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Author Topic: Tow Hitch for 4106 wanted  (Read 7095 times)
phil4501
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« Reply #15 on: June 25, 2006, 01:25:08 PM »

Does anyone have pics of Gary Deans set up, how about a discription?

I bet it's like One Lapper is describing.
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RJ
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« Reply #16 on: June 25, 2006, 01:35:27 PM »

OK, I'll jump in here and throw in my few pennies worth, maybe even a Susie B. . .

The problem with a heavy trailer and a bus is the stress it puts on the engine cradle, both horizontally and vertically.  Ideally, then, the hitch receiver should be designed to relieve as much stress as possible off the cradle.

Daris Boutillier's 4106 has the type of hiitch OneLapper should consider, as it is tied into the rear axle radius rod mounts, thus relieving the engine bulkhead of the horizontal stress of towing:

http://www.thebouthilliers.com/4106/

From the home page > Conversion Articles > Exterior > Receiver Hitch


The vertical loads induced are a completely different matter, and the one area that brings out most of the flack.  The engine cradle literally hangs from the roof at the back, with just the bolts holding everything in place.  TTBOMK, no one's ever really done a thorough engineering study to see how much of a load can be put on these vertical hangers before they fail, so you're off in "no man's land" in that regard.

It's not so much the static load of 500 - 700 lbs that's in question, it's more the instanteous loads induced from normal highway undulations that causes the concern.  Hit a bump, and suddenly that 500 lbs static jumps to 2500 dynamic, as an unscientific example.  Because of this, there has been suggestions made recently (w/in the last couple of years, anyway), that those with heavy trailers seriously consider something like the Tuff-Tow to handle these sharp induced loads, helping to take the vertical stress off the engine hangers.

http://www.tufftow.com/index.html

So that's sort of the latest on hitches for your coach.  Not something you can walk into a hitch outfit and pick up "off the shelf", but something that any competent hitch fabricator can easily put together for you.  Just install one intelligently, and you shouldn't have any problems.

HTH, and enjoy Brock Yate's creative madness!!

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RJ Long
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« Reply #17 on: June 25, 2006, 02:33:20 PM »

OK, I'll jump too.

If you took a stock 4106 with an 8-71 and 4 speed and replaced it with an 8-92 and V-730, wouldn't you be adding about as much weigh as the trailer hitch?

I'm pretty sure such an engine upgrade has been done though I don't really have any idea of the weights involved.† I just think our old GM's were so over built they can take most anything we can throw at them.

Len
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« Reply #18 on: June 25, 2006, 02:48:18 PM »

OK, I'll jump too.

If you took a stock 4106 with an 8-71 and 4 speed and replaced it with an 8-92 and V-730, wouldn't you be adding about as much weigh as the trailer hitch?

I'm pretty sure such an engine upgrade has been done though I don't really have any idea of the weights involved.  I just think our old GM's were so over built they can take most anything we can throw at them.

Len


Len,
An 8V92 actually weighs 35 pounds less thanan 8V71. Thats according to http://www.adieselengine.com/new_page_1.htm

I'm not sure about the difference in a V730 and a Spicer 4speed, but it can't be that much different.

Good Luck!
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phil4501
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« Reply #19 on: June 25, 2006, 03:59:02 PM »

The has to be a better way than the little wheel on the trailer tounge. Backing up would be a nightmare and I can't imagine that thing being reliable or trouble free. How do those weight distribution hitches work or what about the hitch with it's own little suspension setup, with out a wheel,to reduce shock load. If the hitch is trangulated to the radius rods mount that would take care of the lateral loading. It seems to me that toungue weight is the biggest stumbling block.

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OneLapper
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« Reply #20 on: June 25, 2006, 04:49:53 PM »

Russ,

You're absolutely correct.  At static 500# tongue weight is much, much higher when bouncing down the road.  I ran into this problem with my race car.  I built an aluminum hitch frame with a 1" reciever tube bolted to it.  The tongue weight of the trailer I use during our race was only 70#, no problem I figured.  Wrong.  It cracked.  It wasn't until after the race did I call a good friend (he is literally a rocket scientist) and he calculated a dynamic load of over 400#!  Because the suspension of the car is so stiff, I made a hitch that was capable of 1000#.  I have the only 600 hp race car that can tow an Air Stream trailer (if I wanted to)!

