COG Questions

bobndot wrote:
Sleepy is correct, the COG is the balance point of the tc .
Therefore, if you place a SB camper on a LB truck, the campers COG is still in the same place as it is if it were sitting in a SB truck.
The campers rear overhand prevents it from sliding too far forward, it has to be blocked at the front by using a storage box or wood frame block .
The added length to the trucks bed is between the cab and the rear axle, not behind the rear axle and the bumper.
People do put SB campers on LB trucks and the campers COG is still at he same point in relation to the rear axle.




COG spread sheet posted by one of our members

bobndot

THe truck campers design COG doesn't change after it is designed and manufactured and that COG is to be directly over the trucks rear axel.

Using your example:

What happens if you put a truck camper designed for for a long bed truck on a shortbed truck?

I think it will throw the TC's COG as much as 2 to 3 feet behind the trucks rear axel.... the front end of this combination will be so light that a side wind off a passing vehicle might move the trucks front sideways. You'd better have strong tie downs.

This question has been asked many times.

Sleepy is correct, the COG is the balance point of the tc .
Therefore, if you place a SB camper on a LB truck, the campers COG is still in the same place as it is if it were sitting in a SB truck.
The campers rear overhand prevents it from sliding too far forward, it has to be blocked at the front by using a storage box or wood frame block .
The added length to the trucks bed is between the cab and the rear axle, not behind the rear axle and the bumper.
People do put SB campers on LB trucks and the campers COG is still at he same point in relation to the rear axle.




COG spread sheet posted by one of our members

RVIA sets the standards...

the manufacturers must make everything fit and balance to have a product that has the RVIA seal of approval.

RVIA certification effects everything from insurance to financing... while protecting the consumer.

The COG is the balance point of the truck camper... clear and simple.

When the manufacturer finished designing the TC model it should balance front to back and side to side at a point directly over the rear axel and centered from side to side.

Have you ever noticed that very little weight is added to the front axel of your truck when you load your camper on the truck?

My front axel gains 400 pounds with the very large TC loaded. That probable varies slightly as I add or consune water from my water tank/step to the cabover... Adding or using diesel to the trucks tanks wiould also make the front axel gain or lose a little weight.

Other necessary items that cause shifts in balance are the holding tanks, and propane tanks.

To make up for small variations some manufacturers make that balance point as much as a square foot (6" in front of the COG and 6" behind it.

One of the biggest factors about COG of a truck with a truck camper load or any other vehicle for that matter is stearing (too light in the front end you'll have problems with hydroplaning, porporsing, etc) and the loss of distributed braking between all of the wheels on both axels.
If too much of the Truck campers weight is placed on the front axel there will be accelerated wear to all of the stearing and braking componets. And of course tire wear


Most TC's seem to be designed for built in generators like my camper has... and of course a lot of people have aftermarket generators and fuel to haul... so in the end result the weight of a generator is the weight of a generator, some are a lot more convienent.


It is actually fun to try to do things correctly... a challenge.

Some things to think about!

If a truck camper was made like your favorite cake and you started making big changes in the recipe what would happen? would it still be perfect?

Cause and effect... think about it with ever modification or add on.

It's the middle of the night...and I'm

Sleepy

goodnight again

wintersun wrote:
My camper had a dry weight of over 2700 lbs. when it left Lance. The AC added later put on 100 lbs. at the front third of the camper. Full LPG tanks would add 40 lbs. in total at the front third of the camper. I added a 100 lbs. with a second battery and its frame at the rear of the camper though having the generator option would have added as much or more. A full water tank sits in the middle of the camper and if full would add 240 lbs.

Any way you look at it the addition of accessories is going to be less than 10% of the camper's weight so it does not matter where it is placed. The manufacturers all design the camper so the COG is centered as much as possible over the rear axle of the truck. They do this by shifting the location of the appliances and holding tanks and storage areas as needed.

It is not something that anyone buying a camper needs to worry about if they put a camper built for a shortbed truck on a short bed truck and a camper built for a long bed truck on a long bed truck. The only time to be concerned is when the camper is off the truck as it is front heavy with the cabover section.

In my view, your experienced based comments seem far more applicable with your short bed SRW truck having a relatively lightweight camper, but with regards to OP's eventual rig, a likely super-sized camper (say an 11'-6" double or triple slide), the impact of CG cannot be over looked...

While it is true that Mfg's often attempt (as a logical practice) to try and optimize COG's, ultimately its the marketplace (which floor plan is it that sells...) that governs execution. A few rear bath campers (of any length) even have their grey tanks carelessly located beneath the bath. With a lengthy camper, the extra cantilevered weight of a rear slide-out, two 30# LPG bottles, batteries and generator makes this matter more serious.

