BCM Community
Bus Discussion => Bus Topics ( click here for quick start! ) => Topic started by: DKO on February 25, 2012, 07:47:44 PM
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My original question about changing the engine cradle for a 20K hitch is http://www.busconversions.com/bbs/index.php?topic=22889.msg251613#msg251613 (http://www.busconversions.com/bbs/index.php?topic=22889.msg251613#msg251613).
I promised an update when it was finished. This is a huge project. The guys at Prevost worked hard. Below are a few pictures along the way.
The bumper and belts have been removed in this picture. You can see the old 10K hitch.
(http://prevostcommunity.com/forum/UserPics/Cradle%201.JPG)
This is the new engine cradle laying upside down.
(http://prevostcommunity.com/forum/UserPics/Cradle%202.JPG)
They raised up the bus, put supports under the engine, lowered the bus a little, removed the old cradle and put the new one in. It was quite a balancing act and I could hardly watch it much less take pictures. This is the new cradle in place as they were beginning to bolt it in.
(http://prevostcommunity.com/forum/UserPics/Cradle%203.JPG)
This is the 20K hitch. The welding and supports are much better than the original 10K hitch. From what I gather the hitch industry has moved to a 2 1/2 inch receiver for 20K but Prevost chose to stay with the 2 inch. I looked at every late model bus parked on the lot and all of them are 2 inch. A 20K insert for a 2 inch receiver is difficult to find but I located one at Northern Tool. I ordered a 20K ball online.
(http://prevostcommunity.com/forum/UserPics/Cradle%204.JPG)
This is the old cradle and hitch. This hitch was broken when I bought the bus. I took it off and had a welding shop weld it together. I am confident it could tote the weight... I pulled 8-10K with it all last summer. I think it is much stronger than the original hitch.
(http://prevostcommunity.com/forum/UserPics/Cradle%205.JPG)
I kept this old hitch in case I run across somebody that needs one.
(http://prevostcommunity.com/forum/UserPics/Hitch%20Plate.JPG)
Finished - A few more pictures
All finished. They finished Thursday afternoon and I pulled about 415 miles on Friday. All seems well!
Here are a few more pictures from Thursday..
DKO
(http://1.bp.blogspot.com/-i-34XErCJjw/T0arIhFO9oI/AAAAAAAAJxc/_LDgVt4ssDI/s1600/photo%2B1-793803.JPG)
(http://4.bp.blogspot.com/-4T5ahE4LD-k/T0arJx6kEeI/AAAAAAAAJxo/nDBGOpzxDCs/s1600/photo%2B2-799288.JPG)
Out in the sunshine again after 4 days in the shop...
(http://4.bp.blogspot.com/-W8y6FkT-cSY/T0arLmytnyI/AAAAAAAAJx0/m3JoBZeL3b8/s1600/photo%2B3-706180.JPG)
Hooked up but not aired up...
(http://1.bp.blogspot.com/-ZcaIzX6g9LU/T0arL9mh5zI/AAAAAAAAJyA/fr75khtaGOQ/s1600/photo%2B4-707780.JPG)
Home is where you go when there's no place else to go!
1995-96 Prevost XL Vantare
www.boggsblogs.com (http://www.boggsblogs.com)
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DKO -
Nice work.
Which Prevost shop did the install for you?
;)
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I took it to Nashville. I was headed that way to have a few other things done and they had time to do it.
DKO
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Very cool. Never seen a cradle swap like that before.
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DKO, thanks for the great pictures.
Everyone on the board knows that I am very conservative when it comes to towing big trailers behind a bus. I want to make sure that folks understand what is going on here.
Prevost **designed** some of their chassis for towing trailers. I think maybe MCI did a few as well. Eagle DID NOT. If the bus was designed to pull a trailer it should have a tag like DKOs that designates the rating.
There are two components to designing a bus to pull a large trailer. The first is the hitch structure. The second is the bus design where the frame structure and suspension are capable of supporting the hitch structure and trailer load. DKOs bus has a frame structure and suspension that was designed to pull a 10K trailer with a 1K tongue load (per the rating tag). Adding the 20K hitch (and using most of its capability) does not guarantee that there will not be a frame or suspension issue down the road - since the frame/suspension is not rated for 20K. That said, I am sure that there is a good deal of safety margin in the frame/suspension design and DKO will probably not put enough miles on the bus to accumulate fatigue damage that would result in a component failure. Fatigue damage is a cumulative damage process that ultimately leads to a fatigue failure - same process as bending a coat hanger back and forth until it breaks.
To be sure, DKO is to be commended for having the factory service modify the bus to handle the loads he will put on it. If the factory is comfortable installing that hitch, they have some knowledge that the bus design will handle the load.
For other buses with tube or monocoque (GM) frames, that were not factory designed for trailer towing, please understand that hanging a well designed hitch on your bus does not mean that you can **safely** tow a 10K or larger trailer. Even if you have a true frame ("C" shaped steel rails running the length of the bus), that does not guarantee proper frame or suspension capacity.
The main issue is the tongue load. There are ways around placing large vertical loads on your bus. I discuss them here:
http://www.rvsafetysystems.com/Trailer%20Towing.htm (http://www.rvsafetysystems.com/Trailer%20Towing.htm)
Jim
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One would hope that Prevost didn't install a 20K engine cradle and hitch into a bus that wasn't designed for it. It could be that Prevost is more interested in the money for the install than in doing the right thing.
I personally wouldn't tow a 20K trailer behind any bus, but that is just me. The trailer I tow has a max GVW of 7,000 lbs. The trailer probably weighed around 5,500 lbs on my most recent trip. We could definitely feel it on the mountain grades. If I was to tow a 20K trailer I would invest in a medium or heavy duty truck of some type.
