Motor mount fab is not my area, but an idea occured to me. Could you basically build a crossmember under the motor and then link the mounts to that? That would help control flex in the frame itself, and give a platform more under the motor to mount to. There may not be enough room under the motor, but it was just a thought.

Try putting the pivot (bushing) on the engine end of your truss, as opposed to putting it on the frame end. The frame section height is greater than the effective section height included at the engine (whatever the vertical dimension is between the holes of the plate you have bolted to the engine. In other words, I'd rather lever off the frame rail (bushing near engine), with a larger gusset to fight twisting, than lever off the engine (bushing near frame).

Here's a coupla pics of my setup as it was being fabricated:
http://home.4x4wire.com/randii/motor/P3290022.JPG
http://home.4x4wire.com/randii/motor/P3290026.JPG
http://home.4x4wire.com/randii/motor/P3290031.JPG
http://home.4x4wire.com/randii/motor/P3290033.JPG
http://home.4x4wire.com/randii/motor/P3290039.JPG
These may help illustrate what I mean about the taller dimension.

I can't see you motor mounts enough to really say, but try to use them in the plane for which they were designed -- if you're shearing across them at 90 degrees to their design direction, that could be substantially weaker. Ideally, you want to load most rubber/poly more in compression than shear. The tubular bushings as used on leaf springs are pretty resistant to most forces not parallel to their central hole, but I like the Advance Adapters donut style better for their ease of alignment and assembly, if you can cock you mounting surfaces to be more or less in line with the direction of rotation that the motor wants to swing through when it torques.

I have also considered connecting the long frame mounts on my setup with a removable truss, and may add that later if the frame rails show any signs of 'springing' over time.

Randii

Randii, terminology aside, I can see what you mean about the length of the torque "levers", pivoting closer to the crank versus further away. Reason I did it like this was to copy the stock configuration. The stock motor bracket arm thing is creating almost the same size lever as I am building, with the motor mount being just as far away. Actually, the stock cast steel or cast iron motor brackets are longer than what I am building. I'm not disagreeing with you about pivot point location but I am sure it will work this way also.

If I mount the mm this way I think I can avoid the problem with the shear forces.



My 2 questions are:

1: Can I weld in 3/8" steel sprinkler pipe as a bolt sleeve and will it weaken the frame to sleeve it like this?

2: Any tips on making the motor bracket sturdier? Some have suggested it needs more beef. The S-shaped gusset is so I have access to the bolts. The stock mount is not that much beefier looking. (cast steel I think)

Heck, feel free to disagree, Chris! I ain't the all-knowing cookie-dough Oracle (perfect place to mis-mismatch a comic battle cry: "Spoon!" ... "Whoa."). I am sometimes right, sometimes wrong, but ALWAYS slow. <img src="/forums/images/graemlins/pfft.gif" alt="" />

I do think the lever can work either way, but it seems like it would be simpler to build with taller section-height outboard, near the frame. I was pretty tickled to tie mine into my shock towers.

I like your new sketch better for strength, especially if you're willing to through-sleeve the bolts that span the frame. I'd prefer to see you use a known-quantity tube stock for those sleeves, and I can't vouch for black pipe (dunno what it is made of). Galvanized is even worse, as it outgases poisonously when welded, and even a bit when ground. Theoretically, it is better to drill in the web (for Isuzus, vertical) of the frame rail, as opposed to the flange (for Isuzus, horizontal), but if you extend the plate that you sketched adjacent to the frame rail over the top of the frame rail, you'll have effectively reinforced the area. Weld a good-sized washer (recommend mild steel squares, as used on foundation bolts, and bonus points if you clock them 45* relative to the rail) on the bottom any you'll be good to go.

Is the motor plate quarter inch? IMHO, that'll be fine. If you want, you could hammer-form 1/8"x1" strap into a small stiffening-rail facing out around its perimeter, Burn that in hot with the welder and you'll guarantee that the motor plate won't flex.

Randii

OK, like many of my ideas, I start complicated and finish stupid and simple. I've been basing my motor bracket off the length (7"-8") not realizing til now I should just make it simple and meet the pivot point halfway in the middle. Yes, stock, this engine has 8" brackets extending from the engine.

I talked with some people and ditched the 3/8" steel idea alltogether. They told me I could take it out again if I wanted to build some tanks.

