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Douglas Smock
User Rank
Re: We tried that before...
Douglas Smock   9/7/2011 11:15:46 AM
Mea culpa. The sentence should read:

Bearings made from PEEK compounds can take thermal
conditions up to 482F (250C).

Ralphy Boy
User Rank
Re: We tried that before...
Ralphy Boy   8/22/2011 11:53:10 PM
I figured out the math they used for the conversion...

They actually meant 482C = 899.6F

Rounded off 482C = 900F

Flip the 9... 600F

Mathmatical dyslexia kicks in...

600C = 482F

At least that's the answer I got...

btw... 1st ® post

User Rank
I'd like to learn more too.
jmiller   8/21/2011 8:58:41 PM
I'd like to learn about the design as well.  However, I like it when young engineers or in this case a student start to think outside the box and look at ideas that may be overlooked by others.  It's a good opportunity for us "others" to take a second look at something like plastic ball bearings.  I've had a little experience with plastic bearings at lower temps.  My experience was positive because of the chemical resistance of the plastic.

Another idea may be to use plastic slides rather than bearings in some instances.  In some designs a roller bearing type system may be a little overkill.

User Rank
Not enough information here!
BobGroh   8/21/2011 11:51:25 AM
Interesting but way too little information.  And, IMHO, way too little engineering design.

User Rank
didn't work last time
sbkenn   8/21/2011 7:07:25 AM
That something has always been done that way is the worst reason for not changing it !  Congrats to most people for trying new ways, just evaluate the risks, the failures and be careful.  Far too many fail and don't put much effort into finding out why.

William K.
User Rank
Re: We tried that before...Plastic Bearings in Jetpack
William K.   8/19/2011 1:13:24 PM
They all jumped on one error but missed the part about the bearings not being in the high temperature area. So, although there is a serious error, it is in a different area..

If the bearings are replaced every few flights, it would be very interesting to know why, since I don't do any applications where service that often would be accepted. In fact, A lot more information about the jetpack would be interesting. I don't think that the location of the jets was obvious, in fact, I did not see anything that looked like a jet any place above the wearers cg. and so I would really like to know how it is made to be stable. It does seem to be quite different from the other jetpacks that I have seen. So more information on that part would be good.

I do wonder more than a little about the durability of the IGUS bearings if they must be replaced that often, how about a description of why? 

Mission Control
User Rank
Re: We tried that before...
Mission Control   8/19/2011 11:15:04 AM
Welcome to the world of flight.  For the pilot's safety and longevity, a bearing that keeps him secured to his craft is an important component.  The aviation authorities probably thinks so as well.  This old guy would rather see an established material used with a robust configuration (AKA overkill) on this critical component until the loading parameters are better defined and the plastic bearing can be tested and confirmed to a much higher reliability.  Why do you think aircraft cost so much?

User Rank
Re: We tried that before...
Nugent_56   8/19/2011 10:01:41 AM
more like 1112 degrees F!

User Rank
Article's temperature conversion is wrong.
KentAkselsen@KenncoMfg.com   8/19/2011 9:56:49 AM
My conversion formula says that 600C = 1112F, which is way too high for plastics.  
250C = 482F, which is in line with published working temperatures for PEEK.

"Bearings made from PEEK compounds can take thermal conditions up to 600C (482F).Bearings made from PEEK compounds can take thermal conditions up to 600C (482F)."

User Rank
Could ceramic bearings be another viable solution
pshome   8/19/2011 9:46:04 AM
Ceramic bearings may have some of the features of plastic bearings, while being longer lasting -- especially for applications requiring higher bearing loads and elevated temperatures. 

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