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davidbrady · 11-02-2014, 20:47

Ebay item number: 151461373499. NFI

dentmac · 11-03-2014, 19:59

Sad really--- when a 25 foot class B can be $170,000.
Note sticker on dash. -- demanded by recall -Keep front tires at 130 psi cold.

(11-02-2014 20:47)davidbrady Wrote: Ebay item number: 151461373499. NFI

GregOConnor · (This post was last modified: 11-03-2014 23:23 by GregOConnor.)

(11-03-2014 19:59)dentmac Wrote: Sad really--- when a 25 foot class B can be $170,000.
Note sticker on dash. -- demanded by recall -Keep front tires at 130 psi cold.

(11-02-2014 20:47)davidbrady Wrote: Ebay item number: 151461373499. NFI

I wonder what impact to front axle load would there be with a user changing bag pressure on the tag? I remember a discussion about ride comfort and changing tag bag pressure. I also wonder what impact poor shock choice and porpoise'ing (not the fraternity induction task, the back and forth rebounding while highway driving over a large dip) have on the front axle weight? The axle failures must be in times of extremes so a reduction of the extremes would be more of the correction than static weight reduction.

dentmac · 11-03-2014, 23:51

Hi
BB adjusted the the tag/drive ratio lightening the front.
1000 lbs off tag effects front approx 225 lb. The ratio is controlled by Hadley ECU. They also plumbed the front rt and left together to compensate for side to side discrepancies. Shocks are Koni.Failures (3 of four at least) were not at times of extremes. Straight highways Tire failures first,_ then control loss.
Ross

***Arcticdude*** · 11-04-2014, 23:23

It's truly a shame that the front ends got lost in the development of the 450. They were really such great coaches, otherwise. Equal to anything else out there overall if the front axle were right.

GregOConnor · 11-05-2014, 02:23

Ross, reducing the load on the Tag by 1,000 adds 1250 lbs to the drive? I wonder if and what the axle weight change would be when you hang a Harley off the back? Tom, here is an excuse to get a Hog

dentmac · 11-05-2014, 12:01

Hi,
Going to have to get a REAL engineer to calculate that
(David....you're being called Smile

)
FYI
The 450 Tag:Drive ratio was originally set at 40:60 with the max on the tag of 13,000....so the tag topped out at its limit (13,000) when the rear total load was 32,500 . ..13,000 on the tag and 19,500 on the drive. Any additional load was put on the drive.
BB in their wisdom (funny) changed the ratio to 35:65 to show less front end load in the unloaded state. Now the tag doesn't reach 13,000 until the drive gets to 24,142. (beyond legal limits). rear tandem load 37,140.
So adding the Hog would bring the tag up to 13,000. and weight back to the front.
Back to the trailer I guess--( and that limit is 10,000 after the recall... probably due to rear tongue weight being restricted to 1000 lbs.)

(11-05-2014 02:23)GregOConnor Wrote: Ross, reducing the load on the Tag by 1,000 adds 1250 lbs to the drive? I wonder if and what the axle weight change would be when you hang a Harley off the back? Tom, here is an excuse to get a Hog

davidbrady · (This post was last modified: 11-05-2014 20:06 by davidbrady.)

The trick is to calculate the location of the center of gravity of the bus without the tongue weight, add the tongue weight and calculate the shift in the center of gravity, then take the sum of the moments about the steer axle assuming a 35/65 weight split on the tag/drive axles.

Assumptions:
Coach weight: 50000 lb
Wheelbase: 300"
Front overhang: 80"
Rear overhang: 100"
Tag to Drive axle spacing: 55"
Tag/Drive split: 35%/65%

Center of gravity location without tongue weight: 219" behind steer axle.
Steer: 15715 lb
Drive: 22285 lb
Tag: 12000 lb

Center of gravity with 1000lb tongue weight added: 225" behind steer axle.
Steer: 15056 lb
Drive: 23364 lb
Tag: 12580 lb

Delta off steer axle: 658.7 lb

dentmac · 11-05-2014, 20:34

Sorry, Didn't mean to hijack post.
Here are more accurate numbers . Pls do it again. and then using 40:60 with a tag max of 13,000.
Front axle load -- use 17,000 Gross wt 52,500.

Thx,

front overhang back overhang wheel base
Prevost H3 75 107 316
Prevost XL 68 107 314
450LXi 85 113 296

(11-05-2014 19:11)davidbrady Wrote: The trick is to calculate the location of the center of gravity of the bus without the tongue weight, add the tongue weight and calculate the shift in the center of gravity, then take the sum of the moments about the steer axle assuming a 35/65 weight split on the tag/drive axles.

Assumptions:
Coach weight: 50000 lb
Wheelbase: 300"
Front overhang: 80"
Rear overhang: 100"
Tag to Drive axle spacing: 55"
Tag/Drive split: 35%/65%

Center of gravity location without tongue weight: 219" behind steer axle.
Steer: 15715 lb
Drive: 22285 lb
Tag: 12000 lb

Center of gravity with 1000lb tongue weight added: 225" behind steer axle.
Steer: 15056 lb
Drive: 23364 lb
Tag: 12580 lb

Delta off steer axle: 658.7 lb

davidbrady · (This post was last modified: 11-05-2014 23:48 by davidbrady.)

Here you go Ross:

I have six scenarios. You can see going across the top row we have a fixed GVW of 52500. The first set of numbers fixes the steer axle at 17000 lbs. Moving to the right we see the effect on the steer axle of adjusting the tag/drive ratio to .4/.6, finally moving to the far right we see the effect on the steer axle by capping the tag to 13K.

Moving down the columns the only thing changed is the addition of 1000 lbs of tongue weight.