Built engine brackets. Got all the hardware I needed and threw the mounts down and was just about to drill holes. Then.. threw the idea right out the window. Ordered rubber donut bushings from AA. (haha randii is laughing right now I bet) Reason being was my little platform was not level, and the engine bracket was tilted also, so my engine mount through-bolt would have had to been going through the bracket at such a strange angle it would have been impossible to just "eye it" and get it right. The AA donut mounts will let me mount the engine only having to worry about the x and y dimension to drill one hole. Much easier and I can fine tune height with some big washers if needed. Camaro mount= no adjustment possible.

I learned a very big lesson, never just try to copy the factory design without thinking it through to see if it is the best design...

I'll post pics when its done but here is where I scrapped the idea:


Worked on my tranfercase mount. The center section and bushing kit is from Front Range Offroad Fab. The arms are 3/8"thick x 3" wide and the mount brackets I built of 1/4". I was going to add a long triangular gusset on each arm perpendicular to the main arm but decided against it. That would help lateral forces but I think all forces this system will see will be rotational and/or up-down. Not sure if it needs more beef. The mounts welded to the frame defintely need more triangulation... read on below...









I have to build a new mid-frame crossmember and also support those frame brackets, I was thinking about accomplishing both at the same time.

I was thinking 1"x4" box tube (if they make that size) welded to the frame right were that strip of 3/8"x4" is currently clamped. I could run some triangular 1/4" gussets up the side of the frame to support it, then tie some supports between the crossmember and the trans mount bracket to give those little brackets some strength.

Now I would like to just weld it in and be done with it, but I noticed the output of the t-case is going to hit it if I ever had to pull the trans/t-cases at once (like to replace a clutch). i would rather not make it a bolt-in crossmember but it looks like it might have to be. Maybe I could just make a bolt-in centersection. Any feedback would be helpful.

I ain't laughing, I promise... but I like the donuts. You'll really like how easy it is to fab for them, as well, and if you build your bracket low, you can adjust to where you want with washers/shims... and my drivetrain moves very little rotationally (which is good, considering how little space I have between a few key parts). FWIW, you might just order a set of extra bushings from FROR -- that would match all your drivetrain bushings (something I have thought about but not yet done). Dunno if that matters, actually, but it makes sense, y'know?

FWIW, I like the long gusset idea, for stiffness. That's how FROR sets up the ful crossmember version. I agree with what you are saying about the force vectors, but IMHO, you can't have a crossmember too stiff.

As for your crossmember, 1x4 stock is easiest to find in the 1x2 section... just get two and add a little MIG. <img src="/forums/images/graemlins/pfft.gif" alt="" /> If possible, though, I recommend a vertical alighment of the larger section width, as crossmembers take a pretty good beating in the rocks, and this allows better resistance to bending (vertical displacement).

I'm a fan of removable crossmembers, but they definitely require more work. If you go this route, have the crossmember flush up to the bottom of the frame rail to take the big hits and just use the fasteners to hold it in place. I ran a crossmember full-width across and under the frame and wrapped its ends up around the outside of the frame -- which is where I attached it with bolts. Worked well.

Randii

I cut out 2 crossmembers. One was the one I am picturing here that holds the driveshaft carrier bearing, the other was the bolt-on transmission crossmember with integrated mount. I believe I need to restore both of them. The former one was a bit further back as it was the rear support for the gas tank.

I think I will end up building a bolt-on one under the trans and a welded-in one that I have simulated here back about one inch for output shaft clearance. So I could pull the forward one for trans removal, and it would give me a skidplate mounting point.

For gas tank mounting I think I will build a 3rd mini crossmember for gas tank support.

IMHO, the primary reason for the one x-member was supporting the tranny driveshaft carrier bearing, something that you no longer need to do -- I think you can support the gas tank with an arm from the frame. As thin as that x-member was, it really wasn't doing much.

IMHO, the primary reason for the transmission x-member was supporting the tranny -- something your new crossmember does nicely. Yeah, there was pretty good beef to that X-member, but I think that was more about supporting the tranny and skidplate and less about holding the frame rails together.

I may eventually add a removable crossmember connecting the engine mounts, but I'm happy enough the the FROR crossmember by itself. YMMV.

Randii

It's coming together good.
How much higher is the engine,t-cases and tranny sitting?
As compared to stock drivetrain.

Are you going to have to hack up the tranny tunnel?

Bansil