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My head hurts, someone please 'splain!

Sig600

Well Known Member
So I fiddled with the brakes and tires the other night, trying to get everything together. I know the answer is right in front of me, but I can NOT figure out how to get the calipers and wheel/tires on. If you put the calipers on you can't get the wheels on, if you put the wheels on you can't get to the back of the calipers to secure them.

I know it's got to be something stupid/simple, but I'm just not figuring it out. :mad:

Anyone? No one posts pictures of the process in any build logs, I assume because a monkey should be able to figure it out!
 
Here is a discussion of the brakes. The short answer is that you mount the caliper assembly, then remove the two bolts holding the caliper together, where the lining is, and then mount the wheel. Then you can replace the "outer" pad and holder. Be sure to safety the bolts.

http://www.eaa.org/chapters/resources/articles/give_me_a_brake.pdf

John Clark ATP, CFI
FAAST Team Representative
EAA Flight Advisor
RV8 N18U "Sunshine"
KSBA
 
So I fiddled with the brakes and tires the other night, trying to get everything together. I know the answer is right in front of me, but I can NOT figure out how to get the calipers and wheel/tires on. If you put the calipers on you can't get the wheels on, if you put the wheels on you can't get to the back of the calipers to secure them.

I know it's got to be something stupid/simple, but I'm just not figuring it out. :mad:

Anyone? No one posts pictures of the process in any build logs, I assume because a monkey should be able to figure it out!

Dont feel bad...I'd never seen one assembled or disassembled before and the drawings were very inadequate. I must've stared at that darn thing for an hour scratching my head. And I call myself a Mechanical Engineer! :confused: It was a good learning experience and I got a good chuckle out of it later...and I posted it on my blog to help others navigate this puzzle.
 
Dont feel bad...I'd never seen one assembled or disassembled before and the drawings were very inadequate. I must've stared at that darn thing for an hour scratching my head. And I call myself a Mechanical Engineer!

Yep ....exactly the same experience (and I too am a mechanical engineer.):eek:
 
important safety note! Video may mislead us?

http://www.youtube.com/watch?v=sgym2VmQBF8

Best to watch someone the first time.
Schematics of parts available in Spruce Catalogs

Vern, if I'm not mistaken, it is a BAD idea to remove the axle nut before letting the air out of the tire!!! If the rim were seriously cracked, it could blow apart when the nut is removed. A local AME slapped me for doing this at my last annual!...and of course had a story about seeing it happen and someone being injured (perhaps with a larger wheel, but still!)
 
Negative.

Not so, Perry. I've always inflated ALL my tires, including my large Air Tractor tires before mounting them and have never deflated any tires, in 43 years, including my RV-10's before I remove them. The through-bolts hold the wheel together, not the axle nut.

Best,
 
Dont feel bad...I'd never seen one assembled or disassembled before and the drawings were very inadequate. I must've stared at that darn thing for an hour scratching my head. And I call myself a Mechanical Engineer! :confused: It was a good learning experience and I got a good chuckle out of it later...and I posted it on my blog to help others navigate this puzzle.

I know! I've built several cars and do my own maint. This though has me stupefied.

Thanks to all the replies!
 
Not so, Perry. I've always inflated ALL my tires, including my large Air Tractor tires before mounting them and have never deflated any tires, in 43 years, including my RV-10's before I remove them. The through-bolts hold the wheel together, not the axle nut.

Best,

There are a lot of things that individuals do and get away with for years, however all of the maintenance manuals for certified aircraft that I have ever worked on have you deflate the tire when not installed unless it is inside a tire cage.
 
best practices = for dummies ( and me!)

There are a lot of things that individuals do and get away with for years, however all of the maintenance manuals for certified aircraft that I have ever worked on have you deflate the tire when not installed unless it is inside a tire cage.

I think this is under the category where, if you always do it so it's impossible to hurt yourself, you are almost assured not to. I agree it's pretty hard to crack the rim, and shear all the bolts, or have ALL the nuts fall off etc. etc.
........so Pierre I'm sure has good reason for his modus operandii.

that said, there are enough different types of rims, and combinations of inexperience, incompetence & inattention that somehow, somewhere, a guy seems to find a way.
There are about 7000 of us RV'ers who are not mechanics, so need to be told not to pee on the electric fence! ( just because!) :)
 
Brother Killed by Tire

My brother Terry was killed when helping a mechanic change a Jet Commander tire. Mechanic forgot to let the air out before removing bolts. No cage until AFTER the accident.:(

Be careful folks!
 