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???
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Thanks for the comments...I think ;D
In the original post I was asking for advice. The overwhelming advice on this board and a Prevost board was NOT to push over the 10K limit without upgrading. I heeded that advice because the last thing I want to do is cause damage to my home on wheels. I am not planning to pull 20K but with the upgrade, I do have some peace of mind when I ease over the top of 10K. Or I did have some peace of mind before I read your posts... ;D
I do appreciate all the comments and advice.
Thanks much,
DKO
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DKO I, personally, am quite impressed that you were smart enough and dedicated enough to spend the dough on getting your cradle upgraded. Especially since you're not towing 20K but rather a hair over 10K. That being said, I find it interesting that we are so scared of overtaxing, overtowing, overweighing...our coaches are rated for nearly 40,000 lbs. with passengers and luggage...and I for one have a coach that post conversion only weighs 26,500 lbs. I am certainly not worried about overloading it at this point. And you have done the right thing and spent some serious money upgrading your setup...professionally no less. Kudos from me...
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DKO -
Jim makes a good point, but I also agree that Prevost probably would not have installed that heavier-duty cradle unless they felt the coach structure could handle it. Way to many lawyers involved otherwise!
Now, to really make the coach happy, hook your trailer to one of these hitched to your bus:
http://www.trailertoad.com (http://www.trailertoad.com)
FWIW & HTH. . .
:)
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Can you even put 20K lbs in 16 foot trailer....
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In the earlier thread he said he was upgrading his trailer to a Featherlite 20' stacker that weighed 9k lbs empty. I parked next to a guy with one of those once at Mosport, he had a Trailer Toad to help, triple axle stacker with a brand new BMW 5 series as the drive-around car and a Camaro (or maybe Corvette) Trans-Am car in it. Minimum 16K - 18K in that trailer. He was a bit of an @$#, as you sometimes find, but I had the last laugh - as I was pulling out with my little bus he was waiting for a service call to get his slide to go back in... :o
DKO - Awesome trailer, I have trailer envy... I have a 20' 10K GVWR trailer that I am going to build a double deck in, to carry a couple of formula race cars.
Brian
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Thanks for the photos, DKO. I won't need to do this on my bus, but it's good to see how something this heavy-duty works. It's nice installation work, too (BTW).
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The profit from that install job won't even pay the costs of phoning the law firm to tell them someone has filed a suit.
If a Prevost Service Centre did the work, I think there is justification for confidence.
And, go have a read of Jim's work. It is important for a well rounded presentation on here for those without experience, to offer a word of caution to not just saddle up and weld stuff on and call it done.
A coach has been designed to haul people, evenly spread in those chairs we tore out, and a bit of luggage and freight down below.
An egg is very strong, for the purpose it was designed, however, it isn't very strong when subjected to forces it was not intended to.
Your coach is an egg?
happy coaching!
buswarrior
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buswarrior is right. Pevost is taking the liability for their instillation, so they would logically make sure the hitch will perform at its full capacity.
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buswarrior, I always stand in amazement of your phraseology and analogies!!! ;D ;) As is almost always the case, you hit the nail on the head, or cracked the egg, or whatever :D
Yes, our buses have a pretty substantial GVWR. However almost all DO NOT have a GCVWR (gross combined weight rating. Most have an "arse end" design that will only accommodate the engine/transmission. Hanging a bunch of weight way out past the engine can really do a number on the structure/suspension capacity.
One of the things I always forget to say is that the 1-2K hanging on the engine cradle is only part of the picture. The other big component is the dynamic loading of the tongue load as the bus/trailer goes over the bumps and swells on the highway/roads/parking lot approaches/etc.
When I write about my concerns, I often mention that my other concern is the consideration of degradation of structural strength of the engine cradle system due to corrosion and fatigue.
It has been said a couple of times, but I want to emphasize that my reason for posting my concerns is not DKO's situation - he handled the situation very well. It is to make sure that the readers of this thread understand the implications trying to pull large trailers behind their buses - that may not be able (or designed) handle the loads correctly.
Jim
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One of the things I always forget to say is that the 1-2K hanging on the engine cradle is only part of the picture. The other big component is the dynamic loading of the tongue load as the bus/trailer goes over the bumps and swells on the highway/roads/parking lot approaches/etc.
As a supplement to Jim's comment, next time you're in the neighborhood of a stick 'n staple dealership, stop by and have a chat with the service dept. Ask the fellow if he's got any RVs in his shop with structural damage from pulling a heavy trailer, and go have a look.
My neighbor is the service mgr at the major RV dealer here in town, and he's shared with me some of the horror stories that are trailer-related. For example, a fellow brought in a two-year old 32' Class A non-pusher where the walls had split and separated from the roof almost directly over the rear axle. At the very back of the coach, the top of the rear wall was almost a foot below the roof from the frame's bending. Vehicle was considered a "total."
The sad thing? Insurance wouldn't cover it (abuse), manufacturer's warranty wouldn't cover it (abuse), and the guy still owed over $75K on the rig. :'(
After Mel showed me a couple other rigs with similar, yet not as severe damage, I've become a firm believer in using a Trailer Toad. At approximately $3500 new, it sure beats the cost of repairing a coach chassis should a failure take place. And no, I'm not a dealer nor do I have any financial interest in the company! Just being SAFETY-minded!!
Trailer Toad Link: http://www.trailertoad.com (http://www.trailertoad.com)
FWIW & HTH. . .
;)