To compensate for CG, the MFG of a well engineered jumbo camper will endeavor to place the tanks (and sometimes batteries) as far forward in the basement as possible.

One example is the Chalet DS116, where one will find the battery bank and fresh tank well forward within the basement with the grey and black closely alongside...(Note, the same tank placement is true for the Eagle Cap 995, 1160 & 1165).

In the case of Chalets 66 gal, and EC's (1160 series) 75 gal water capacity, this would mean a whopping 549lbs & 625lbs applied forward of axle respectively.

Its interesting here to note that with Chalets batts forward design, a dead battery means the slide-out won't work nor will the jacks. Chalet wisely planned for this possibility by extending a set of jumper terminals to the campers rear.

In my case (EC 995) we dry camp almost exclusively, and its not uncommon to haul nearly 60gals of water. A bonus of forward tank layout is that the weight of a full tank (500lbs) is nearly imperceptible. This would not be the case with a center or rear mounted tank.

Best Regards,

3 tons

The horzontal center of gravity on my Lance 1191 is measured from the rear to a point that is above center of the trucks rear axel. It is diagramed in my campers manual!

The reasons

1) my camper hangs off the back of the trucks bed 4 feet (and yes,
that 4' is lower than the bed of the truck.)

2) by designating that point as the center of gravity it tells folks that it won't fit their short bed truck.

3)the bigger cabovers with north/south mattresses and lots of cabinet space is to balance the 4' beyond the truck bed... the rear has holding tanks, etc under it too.

note: some models look esentially the same but will be a few inches shorter or longer to maitain that "build" balance. I believe the Lance 1191 is 5" shorter than the 1161. Even though they appear to be a twin, one with a basement

Look at heavy appliance placement... and then basement models... keep the tanks low and positioned to keep the verticle COG as low as possible,

The engineering that goes into every truck camper is exacting... down to ounces and fractions of an inch. Some of what we see as wasted space is designed to keep us from overlading particular areas with junk... especially heavy junk... to protect the camper. (not the truck)...

Another "user" changes that effect the horzontal COG is some of the porches that people hang off their campers, and storage boxes bolted to the campers back walls.

So, we should make intellegent decisions about what, where, and how we add to or remove from the original items designed with our truck campers


The user does actually effect the vertical center of gravity... by putting all kinds of stuff on the roof, putting canned foods in the upper cabinates, every tool they own in the campers outside accessable storage areas... over sized wheel and tires...

I'm sure that you can add to this list.

I'm sure I forgot a few things. I admit to being old... and sleepy


If your truck camper fits, and the truck isn't a grocery hauler... go camping.. (you do not want to alter the COG...either the horzontal factory designated one.. orraise the verticle COG which is up to you.

Sleepy

In case this helps some one else. I spoke with Greg ( very patient and helpful) At Adventurer. In their language COG 54 means 54" from the front of the bed. They actually place a red decal on there TCs showing the COG center when it leaves the factory.

My camper had a dry weight of over 2700 lbs. when it left Lance. The AC added later put on 100 lbs. at the front third of the camper. Full LPG tanks would add 40 lbs. in total at the front third of the camper. I added a 100 lbs. with a second battery and its frame at the rear of the camper though having the generator option would have added as much or more. A full water tank sits in the middle of the camper and if full would add 240 lbs.

Any way you look at it the addition of accessories is going to be less than 10% of the camper's weight so it does not matter where it is placed. The manufacturers all design the camper so the COG is centered as much as possible over the rear axle of the truck. They do this by shifting the location of the appliances and holding tanks and storage areas as needed.

It is not something that anyone buying a camper needs to worry about if they put a camper built for a shortbed truck on a short bed truck and a camper built for a long bed truck on a long bed truck. The only time to be concerned is when the camper is off the truck as it is front heavy with the cabover section.

It would also be interesting to know IF the CG was determined on a 'base' camper (no batteries, Air cond, LPG) or 'real-world' after having added a few everyday options.

My AF 811 has an arrow on the outside showing where it's COG is (supposedly) located, length-wise -- which is about 10 inches or so in front of the rear axle.

I really wish COG was also marked height wise too.

As far as COG goes, AFAIK any 'rear slide' jumbo camper will likely have its CG a bit south of the rear axle, however for this reason the wise MFG often mounts the fresh tank forward (and with Chalet the batts too), thus the CG will advantageously move forward depending on the quantity of water carried...