OK, but before folks get too wound up about tire cages and the like - there is a HUGE difference in pressure between "big airplane" tires and the 30 psi tires/wheel we use on the RV's. We've got a lot of A&P's here who work on big iron, and the procedures they use are absolutely correct for that equipment. It might or might not pertain to RV tires.

Paul
 
Where I used to work (heavy iron) we deflated prior to removing/shipping the old tires but the new tires from the shop were shipped and stored fully inflated.
 
My brother Terry was killed when helping a mechanic change a Jet Commander tire. Mechanic forgot to let the air out before removing bolts. No cage until AFTER the accident.:(

Be careful folks!

Are you talking about the axel nut of the wheel bolts?
 
I just changed my tubes and tires for the first time (220 hrs) and the one bit that I had to redo pertained to the washer and nut that came with the air stop tubes. On the first tube/tire change I had some friends in the hangar and when they saw the washer and nut threaded loosely on the stem of the tube told me that they weren't needed, so I removed them. When everything was back together and I inflated the tire I noticed that the valve stem was cocked to one side. I did the other tire when people weren't there and had a close look at the washer and nut. I noticed that the washer had a convex and concave side and was bigger than the cut out in the wheel halves for the stem, while the nut was smaller and fit inside the cutout. I had a bit of an "aha" moment and realized that if I threaded the washer onto the stem with the concave side to the rubber and then put the nut on, the washer would protect the rubber from chaffing on the cutout edges on the wheel for the valve stem, almost like it was designed that way:D

I don't know if this is the correct way of doing it (no paperwork or how-to) but the valve stem is straight and there is no way the rubber can chaffe on the metal!

One other aha moment I had when trying to balance the tires was to use the full depth of the wheel to "stack" the weights rather than stringing them out along the circumference. The weight is then concentrated where you need it and you need much less weight. I'm sure these observations will come as no surprise to many, but it was a learning experience for me:eek:
 
Paul, Un unh. Don't even think that way. A little bitty tire can kill you. That's like saying it's okay to get stabbed with a little knife or shot with a small gun. Pierre has been riding with Lady Luck drivin' his Ol' 55. Jump me if you want, but if you don't deflate before you pull an axle nut you're begging for it. I once had about 1 PSI in a tire I was struggling with to keep the wrinkles out. I had the nuts on about 2 or 3 turns each (remember only 1 PSI on a 6-6). It stripped the threads and the hardware ricocheted off stuff 200 feet away. One of them caught my thumb on the way by. Loud 4 letter words buddy.
 
Paul, Un unh. Don't even think that way. A little bitty tire can kill you. That's like saying it's okay to get stabbed with a little knife or shot with a small gun. Pierre has been riding with Lady Luck drivin' his Ol' 55. Jump me if you want, but if you don't deflate before you pull an axle nut you're begging for it. I once had about 1 PSI in a tire I was struggling with to keep the wrinkles out. I had the nuts on about 2 or 3 turns each (remember only 1 PSI on a 6-6). It stripped the threads and the hardware ricocheted off stuff 200 feet away. One of them caught my thumb on the way by. Loud 4 letter words buddy.

...............................................................................:rolleyes:
 
?? 6? diameter wheel with 1 PSI pressure equals 28 lbs of force. Strips the threads on a ?-28 AN bolt?????? Seems odd to me. But hey I wasn?t there.
 
Watched it happen! 6x6 inflated, removed from axle, bang! Nasty broken arm. He was lucky.
 
I think one just came off and the wheel halves cocked and blew the other two off. Like I said, I was only on a couple threads and it might have been 3 PSI or something. Just a shot of air to swell the tube. Sure surprised me. Point is, when removing a wheel, you really don't know what's holding the wheel halves together until you've got it apart. Going the other way, when you've just assembled a wheel is a bit different because you've just looked at the bolts and wheel halves etc. It should still be in a cage to inflate but nobody does that except airline shops (unions). The rest of us just trust our eyes on assembly.
 
Aww.

. Pierre has been riding with Lady Luck drivin' his Ol' 55. .

So,do you guys mount a new tire and tube assembly on the axle deflated, not knowing whether or not you've pinched the tube? C'mon guys, I've also seen a newby wannabe A&P start removing wheel bolts without deflating it first...yeah, it burst. Some people are very intent on removing themselves from the gene pool.

