Long Jeep.....chasing unicorns

[Metcalf]

Thinking for the day.....

Frame design and permanent crossmembers.

Looking at your typical TJ frame there really are not that many side to side crossmembers. There is the front tube crossmember under the grill, the rear fuel tank/shock crossmember, and the rear bumper. I am fairly sure that the belly plate is designed to function as a major structural crossmember when installed?

As I lay out the frame design this makes me a little nervous, especially on the longer LJ length frame. My plan so far is to have crossmembers....

-at the front end of the frame to form the 'bumper', the winch mount, and provide the body mount for the center mount in the grill. This will be a welded in assembly.

-at the engine mounts. I would like to have a subframe all the way under the engine. It would be nice if this was in more than one part perhaps. It will be a bolt in unit however to allow me more room to move the engine around. The portion under the oil pan will provide a forward attachment point for the belly skidplate. It would be nice if the lower portion of the mount came out perhaps to allow dropping the oil pan off the engine?

-at the transmission mount. This will bolt in also as well as provide the rear end attachment point for the belly skidplate. On the LJ length chassis this is pretty far forward really.

-at the step in the rear floor? I was thinking of adding an arched crossmember that would go above the rear driveshaft at this location. It would be about 18" or so behind the transmission crossmember ( that is removeable ) to provide support to the middle of the chassis. I think with a little planning this could be a welded in unit that may be able to provide support to the B-pillar of the cage where it would tie into the body. I have to run the exhaust, fuel, and brake lines through this area too. It would also be close to the attachment point for the triangulated upper frame side control arm mounts which I think will be important on the longer LJ length frame rails?

-somewhere slightly behind the rear axle. This would be for rear floor support along with providing a mount for the front of the fuel tank. This would also be in the same area as the rear air bag mounts and shock mounts to provide a little more structure in that part of the frame.

-at the rear bumper. I am trying to design a rear bumper crossmember assembly that integrates the rear body mounts, a tube crossmember for a swaybar, a receiver hitch, and a rear 'bumper' of sorts to protect the body. Oh...and it needs to provide a mount for the rear of the fuel tank....

Think that will give me enough support in the long chassis?

I am still very much on the fence about tying in the cage mounts solidly to the frame. I don't think I want to go all uni-body buggy spaceframe on this vehicle. I think the body and cage tie-in mounts will have to be isolated at this point....

Fun stuff. Once I get some better measurements on the frame I will posts some pictures from Solidworks. I am trying to design the frame in sub-assemblies so that I can just weld in the computer cut crossmembers to the main frame rails once I have the chassis main rails welded up. I finally found a decent solid model of an LS engine so I can computer design the engine mount subframe assembly. The transmission crossmember will probably have to be designed on the fly once I get some parts and see how the clocking on the NP205 ends up.

 

[Metcalf]

Rear suspension note...

I was doing a little digging on air bags. I think this would be a good one to use...

http://www.truckspring.com/products/Firestone-Reversible-Sleeve-Air-Spring__W01-358-5429.aspx

Anyone know how to figure a rough spring rate based on load capacity at a given ride height?

 

[86tuning]

Would it be easier to register and modify an older truck instead of registering a u-built?

 

[24HOURSOFNEVADA]

I get it that you want to build it. I had an '04 Unlimited and sold it. Talked to a few guys about stretching a JK for me and test drove a few two door Jk's as donor vehicles. I even looked at importing another rig. In the end, I found myself a nice, low mile 2006 Unlimited Rubicon and I'll be happy with that until something better (My opinion) comes along.

I think this thread lacks pictures on your end, get to building and posting.

 

[Metcalf]

Would it be easier to register and modify an older truck instead of registering a u-built?

Sure, but its not THAT big of a deal. Old iron is getting harder and harder to find.....and I just built something old...I want something 'new'

 

[Metcalf]

I get it that you want to build it. I had an '04 Unlimited and sold it. Talked to a few guys about stretching a JK for me and test drove a few two door Jk's as donor vehicles. I even looked at importing another rig. In the end, I found myself a nice, low mile 2006 Unlimited Rubicon and I'll be happy with that until something better (My opinion) comes along.

I think this thread lacks pictures on your end, get to building and posting.

Yeah, a stock rig just isn't going to cut it for me. I would just rip everything out and chop, cut, rebuild it.

All my work is on paper and in CAD right now. I am waiting for Aqualu to get me a quote on the body tub selected and I am sure that I will have a few back and forth changes with them on the little stuff.

This isn't going to be a simple bolt on build. I am designing and building a vehicle from basically scratch. It will take time......probably about 2 years, or that is the rough goal at this point.

 

[gavan]

Just a quick FYI. I had the -10 weighed recently. Full tank of diesel, but otherwise completely empty. Heavy front bumper, but no cage, and the trailer body is lighter that you would think.

5600 pounds.

 

[Metcalf]

Just a quick FYI. I had the -10 weighed recently. Full tank of diesel, but otherwise completely empty. Heavy front bumper, but no cage, and the trailer body is lighter that you would think.

5600 pounds.

I wonder what a good realistic goal would be for this project.....5000, 4500, 4000......

 

[Metcalf]

Not much to report on this project. I am still waiting for the quote from Aqualu. I'm not in a rush so its no big deal. I am continuing to work on the major sub assemblies to the frame like the front and rear bumpers, engine crossmember, etc. No rush....not really on much of a time table at this point.

