Today's Message Index:
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1. 05:25 AM - Re: CH701 builders & fliers - Tunnel & Seat front questions (Randall J Hebert)
2. 07:36 AM - Re: CH701 builders & fliers - Tunnel & Seat front questions (Tommy Walker)
3. 08:47 AM - Re: CH701 builders & fliers - Tunnel & Seat front questions (johndread@aol.com)
4. 09:21 PM - Re: Fork tube analysis and prospective stainless steel substitute (Les Goldner)
5. 09:29 PM - Re: Fork tube analysis and prospective stainless steel substitute (Les Goldner)
Message 1
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| Subject: | CH701 builders & fliers - Tunnel & Seat front questions |
Keith
I believe that is just showing the orientation of the objects that are
riveted to the seat front 7-F-11-1.
I didn't put anything else in.
The section just to the left shows the objects that are attached to the seat
front but there is no section from above that would show their orientation,
so I believe they used that method to show that they are Ls
Randall J Hebert
Randall J Hebert & Associates, Inc
Consulting Engineers
Ph 337-261-1976 Fx 337-261-1977
From: owner-zenith701801-list-server@matronics.com
[mailto:owner-zenith701801-list-server@matronics.com] On Behalf Of Keith
Ashcraft
Sent: Sunday, January 17, 2010 6:27 PM
Subject: Zenith701801-List: CH701 builders & fliers - Tunnel & Seat front
questions
All CH701 builders/fliers,
On page 7-F-11, in the center of the page, to the right of drawing 1&1A,
there is a view showing the section of the tunnel mated with the seat front.
I see there are 2-"L" that are shown about midway up on the inside of the
tunnel.
I don't see these depicted on any side views of the tunnel, and the assembly
guides do not mention installing these.
Any ideas?
Keith
CH701 - scratch
Message 2
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| Subject: | Re: CH701 builders & fliers - Tunnel & Seat front questions |
Same for me Randy.
There will be an L placed on the outside of the tunnel to support the seat pans.
Perhaps that is what is depicted in the drw.
Tommy Walker in Alabama
N8701T Getting close
--------
Tommy Walker
N8701 - Anniston, AL
Read this topic online here:
http://forums.matronics.com/viewtopic.php?p=282069#282069
Message 3
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| Subject: | Re: CH701 builders & fliers - Tunnel & Seat front questions |
Hi Keith;
The "L" that seem to be shown halfway up the tunnel are the
"L" that attach the front of the tunnel to the Seat Front 7F-11-1, what is
shown is a cross section of the "L" along with the notation that the "L" is
"Bend up" There is a stiffener that is applied to the Tunnel, it is shown
on 7F-16 center right of the drawing. That "L" goes from the top of the
seat front "L" to the aft end of the "L" that attaches the bottom of the
tunnel to the floor. Hope that clears up any confusion.
John Read
CH701 - Elbert CO - Jabiru 3300
Phone: 303-648-3261
Fax: 303-648-3262
Cell: 719-494-4567
In a message dated 1/17/2010 5:54:14 P.M. Mountain Standard Time,
ch701builder@yahoo.com writes:
All CH701 builders/fliers,
On page 7-F-11, in the center of the page, to the right of drawing 1&1A,
there is a view showing the section of the tunnel mated with the seat front.
I see there are 2-"L" that are shown about midway up on the inside of the
tunnel.
I don't see these depicted on any side views of the tunnel, and the
assembly guides do not mention installing these.
Any ideas?
Keith
CH701 - scratch
(http://www.matronics.com/Navigator?Zenith701801-List)
(http://www.matronics.com/contribution)
Message 4
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| Subject: | Fork tube analysis and prospective stainless steel |
substitute
Thank you for the analysis Curt. Looks like Chris Heintz picked the best way
to go from a weight, strength, and cost standpoint.
FYI, when the front gear folded, (the one I posted a year ago) it did do
some damage to the firewall, which also had to be replaced.
