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Author Topic: Tow capacity of MC9  (Read 2786 times)
Stolaas
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« on: August 08, 2010, 10:00:40 AM »

I just installed a hitch on my MC9 and the hitch is said to be rated at 6,000lbs.  Its the heaviest hitch i could find, got it through mci102.com. The question is that I have seen a lot of people pulling more than 6,000lbs.  Are you using a different hitch?  Also, i want to pull my dodge ram 2500 (deisel) four down. The truck weight is around 6000+, is this a problem?

The tow bar will be ratedat 10,000lbs, just don't want anything tearing apart at the bus connection.
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bevans6
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« Reply #1 on: August 08, 2010, 03:13:31 PM »

The common wisdom is that the MC9 (and my MC5C which has about the same rear chassis) are limited in tongue weight capacity more than anything else.  The engine/drivetrain, which itself weights around 3,000 lbs, is basically hung from the monocoque frame and actually largely supported by the roof and side wall structure moreso than anything down low.  So you are reacting loads into a fairly sophisticated structure made of tube framing and hung/attached to a monocoque - an interesting problem.  My thought, having about the same hitch you have (it was rated at 10K lbs when I bought mine) is that the condition of your structure in your bus is far more important than what you see other people doing.  You need to seriously clean and investigate the welds and material in your engine support subframes and the structure going upwards from the bumper mounts to the radiator support shelf and the roof.  That will tell you if you will be ok.  What I can say is that I wouldn't think all that much, having done the above investigation, of towing a truck such as yours 4 down.  I know a lot of people who do exactly that with MCI's, and I personally am going to be towing a 7,000 lb trailer with 700 lbs of tongue weight with the same hitch as yours.

Brian

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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
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Stolaas
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« Reply #2 on: August 08, 2010, 03:32:15 PM »

Thanks Brian for the info!  Glad to see someone with the same hitch pulling a good load. Yhe steel looked great when I took it all apart.  Just a rust rust forming at the bolt connections where the bumper and frame meet.  I cleaned it all off and primed the area.  So everything should be good.

Now I have to make some relays or use some transformers for the 12v conversion.

Any thoughts on the two way of doing it?

Thransformers reducing the voltage or relays switching to the 12v source?
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buswarrior
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« Reply #3 on: August 08, 2010, 03:44:17 PM »

When Brian recommends checking the metal, he means the ENTIRE engine cradle, supports, rails, all the way back under the engine and all connecting pieces.

There are lots of broken welds and rust in some of these engine supports, which means the structure is compromised. Best to think of it like the engine rails are barely strong enough on their own to hold up the drive train, they must be in great shape, and all the tie in to the rest of the coach structure is part of keeping it whole. And the trailer hitch is hung out on the end of them for maximum abuse.

The issue at hand is breaking the coach's back, putting the engine to the ground after the last big bump.

happy coaching!
buswarrior
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rv_safetyman
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« Reply #4 on: August 08, 2010, 07:12:52 PM »

Stolaas, you asked about how to hook up the taillights.  There have been many threads on the subject.  One of the better ones is:  http://www.busconversions.com/bbs/index.php?topic=11296.0  As noted in that thread, I wrote an article for BCM that shows how to make the relay system and where to get the parts.  This article was based on the great work of several members of this forum.

To further buswarrior's comments go to this thread:  http://www.busconversions.com/bbs/index.php?topic=16871.0

Jim
« Last Edit: August 08, 2010, 07:20:48 PM by rv_safetyman » Logged

Jim Shepherd
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TomC
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« Reply #5 on: August 09, 2010, 03:35:01 AM »

If you have a manual transmission, you might run into a startability problem with the extra weight.  If you have an automatic, you'll be fine.  Good Luck, TomC
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robertglines1
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« Reply #6 on: August 10, 2010, 04:56:37 AM »

From the dumb mistake person.I put my tow safety chains to tight=cracked frame cross member..caught problem and fellow busnut Dick came to my rescue and saved tripp doing emergency repair for me....I have been towing for over 40ty years..Dumb mistake! would make sure I have aux brake system with that weight...stopping weight pressure would be greatest stress.
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kyle4501
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« Reply #7 on: August 10, 2010, 06:07:58 AM »

What does MCI say the tow capacity is?


Surely the ones that designed & built them should know best.
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bevans6
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« Reply #8 on: August 10, 2010, 07:09:53 AM »

Since it didn't come with a hitch, the factory tow capacity is nothing...  Adding a hitch is kind of "you're on your own" so to speak.  I will personally be trying to keep under the factory GVWR as a combined weight, or within a thousand pounds of that anyway.  I optimistically figure that the brakes will be OK since the trailer has it's own brakes, the tongue weight will be OK since I have taken out the AC compressor (couple of hundred pounds I figure, with all the mounts and such) taking that load off the engine cradle area of the chassis, I have quite light bedroom fittings and no rear loo any longer, taking that weight out of the rear structure of the bus, and I don't carry a bunch of passengers over the engine, further reducing the load on that part of the chassis, so adding in 600 to 700 lbs of tongue weight with a weight distributing hitch should be fine.