 

[Metcalf]

Just some quick screen grabs of the front bumper sub assembly....





This is basically the front 'bumper' sub assembly.

It is designed to fit on the end of a 2x4 box rail frame horn ( in 3/16" wall ).

The winch mount is designed to use a normal low profile winch that would be mounted foot forward and flipped to get the hawse up out of the way. This is set up for a 34" wide frame with 30" inside the frame rails for the winch. This should allow just about any regular winch to be used, some of the newer winches with the long heat sink motors would be a little tight. The mount is currently centered but could be offset easy enough.

The winch mount plate has a lightened bottom that protects the winch from the odd rock. The winch line can also be run down out the center hole to hold the front axle down if that is needed. The main winch plate also is designed to provide a crossmember under the grill with the rear 45 degree lip. That area will also provide the center grill body mount ( not shown ) and an area to run the right front brake line across the frame if I decide to go that way.

The front bumper tube is 1.75" tubing. It can be whatever wall thickness to make the winch mount stronger. The bumper is tied into the main winch mounting plate using weld slots. This ties the entire unit together to make a VERY strong assembly. The front bumper can also be used for a torsion style sway bar or can just be capped on the ends.

The clevis mounts are profile cut from 1" plate steel. They provide a ramp off the bumper tube to help the front of the frame get over tall ledges. They are designed to use a 5/8 screw pin anchor shackle for recovery points.

Total weight, including the 12" of frame horn on each side is about 45lbs plus welding ( with .120 wall 1.75" tubing )

Thoughts?

 

[bishopdunn]

Looks stout and functional. How does the steering box fit in?

 

[MrBeast]

One issue I can think of looking at your plans to use a TJ windshield with a CJ dash, what are you going to do for defrosters?

 

[Metcalf]

Looks stout and functional. How does the steering box fit in?

The steering box is going to be an outside the frame unit with a forward facing pitman arm.....FJ60/80, scout, early bronco, etc.

This lets me have a longer drag link. The front of the frame can be shorter for a given axle position. The steering shaft doesn't have to snake inside the frame. Etc.

 

[Metcalf]

One issue I can think of looking at your plans to use a TJ windshield with a CJ dash, what are you going to do for defrosters?

The dash will be CJish.....probably not completely flat with the dash but angled up just slightly. I will probably use some custom defrost ducts from vintage air in the top of the dash connected to a later YJ heater unit.

Maybe something like this....



Walker Evans's Cambell Ent built jeep.....one of my favorite vehicles of all time.

 

[Metcalf]

Here is the first major iteration of the rear crossmember bumper reciever hitch assembly....









Details and thoughts...

-The main rear crossmember is a piece of 2x3, .188 wall tubing. It is snugged up against the bottom of the tub as tight as possible. There needs to be a little room for a small body mount puck between the body and crossmember. This crossmember has a long list of functions. It provides the main support for the receiver hitch. It is wider than the frame to provide a body mounting area out from under the body. It is also sized so that a torsion style swaybar can be run through the tubing. It will also provide some mounts for the fuel tank on the bottom surface.

-The rear bumper is the same 1.75" tubing as the front. The ends are trimmed at a 30 degree angle and capped to hopefully help follow the lines of the chassis. This bumper is very high and tight on the body. This gives should provide excellent clearance on the rear of the body when dropping off a ledge or hard corner with the rear tires. I may end up trying to wrap the tubing around the corners but haven't decided on that yet. I tend to be pretty minimalism. The high bumper should not interfere with a normal CJ/YJ/TJ tailgate.

-A 2" receiver hitch is tucked down under the crossmember as tight to the chassis as possible without getting into the space available for the rear mounted fuel tank. I will probably extend the inner brace plate down to grab the back end of the receiver tube. I tried to brace the front and provide some normal trailer chain slots. So far the hitch is being designed at the primary rear recovery point. There just isn't a lot of other places to tuck a recovery point that don't get in the way of other stuff.....

-There is no inward bracing to allow the most room possible for a rear mounted fuel tank.

-Some small 1" plate, profile cut, braces are integrated on the bottom of the frame. These would be made the same time as the front shackle mounts.

-Most of the steel in the rear is 3/16" plate to be cut at the same time as the front winch mount plate.

-The rear cover plate, with the elliptical holes helps brace the main tube. There are small gussets on the inside to brace everything together and help align things. I don't know if I like the cut outs yet. They same weight and make it a little more interesting. I should probably add some drain holes or slots to the bottom.

-Total weight is 51lbs ( plus welding ) at this point. That includes 12" of frame on each side also ( 6.84lbs per, 13.68 total ).

-The rear 2x3 crossmember could be lightened with a hole saw without loosing much strength but I think I will keep it fully intact so that when the rear swaybar installed the crossmember will be somewhat sealed to keep mud and dirt from hiding in there.

-Keeping the rear bumper from levering off the end of the frame is my main concern. I will probably make the profile cut bottom brackets much stronger as I move forward with this design. I may be able to sneak a recovery point that change also.

Fun stuff.

I have the basic frame designed as far as the cuts for the front and rear kicks but I don't really have an overall length to put on any of the parts yet without more data on the body.