From: owner-zenith701801-list-server@matronics.com
[mailto:owner-zenith701801-list-server@matronics.com] On Behalf Of Curt
Thompson
Sent: Sunday, January 10, 2010 9:01 PM
Subject: Zenith701801-List: Fork tube analysis and prospective stainless
steel substitute
On my plans built CH701, I have been polishing a few of the parts like the
landing gear and front fork. I was wondering if I could replace the front
fork tube with stainless steel parts and get a similar look. I would need
to make sure that the replacement had the same strength as the original.
So, with the help of my son, we did a SolidWorks analysis of a 4130N tube, 2
inch diameter, 21 inches long with a 0.065" wall. The top is solidly
anchored and a force is applied horizontally at the bottom. Here is a link
of the simulation video that SolidWorks made:
http://www.youtube.com/watch?v=w8uamuysV_8
The video ends when the fork tube fails. It took a force of 540 lbs. As
you can see, the tube bent a lot before it failed. If you make the fork
tube stronger you are likely to move the loads elsewhere and it will break
somewhere else.
One thing comes to mind here, if you bend the front axle and lock up the
wheel you are going to see a lot more than 540lbs. There was a picture on
this list over a year ago that showed a bent fork tube after what was
claimed to be a normal landing. I don't know how common this problem
actually is.
We substituted the fork tube with T-316L stainless steel in the simulation.
It took a wall thickness of 0.250" before we arrived at a similar result.
Since that would make the fork tube about four times as heavy, I have
decided to stay with the 4130N of the plans. I may go up one notch in
thickness of 4130N though. I might also replace the front axle with a solid
shaft. On the shaft I have now, I machined bushings and welded them in
place.
Curt Thompson
Redmond, WA, USA
Message 5
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| Subject: | Fork tube analysis and prospective stainless steel |
substitute
JG,
There were two scenarios re this failure after ruling out construction error
(which I say no sign off). First, some small metal debris was discovered on
the runway that may have impacted and contributes. Second, the student pilot
was on his check ride with a flight examiner and was making a short field
landing. Some speculated that she may have applied brakes before touching
down, which would have made the nose wheel impact hard. The student pilot
said this was not the case, but we know how nervous we can be in a test
situation.
Les
From: owner-zenith701801-list-server@matronics.com
[mailto:owner-zenith701801-list-server@matronics.com] On Behalf Of JG
Sent: Monday, January 11, 2010 3:52 PM
Subject: Re: Zenith701801-List: Fork tube analysis and prospective stainless
steel substitute
I once helped re-build a 701 that had hit a fence on take-off. A heavier
nose leg had been fitted, causing the firewall to be damaged as well.
Replacing the firewall is a MAJOR job........ A new nose leg and prop are
much easier and less costly......
Don't know how you can bend a nose leg on a 701, even in a heavy landing
scenario. The nose wheel should be way high off the ground at landing AofA,
and the weight distribution should be such that you can hold the nose up
after the mains take the weight. The vertical CofG of the aircraft is quite
high, such that at the AofA at touchdown it effectively moves back and the
aircraft nearly balances on the mains at that attitude. If you can't hold
the nose up and it comes down hard, then either the horizontal CofG is way
forward, or the main gear is canted back somewhat. The 'angle of dangle' of
the main gear is often not noticed, but can vary due to wear or improper
fitting of those rubber blocks. If the gear is angled back just a bit it
puts much more load on the nose wheel. For real STOL use, especially on
rough strips, it's best to try to have the weight on the nose wheel to be
minimum. Fully loaded to aft CofG, if someone pulls the tail down to the
ground, it should just about stay there. The angle of the main gear can be
adjusted, often by just reversing those rubber blocks, or if necessary by
grinding a slight taper on them with a course sanding disc in an angle
grinder. But of course, first must get the CofG of the aircraft correct, by
weight and balance measurements.
JG
www.stolspeed.com
On Tue, Jan 12, 2010 at 7:18 AM, Curt Thompson <Curt.Thompson@verizon.net>
wrote:
Here is a link to the previous thread that has pictures of how the fork tube
bent.
http://forums.matronics.com/viewtopic.php?t=56639
<http://forums.matronics.com/viewtopic.php?t=56639&highlight=weak+701+nose+g
ear> &highlight=weak+701+nose+gear
Curt
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