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  #181  
Old 01-10-2019, 08:25 AM
rvbuilder2002 rvbuilder2002 is offline
 
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Location: Hubbard Oregon
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Quote:
Originally Posted by charosenz View Post
3) Dan. Thanks for clarifying the comment about "top" vs "Bottom". I do agree that it would be good to add additional members to gain more strength laterally - both top and bottom. As fate would have it there is a in interference conflict with the hall effect sensor on the crank pulley where the proposed lower "A+B" cross member will be. But as you mentioned, this is primarily serves as a "tension" support mechanism and with that in mind, I am comfortable with this particular piece being angle "iron" in shape. While I agree adding "G" and "H" (in addition to "A+B") would add even more support, I (at this stage) am comfortable with adding just "A+B" but not "G+H" to the structure. Ill explain, part of the reason is that the length of the members that lead to "A+B" are considerably shorter than as you have drawn - hence, their moment arm (so to speak) are stronger in the lateral sense. I hope that makes sense to the readers.
When I first saw the photos of your engine mount I had immediate concerns but refrained from posting because any time I do post in a thread related to alternative power it seems to be taken as an attack on the practice (the reality is I would love to see a proven, viable alternative to a Lycoming for RV's but I digress.....)
I fully agree with Dan and I hope you will seriously consider his suggestions. As it is now, I think your engine mount has some serious compromises when compared to the standard mount. Hopefully an interference problem wont be allowed to drive your engineering process.... instead think of it as a problem that requires being creative.
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  #182  
Old 01-10-2019, 08:30 AM
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rv6ejguy rv6ejguy is offline
 
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Location: Calgary, Canada
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Best practice is to triangulate all engine pickup points although I've seen a number of designs with multiple airplanes flying successfully for years which didn't and had cringeworthy tube layouts.

The last thing you need is the engine departing the airframe, so play this area safe. You can move the crank sensor to the flywheel end of the engine if there is tube interference at the rear. As Scott says, don't let this drive any compromises in the tube layout of the mount. I can supply you with alternate sensors and magnets if you need to re-position things.
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Last edited by rv6ejguy : 01-10-2019 at 08:38 AM.
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  #183  
Old 01-10-2019, 08:03 PM
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charosenz charosenz is offline
 
Join Date: Aug 2009
Location: Longview, Wash
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Quote:
Originally Posted by rvbuilder2002 View Post
When I first saw the photos of your engine mount I had immediate concerns but refrained from posting because any time I do post in a thread related to alternative power it seems to be taken as an attack on the practice (the reality is I would love to see a proven, viable alternative to a Lycoming for RV's but I digress.....)
I fully agree with Dan and I hope you will seriously consider his suggestions. As it is now, I think your engine mount has some serious compromises when compared to the standard mount. Hopefully an interference problem wont be allowed to drive your engineering process.... instead think of it as a problem that requires being creative.
Scott,

Thanks for posting. The pic that is referenced the most was of the mount as it was being built was not the final product.

I will post some new pics with the additional support members in a week or two.

Charlie
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  #184  
Old 01-10-2019, 08:43 PM
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charosenz charosenz is offline
 
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Location: Longview, Wash
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Quote:
Originally Posted by rv6ejguy View Post
Best practice is to triangulate all engine pickup points although I've seen a number of designs with multiple airplanes flying successfully for years which didn't and had cringeworthy tube layouts.

The last thing you need is the engine departing the airframe, so play this area safe. You can move the crank sensor to the flywheel end of the engine if there is tube interference at the rear. As Scott says, don't let this drive any compromises in the tube layout of the mount. I can supply you with alternate sensors and magnets if you need to re-position things.
Ross,

Thanks for the offer on the hall effect, but there is no need to relocate it.
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  #185  
Old 01-10-2019, 09:02 PM
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charosenz charosenz is offline
 
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To all,

As far as the A-B, A-G, B-H goes I am still studying the issue. I hope to get some time on the project this weekend.

I also need to get out some better pics so people can get a better understanding of the angles of the mount for what they really are. Which is particularly valuable to the decision as it relates to the A-G, and B-H members.

