| Author |
Message |
Captain Ron
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 25, 2005 - 8:24 pm: | |
I currently pull a 7X12 enclosed single axle trailer with a Harley large tool chest full. and other misc. items that vary. like an old gas pump i've been restoring for the last year. I want to get a 8X16 or 18' trailer with tandem axle and brakes. is this too much for my 4905 and 8v71. And how different is the brake hook up from a regular vehicle? |
mclough
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 25, 2005 - 8:54 pm: | |
i dont know about you, but ive got a 6-71 in a 4104 and am going to try to pull a 20' trailer with a racecar in it.
I am having a prodigy brake control(camping world $149) installed. this will control the brakes on the trailer. |
TWODOGS (Twodogs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 25, 2005 - 9:19 pm: | |
surge bakes seem to be best....tounge weight needs to be below 500...BALANCE your load |
Captain Ron
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 25, 2005 - 9:51 pm: | |
Most trailers actualy all trailers I've looked at have electric brakes. does any body know approximent tounge weight of a trailer that size? |
TWODOGS (Twodogs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 25, 2005 - 10:13 pm: | |
RON...the tounge weight varies by HOW you load your trailer...if it's more than 500# move the load back...if it's less... move the load forward |
captain Ron
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 25, 2005 - 10:37 pm: | |
TwoDogs I'm not stupid I just apear that way. I was talking about the tounge weight before load. as I found out one manufacturers trailer was 340#
so I have a window 160# to deal with. I always try to keep my weight centered over the axles |
Jerry Liebler
Rating: N/A
Votes: 0 (Vote!) | | Posted on Tuesday, January 25, 2005 - 10:47 pm: | |
Ron,
My bus is the 35 foot ancestor of the 4905, but my 4107 has the same engine and manual transmission.
I've pulled an 8.5'X18' trailer with a GTW of 9000#, it's rated for 10,000#,
and a tongue weight of aprox 1000# on each of two 2500 mile trips from Oregon to Kentucy & pulled the empty trailer back in between. The Bus was also loaded very heavily (we were moving) The bus did fine & no hill slowed us below 30 in second. After each trip I jacked up the cradle and removed the two attach bolts, dye penetrant inspected the bolts and fittings. No cracks or deformed metal. My trailer has electric brakes and I have installed a Teconsha Voyager controller, it works fine. I feel it's totally safe to carry 1000# of tongue weight in a manual transmission bus because the V730 adds 900 pounds to the cradle & GM even put them in. Most athourities suggest that tongue weight should be 10% of GTW. Since your bus is 24 volt you would need a 24 volt relay energised by yourbrake lights and a source of 12 volts for the trailer brakes.
Regards
Jerry 4107 1120 |
Jim (Jim_in_california)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 1:17 am: | |
Whoa. That is a VERY good reason to go with a manual tranny!!! |
RJ Long (Rjlong)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 1:55 am: | |
Jim in CA -
Let me see if I get this straight: It's a good reason to go with a manual transmission because an auto trans weighs 900 lbs? Not sure I follow the logic here. . .
Hmmmm. . . IIRC, the V-drive 4-spd manual gearbox assembly in GMCs weighs in around 650 lbs or so - less than two passenger's weight difference.
I think you missed an important point in Jerry's comment - and that was that GM installed the V-730s in their own coaches from the factory. Certainly you would think that the factory would be confident in the cradle's ability to handle the load, wouldn't you??
And for Captain Ron, if you build a hitch similar to the one Daris Boutillier did on his coach, your 4905 will pull your trailer w/o causing you a heart attack from undue stress. Especially if you include a Tuff-Tow on the tongue of your trailer.
Daris: http://www.freewebs.com/darisb/ Click on the exterior link on the LH side. While you're there, play w/ the MPH calculator, too!
Tuff-Tow: http://www.tufftow.com/index.html
HTH,
RJ
PD4106-2784
Fresno CA |
Brian (Bigbusguy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 4:40 am: | |
I have heard of a lot of GMC owners pulling very large trailers . And have never heard of any ripping off the motor. I think a lot of people think it cant be done or should not be becouse of the rear motor and bulkhead. I think a lot of the cracks that some people report finding is from lots and lots of miles of hard driving.
The GMC Coaches are built like airplanes and like airplains they only last for so meany landing and take offs before cracks or other problems show up, If your GMC still has a few 1000 more landings you should be able tow a large trailer and not have any problems 500 lbs is nothing and 700 lbs hitch weight would be ok. The rear seat across the rear W/O rest room holds 4 to 5 people and that could be 800lbs or more. I know that the motor is hanging from the roof but it is also tied into the rear seat aera.
There is some safety built in so the motor dont just drop out the rear when hitting some large bumps like RXR crossings.
