Need some advise/help

[Casper]

Ok, I am currently working on a project for the X. What I need help with is figuring out the wieght of the rear hatch. I would rather not pull the whole thing off and put it on a scale, as it is quite heavy. So here is my idea, if I remove the gas springs that hold the hatch up (being carfull not to squish myself) and then put a ladder under the hatch with a scale on it and let the hatch come down and rest on the scale would that give me and accurate messurment on its wieght? It seems like it should work, however something in the back of my mind say's it will not be accurate because it is hinged, and therefor not all the weight is on the scale. I would like to get as close as possible to the wieght, but would be happy to be within 10 lbs.

Is there a better way? I have looked on the web with no luck, and have even tried the dealer to no availe.

Thanks for the help.

Casper
:smiley_drive:

 

[madizell]

No it wouldn't, because some part of the weight will necessarily be help up by the hinges. If the hatch is horizontal, supported on one end by hinge and the other by a scale, the weight seen at the scale would be roughly half of the actual weight.

However, if you are wanting to know how much gas spring force is needed to lift the hatch, what you propose would give you a rough guide, as it isn't necessary to lift the entire hatch, only the working load, which will never be higher than the weight at the attach point when the load is horizontally opposed to the hinge.

Or, if you need the weight for some other reason, I would be curious to know what the project is. Perhaps some other suggestion would work better if we knew what you were attempting.

 

[Casper]

Ok, that sounds about right.
As for the project, I am fabing up a way to attach my spare tire to the rear hatch, so I can get rid of my swing bumber. It gets in the way when I am towing the Chaser, and I can't open the rear hatch. I am trying to figure out the gas spring force needed to assist with lifting the hatch, and holding it open. I can get gas springs that will lift up to 300 lbs each so I know they make one that will work, and I think I have all the reinforcments for the mount. I just need to know the weight to finish it up.

If I am understanding what you wrote, if I weigh the hatch in the manner I discibed, with the tire on it then that will give me the # I am looking for. Correct? Then all I need to do is cut the # in half and I know what gas springs to order.

Thanks for the help madizell

Casper
:wings:

 

[michaelgroves]

Put a little warning on the hatch not to open it without a wheel on it! LOL

 

[madizell]

Is this a Wrangler X? Are we referring to a hard top lift gate? If so, I would not attempt to attach anything to the lift gate, and especially not a tire.

The reason is that the forces exerted by a tire on the back of a bouncing vehicle are extreme. I have had a full sized spare on a bumper mounted tire carrier actually dent the tail gate due to load shift on rough roads.

The lift gate is built to handle only the weight of the window glass, and has torsional rigidity only when firmly closed against the frame. Putting the tire on the upper gate will destroy the gate in short order, in my opinion.

If you don't like having the tire attached to the tail gate or to a bumper mounted swing out, I would recommend a roof rack as the next most likely way to mount a spare.

I can't tell from your avitar what kind of vehicle that is, nor if that is the vehicle we are discussing, but I would be very hesitant to put a tire on a lift gate on any vehicle.

 

[Casper]

It is a Nissan Xterra, 2000. The rear hatch lifts up. I am putting reinforcment in the gate to help with strength along with beefing up the hinges. I know of one other person who has done this and been succesfull. Just can't seem to get ahold of him. As far as attaching the tire, I have four attachment points that go along the outside/edge of the hatch. In talking with several fab shops they think this is a much better way to spread the load of the wheel out so it does not distroy the hatch. I am also considering adding one or two more latches to hold the hatch shut when offroading, although that is still in the "design" stage.

I see what you are saying, but I think I have everything covered. That being said, I am always open to suggestions. I would rather rethink the entire design, then have my rear hatch fall off on the highway.
As to putting the tire on the roof, I have never liked that. Seems like too much weight up there if I get off camber. Not to mention the lose in MPG. Do you think my idea might work with the added info?

Casper
:smiley_drive:

 

[viatierra]

Put a little warning on the hatch not to open it without a wheel on it! LOL

No joke... that sounds like a good way to loose your teeth!

