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Author Topic: Weight Distribution  (Read 7473 times)
mc8 tin tent
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« Reply #15 on: April 17, 2007, 04:54:55 PM »

Kevin
 Please don't take this the wrong way....PLEASE JUST ENJOY YOUR BUS!!!
It is reassuring to see you care about your fellow man in trying to make your bus as safe,efficient ,environmentally friendly as possible , AND FOR THAT I/WE ALL THANK YOU!!!!!!   PLEASE DO TAKE TIME AN ENJOY DRIVING AND USING YOUR BUS there are a lot great bus nuts out on the road.I hope you find that when you get out on the road YOU WILL FIND AN EXTENDED FAMILY JUST ABOUT EVERY WHERE YOU GO!!!!! Please take time enjoy your bus,family,friends,and a few loose nuts Smiley.
  Dwane MC8 Tin Tent
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WorkingOnWise
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« Reply #16 on: April 17, 2007, 05:09:05 PM »

Don4107- Thats It! I draw The Line At Uncle Al!!! You have gone Too FAR Now!   Cheesy
Kidding.

Don't know much about him other that he is a politician. Unless he runs for president, That's all I want to know of him.

I think the number problem arrises from where I believe the fulcrum to be, and where you believe it to be? I say it is at the center of the rear wheels for all weight behind them. 

AFAIK, the position of the front axle has no bearing on this situation. It is after the fulcrum here, so it is part of the effect, not the cause.

mc8 tin tent- Thankyou sir. I will.  Smiley

Thanks
Keith
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Stan
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« Reply #17 on: April 17, 2007, 06:09:43 PM »

Any weight you remove from behind the drive axle will have significant effect on brakeing so you need to do another vetor analysis on the rear axle when the back end wants to pole vault over the front in hard braking.

 BTW I agree with you that what you are suggesting is possible with enough time and money, but most of us will not live long enough to accomplish all the the things you are suggesting even with a lot of money. Even with the best of computer modeling there will be a lot of test and fine tune time.
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HighTechRedneck
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« Reply #18 on: April 17, 2007, 06:16:02 PM »

WoW, first, I agree with Dwane.  Build your bus the way that you will enjoy it most and then enjoy it.  A common motto here is 'Do it your way".  In spite of the conflict over theories, concerns about over thinking design, etc., I think everyone here wants you to succeed and enjoy your conversion and the process of getting there.  Always listen carefully, as this board is loaded with people with vast experience as bus mechanics and converters, and a few engineers.  But in the end, it is your bus, your time, your money and your potential success or failure.

OK, now, I can't resist discussions in physics.

AFAIK, the position of the front axle has no bearing on this situation. It is after the fulcrum here, so it is part of the effect, not the cause.

You can't evaluate a lever without considering the length on both sides of the fulcrum and the placement of all positive or negative weights along the way.  This would include the placement of the front wheels, the presence or not of a spare tire/wheel under the front, placement of all tanks and their state of fill.

Now back to practical matters.  On a 30,000 pound bus, the placement of a few hundred pounds with our without leverage, isn't going to make a noticeable difference in handling.  Consider, most commercial buses were designed to carry a variable number of passengers ranging from just a few, or even just the driver, to 40 or more.   The driver has little or no control over where the people sit or stand.  Yet the bus is still deemed safe for public transportation, a standard far more stringent than the needs of private personal use coaches.

Anyway, as I said, this is not to discourage you from calculating everything and doing all the planning you choose to.  It is your bus to enjoy and that includes the planning and conversion process.  Do it your way.
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HighTechRedneck
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« Reply #19 on: April 17, 2007, 06:18:23 PM »

Any weight you remove from behind the drive axle will have significant effect on brakeing so you need to do another vetor analysis on the rear axle when the back end wants to pole vault over the front in hard braking.