I estimate that the appropriate hitch will have to be able to support 2500 to 3000#.  This number may not need to be this high because of the air suspension and the amount of travel the rear axle has.  I think that a hitch can be made to handle this type of dynamic load.

Mark
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OneLapper
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tucsontattoo
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« Reply #21 on: June 25, 2006, 05:17:20 PM »

Whew!! † †been under there all morning,Last wheel work musta been done by some old oil-patch hands.Didn't know you could get wheel lugs that tight,got them brok after a trip to the Home-depot for 6 foot cheater pipe and a short brake to weld tools back together! Got the axles knocked loose, Now I gotta find out where to buy that diff. grease with the glitter in it cuz Dallas said I should change that stuff while I'm in there!!! †Feels like I,m losing the left wheel bearings,so tomorrow I'll track those down( not smooth at all, tight spots) Grease is very metallic.Will tell you more of the tail of wo as the week progresses.
 †But enough about me. concerning your problem.. †Took a look at my hitch,its †held on by two big bolts(about 3/4 inch dia) about a foot inside the the bumper, bolted to a triangular plate built onto the bottom of the cradle (guessing here,what ever the structer is that holds the rear bumper), the triangle plate points rearward and the sides are formed by two weldment I beams going forward, dipping under the oil pan and attaching to the bottom of the bulkhead. really don't think it's built for a very heavy tongue weight, looks substantial enough for tow bar work though. If I were going to tow a trailer I think it would have to be a tandem where I could control the tongue weight..
 †Took some pictures,will get them out of the camera tonight and put them in the mail to you!!!
 † † † † † † † †Tucson
 P.S. †noticed in your pictures your brake linings have the standard through bolt set up that uses a countersunk flat head screw with nut and lock washer. The blocks they sent me are bonded and use a fine thread half inch bolt from the inside of the shoe,no bolt hole visible from the top. Know any thing about this? †Other than that they look the same..?? Huh
« Last Edit: June 25, 2006, 05:25:19 PM by tucsontattoo » Logged

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« Reply #22 on: June 25, 2006, 05:37:58 PM »

 †Took some pictures,will get them out of the camera tonight and put them in the mail to you!!!
 † † † † † † † †Tucson
 P.S. †noticed in your pictures your brake linings have the standard through bolt set up that uses a countersunk flat head screw with nut and lock washer. The blocks they sent me are bonded and use a fine thread half inch bolt from the inside of the shoe,no bolt hole visible from the top. Know any thing about this? †Other than that they look the same..?? Huh
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Tucson,

TIA for the pictures, but I agree that for my goal I'm going to have to anchor to the raduis arm brackets.  I'd still like to see what you have, though.

As for the shoes I imagine there is little to no difference other than you won't need to buy the brass slotted bolts! 

BTW, I used about 3/4 lbs of high pressure axle grease per side.  Nothing fancy, Valvoline brand I recall.

Mark
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OneLapper
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« Reply #23 on: June 25, 2006, 08:17:58 PM »

This is a thread I have been watching closely. My 4106 has a receiver attached to the engine cradle and the previous owner towed a Jeep Cherokee. I need to tow a full size Suburban which GVW is above 7000lbs. From what I am reading here, it seems to me that I might need to beef things up underneath. Can anyone post some pictures or plans? If I tow four down, will the existing hitch be adequate?....Thanks
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akbusguy2000
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« Reply #24 on: June 25, 2006, 08:28:37 PM »

Here's how one person did it.

http://www.thebouthilliers.com/4106/



tg
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RJ
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« Reply #25 on: June 25, 2006, 09:53:33 PM »



The has to be a better way than the little wheel on the trailer tounge. Backing up would be a nightmare and I can't imagine that thing being reliable or trouble free. How do those weight distribution hitches work or what about the hitch with it's own little suspension setup, with out a wheel,to reduce shock load. If the hitch is trangulated to the radius rods mount that would take care of the lateral loading. It seems to me that toungue weight is the biggest stumbling block.




You're right, Phil - tongue loading is the stumbling block for hauling heavy trailers.  Not so much an issue for 4-down toads - they have to deal with the lateral loads.

