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BizFlyer
Topic Author
Posts: 39
Joined: Thu Jul 08, 2004 12:40 am

B737-200, -200, -400 And -500: Wheel Assembly

Wed Jul 06, 2011 2:28 pm

Good Day to All,

is here anybody around, who can post a cut-drawing or an explosion-drawing of the main-gear wheel-assembly of the B737 (-200, -300, -400 and -500. Not the newer types...)?

I am asking, because I would like to know how the procedure is for assembling and disassembling a wheel from the main landing gear strut and how the bearings within are assembled.

Any help would greatly be appreciated.

Kind regards,

BizFlyer
Stay belted as long as you can!
 
fadecfault
Posts: 164
Joined: Mon Nov 05, 2007 8:44 pm

RE: B737-200, -200, -400 And -500: Wheel Assembly

Wed Jul 06, 2011 5:58 pm

A wheel itself is not dissembled off the strut. It's removed and replaced as an assembly.
There is typically an axle nut and spacer that holds the wheel assembly on the axle. The axle nut will have a retainer to hold it in place. Our -200's had a retaining ring and the -700's had nuts and bolts. Removing the bearings usually requires removing a grease seal and retaining ring. That's really it.
The views and opinions written here are my own and do not reflect those of my employer.
 
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n901wa
Posts: 459
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RE: B737-200, -200, -400 And -500: Wheel Assembly

Wed Jul 06, 2011 11:42 pm

I checked around, and could not find my old manuals. But like fadecfault said. The Bearings were part of the wheel assy. When I was in the Wheel Shop we built -200 and -300 wheels and they were different wheel's but were removed the same way. The inner and outer bearings had a rubber grease seal and a retainer clip that held them in place.
When I worked the line and changed 737 wheels, first was to remove the pressure from the wheel, then remove the anti-skid cap ( 3 bolts and safety wire ) then remove the Bolt that kept the Gland Nut from turning, Than the Gland nut, a Spacer and then the Wheel assy. On the Outbd Wheel - Remove the cap 4 bolts, Then the Cover 3 bolts and Safety Wire ( the cover is like the Wheel cap on the inbd side), then the same as the inbd side. I hope this kinda makes sence. I will post a picture if I can locate the IPC I have.
 
BizFlyer
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Posts: 39
Joined: Thu Jul 08, 2004 12:40 am

RE: B737-200, -200, -400 And -500: Wheel Assembly

Thu Jul 07, 2011 4:22 pm

fadecfault and n901wa,

thanks for having taken the trouble to reply.

What is not quite clear to me, is the following:

Without thinking about any grease-seals and retainers etc, is the wheel just slipped onto the axle complete with the bearings?
In my layman´s view I had thought, that at first there must be an inner bearing (cone and cage with roller-race) fitted to the axle. Then the wheel is fitted, with the cup-ring shrunk into the wheel-rim on the inside of the wheel.
Then from the outside (open end of the axle, the outer bearing (again, cone and cage with roller-race) is fitted onto the axle and is adjusted with the axle-nut against the wheel (where on the outer side of the wheel of course also a corresponding cup-ring is shrunk into the rim). The adjusting with the axle-nut to be done for the required bearing-clearance of the wheel-assembly.

Except that this all must then be wire-secured or however, is this basically how it is done?

Greetings from Hamburg,

BizFlyer
Stay belted as long as you can!
 
fadecfault
Posts: 164
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RE: B737-200, -200, -400 And -500: Wheel Assembly

Thu Jul 07, 2011 5:14 pm

The 737 main wheel is installed as a complete assembly onto the axle, bearings and all. The bearings are already pre-installed. The wheel assembly goes on, then the axle nut spacer and then the axle nut and retaining hardware.

One should not be handling the bearings unless they have popped out which does happen.
The views and opinions written here are my own and do not reflect those of my employer.
 
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fr8mech
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RE: B737-200, -200, -400 And -500: Wheel Assembly

Thu Jul 07, 2011 6:17 pm

I've changed 1 or 2 wheel assy's on a B737 about 20 years ago, but I've changed or been witness to several hundred wheel changes on different aircraft over the last 20 years and they're all about the same.

There is an inner bearing and an outer bearing. None of the bearings are pressed in. They are retained in the wheel assy by a snap ring or sometimes just the grease seal. The axle nut is usually torqued against a spacer ring which lays against the outer bearing. The inner bearing sits up against a flange on the axle (B747 Classic) or a spacer (just about every other aircraft I've dealt with).
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737tdi
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RE: B737-200, -200, -400 And -500: Wheel Assembly

Fri Jul 08, 2011 9:21 pm

There really isn't a good pic. of just a wheel and tire assy. here but if you scroll down you will see a pic. of the axle.

http://www.b737.org.uk/landinggear.htm#Tyres

The two wheel bearings (already installed inside the wheel) simply slide onto the axle and ride on the silver portion of the axle. This particular picture has axle thread protectors installed to prevent damage to the axle nut threads when sliding the assy. off and on.

If you know older cars, the old verbage for the type of bearings used are "tapered timkin" bearings.

