy
  • Lower tail servo current draw = longer flight time and longer electrical servo life.
  • Lower pushrod forces = lower servo gear & bearing wear = longer mechanical servo life.
  • Lower pushrod forces = less mechanical stress on the entire linkage system from the servo to the tail blade grip = longer life.
  • pushrod forces are typicaly reduced to 1/10 to 1/20 of before precision chinese weights forces.
  • Max. tail servo current draw can be reduced to 1/4 of original value
  • Ability to use smaller size tail servo than typicaly recomended with no loss in performance.
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Old 12-02-2008, 10:45 PM   #14
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Just sent a PM, hope to get a set soon. I can see how servo manufactures may be shaking in their boots with results like this. We've all come to learn that bigger is better, and now it turns out that this is not true for tail servos anymore as long as the grips are balanced correctly. I wonder if this is why the the kit makers have yet to really incorporate these relatively simple mods into their grips.
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Old 12-03-2008, 10:49 AM   #15
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Are you planing on doing it for any other heli? For example for a T-rex 450 and/or Vibe 50?
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Old 12-03-2008, 11:35 AM   #16
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Bob, I have a question for you.

Based on the evidence presented it seems obvious that the mod works and works very well.

So the question is, with this mod being fairly commonplace on the net for at least a year, why do you think none of the latest released helis have implemented this design yet?
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Old 12-03-2008, 11:52 AM   #17
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Quote:
Originally Posted by ajnstajn View Post
Are you planing on doing it for any other heli? For example for a T-rex 450 and/or Vibe 50?
Yes, I plan to do them all as quickly as I can. I will post in each forum as they become available.

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Old 12-03-2008, 12:05 PM   #18
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Default Faster tail servos are possible now

Bob,

With the pushrod forces now being so very low using my precision Chinese weights.
Servo manufacturers could easily decrese their speed by at least half. Take a hitec 5083MG at 20.85 oz.in and .07 sec/60 speed. They could just change gearing only by a factor of 2 and have 10.4 oz.in and .035 sec./60 speed. in the same servo. With a .5 ball distance on the servo arm that would give 21 oz. pushod force when the max. needed is 2 - 4 oz. thats at least a 2.5 : 1 safety margin. This could be just a gear set available for those running precision chinese weights. Do you know anybody in the servo business to approach about this?

Thanks for all your help,
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Old 12-03-2008, 12:29 PM   #19
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Honestly no I sure don't and I don't think this will be noticed that much by them until more and more helis start doing it in the design thus the SPECS needed for the heli cause the change. Just my thoughts on how this would roll out long term.

Bob
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Old 12-03-2008, 07:14 PM   #20
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Weight mod built in on the 450 furion. I think there is more but they don't come to mind right now.
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