I would just make sure every thing is in good shape no cracks or rust outs and I would like others been saying is to tie your hitch to the axle rods.
And not all GMC's have any cracks I looked all over on mine and not found any .
I would like to know has any one heard of the motor pulling off or bending the rear bumper to the ground from pulling too heavy a trailer on a GMC??? Get 3 of your frinds and all 4 of you stand on the rear bumper and try to jump up and down you will see you will not rip the motor off I dont care how long you try.
If pulling a car on a trailer I would have the weight checked so you know whats where and adjust the car to get it right.
And for the electric brakes do like some have said earler.
Your hitch weight will depend on where the axles are and how you load it most trailers are built so if its loaded even you will be ok.
I would look out for too short from the ball to the box of the trailer to short you will hit the corner of your bus when turning or backing.
Build your hitch good and dont worry about it.
Brian 4905 Klamath Falls Oregon |
Jim (Jim_in_california)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 4:47 am: | |
In addition to tranny weight: how many people are converting, say, 4104/4106 series from a stock 671/manual combination to an 8v71/auto? I see a lot of the latter in those series buses. Between the motor AND tranny upgrades I would guess they're adding quite a bit of weight? Possibly 1,000lbs or more? What effect is THAT going to have on engine mount cracking and/or safety margins for big trailers?
Maybe a 671T upgrade might be a better idea? Almost as much power as an 8v71 tuned for the basic 318hp, but weighs less and is easier to run the rack on? |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 9:48 am: | |
Too little tongue weight is just as bad, or maybe worse, than too little tongue weight. I believe the rule of thumb is that the tongue weight should be between 10-15% of the total trailer weight, loaded.
With too little tongue weight, the trailer will start whipping from side to side when you get up to speed in the 45-50 mph area. I had a buddy lose a car completely off his trailer when this happened. It is very difficult to stop the whipping, once it starts. Driving in heavy winds can also cause it to start whipping.
The best way to stop this is to apply the trailer brakes only. That is one reason I hate surge brakes, as Two Dogs recommended. There is no good way to determine how much braking they are actually doing and there is no way to apply them independently of the vehicle brakes. My recommendation is to avoid them like the plague.
BTW, I pulled a 24 ft box trailer from Pasadena to Glamis for many years with my 4104 with no problems. I usually had two sand rails plus several quads, tool boxes ect. I never really checked the total weight.
Richard |
Marc Bourget
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 10:19 am: | |
Hey, Guys
The point about tounge weight is related to a physical attribute.
Forward tongue weight on a trailer resting on it's wheels means that the center of mass is "in front" of the center of drag.
This is an inherently stable dynamic situation. The lever arm of the center of drag is longer than the lever arm of the center of mass. The mass being equal, the drag will theoretically aways be "stronger" than the mass and therefore, with the bus pulling the trailer forward, it will exhibit "negative divergence" i.e. it will "fall into line" easier.
The 10-15% guideline is intended to absorb other outside influences (like the cross winds mentioned above) that may tend to "tip the scales" (pun not intended)to "positive divergence" which is when the occilations increase until something breaks or the combination of trailer and tow vehicle loses directional control.
I mention this in view of the possibility that someone could load a trailer with the weight forward and then put high cross-section boxes in back that would cause the aero loads to overcome the 15% cushion.
Onward and Upward |
RJ Long (Rjlong)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 11:10 am: | |
Jim in CA -
The 4104 came stock with a 6-71/4-spd manual gearbox.
The 4106 and subsequent GMC highway models all came with 8V71/4-spd manuals, with the VS-2 and then the V-730 as options in the later years.
When the 4106s first came out in 1961, they had some bulkhead cracking issues, but GM made the necessary changes on the production line to correct the problem, and their field service reps oversaw a retrofit program for those coaches already "working".
There is only a 150 lb difference in weight between a 6-71T and an 8V71. With N-75 injectors, the 6-71T puts out 275 hp, same as a stock 8V71 coach engine with N-60s. "318" is trucking industry slang for the 8V71 with advanced timing and N-65 injectors, which actually produces 304 hp.
A powertrain swap in a 4106/4107/4108/4903/4905 from the OEM 8V71/4-spd to a 6V92TA/V-730 is, for all practical purposes, weight neutral. The 92 weighs less than the 71, but the 730 weighs more than the 4-spd, so they cancel each other out.
Jim, I highly recommend you spend a few $$$ and pick up a copy of Larry Plachno's "Modern Intercity Coaches". You'll find a wealth of information in that book that will make it well worth the money spent. Available thru Amazon or directly from the publisher: www.busmag.com
HTH,
RJ |
Albert E.
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 11:22 am: | |
Just an observation.