As said above, the wheel and tire assy. simply slides onto the axle then the spacer is slid on (it has an anti-rotation tab that engages the axle), the nut is then installed and torqued to a final torque of 150 ft./Lbs. A retaining ring is then installed around the axle nut to prevent loosening.

I would copy and paste our manuals but I can get in trouble for doing it.
 
yeelep
Posts: 766
Joined: Mon Apr 04, 2011 7:53 pm

RE: B737-200, -200, -400 And -500: Wheel Assembly

Sat Jul 09, 2011 8:57 am

Quoting BizFlyer (Reply 3):
Without thinking about any grease-seals and retainers etc, is the wheel just slipped onto the axle complete with the bearings?

Yes.

Quoting BizFlyer (Reply 3):
In my layman´s view I had thought, that at first there must be an inner bearing (cone and cage with roller-race) fitted to the axle. Then the wheel is fitted, with the cup-ring shrunk into the wheel-rim on the inside of the wheel.

From the inner to outer side of the wheel there is a retaining clip, grease seal, the inner ring tapered roller bearing, the bearing cup (press fit in the wheel), the outer wheel bearing cup, outer bearing inner ring, and grease seal.

The wheel is slid onto the axle until the inner bearing/inner ring seats against a step in the axle. The spacer is installed against the outer bearing/inner ring. the spacer has a tab in the inner radius which slides in a keyway cut in the axle, which prevents the spacer from rotating. The axle nut is installed and torqued to seat the bearings, then loosened and tightened to the final torque. There are holes drilled axially in the wheel nut and spacer in which the retaining ring is inserted as a saftey device to prevent the wheel nut from loosening. Install and saftey wire the hubcap (which also serves as the drive connection for the antiskid transducer) and install the hubcap fairing if its an outboard wheel.

Quoting 737tdi (Reply 6):
There really isn't a good pic. of just a wheel and tire assy. here but if you scroll down you will see a pic. of the axle.
http://www.b737.org.uk/landinggear.h...Tyres

Thanks for the link, i've never seen that site. Another 737 site is http://sjap.nl/
 
BizFlyer
Topic Author
Posts: 39
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RE: B737-200, -200, -400 And -500: Wheel Assembly

Wed Jul 13, 2011 10:57 am

Folks, thanks a lot for your informative postings.

All in all I had the right ideas, but not in detail, as I come from a complete different corner of machines, namely large-bore Diesel engines for marine applications.

But you gave me a good insight and now I have a better understanding than before, without your posts.

Also, thanks a lot for the Dutch 737 link. - Interesting!

Greetings

BizFlyer
Stay belted as long as you can!
 
UAL Bagsmasher
Posts: 1839
Joined: Wed Sep 08, 1999 12:52 pm

RE: B737-200, -200, -400 And -500: Wheel Assembly

Mon Jul 18, 2011 2:08 am

Quoting 737tdi (Reply 6):
As said above, the wheel and tire Assy. simply slides onto the axle then the spacer is slid on (it has an anti-rotation tab that engages the axle), the nut is then installed and torqued to a final torque of 150 ft./Lbs. A retaining ring is then installed around the axle nut to prevent loosening.

Wow. On the CRJ-200 the initial torque for a MLG tire/wheel Assy. is 30 ft./lbs. Final torque is 15 ft./lbs. Pretty low if you ask me, but I'm not the engineer who designed the aircraft  The procedure for installing a main on the CRJ is pretty much the same as everyone else has described. An inner spacer cone is installed on the axle first, followed by the tire/wheel Assy. (with bearings pre-installed). An outer tang washer comes next, followed by the axle nut (with its two lock bolts), then finally the anti-skid transducer wheel cap and its mounting hardware. Can't forget the safety wiring on everything too.

The bearing grease seals have a habit of popping out when changing the mains especially on the O/B wheels due to low clearance between the flap canoe and wheel during install. They can be a load of fun to reseat properly too, especially if they are creased or out of round in any way. It's not all that uncommon to have to get another tire/wheel assy. due to grease seal issues during installation.
 
Fly2HMO
Posts: 7184
Joined: Sat Jan 24, 2004 12:14 pm

RE: B737-200, -200, -400 And -500: Wheel Assembly

Mon Jul 18, 2011 4:02 am

*sigh* There's this awesome thing called google ya know...



It's from an Airbus, but I doubt they're siginificantly different to other aircraft wheels.

There's dozens of pics on here showing the axle itself during a wheel change as well and you can clearly see where the bearings ride.


View Large View Medium
Click here for bigger photo!

Photo © Joe Pries - ATR Team

 
yeelep
Posts: 766
Joined: Mon Apr 04, 2011 7:53 pm

RE: B737-200, -200, -400 And -500: Wheel Assembly

Mon Jul 18, 2011 4:14 am

Quoting UAL Bagsmasher (Reply 9):

A 737NG main has an initial torque of 500-600lbs/ft.
 
737tdi
Posts: 1116
Joined: Sun Sep 02, 2007 10:05 am

RE: B737-200, -200, -400 And -500: Wheel Assembly

Fri Jul 22, 2011 4:43 am

yeleep: You're correct. We torque 600 lbs/ft initial and final torque to 150 lbs/ft. rotating the tire as you tighten.

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