It is a bit hard to explain without pictures but because the "bolt" tubes (section of tube the bolts pass through where the members attach) between the A-G and B-H are virtually pointing at each other, think parallel. ... welding a tube between would be less than ideal as it relates to the attachment angle. Another option is to use gussets...or....move the G and H over to the top of the top of the nose gear mount support. That also is not ideal as it puts compression pressure on the top of the nose gear mount which accentuates the pressure it receives on landing.

Ill try to get some more pics soon.

P.S. when it comes to tension force, I do not consider an angle shaped member as a compromise of strength compared to a tube shaped member. Anyone care to dig up and post those numbers?

Good discussions!

Charlie

Last edited by charosenz : 01-10-2019 at 09:38 PM.
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  #186  
Old 01-11-2019, 04:22 PM
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charosenz charosenz is offline
 
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Here is a better view of the lower section of the mount. There has been some reference and diagrams to the the "A" and "B" points and I thought it would be good to see it from a better view.

Note there are three colored lines, light blue, dark blue and brown.

While I agree you can always add additional triangulated members such as the adding another member where the brown line is drawn. I did want to shed some light on the triangulation that exist in the sturcture by showing the light blue and dark blue lines.



Sorry the image is a bit oversize. I will work to get it smaller next time. Also, the point labeled "G" really should have been "H" but I know everyone gets the picture.

Charlie

Charlie

Last edited by charosenz : 01-11-2019 at 04:27 PM.
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  #187  
Old 01-11-2019, 06:06 PM
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charosenz charosenz is offline
 
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Quote:
Originally Posted by RV8JD View Post
For halie.com pics, insert "scale/xx/" immediately after "... halie.com/", where "xx" is the percent scaling you desire. So it looks like "www.halie.com/scale/xx/oWc.jpg"

Here is an example using your picture at 65% scaling:
Carl,

Great tip, thanks.

Charlie

(I miss Arlingtons "hay-days of the 80's!)
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  #188  
Old 01-11-2019, 07:10 PM
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DanH DanH is offline
 
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Quote:
Originally Posted by charosenz View Post
I did want to shed some light on the triangulation that exist in the sturcture by showing the light blue and dark blue lines.
One more time.



The tubes marked in red have nothing to do with triangulating points A and B. They support the gear tube, and rely on good fixation of A and B to do it well. To fixate A and B, you need to add members A-G and B-H.

Quote:
Also, the point labeled "G" really should have been "H" but I know everyone gets the picture.
You labeled G correctly.
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  #189  
Old 01-11-2019, 08:29 PM
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charosenz charosenz is offline
 
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I think we have kicked this can (lower mount support topic) down the road far enough that out of respect to those who want to keep up with my project I say we move on to some updates on the project. (But I will post some pics on the new members on the top of the mount because that got overshadowed and I want to circle back to it. But due to other commitments it will be a few weeks.)

UPDATE: I happy to report that I got the new Heavy Duty "Turbo" PSRU gearbox from Viking. I am very impressed with what I see. It uses larger bearings, larger back plate and an improve venting system with a very nice glass window to easily check oil reservoir levels. Viking recommended the upgrade since I am planning on using a turbo. They were very quick to get it sent out. I expect this set up to produce up to and may be over 160hp.

I have not mounted it yet but I will probably be able to post pics of it this weekend.

Charlie
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  #190  
Old 01-12-2019, 07:06 AM
BillL BillL is offline
 
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Location: Central IL
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Quote:
Originally Posted by charosenz View Post
P.S. when it comes to tension force, I do not consider an angle shaped member as a compromise of strength compared to a tube shaped member. Anyone care to dig up and post those numbers?

Good discussions!

Charlie
I would agree with that, but vibration will be another matter. You can use thinner wall or smaller diameter tube for a tension only link. Just for the esthetics. I see Ken Krueger post here sometimes as "Sky Designs". A static stick modeling of this should not take much computer work and will answer all the questions of loading.

When my SAE mini BAJA team did our design ('77), it was before ready availability of FEA models. My team member with the structural/frame assignment came in with a model made out of coat hangers and soldered together. It was wonderful because we could see the stiffness and load it by hand. We immediately found the weak area and added a cross brace. It was Auburn's only National 1st place.
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