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Failed Lift Tag Axle, 1997 WB (youtube)
03-24-2019, 10:44 (This post was last modified: 03-24-2019 10:48 by travelite.)
Post: #1
Failed Lift Tag Axle, 1997 WB (youtube)
Anyone have any help for a stranded bird? (video published on March 23, 2019)




david brady,
'02 Wanderlodge LXi 'Smokey' (Sold),
'04 Prevost H3 Vantare 'SpongeBob'

"I don't like being wrong, but I really hate being right"
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04-02-2019, 20:02
Post: #2
RE: Failed Lift Tag Axle, 1997 WB (youtube)
https://www.youtube.com/watch?v=fTSrv_IZJaw

We're working on getting a new axle made, however, we will continue to explore other options until we have the new axle in-hand, or at least until it's in the process of being manufactured.

Over the past 6 weeks we've learned a lot about how Blue Bird built their liftable tag axles as well as what options are available when one breaks. For anyone interested, we'll share our findings here once the axle is replaced and the work is complete.

Kevin & Kerry
1997 WLWB 43' "BB Belle"
2005 Jeep Liberty Limited 4x4
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04-03-2019, 10:02
Post: #3
RE: Failed Lift Tag Axle, 1997 WB (youtube)
wonder how it broke?

Ernie Ekberg
Prevost Liberty Classic XL
Weatherford, Tx
http://www.ernieekbergflooring.net
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04-05-2019, 11:43 (This post was last modified: 04-05-2019 16:50 by travelite.)
Post: #4
RE: Failed Lift Tag Axle, 1997 WB (youtube)
(04-03-2019 10:02)ernie ekberg Wrote:  wonder how it broke?

Hi Ernie, To put some numbers to it, here's my envelope drawing for loads, shear, and moments:
.pdf  1997WB_TagShearMoment.pdf (Size: 296.61 KB / Downloads: 58)

The max bending stress is: s = M/Z where M is the max moment, Z is the section modulus and for a 5" diameter tube with 0.5" wall thickness Z = 7.25, which gives us a max stress (s) of s = 80,000/7.25 = 11034 psi. Suspensions are built to handle 3G of vertical load. This simple analysis shows this axle has the required safety factor and stays clear of the metal fatigue limit during normal driving which is less than half its UTS (Ultimate Tensile Strength), or around 32000 psi for mild carbon steel. IOWs, something else is going on.

david brady,
'02 Wanderlodge LXi 'Smokey' (Sold),
'04 Prevost H3 Vantare 'SpongeBob'

"I don't like being wrong, but I really hate being right"
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04-07-2019, 11:40 (This post was last modified: 04-07-2019 11:44 by davidbrady.)
Post: #5
RE: Failed Lift Tag Axle, 1997 WB (youtube)
(04-03-2019 10:02)ernie ekberg Wrote:  wonder how it broke?

You know how Wanderlodges fall off the jacks sometimes? Often we park for the night, dump the air, and deploy the HWH jacks to level the coach. When it's time to leave some of us may neglect to air up the suspension before we retract the jacks. I'm sure most of us have experienced the result when we hit the HWH jack retract button w/o first airing up - the bus drops onto the bump stops. What if the tag bottoms first, what if the tag carries all of that falling weight and the drive axle none? This could hit double digit g forces. Always good to air up first.

david brady,
'02 Wanderlodge LXi 'Smokey' (Sold),
'04 Prevost H3 Vantare 'SpongeBob'

"I don't like being wrong, but I really hate being right"
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