Tuff-Tow has been on the market over 10 years now. . . that has to account for something.  And, if you look at the FAQs, they address the backing issue.

There's another unit out there that's different, called "The Hitch Buddy", that might also be an option for you or Mark:

http://www.hitch-buddy.com/Hitch.htm


This is a thread I have been watching closely. My 4106 has a receiver attached to the engine cradle and the previous owner towed a Jeep Cherokee. I need to tow a full size Suburban which GVW is above 7000lbs. From what I am reading here, it seems to me that I might need to beef things up underneath. Can anyone post some pictures or plans? If I tow four down, will the existing hitch be adequate?....Thanks



Take a look at Daris Boutillier's pics, both TG and I posted the link to his page.  If you're pulling on just the cradle, you're pulling on just the lower motor mounts at the bottom of the engine bulkhead - suggest you inspect the bulkhead and the motor mounts closely for wear and/or cracking.



I estimate that the appropriate hitch will have to be able to support 2500 to 3000#.  This number may not need to be this high because of the air suspension and the amount of travel the rear axle has.  I think that a hitch can be made to handle this type of dynamic load.



Mark -

Thanks for the kind words, they're appreciated.  IMHO, I don't think the suspension travel of the coach is as big an issue, compared to the movement of the trailer.  I know when I hook my utility trailer to my pickup, I can feel it buckin' 'n kickin' around back there, transferring it's motion back to the truck.  That, to me anyway, is the issue related to tongue weight and the forces induced.

Check out that Hitch Buddy mentioned above, it might be more suitable for you than a Tuff-Tow.

NOTE: All of the above primarily pertains to GMC coaches, altho there are corresponding issues with MCIs, Eagles, Prevosts, etc.

HTH y'all. . .
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RJ Long
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« Reply #26 on: June 26, 2006, 06:06:07 AM »


OneLapper: I will try to give you a more serious answer. There is no problem pulling from somewhere on the rear axle, other than HP, clutch and high first gear.  The problem is hitch weight. You should be running with 800 - 1000 pounds on the hitch.  This is more weight than most people consider safe. The rear wall of a 4106 supports the back of the engine through the skin and tubular framing to the roof. Thus the reason for the comments about the rear of the bus falling off.

All the weight behind the axle is hanging on the rear bulkhead and the rear skin. The first 4106 buses had to have the bulkhead reiinforced as a retrofit so it is marginal at best. Pulling a car or 4 wheel trailer,  from a point on the rear axle,  puts minimum downward force on the rear. Although there are people who have pulled heavy trailers behind GM buses, not many people would  willingly give you a design to work from.
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phil4501
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« Reply #27 on: June 26, 2006, 07:52:40 AM »

I don't understand why one couldn't just distribute as much of the weight froward to the radius rod mounts as possible with one of those weight distribution hitches, then control the shock of the bouncing on the bumper end of the hitch. With a three axle trailer, and a reasonable amount of toungue weight, it just doesn't seem that bad.

« Last Edit: June 26, 2006, 07:54:32 AM by phil4501 » Logged
TomC
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« Reply #28 on: June 26, 2006, 08:40:32 AM »

Mark- I realize you already have the 4106, but maybe you should consider using one of the mid engine framed buses like the Crown or Gillig since you can use the NTC350 or even NTC400 Cummins with a Allison 740.  With the 40ft, most had tandem drive rears, and then you could use the ever so cool looking Michelin X-one super single drive tires.  The 455/55R-22.5 is equal to the 11R22.5.  The 35ft version would have the same interior space as your 4106. Look at the classified ads in this site, there is a raised roof Crown that Red Skelton used that looks really nice.  If that had been available, I might have bought that instead.  Then also with a truck framed bus like the Crown, it wouldn't be much trouble to build in 3 or 4 sliders.  Even making a roof top observation platform isn't a problem either since the Crowns roof bows were made to be roll cages.  Just a thought-probably will be shot by the GMC nuts.  Good Luck, TomC
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phil4501
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« Reply #29 on: June 26, 2006, 08:48:26 AM »

Edit: Tom, Gilligs and Crowns are very nice. I like the looks of the Tandem Crown alot.
« Last Edit: June 26, 2006, 11:56:17 AM by phil4501 » Logged
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