In the Ag business, Lady Luck has no place...it needs to be calculated. Same thing goes for mounting/dismounting tires and tubes. I have many A&P friends and have never heard of deflating our tires before removing them...so do whatever floats your boat. All ten of my big 10" ag airplane tires gets torqued to 150 inch-pounds before I air it up.

I didn't get to be 68 because I'm stupid, doncha think?

Best,
 
Pierre, my initial reply was about safety and not intelligence. After reading the replies in this thread I recognize that my post is from habit of working on high pressure wheel/tire assemblies and probably not as applicable to our smaller tires. I do partially inflate my tires after working on them before putting them back on the axle. Once installed I fully inflate them.

Curtis
 
So I went back to the hangar yesterday, looked at the parts for about 12 seconds, and then put everything together.

1644094_o.gif
 
I have many A&P friends and have never heard of deflating our tires before removing them...so do whatever floats your boat.
Most of my best friends ARE A&P's. Didn't mean to dig at ya Pierre, but I think I went to a pretty good school for six years. My profs were pretty adamant about deflating before wheel removal. Since then I've been in the field for almost thirty years. When I got maintenance training for American we hit wheels and brakes pretty good. Rule one for wheel removal was deflate first unless it went in a caged dolly first. Same thing for Delta and the other four airlines I got maintenance training on. My boat floats okay and if I ruffle a few feathers while I'm paddling I apologize. But...when I hear a waterfall you can bet that I'm paddling the other way. I also don't have a problem admitting that I sometimes still do things wrong. When I hear a new tip I usually try to think it over before I dig in my spurs. Sometimes my neck hair comes up and I think "I've been doing that?" Sometimes I get muley and then years later it hits me...like a bolt out of the blue.
 
Most of my best friends ARE A&P's. Didn't mean to dig at ya Pierre, but I think I went to a pretty good school for six years. My profs were pretty adamant about deflating before wheel removal. Since then I've been in the field for almost thirty years. When I got maintenance training for American we hit wheels and brakes pretty good. Rule one for wheel removal was deflate first unless it went in a caged dolly first. Same thing for Delta and the other four airlines I got maintenance training on. My boat floats okay and if I ruffle a few feathers while I'm paddling I apologize. But...when I hear a waterfall you can bet that I'm paddling the other way. I also don't have a problem admitting that I sometimes still do things wrong. When I hear a new tip I usually try to think it over before I dig in my spurs. Sometimes my neck hair comes up and I think "I've been doing that?" Sometimes I get muley and then years later it hits me...like a bolt out of the blue.

You are talking about 150 to 200 psi...... in a wheel / tire assy that is how big??
 
I may be wrong here but I assumed that a 6.00 X 6 wheel is 6? in diameter. 1 PSI on a 6? diameter makes 28 lbs of force on that disk. I think I did the math right??? So the wheel halves would be being pushed apart with a 28 lb force. Or each ?? bolt (4 bolts on the wheel?) would have 7 lbs of tension on them.
 
Let's see if my Math/Physics is accurate OK.

The surface area of a torus is: 4 ? (pi squared) ? R ? r
See image for what R and r are.
torus-radii.jpg



I don't have a 6" wheel in front of me, but let's say R is 5" and r is 2":
4 x 3.14159 x 3.14159 x 5 x 2 = 394 square inches. So 1 psi would exert 394 lbs of force distributed evenly.

Not a tremendous amount of force.
 
Well . . . - lets think Bagel . . .

OK, this is off the OP, but lets take the tire assembly and slice in the middle plane like a bagel. Then the projected area of the slice is the area acted on by the pressure.

If the ID is 5" and the OD is 12 " the it is 3.14 X (12^2-5^2)/4 or 93 sq inches.

So lets say it is 100 sq-in , so 1 psi would be about 100 lb force. 28 psi is 2800 lb force, half of which is equivalent to acting on the OD perimeter of the tire. So, the rim sees 1400#. Still not a lot for 3 1/4 AN bolts, but the axle nut would retain the halves (of the RV design) if the rim fasteners were to fail. The Cessna in the video posted earlier would NOT be retained by the axle nut, so all wheels are not created equal. Thinking is in order.

I had not thought about this before and will certainly give consideration to the potential energy involved. Knowledge helps in flying and working safely.

To the OP, I did not see the assembly procedure on your blog, did I just blank out and not see it?
 
Thanks for the knowledge that is passed on

I am neither a mechanical or electrical engineer (though I was a fire department Engineer for two years) and have decided that when I change my first tire ever, I'll let the air out first - just don't like to see things flying around the maintenance area at near the speed of sound - just makes sense to me!
 
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