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  #1  
Old 09-26-2022, 07:17 PM
claycookiemonster's Avatar
claycookiemonster claycookiemonster is offline
 
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Location: Midway, UT
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Default Attaching Grove Airfoil Gear legs

It's time. The fuselage is lifted high enough to allow wheels to be mounted after the legs are.

On both sides, one of the NAS 6206-27 bolts used to attach the U-803 Main Gear Attach Bracket has already been inserted from the top down. This is a project, and the bolts were this way when I brought it home. I can see that this bolt head (or nut) would interfere with one of the smaller screws bolted into the side skin. I can find no reference to this slight alteration in the assembly manual, but it seems reasonable. Anything to be specially careful about here?

Also, "hardened" 3/8" washers are specified for the inner attach brackets. How can I tell a "hardened" washer from your average, run of the mill, wishy-washy washer?
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USAF: T-38, F-111F
American Airlines: 727, MD80, 757, 767, 737
RV8 #81751 project sold
RV8 #81651 project acquired
https://theonceandfutureflyer.wordpress.com/
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  #2  
Old 09-26-2022, 07:55 PM
scsmith scsmith is offline
 
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On balance, I think it is better to have the bolts drop down from inside, if you can do it. As you say, there are a couple of AN3 nuts and bolt-tails in the way. During the build, if you can loosen those enough to drop the bolts in from the top, thats good.

But...

If it turns out the bolt isn't long enough, because your Grove gear are thicker than standard steel gear struts, you will have to reverse the process to get those out and put longer ones in. So just be prepared for that possibility. (you may also want to switch to NAS6606 bolts, see below).

Pros: mainly that you will be able to torque the bolts by torquing the nuts on the bottom, which is a more accurate way to torque them. You will still need someone to put a wrench on the bolt heads inside the gear tower to do the torquing. The gear tower mod to make these more accessible is absolutely worth doing.(see note below)

Cons: Only really that the nut and bolt-tail sticking down will require a bigger bulge in the gear strut intersection fairing to cover them, compared to just a bolt head. Small price to pay if you ask me.

Most RV-8s have been built with the bolts installed per plans, up from the bottom, with the washer and nut inside the gear tower. This is OK, but it means that when you torque the bolts from below, with the torque wrench on the bolt head, you must add to the specified torque an additional torque equal to the friction torque to turn the bolt in its hole. Of course that torque changes as the bolt tightens because the slight deformation of the U-803 saddle makes the bolt rub on the side of the hole, so this is a less-than-perfect solution.

Finally, PLEASE PLEASE PLEASE be sure to use the strong NAS1804-6 nuts, not the horrible NAS679 nuts that are supplied with the kit.(or used to be, anyway). You may find that you need bolts with a longer threaded portion since these nuts have more grip length, so you would want NAS6606 rather than NAS6206.

The easiest way to be sure you have hardened washers is to buy them fresh. I think Vans has them, although I couldn't find them listed specifically in the 'store'. Or go buy SAE Grade 8 washers. With the NAS1804-6 nuts, there is not a lot of contact area on the base of the nut, so I recommend getting close-fitting washers (have a smaller hole in them that is a closer fit to the bolt). I actually think that getting more contact area under the nut from the tighter fitting washer is more important than the hardness. NAS1149 washers seem to have the closest fit specs (0.390" I.D.). A normal NAS1149-F-0663 (replaces the old standard AN960) is not very hard, but if you can specify NAS1149-G-0663, those are made of 4130 alloy steel, and are moderately hard. You may be able to order those from www.genhardware.com (also a good source for longer NAS6606 bolts if you need them)


Note: I started with a Quickbuild fuselage, and the gear towers were all completed, so I didn't tackle the challenge of modifying them with the removable panel. In hindsight, I really wish I did. Doing that mod on the completed structure would not have been that hard, and it would have saved a lot of blood, sweat, swearing. I would definitely recommend doing it, even if it means back-pedaling on some other work, like final cabin parts installation, gear installation, panel, etc.
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RV-8 N825RV
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WW 200RV
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Hobbs 725
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Last edited by scsmith : 09-26-2022 at 08:10 PM.
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  #3  
Old 09-26-2022, 08:11 PM
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Carlos151 Carlos151 is offline
 
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If these had been around or thought of when I built mine I would have put them in. They make checking the torque A LOT easier.
Here's a link to the landing gear nut and bolt tests that Steve did a while ago. If I remember correctly, Grove shipped a set of bolts and nuts with the gear since they're different than the stock bolts.
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  #4  
Old 09-26-2022, 08:24 PM
scsmith scsmith is offline
 
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Quote:
Originally Posted by Carlos151 View Post
If these had been around or thought of when I built mine I would have put them in. They make checking the torque A LOT easier.
Here's a link to the landing gear nut and bolt tests that Steve did a while ago. If I remember correctly, Grove shipped a set of bolts and nuts with the gear since they're different than the stock bolts.
Good points Karl.