I just looked at the photos of Daris' receiver. While it looks good, the fact is that this hitch is really only good for pulling 4 down, or light tongue loads. The two bolts at the rear which connect the hitch to the engine cradle are the only thing supporting a vertical trailer tongue load. The two arms attached to the radius rod are not supporting any of the vertical load. They would only be good for horizontal load, as seen pulling 4 down.
I wouldn't put more than 200-300 lbs vertical tongue weight on that hitch. |
Jim (Jim_in_california)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 11:56 am: | |
I'm looking only at "closed box" trailers so aero effects from the cargo isn't at issue. |
TWODOGS (Twodogs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 12:03 pm: | |
everybody wants to argue...everybody says they have been getting by with heavy tounge loads...& some say 10% is the rule....THERE ain't nothin' to fasten to but sheet metal...unless you have a REAL frame....& it really doesn't matter what the mfg. says the unloaded tounge weight is ...it changes when you load the trailer...& ...surge brakes are very good...because they vary the brake pressure by how the tow vehicle is stopping or slowing down. |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 1:25 pm: | |
And how do you know they are actually working, and how much? With electric brakes you can control the amount of braking and can also use them to reduce or stop trailer sway when towing in windy/gusty areas.
Once I connect a tow vehicle up to one of my equipment trailers the first thing I do is check that the brakes are working and then adjust the amount of braking I need for the specific load on the trailer. Maybe a load of crushed rock, a skid steer or an excavator or tractor or whatever. No way can you do this with surge brakes.
Richard
I have gotten rid of all the surge brake trailers in my rental fleet, except for one, and it will be gone within the next couple of months as soon as I can sell it. (12,000 lb. rating, two axle lo-boy equipment hauler). |
Brian (Bigbusguy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 2:04 pm: | |
Two dogs says "THERE ain't nothin' to fasten to but sheet metal"
Well its mostly aluminon . Its very strong that way just the way airplanes are strong.
And there is a REAL frame the fasten to it the engine cradle and rear bumper holder.
Albert is right on daris hitch I would build one like it but a little stronger and would try not to have the bends in the arm going to the radius rods. And if you used equlizing type load leveling arms it would tranfer the down weight at the bumper to the radius rods where its much stronger there.
I do agree thet MCI Eagels have more to mount a hitch from but you dont see large airplanes with a frame and there motors dont fall off very often a few have from bad bolts holding them on.
Every one that has pulled a trailer with a GMC I have not heard of any problems I only hear its not a good idea or bad becouse of no frame from others that dont have a GMC.
If you can pull a 5th wheel trailer from a roof of a car you can pull from a GMC bus without worring to much. Just dont go stupid and try to use one of the dubble decker hauling 2 cars.
Brian 4905 Klamath Falls Oregon
GMC the best busses ever made. |
Brian (Bigbusguy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 2:26 pm: | |
And the surge brake trailers They can be good and bad . The one good they stop there most of their weight with out haveing the driver do any thing or any set up. But you cant add more braking to help slow your coach in a fast stop and if the trailer does start whiping you cant apply just the trailer brakes.
Electric brakes I would feel it would be hard to adjust the % of applaction with a heavy coach.
With the loaded trailer your still under what most buses GVW is any way and the bus would stop it with out any brakes but I would have them any way.
The newer electric brake controlers use G force to work And I would set it up on a pick up so you will have some feel of the % of braking force before putting it on your bus.
Brian 4905 Klamath Falls Oregon |
TWODOGS (Twodogs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Wednesday, January 26, 2005 - 3:21 pm: | |
come on...there is no need to "adjust"surge brakes ,because the harder the bus is stopping the more pressure is on the surge brakes...AND....the engine cradel....is fastened to....sheet metal/sheet alum. |
Geoff (Geoff)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 27, 2005 - 7:59 am: | |
As far as electric brake controllers goes, there is an air over electric controller available that works off the applied brake air pressure. I have one in my bus. It is a much better system for a heavy truck or bus-- the inertia controllers are designed for pickups.
--Geoff
'82 RTS CA |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Thursday, January 27, 2005 - 10:47 am: | |
Geoff, sorry, but I have to disagree with you on this, based on my personal experience.
I purchased one of the air over hydraulic controllers for my Tahoe which I was towing behind an Eagle. It was a fairly expensive system, as I recall, and it operated the same as the surge brake trailer system. There was absolutely no way to determine if it was working, and if so how much braking force was being applied. Also, like the surge brakes, no way to independently apply them.
The new style electric brake controllers are not inertia operated. They only connect to the brake light system of the tow vehicle and do not have to be mounted in a horizontal plane like the old ones. I really do not understand exactly how they work but they work great, and they are NOT only for pickups.
