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Author Topic: Tag axle  (Read 2135 times)
stomp
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« on: February 06, 2007, 04:09:40 PM »

Hello,

I am converting a 1973 GMC 4905. Im considering removing the tag axle to free up some space. What do you think? Good idea? Bad idea?

Thanks!

stomp
 
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TomC
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« Reply #1 on: February 06, 2007, 04:26:11 PM »

Most people have done just that, to get another storage compartment.  As example, I have a transit 40x102 that is much heavier than the GMC.  Stripped it weighed 28,000lb.  Now fully loaded in travelling form it weighs 31,000lb-so I added 3,000lb.  And with a 36,000lb gvw, I'm still 5,000lb from maximum (I just love these buses!).  The only dissadvantage is that you'll be loosing those two brakes.  I know the transits have the maximum sized brakes-mine are 14.5 x 7 in front and 14.5 x 10 in the rear for comparison.  Personally, if I had a tag axle on any of the buses, I'd remove it simply because you just don't need the extra weight carrying capability.  When you consider most of the tags add about 10-12,000lb of extra lift, and considering the actual weight of the tags, wheels, brakes, tires, etc, I'd bet you're only really getting about 8-10,000lb of extra lift.  Then also, you'll only have to take care of 6 tires, not 8.  Good luck, TomC
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Tom & Donna Christman. '77 AMGeneral 10240B; 8V-71TATAIC V730.
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« Reply #2 on: February 06, 2007, 04:39:02 PM »

Tom,

According to the Manual, the 102A3 carries less than the 102A2 as does the 96A3 compared to the 96A2

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Jerry32
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« Reply #3 on: February 06, 2007, 05:12:02 PM »

I was wondering if the tail would drag a lot without the tag?  It looks like the tail end is pretty low to the ground. Jerry
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1988 MCI 102A3 8V92TA 740
pabusnut
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« Reply #4 on: February 06, 2007, 06:37:03 PM »

I have a 73 4905A that I removed the tag axle. 

I looked at a few that came standard without the tag axle before I removed it.
The bay structure of a non-tag equipped bus looked just like the structure for the other two forward bays.

The easy part was cutting out the A-arms and removing all the stuff attached to the big C-channels.
The hard part was designing and fabricating a structure for the floor that would give adequate strength for the weight of all the tanks and provide replacement strength for when the C-channels were eventually removed.

I did take out the Big C-channels(the ones with holes in them), but only after I was satisfied that the floor structure would provide enough strength.  If you look closely at the structure, those tubular things in the center and edges of the bay next to the door actually do very little other than keep those walls from pushing out at the bottom.  Again if you look how the C-channels are attached, you see a lot of bolts and a stiffener on the opposite side of each wall, but the bay walls themselves are not very stout.

I got a good price from a respected bus parts place for a take-out floor, but to get it out it would have to be cut, and all the rivets drilled out.  To get the original strength, I figured that the floor would have to be installed the way it was at the factory, but some of the parts were no longer straight or even.  Plus cutting the B-decking would severly reduce the rigidity, which would have to be spliced, and where would I get that piece.

I ended up using a combination of 1-1/2" x 1-1/2" x 1/4" wall thickness and 1-1/4" x 1-1/4" x 1/8" wall thickness mild steel tubing and 1-1/2" x 1-1/2" x 1/4" thickness angle.  The 1-1/2" square tubing has the 1-1/2" angle welded to it to form a shelf.  This slips inside the aluminum C-shape on each bay wall and is bolted through the walls with cad-plated bolts and washers.  I would have used stainless, except for the cost, and the original bolts were steel.  Then on top of this "shelf" I sat the 1-1/4" square tubing ladder frames, clamped them and bolted down through vertically.  When I put the 3/4" plywood on top, the floor will be flat.  There are actually three frames; two identical "ladders" on each outside toward the bay doors and a wider one in the center.  I will try to post pictures when the temperature  outside gets UP TO FREEZING!!! 

My only fear with the structure I created is that it may not flex as much as the original structure would have.
My plan is to get all my utilities in there except for AC& DC Power.  I don't like to mix liquids and electric!!!

I don't feel so bad about not working on the bus tonight and being inside on the computer Wink

But, you have to do what you are comfortable doing and living with. 
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Steve Toomey
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« Reply #5 on: February 06, 2007, 07:20:44 PM »

Removing forward located tags (GM and some Eagles) may be doable without major structural refit, but removing an aft located tag axle (MCI and Prevost) would be a bad idea.  Not that it couldn't be done...
The drive axle location on an MCI A2, unlike a GM, is moved to the rear when produced in a 2 axle configuration.   Rear tags keep weight on the steering axle and carry loads that may get you over a bridge or scales if you get heavy.  An MCI tag coach grosses in the 42K range.  A Prevost may be a good bit heavier yet....recognized by Super Singles on the steering axle.
A benefit of forward drive axle with a rear tag is a smaller steering turning radius.   A coach with a rear drive axle wouldn't alter the turning radius by removing forward mounted tags. 
A 40' GM with a very rear drive axle will, for reasons beyond my simple mind (quirk of geometry? Or clever design) , will turn a foot inside a tag axle MCI.  But an MCI A3 will turn several feet inside an A2...albeit, as Dallas sez, the A2 carries a few more lbs of freight.   
You get 20-25K lbs on an axle and you'll find a small bridge that will stop you.....  This would be possible in single rear axle buses.
That's my story and I'm stick'in to it!  JR  Smiley


 
 
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JR Lynch , Charlotte, NC
87 MC9, 6V92TA DDEC, HT748R ATEC

"Every government interference in the economy consists of giving an unearned benefit, extorted by force, to some men at the expense of others.

Ayn Rand
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« Reply #6 on: February 06, 2007, 09:08:35 PM »

The GMC is a retractable smaller tire. Piece of junk. I had a 4905 back in the 90s. Easily removed and made great gen compartment with no bay floor. Plenty of air flow. I picked up one of the last 1980s with single axle and drove several year with the folks I worked with then. Ahh the Buffalo days!!
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roadrunnertex
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« Reply #7 on: February 07, 2007, 07:14:59 AM »

The P8M4905A Maintenance Manual X-7564 per section 2 page 19&20 gives the tag axle removal instructions.
I have a P8M4905A that has the 3rd baggage bin from the factory (No tag axle).
I have seen some P8M4905A's that had the tag axle assembly removed and a plywood floor installed with structure installed under the plywood.
This area makes a good place for holding tanks black&gray water and potable water.
jlv Roll Eyes
 
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Runcutter
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« Reply #8 on: February 07, 2007, 07:45:07 AM »

Stomp, welcome to the board - there's a lot of knowledge and experience here - and many of us own GM's (ours is a 4107).  When I drove 4905's in New England, I only used the tags in slippery conditions for the extra braking power - coach weight/load distribution was not an issue.

Where are you, and what's your serial number?

Arthur Gaudet
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Arthur Gaudet    Carrollton (Dallas area) Texas 
1968 PD-4107

Working in the bus industry provides us a great opportunity - to be of service to others
tekebird
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« Reply #9 on: February 07, 2007, 09:55:10 AM »

not sure of the numbers but the tag was an option and only purchased by people in states with low axle loading regulations.

still alot of tag equiped buses had the tag removed when the regulations changed.

Very few probably stiill around with the tag, which is actually a bogie as it is in front of the drive axle

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