In concept I agree, but with a 2000-3000 drivetrain hanging from the back, I don't think removing 125# or even 400# is going to make that difference.  Consider, how much weight is typically removed from the back when the OTR air conditioning system is removed?
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WorkingOnWise
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« Reply #20 on: April 17, 2007, 07:01:09 PM »

Hello HighTechRedneck,
True, a few hundred pounds here or there will not impact anything in a measurable way, but 160lbs of batteries, and 300 lbs of A/C equipment, and 100 lbs of washer/dryer, and a dozen other things in the 100lb and up neighborhood, if placed thoughtfully, can make a nice driving coach great, and carelessly placed can make a nice driving coach a terror, or so I imagine. I'm looking at easily 3000 lbs of stuff that I can control where it gets placed in the coach. I'm looking for more, if there are some things I may miss.
I am no bus expert (I know, I know, some of you are shocked to hear that!  Smiley  ), so I don't know how much weight the OTR a/c weighs. If is more that a few hundred pounds, I would imagine that there would be a noticeable difference in an unloaded coach, wouldn't there be?

Part of the reason for my questions is this. Like in any brainstorming task, I start with everything that comes to mind. Everything! Then I sift out the things that are just wayyyyy too costly or time consuming, then sift out the ones that are just flash and not needed and not wanted. Then I prioritize the rest, based on desirability. Then I look at reasons y not to do each one. Then I study the ones that are left. Thats where I am now.
You may not believe some of the ideas that survived all the way thru to deciding y not to do them! My current list is conservative compared to 6 months ago!   Smiley

Thanks for the consideration and perspective. I am rapidlly learning that this board is very different from many I have been on. A ton of knowledge and experience here, and a great willingness to share it, peppered with some spicy personalities! lol

Thanks
Keith
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Don4107
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« Reply #21 on: April 17, 2007, 08:49:29 PM »

Keith, when you change the weight of a vehicle, unless the weight is perfectly situated over an axle, it affects the weight on both axles. If I put my considerable weight (not 400#  Huh and definitely not 125#)  on the rear bumper it adds weight to the rear axle and removes weight from the front axle.  If I stand half way between the axles it puts about equal weight on both.  If I stand on the front bumper the front axle weight goes up and the rear goes down. 

I agree that for your reference the rear axle is the fulcrum, if you remove weight from behind the axle the lever (frame) on the other side of the fulcrum, has less force trying to balance it and therefore the front axle has to support that weight with a ratio of about 4-1.  If you hold a pencil (frame) in the middle(rear axle) and remove weight from one end by pushing up on it what happens to the other end(front axle).  It pushes down.

If your are worried about balance, I would spend my energy trying to keep it roughly balanced from side to side and not worry much about front to rear.
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Don 4107 Eastern Washington
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RJ
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« Reply #22 on: April 18, 2007, 07:25:09 AM »

Keith -

Based on my real-world industry experience, there is no significant difference between a fully loaded Fishbowl and an empty one when it comes to handling.  Only exception is the difference between one with power steering and one without.  Period.  BTDT.

The above statement refers to your bus.

However:

MC-7s, 8s, and 9s like to corner on the rub rails, especially when loaded with passengers and no luggage downstairs.  Later models, starting with the 96/102A3s are much better in this regard due to changes in suspension geometry.

Prevosts have always handled well, but do get a little bouncy if you lift the tag axle and run down the highway.

Eagles, with their Torsilastic suspension, ride and handle very well, unless the shocks are worn, then they tend to porpoise - sometimes to the point of actually bucking the driver out of his seat, unless he's belted in (which he should be anyway.)

Setras handle like a big BMW, but that makes sense - they're German.

The only coach I've ever noticed a significant difference in the handling based on loading is the GMC PD4107 and 4108 (same bus, latter's a little newer).  Due to their design, when fully loaded with passengers only, they have a greater tendency to list when cornering.  However, if the baggage bins are loaded too, that tendency is reduced.  (Still not my favorite coach to drive - search the archives.)