I have several installed on various vehicles I use for towing from a Suburban to a 26,000# dump truck towing an 18,000#, three axle trailer with electric brakes on all three axles. I primarily use this rig for towing a dozer or an excavator. Even with this combination it is easy to adjust the amount of braking that I want to use, depending on the actual piece of equipment being hauled or when the trailer is empty.
As I stated in a previous post, I also have a 12,000# equipment trailer with surge brakes and the only time we ever use it is in an emergency situation when we have no other trailer available. Although I completely rebuilt the brake system, there is no way to determine the amount of brake action I am getting during normal operation and no way to apply the brakes independently. Also, if I have to back up, I have to get out of the truck and pin the actuator so that it does not apply the brakes while backing! All in all, I THINK SURGE BRAKES STINK.
Richard |
Geoff (Geoff)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 28, 2005 - 7:37 am: | |
Hi, Richard
The new electronic controllers DO work off inertia. How else could they work if you are only activating them with the brake light? I have installed several of these controllers in 3/4 to medium sized trucks and there is a process to adjusting them and it is based on the movement of the truck when the brakes are applied. Air over electric controllers are based on APPLIED air pressure so the amount of trailer brake activation is based on the amount of air brake pressure applied. Also, on my air over electric controller I have a handle to apply the trailer brakes independently, which also tells you by its movement how much the trailer brakes are being applied.
The system you used in your Eagle is attached directly to the master clyinder on the towed vehicle, I am not familiar with it.
I am not disputing that an electronic trailer brake controller wouldn't work in a bus, I am just saying that the air over electric is a better system designed for heavy trucks and buses with air brake systems.
And surge brakes do have their drawbacks, but they are good for fleets where no controller adjustments have to be made by employees ("dummies"). I have never had to pin a surge brake when backing up (where you backing up a hill or something?).
Anyway, I would like to hear from people that have installed electronic controllers in their buses-- do they really work that well?
--Geoff |
TWODOGS (Twodogs)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 28, 2005 - 9:53 am: | |
yep...I have had to pin surge brakes when backing up....but...best thing is not get into a situation where you have to back up...the one I used had a master cyl. on the trailer...the harder the tow vehicle was stopping ,the more pressure was applied to the towed vehicle...elec. brakes are very cheaply made & very expencive to replace parts..I'm not trying to argue...it's just my opinion |
Richard Bowyer (Drivingmisslazy)
Rating: N/A
Votes: 0 (Vote!) | | Posted on Friday, January 28, 2005 - 1:56 pm: | |
Geoff,
The old inertia controllers had to be mounted and maintained in a horizontal position. The new electronic controllers can be mounted in any position, including upside down, according to the installation instructions. www.trailerwiring.com
There are no special instructions regarding adjustment other than apply the vehicle brakes and adjust the thumb wheel for the amount of breaking desired. I really do not understand how they work, but they work great. The old inertia controllers had a swinging pendulum and had to be maintained in a level position.
I have a fleet of rental equipment consisting of several trailers from 3000# capacity up to 18,000# capacity. I use these trailers to move various pieces of construction equipment from lawn tractors to dozers and excavators. Living here in the hills of WV, I sometimes get on some very secondary/unimproved roads and or farm roads and turning around at the end of a “holler” can sometimes be a challenge. I have to back up many times on the very uneven or rough road surfaces or a farmer’s field and many times it is uphill backing. This is where the trailer with surge brakes gives me the most problem. Quite truthfully, this is the only time I am really certain the surge brakes are operating, when I try and back up. LOL
When I am on slick (ice, snow, mud) downhill roads it would really be nice to be able to apply the trailer brakes separately but unfortunately I can not with the one trailer that has surge brakes.
I am also the U-Haul store here and the two axle U-Haul trailers we rent have surge brakes. They are specially designed so that the service representative can insert a 36 inch rod in the unit to activate the brakes and make sure they are ok. This would be similar to pressing on the brake pedal of your car and ascertaining that it does not go to the floor. This is one application where surge brakes are really the only answer since the trailers are rented for either local or one way use and the customers would not want to install a controller.
And 2D, the only ones I have seen have the hydraulic master cylinder mounted on the tongue of the trailer.
I did have an inertia controller on my 4104 for towing my sand toys trailer. It was also great for combating the high winds prevalent on the route from Indio to Glamis.
Richard |
04bud
Rating: N/A
Votes: 0 (Vote!) | | Posted on Monday, January 31, 2005 - 6:08 pm: | |
My race car trailer and 04 didnt like each other, i tow a 26 ft enclosed trailer with a dragster and golf cart in it 853 lbs tounge wgt.
I was coming home 90 miles from the world finals the trailer looked funny in the mirrors,pulling in my shop i got out and found the alum channel under the bumper torn into three pieces. and the trailer almost draging the ground.
Fix was to replace that alum channel with a nice new steel piece we made(not easy but doable) no more problems
Bud |