On the build-log that you linked to for the little retainer clips, I do have a concern:
In his first photo of the normal, per-plans installation, the horrible NAS679 nuts are installed. I do hope that when that builder installed the clips and turned the bolts around, he also installed the better nuts.
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Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet" Flying since Sept. 2009
Hobbs 725
also
1/4 share in 1959 C-182B (tow plane)
LS6-15/18W sailplane SOLD
bought my old LS6-A back!!
VAF donation Dec 2021
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  #5  
Old 09-26-2022, 08:35 PM
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Carlos151 Carlos151 is offline
 
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Quote:
Originally Posted by scsmith View Post
On the build-log that you linked to for the little retainer clips, I do have a concern:
In his first photo of the normal, per-plans installation, the horrible NAS679 nuts are installed. I do hope that when that builder installed the clips and turned the bolts around, he also installed the better nuts.
I hope so too
I like the clip idea but it also seems to me that it would force a slightly longer bolt.
Meanwhile, I stand on my head while my helper has a wrench on the bolt head once a year
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TN26
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  #6  
Old 09-27-2022, 12:24 AM
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claycookiemonster claycookiemonster is offline
 
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We have done the gear tower mod, so that helps. Thanks for the expansive advice. I wasn't considering that the specified bolts might not be long enough. That would make it worthwhile to simply get new hardware for the whole thing.

Let me back up a few yards and survey the field. I'm taking this very seriously because failure isn't an option in this area.

Is there some sort of aviation standard that caused the bolt orientation to be specified as bottom up, when it causes so many other issues?
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Clay "Cookiemonster" Cook
USAF: T-38, F-111F
American Airlines: 727, MD80, 757, 767, 737
RV8 #81751 project sold
RV8 #81651 project acquired
https://theonceandfutureflyer.wordpress.com/
Donations up to date thru December 2015

"...serenity...courage...and wisdom..."
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  #7  
Old 09-27-2022, 01:59 AM
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rv8ch rv8ch is offline
 
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Clay, my Grove gear came with longer bolts, so perhaps you have them somewhere in your shop.

In the middle of my CI now, and having to tighten those nuts/bolts was not easy. I can only echo the excellent advice given by Steve and Karl, and to also follow Steve's advice on the high quality nuts.

I could not get my bolts in from the top, since I also had a QB, so it is worth the time to find a way to hold those nuts. I bought some "disposable" wrenches from the big box store, cut them down to size, and somehow got them onto the nuts. I have not yet glued them, but that would be a good idea.

The main point is to do something to reduce the hassle of tightening them regularly. Many threads on this topic on VAF.
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  #8  
Old 09-27-2022, 07:49 AM
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claycookiemonster claycookiemonster is offline
 
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I will search my box of bits and bots to see if I already have longer bolts. I began by mentioning that one bolt on each of the outboard attach brackets had already been installed top down, and these are the NAS 6206 bolts. The three bolts holding the inner attach bracket are specified as AN bolts. Are you suggesting that ALL 5 bolts on each side be replaced with NAS 6606 bolts, and ALL nuts with NAS 1804-6 nuts? And, install all 5 bolts on each side top down?
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Clay "Cookiemonster" Cook
USAF: T-38, F-111F
American Airlines: 727, MD80, 757, 767, 737
RV8 #81751 project sold
RV8 #81651 project acquired
https://theonceandfutureflyer.wordpress.com/
Donations up to date thru December 2015

"...serenity...courage...and wisdom..."
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  #9  
Old 09-28-2022, 09:58 AM
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claycookiemonster claycookiemonster is offline
 
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Guys, thanks for all the input, but one question remains; is it wise to replace ALL 5 bolts per side with the NAS 6606 bolts? Is it wise to similarly replace all 5 nuts with the NAS 1804 nuts?
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Clay "Cookiemonster" Cook
USAF: T-38, F-111F
American Airlines: 727, MD80, 757, 767, 737
RV8 #81751 project sold
RV8 #81651 project acquired
https://theonceandfutureflyer.wordpress.com/
Donations up to date thru December 2015

"...serenity...courage...and wisdom..."
Reply With Quote
  #10  
Old 09-28-2022, 01:31 PM
scsmith scsmith is offline
 
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Quote:
Originally Posted by claycookiemonster View Post
Guys, thanks for all the input, but one question remains; is it wise to replace ALL 5 bolts per side with the NAS 6606 bolts? Is it wise to similarly replace all 5 nuts with the NAS 1804 nuts?
The inboard attach point uses standard AN bolts and nuts. Those are fine.
__________________
Steve Smith
Aeronautical Engineer
RV-8 N825RV
IO-360 A1A
WW 200RV
"The Magic Carpet" Flying since Sept. 2009
Hobbs 725
also
1/4 share in 1959 C-182B (tow plane)
LS6-15/18W sailplane SOLD
bought my old LS6-A back!!
VAF donation Dec 2021
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