The 4107/4108's bigger brother, the 4905, did not seem to suffer the same between loaded and empty.  The longer wheelbase of that model "tamed the beast", so to speak.

My own coach, a 4106, has the industry nickname of "Sports Car of Buses". . . GM really got this one right, as they did with the RTS, which is the next generation sports car of buses.  (Think 1964 Corvette vs 1977 Corvette - same car, different generation.)

So, based on my experience, I think you're worrying about a minor thing.

FWIW & HTH. . .

 Wink

PS:  What's the VIN on your coach?



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RJ Long
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« Reply #23 on: April 18, 2007, 09:26:14 AM »

Hi Russ,
So that puts a very different spin on it. Do you think that is because the fishbowls have a floor that is 18" lower than the highway buses, putting all the weight lower, lowering the cg?

I saw your question about the VIN and totally forgot. Sorry. Its TDH45191552.
It was purchased by the city of Lansing for their transit system, LATA, sold to a guy from Dearborn about 1992, gutted and turned into a very rough hunting shack, then driven to Millbrook MI, where it got driven around his hunting camp once a year until 2005, when My wife and I bought it.

Thanks
Keith
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DuaneMC7
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« Reply #24 on: April 18, 2007, 12:50:31 PM »

Keith

You seem to be very concerned about getting the weight in your bus just right. You talk about the fulcrum and moving 100-300# on either side will make a difference on how the bus handles. Are you going to stop and move your weight when you encounter a 40 mph head wind? Are you going to stop and move your weight when you are not traveling on absolute flat ground? My point is when driving down the road your weight is constantly being transferred front to back and side to side. A few hundred ponds here or there is not going to make a difference.

My .02 Duane
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« Reply #25 on: April 18, 2007, 03:31:14 PM »

ahh more people are joing my camp....I beleive I stated no noticable handling difference pretty much whatever he does save a few thousand pounds of lead in one spot.

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Chaz
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« Reply #26 on: April 18, 2007, 04:56:02 PM »

Quote
ahh more people are joing my camp....I beleive I stated no noticable handling difference pretty much whatever he does save a few thousand pounds of lead in one spot.


You aren't gloating............. are you?  Roll Eyes I was/am hoping you are offering your information to help someone as opposed to having an opinion and needing to be right. That would kind of ruin it.  Tongue           

   Just an observation,   Wink
       Chaz
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« Reply #27 on: April 18, 2007, 05:29:53 PM »

Hey Russ Your getting pretty close to home with your comments Smiley  I have a 77 Corvette and a Fishbowl I can relate to how they both handle. Smiley
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« Reply #28 on: April 18, 2007, 05:39:58 PM »

nope not gloating....just a indirect response  to another member who thought I was spounting off and questioning my "expurt" staus as he put it.

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RJ
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« Reply #29 on: April 19, 2007, 07:24:47 AM »


So that puts a very different spin on it. Do you think that is because the fishbowls have a floor that is 18" lower than the highway buses, putting all the weight lower, lowering the cg?


According to GMC's own sales literature, my 4106 is all of 1.5 inches taller than a Fishbowl.  Don't think an inch and a half is going to make any significant difference in the CG.

OTOH, the 4107/4108/4905 are nearly a foot taller at 131".  As I said in my original post, the shorter 35' models were affected more with a full passenger load and nothing downstairs compared to the longer 40' models.

BTW, the RTS sales brochure says that model is 118" tall. . .




I saw your question about the VIN and totally forgot. Sorry. Its TDH45191552.  It was purchased by the city of Lansing for their transit system, LATA, sold to a guy from Dearborn about 1992, gutted and turned into a very rough hunting shack, then driven to Millbrook MI, where it got driven around his hunting camp once a year until 2005, when My wife and I bought it.


Are you sure you got the VIN correct?  According to my sources, TDH4519-1552 was delivered new in July of 1967 as fleet number 110 to Gray Line Motor Tours of New Orleans, LA.

FWIW & HTH. . .

 Wink
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RJ Long
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