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HomeAircraftHelicopterHelicopter Main Discussion › Grip Bearing Arrangement
01-29-2013 02:45 AM  5 years agoPost 101
steve9534

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yakima, wa.

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BobOD
I have no idea of the motivation, but Bob is correct, and you all can learn something from his posts. It matters not so much where the thrust bearing is situated as how far apart the radial bearings are. Putting the thrust bearing between the radial bearings would be the most efficient use of space, and is the most sensible arrangement. This issue has been discussed before. John Beech asked the question some years back when designing his Audacity helicopter and I believe went on to build it with R/T/R blade grips, FWIW. steve.

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01-29-2013 02:57 AM  5 years agoPost 102
OICU812

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Edson, Alberta, Canada

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In order to get respect you must give some to others and have earned it? Think its respectfull enough to answer Aces "simple" questions to learn as well no? Bobs discussion is not something new nor mind blowing however its meaning and motivation is. A janitor can know as much as another guy that's an engineer or a doctor, title itself states nothing in a hobby to be enjoyed by anyone of any education level, race, age etc.... Back to simple questions and whether those will be answered? This is a silly thread with no real need in a rc hobby, the answers have been given long ago, it makes NO difference what the arrangement is really in a RC helicopter not to a degree that one is truly "needed" over the other, only the bearing quality and the fitment of its' holder is key. ONLY on large scale industrial equipment does actual arrangement need to be truthfully considered a NEED.

I have an Engineering degree and know what that means to my credibility in the RC Hobby ?..... ZERO. Experience in the hobby and sharing that experience and teaching those that you can is what counts not your real life degree, no sir... Learn that Bob it will improve you as a person and perhaps you may make some real friends on the way.

...Once upon a time there were Nitros, flybars and frequency pins...

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01-29-2013 03:47 AM  5 years agoPost 103
BobOD

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New York- USA

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Thanks Steve.

Shawn,
Get respect? From who? You?

Team POP Secret

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01-29-2013 03:56 AM  5 years agoPost 104
Ace DuderrProfessor - USA - My Posts: All  Forum  Topic

Still can't answer the simple questions?

1) Which r/t/r helicopter(s) do you own?

2) Do you believe Henseleit Helicopters won the 2012 IRCHA Seed Cup simply because of their grip bearing arrangement?

3) The real practical question is, how much better is r/t/r vs. r/r/t in our specific (i.e., 500-800 size R/C helicopters) application.

If you can't measure the difference in question 3 then what exactly have you shown?

  

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01-29-2013 04:23 AM  5 years agoPost 105
BobOD

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New York- USA

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Such answers derail. I did not want to bring in specific manufacturers but I suppose I can give a little advise. I imagine this will start more silly fights but now we'll leave fact and enter some opinion.

The TDR is very well designed. Very little corner cutting, that is clear. I love many things about it. It is astonishing to see the loads put on that heli with 8x16x5 grip bearings (rated at a mere 1200N). But, my Trex 700 also has R/T/R setup in a very similar design but it uses 10x19x5 bearings (rated 1700N). Better for a daily flyer I think. Not that the TDR isn't worth owning, it is. Align stuff is a lot cheaper and more readily available too. So, start with the Trex 700 head.
For the tail, the TDR one is unbeatable IMO. If you can get one, do it. There may be other good designs out there but I know of none better for a 700 class.
For everything in between, I go with the Trex but you could retro them to anything if you're crafty. Align recently changed their tail shaft and hub so the TDR one no longer fits...unfortunately.

Team POP Secret

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01-29-2013 10:21 AM  5 years agoPost 106
wrongler

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Brewerton, New York

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Is it over?

Bill Whittaker

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01-29-2013 11:12 AM  5 years agoPost 107
Wave

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Illinois

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Cabin fever is hitting hard up in Alaska.

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01-29-2013 12:19 PM  5 years agoPost 108
Noobyflyer

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Clearwater, FL

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Can you put me on that list too BobOd?

I think you suck and I want to be reminded what a waste of time it is to post in your thread the next time I try.

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01-29-2013 12:44 PM  5 years agoPost 109
Climax

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West London, United Kingdom

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Wasn't sure which of the 2 threads to post in, so here goes for this one!

The design of the Blitz Avro lets you choose the grip bearing arrangement... One that is essentially for F3C (outermost thrust bearing) and the other for 3D (sandwiched thrust bearing).

This is probably still going to be controversial, but their how and why is briefly described starting on page 35 of the Avro's manual. The PDF won't let me cut'n'paste the text so I've not included it here, however it's easily downloaded from their web site!

Electronics, Physics, Helicopters, Fixing Things...

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01-29-2013 02:11 PM  5 years agoPost 110
Mark Ryder

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Ann Arbor, Michigan

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For This To Work...
One has to ignore personal reference and instead stay on topic.

On the other hand, people are getting way too personal in this topic and it's unfriendly. The grudges have to stop!

Mark Ryder

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01-29-2013 03:09 PM  5 years agoPost 111
icanfly

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ontario

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um, have a listen. With all good intentions aside, this topic can be better described in laymans terms.

If you assemble rrt your ok but may loose lateral rigidity in the grip. The radial bearings are closely spaced.

When the radial bearings are further apart the amount of free play (deflection) decreases.

I mounted my bearings rrt but will change them shortly, why? It's simple to see that in the rtr arrangement the thrust races cannot press against the outer and inner races of the radial bearing.

Therefore, placement of the outer radial bearing in a rtr assembly will permit free movement of its outer race when the feathering shaft bolt is secured at it's center.

The thrust bearing races will not act like ONE BIG WASHER pushing against both outer radial b races at the same time.

When the clamp is thrust outward, pulling force will transmit through the inner race of the first radial bearing to the outer thrust bearing race, thru its balls to the inner race, then into the shoulder machined into the clamp.

Both radial bearings have an outer race with no binding forces in rtr.

Let me repeat myself, lol.

You can have it either way if, in the rrt assembly, you have an inner thrust race which will not press against both races of the outer radial bearing. It, the inner thrust race, must have a larger center hole.

(my untrained 2 peunies)

A 450 Align f shaft has a machined section for the thrust bearing which will only be rrt. Not to worry, the inner radial bearing race has no pressure against it.

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01-29-2013 04:14 PM  5 years agoPost 112
Wynn1427

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Ca. 93612

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This is sort of an expansion on ShuRugal post but with a smaller sholder in the grip in mind (his picture dipicts if the grip sholder was solid except for the feathering shaft (Question: Are there mutiple variations to where the sholder will be in contact as shown in ShuRugal pic?.

Going back to an
FYI, by efficiency of design, I mean highest strength in the most compact space.
rtr has smaller bearing area (less strength unless stronger materials are used throughout to transmit forces) and by compact I am not sure why this was part of the criteria since a washer orientation doesn't appear to make it more or less compact.

Wynn

Logo 550sx

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01-29-2013 04:31 PM  5 years agoPost 113
icanfly

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ontario

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if you want peace of mind on high speed you have to go rtr. The force against the grip shoulder is transmitted in a cone shape from the f-shaft bolt (or nut) through an rtr assembly.

It's also easy to oil/grease the bearings without a huge washer (softer metal than b-races) in the way.

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01-30-2013 12:05 AM  5 years agoPost 114
BobOD

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New York- USA

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Climax,
That was a good find. Pretty interesting. I never thought of that.
Thanks for sharing.

Team POP Secret

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01-30-2013 12:18 AM  5 years agoPost 115
BobOD

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New York- USA

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Wynn1427,

You bring up a good point. This is one of the many challenges the engineer needs to account for.
The manufacturers of the thrust bearings suggest the amount of supported surface, from the ID as well as the OD. Perhaps I'll dig up some info to see if it is all that significant. Good call though...worth a check and see.

Team POP Secret

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01-30-2013 12:25 AM  5 years agoPost 116
Climax

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West London, United Kingdom

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I wasn't really a good find as I have an Avro and have tried both arrangements... I preferred the 3D setup for my personal style of flying.

However specific testing with this heli showed that for F3C the other arrangement definitely helped the machine to maintain a locked in hover (along with the other suggested head setup options, trailing link, appropriate mixing/fly-bar ratios etc...)

Electronics, Physics, Helicopters, Fixing Things...

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01-30-2013 02:55 AM  5 years agoPost 117
skybob

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Park Ridge NJ USA

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I find this whole discussion to be over bearing

Team Boobie

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01-30-2013 09:40 AM  5 years agoPost 118
wrongler

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Brewerton, New York

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^^^^Well Said^^^^

Bill Whittaker

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02-07-2013 03:19 AM  5 years agoPost 119
BobOD

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New York- USA

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I'll answer a question been repeatedly asked in multiple threads.
It is,
"The real practical question is, how much better is r/t/r vs. r/r/t in our specific (i.e., 500-800 size R/C helicopters) application."

It is answered above in simple, calculated terms. On the order of 50% lower bearing loading. There are helicopter manufacturers sited which demonstrate the point. And I have flown and tested many that demonstrated the point. So that's how much better.

Team POP Secret

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02-07-2013 03:57 AM  5 years agoPost 120
pjones

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Vancouver, Canada

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To save people some looking time the literature that Climax referred to is located at...

http://www.blitz-helicopters.eu/site/avro_manual.html

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