I take TomC's point on startability very seriously.  On Saturday I spent an hour (!!!) in a customs lineup on the Blue Water bridge between Sarnia Ontario and Port Huron MI.  The up side of the bridge is about a 6% grade or possibly more, and I went up it stop and go all the way, with a remarkably heavy clutch in the old MCI...  Not my happiest hour, I will say that for free.  AFter I got to the top of the bridge I turned the engine off and rolled the rest of the way down the other side.  I would have been in deep trouble with a big trailer in that circumstance, I expect...

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
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1972 NTM MK-4 B/SR
kyle4501
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« Reply #9 on: August 10, 2010, 07:43:49 AM »

Brian,
You did a nice job of summarizing how removal of other loads ease the burden a hitch places on the structure.

All the things mentioned are essentially static loads.
However the thing that still concerns me is the dynamic loading resulting from the mass of the trailer. When the hitch moves, the trailer has to move & that inertia is what places the problem loads on the structure.

Then there is the fact that the hitch moves the load further away from the structure which gives the trailer more leverage against the bus structure - just like putting a cheater pipe on a wrench.

In some cases the reason they didn't put a hitch on is because there is no tow capacity that won't damage the structure.

Sure people do lots of things with no "observed" problems . . . . But that is no reason to blindly follow them.

Brian is 100% correct that in adding a hitch "you're on your own", so at least understand the significance of how a change in structural loading can create additional preventive maintenance.
And yes, I also plan to have a hitch on the back of my bus for pulling whatever I desire.  Grin

I'd rather not see someone have problems that are easily preventable.
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I know you believe you understand what you think I said, but I am not sure you realize that what you heard is not what I meant. (R.M. Nixon)
Stolaas
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« Reply #10 on: August 10, 2010, 09:23:53 AM »

Thanks everyone!  I've got a trip lined up to take her to lebanon's MCI service center to have the roling lobes put on the back and have all the air lines checked out.  The bus is not 100% done yet but plan on it being in about another month and a half.  We just want to go ahead and pull the truck up there with us so we can all ride together Smiley. I did a pretty good inspection of the frame yesterday and it all looks in really good shape.  It has a new engine and transmission and everything is pretty clean.

Got the relays ordered too for the lights, thanks for the link with the exact part numbers too, that was a huge help!

I plan usually pulling a Saturn Outlook but for beach trips we would pull the 2500D.  The Outlook will be MUCH lighter but 2500D was my big concern even though there wouldn't be any tounge wieght.  And of course I'm looking into the future here and would like to get a golf cart to load up on the truck for those beach trips as well Smiley

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Stolaas
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« Reply #11 on: August 18, 2010, 12:03:57 PM »

Finally got a 12v lead to the engine room!  Have it piggybacked on the fire control wire from ten front Jbox to the rear Jbox.  This took forever finding an appropriate through wire.  I wanted to use the lavatory wire but it occurred to me that the switch would be open and it would give a flow through current. 

The 12v lead in the rear Jbox didn't yield anything, even when i hooked the 12v to the front 12v wire.  It appears in the A/C box that wire is there, but no wire continuing to the rear?!

So the fire wire it  Grin

Just for anyone wanting a quick way to do it, its circuit 50 on stud 32
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bevans6
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« Reply #12 on: August 18, 2010, 12:39:21 PM »

Look in your battery compartment up on the right hand side.  On my bus there is a little fuse holder for the 30 amp fuse that protects the 12 volt feed.  In case your fuse ever blows, that's where it might be.  Mine also had no 12v in the rear, only to the front panel stud 53 (I think).  Just make sure the wire you decided to use (there are a fair number of spare wires in the stock wiring harness) is a gauge that can support the current draw of your lights.  Most of the wires are 16 ga, a few are 14 ga. and they are listed in the wiring diagram section of the manual.  For my trailer lights I decided to install a dedicated 24v to 12v converter in the back.  I just this week pulled several 10 gauge wires through the abandoned AC line from the AC bay to the rear pass. side bay so that I can finally install my brake controller, which needs 10 gauge for the brake control line.

Brian
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1980 MCI MC-5C, 8V-71T from a M-110 self propelled howitzer
Spicer 8844 4 speed Zen meditation device
Vintage race cars -
1978 Lola T440 Formula Ford
1972 NTM MK-4 B/SR
Kenny
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« Reply #13 on: August 18, 2010, 12:47:05 PM »

Cracked MCI 9 engine cradle. Looks as if its been repaired before. Never pulled a trailer. Proof they will crack just by the weight of the engine.
Kenny
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Stolaas
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« Reply #14 on: August 18, 2010, 08:03:54 PM »

Sounds like you had fun Brian!

I looked for some spare wires but the only one I could find listed on the Rear Jbox didn't match up with anything up front.  The spares up front all had different circuit numbers so ended up looking for something I wasn't using or been torn out. 

Now if I ever want to add a fire alarm I will have to find another Smiley   The 16g should be more than enough to run a few bulbs.   It would of been nice to use a 12g but since my Vanner only puts out 20amp max it should never need more than 16g anyway.

I'll look for that fuse but I don't think I have any 12v other from the output of the Vanner.  There is no wire from the rear battery which I guess means I still have 24v head lights.  sucks...


Kenny, hope mine doesn't crack, that would suck while on the road.
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