 

[madizell]

I can't say it won't work. I am just skeptical of the result. Tire/wheel combinations routinely weigh 50 plus pounds. That's a lot of weight to control, and it will move around no matter how hard you try to lock down the hatch. Rigidity of the hatch depends in some part on the back glass, and I would not personally want to stress the framework around the glass. Reinforcing the hinges doesn't sound feasible short of doing some Frankenstein modifications. Perhaps I have just done off road work in rougher areas than your friend who has tried it and succeeded, but long term rough country will shake and bake anything that is not over-engineered.

As for extra weight on the roof causing problem with off camber terrain, until you have rolled a car you won't have a real idea of just how far you can push a vehicle without tipping. It isn't as easy to do as you might think. Surely you are not rock crawling with an Xterra. One spare tire mounted on a roof rack will not jeopardize your ride in expedition mode up to and including relatively aggressive driving, and unless you drive over 75mph, you won't be able to measure a difference in fuel consumption. Bit of wind noise maybe, but that would be all.

If you can find photos of your buddies build, let's see them. Perhaps he has found answers that I don't anticipate.

I would rather see the tire mounted to an exo-skeleton, hinged above the rear lift hinge ( such as to the rear of a roof rack), secured to the bumper or thereabouts or to the bottom edge of the lift gate, that lifts with the rear gate rather than attached directly to it and dependent on the gate for major support, something of a parallelogram arrangement. That way the weight would be on the rack and at the bottom of the gate, not on the frame of the gate, and that might live.

 

[michaelgroves]

I would rather see the tire mounted to an exo-skeleton, hinged above the rear lift hinge ( such as to the rear of a roof rack), secured to the bumper or thereabouts or to the bottom edge of the lift gate, that lifts with the rear gate rather than attached directly to it and dependent on the gate for major support, something of a parallelogram arrangement. That way the weight would be on the rack and at the bottom of the gate, not on the frame of the gate, and that might live.

Yes, that sounds a better arrangement to me too. You could have it lift or open sideways too, if you're going to the trouble of building proper independent mounting points. Sideways has the advantage of not needing those gas struts (and still being manageable with or without a wheel mounted).

 

[Casper]

Perhaps I have just done off road work in rougher areas than your friend who has tried it and succeeded, but long term rough country will shake and bake anything that is not over-engineered.

As for extra weight on the roof causing problem with off camber terrain, until you have rolled a car you won't have a real idea of just how far you can push a vehicle without tipping. It isn't as easy to do as you might think. Surely you are not rock crawling with an Xterra. One spare tire mounted on a roof rack will not jeopardize your ride in expedition mode up to and including relatively aggressive driving, and unless you drive over 75mph, you won't be able to measure a difference in fuel consumption. Bit of wind noise maybe, but that would be all.

I have considered having it hinged to the roof rack (not stock) of my truck, it seems to be quite a hard thing to design. Maybe I should revisit that. I could not figure out how to get the tire carrier to lift and stay up without attaching it to the hatch.
As to the off camber ability of an Xterra, 47* is as far as mine can go without flopping on its side. About the same as my old Toyota. Been there, done that. Thank god for soft dirt. I also have to laugh every time someone says "Surely you are not rock crawling with an Xterra." You would be surprised what it will do. :yikes: It's not a Jeep, but I can go quite a few places. Been on the Rubicon twice, Four Dice Creek once. Of course I will not do either one again until I have a SAS. It's always fun to see the look on peoples faces when they see us on the trail.
Keep the ideas coming, I am no where near done with this project.

Casper

 

[ntsqd]

My best guesstimate is that even if you do up the gas spring force enough to open the hatch that the internal structure of the hatch isn't enough to support the weight. Semi-exo looks like the only viable option. I detest the look of those.

Current tire size no longer fits in the stock location? FWIW your problem is exactly why I quit building the swinger for Patch & went to the "Pro-Farm" in the bed mount.

Can you make the swinger part easy to remove & replace? If so, consider carrying the spare on the trailer and removing the swinger when towing.

 

[Casper]

These are all great coments and concerns. I though I had come up with enough strengthening of the hatch, but I am now reconsidering it. As it stands now, the swing arm the tire is removable, just have to pull the main hinge pin. I have brackets on the back of the Chaser to then mount the swing arm and tire there. I just was not happy with having to move it every time I want to go out, and then move it back when I set up base camp and so on. I still don't like the tire on the roof, just personel preferance. I guess its back to the drawing board. If anyone has any other ideas, coments please keep them coming.

Casper
:coffeedrink: