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HelicopterMain Discussion › what goes into a swashplate
03-10-2006 03:40 PM  11 years agoPost 21
Branzzz

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okay guys...i'm just a second eyar student in a polytechnic here, so i need a little help. i've done up my design of the swash and all looks ok...the things i need to know are...

how am i going to specify the tolerances for the parts? i know they're all press fit and i'm not really familiar with this area.

i've gone around the brass lining and put in a teflon liner for the ball instead. i can only hope it will bend so i can fit it around the ball...

tmoore:what exactly is a heim ball and why is it so specially named? can it be sourced from a company?

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03-10-2006 04:11 PM  11 years agoPost 22
TMoore

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http://www.aurorabearing.com/

This site shows spherical bearings like those in use on a swashplate.

The bearing sizes are published sizes and the mating parts should be sized so that they make up a light press fit. Typically this will be size for size.

Don't get carried away on Pro E, at the end of the day you might have a lot of pretty pictures with little chance to actually make what you drew.

TM

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03-10-2006 06:07 PM  11 years agoPost 23
Branzzz

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i'm actually doing this for a company as part of my industrial attachment... what i've been told is that the production of parts will be outsourced to industrial contractors. the problem remains the telerances. how can i specify the kind of friction fit that i want?

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03-10-2006 06:21 PM  11 years agoPost 24
TMoore

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If you are in class it might be good to ask the instructor. There are several ways to specify interference fits. These are covered in the Machinery's Handbook and most good engineering texts.

I will look in the handbook after lunch.

TM

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03-10-2006 06:28 PM  11 years agoPost 25
w.pasman

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TMoore,

Your comments sound a bit negative to me. Branzzz asked for a cross-section to start with and I made one of my raptor swash. I don't have a sloppy bearing in my TT swash. I never suggested that this was the solution with the least slop, or whatevery you may imply with "poor". But you do not even explain your suggestion that the particular design of the TT swash causes such sloppyness. Finally I don't see much difference between what we discussed here and what you wrote. The only difference so far is a press-fit heimball instead of a two-piece clamp-heimball.
The TT swash is a very poor implementation because the bearing is sloppy. Look at the QUK swash and it's designed and built like I said. I've built lots of swashplates and there are no issues in pressing in the heim balls, it doesn't damage the heim ball or the center hub. Robbe has been building swashplates like this for years.

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03-10-2006 08:16 PM  11 years agoPost 26
TMoore

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The title of the thread is: what goes into a swashplate

Are my comments negative or just the plain truth? If you are looking for something that's sugar coated it's not here.

I didn't see that this was a TT specific thread. The fact remains though that the TT swashplates are sloppy and the slop comes from the large bearing not the heim ball. The machining and fit of the TT swash is fine it's the large bearing that is the culprit. If you use an adjustable heim ball you will have to make provisions to clamp it into the center hub somehow. This is usually done by swaging the material in the hub to lock the ball race in place.

I don't have any issues with your illustrations. It's fine.

TM

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03-10-2006 08:46 PM  11 years agoPost 27
Branzzz

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well guys nothing bad about both. swashplates are so simple in concept yet so difficult in design and production. we all learn new things everyday, that's the purpose of this thread, and for that both gave very positive notes and diagrams to add.

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03-11-2006 02:37 AM  11 years agoPost 28
Ramster

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Swashplate section views


w.pasman,

Your illustration doesn’t show how in an in-line swashplate all the ball link centers are located on the same plane (In a non in-line swashplate only the upper ball links and the spherical bearing share the same plane).

.

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03-11-2006 10:51 AM  11 years agoPost 29
w.pasman

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Ramster,

Yes I know. I thought it was not important at this point.
My drawing is to illustrate the construction and materials, and is not intended as a production-ready CAD drawing or so.

Your cross-section pictures are also very nice.
I see that in your case also the heim ball is housed in a separate unit. Any idea why they don't just build the top piece in one part?

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03-11-2006 11:05 AM  11 years agoPost 30
w.pasman

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TMoore,

I'm not expecting sugar. But you started the TT versus Quick versus whatever. I gave a comment on this because your comments were just comments, and did not give hints to what MAKES one better than the other.

But I see that you have added more useful info, also on correctable Heim balls. I think this kind of info is what Branzz was looking for.

What's the idea behind adjustable heim ball, to remove the slop or to move it vertically with respect to the swash bearing (centering)?
This is usually done by swaging the material in the hub to lock the ball race in place.
Can you explain this in another way? I can't find what "swaging" means.

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03-11-2006 05:52 PM  11 years agoPost 31
Branzzz

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i did a little practical lesson on swaging on aircraft control cables...

there was a machine which hammered the part concerned till it deformed around the cable. the part then had a very tight and secure grip around the cable i supposed this is the same as whats going on around the heim ball.

by the way i read that quick uk swashes can be adjusted for slop by tightening some screws. how is this done anyway?

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03-11-2006 06:08 PM  11 years agoPost 32
Ramster

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w.pasman,

I surprised you choose to omit this KEY feature from your illustration.

Plain spherical bearings are off the shelf items readily available from most bearing manufactures. They are precision and cost affective parts. A spherical bearing is pressed into the swashplate’s top part just like a ball bearing is pressed into the lower part.


.

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03-11-2006 06:59 PM  11 years agoPost 33
w.pasman

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Ramster

What is a key feature for one drawing is not for another.
My drawing aims at illustrating how the parts fit together. By placing those links in line it would make the distinction between upper and lower swash less clear

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03-17-2006 03:29 AM  11 years agoPost 34
Branzzz

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Ramster:Ive been trying to find a source for the spherical bearings but there seem to be none locally. may i know which companies make these bearings?

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03-17-2006 04:22 AM  11 years agoPost 35
TMoore

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HelicopterMain Discussion › what goes into a swashplate
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