Tranny skid

[Paradiddle]

Originally posted by blkTJ
the only remaining question is... what would you like to receive for it???

Brain,

Only you would buy the wrong tranny TWICE!!!



Jeff

[blkTJ]

Originally posted by Paradiddle
Brain,

Only you would buy the wrong tranny TWICE!!!



Jeff

that's freakin' hilarious... LMAO.

[Jays89YJ]

Someone please answer this question I have regarding these 2 pictures.

Why? Why would ANYONE want a tranny skid tied into their motor mounts?!?

When your tranny skid takes a hit guess where the force is going to be distributed? TO YOUR MOTOR MOUNTS. Guess what's going to break? YOUR MOTOR MOUNTS. Motor mounts are for motors and the forces put into them/onto them by motors. Not the force of your Jeep slamming the tranny skid down on a rock.

Are these guys at Boulderbars engineers? Did they do calculations to show the motor mounts won't break?

I hope you have spare motor mounts in your Jeep at ALL TIMES.

[blkTJ]

even I might make some popcorn for this one...

[Tumbleweed]

Jay-I am pretty sure they are mounting to the frame mount for the motor mount, not the motor mount itself. Not really any different than attaching to any other frame extension. Someone correct me if I got it wrong.

[Darrell C]

Originally posted by Tumbleweed
Jay-I am pretty sure they are mounting to the frame mount for the motor mount, not the motor mount itself. Not really any different than attaching to any other frame extension. Someone correct me if I got it wrong.

That looked correct to me. They were mounted to the frame bracket that the motor mount sits on.

[mrblaine]

Semantics Jay. It is the motor mount, just the frame side of it. Very nice clamshelled bits of formed sheetmetal gusseted to the frame and very stout.

Also acts as an intermediate crossmember using the block of the engine.

[Jays89YJ]

Semantics Jay. It is the motor mount, just the frame side of it. Very nice clamshelled bits of formed sheetmetal gusseted to the frame and very stout. Also acts as an intermediate crossmember using the block of the engine.

Mounting to the frame is a different story. From the picture, it looks like the skid is going directly underneath the bottom of the motor mount. I still wouldn't mount a single thing to my engine mount brackets besides my engine mounts. 2 members dropping down over a foot to a skid plate is not going to strengthen the frame per say... Especially with the angles and size of the square tubing used. If and when it fails, it will puncture your exhaust.

Was there a testing phase for this product? What is the material selection? Specs? Welds used? Fasteners used?

I would fear broken motor mounts with the engine revving?

[Jeff Weston]

Jay,

It's a skidplate, nothing more. If every product brought to market was developed using finite analysis, your only parts available for your Jeep would come from the factory. The truth of the matter is that experience, intuition and rules of thumb go a long way in fabbing bolt-on parts for your Jeep. I've seen the frame mounts and am comfortable that my skid would collapse long before I could shear off those mounts. Just like I wouldn't expect my engine to drop to the ground because I came off of a 3' drop, I wouldn't expect it to push up because I landed on a rock.

As for the testing, I've hit it and lived to tell about it.

[edit] Jay, I just re-read your concerns and can't tell if you were kidding or not? Puncturing exhaust and spinning the engine with a broken motor mount? I've crushed my exhaust from rocks (as have almost all of us here) and have bent control arms and belly skids. $hit happens when you play in the rocks.

[mrblaine]

Originally posted by Jays89YJ
Mounting to the frame is a different story. From the picture, it looks like the skid is going directly underneath the bottom of the motor mount. I still wouldn't mount a single thing to my engine mount brackets besides my engine mounts. 2 members dropping down over a foot to a skid plate is not going to strengthen the frame per say... Especially with the angles and size of the square tubing used. If and when it fails, it will puncture your exhaust.

Was there a testing phase for this product? What is the material selection? Specs? Welds used? Fasteners used?

I would fear broken motor mounts with the engine revving?

Jay, you missed the part about the intermediate crossmember. We are not trying to strengthen the frame, we are just controlling the movement of a skid in one direction.

You really need to examine the frame and mounts on the TJ before you make any judgements. Their design and strength will surprise you.

It's very common to place a board on the oilpan and jack up the whole front end of the rig.

[Chris L]

Darrell here is how I made mine out of one that was laying in Blaines back yard. I am not sure what kind of skid it started out as but it was flimsey so I welded some plates on the bottom to stiffen it up.
Mounts to the frame



I welded a small piece of angle to the top rear of the RE skid and that bolts to the top of tranny skid.

[Darrell C]

Originally posted by Chris L
Darrell here is how I made mine out of one that was laying in Blaines back yard. I am not sure what kind of skid it started out as but it was flimsey so I welded some plates on the bottom to stiffen it up.
Mounts to the frame



I welded a small piece of angle to the top rear of the RE skid and that bolts to the top of tranny skid.

Thanks, Chris. I take it no problem clearing the front driveshaft during compression of the front suspension. Looks like it might be tight to that crossmember holding the front of the skid up.

[Jays89YJ]

Originally posted by Jeff Weston
Jay,

It's a skidplate, nothing more. If every product brought to market was developed using finite analysis, your only parts available for your Jeep would come from the factory. The truth of the matter is that experience, intuition and rules of thumb go a long way in fabbing bolt-on parts for your Jeep. I've seen the frame mounts and am comfortable that my skid would collapse long before I could shear off those mounts. Just like I wouldn't expect my engine to drop to the ground because I came off of a 3' drop, I wouldn't expect it to push up because I landed on a rock.

As for the testing, I've hit it and lived to tell about it.

I disagree with your thoughts on finite element analysis. I know many companies who use them. Hell I used it in NH when I was working with a ME who owned his own business. I'm glad I'm going back to school for it actually. In this case, I don't think finite element analysis is needed. I do think the design should be backed up by force calculations. They're very easy to do. Then the document should be filed.

When I design a guard tower for the military, do you think I just say it'll work, don't worry about it? I sit down, sketch it out, determine a max design load, assign my design factor and start calculating the forces running through the members I chose. If a member needs to be changed, so be it. I then tell them at what weight the tower will crumble.

What do you think will happen when you break your motor mounts when you come down hard onto a rock? Nothing?

mrblaine, I've seen TJ motor mounts. I also know about jacking up an engine. I would not jack up the front end of my YJ using a board under my engine. If you notice, the complete structure of the frame mounted motor mounts is designed for downward force applied to them. The weight of the engine for example. If a mirror image of the existing motor mount was made for this installation and put beneath the motor mount, that would be MUCH better for mounting purposes. I also believe a cross member should be put between those pieces of square tubing. I would put a rib down where the obtuse angles are.

Look. Show me math and calculations to determine the collapsing force. Or when selling the product, tell me the weight/collision a skid can take. If not, I don't purchase. If you try to put something out on the market and a human's safety is at stake, engineering & testing is DEFINITELY called for. Backyard businesses can sell this stuff and think everyting is fine and dandy. Then one day it's there to bite them in the ass with a lawsuit.

If you buy a full size spare swingout mount, you don't buy one that says it will "fit" a 35" tire. You buy one that says it will "hold" a certain sized tire and it gives you a weight in lbs/kg the spare can weigh.

I don't want to argue about a few pieces of steel making a skid. It looks like a great beginning of a possible product to hit the market, IMHO. If you feel it's ready for the market, let it fly.

[Chris L]

Um...hehe...um...its a skid plate...hehe...um...hehe...


:newsflash:

{spoken with a slight English accent}
"A man in his mid thirties was running sledgehammer today, doing around 55 MPH. After running into a boulder field he was abrubtley stop by one large so called rock. The vehicle afore mentioned, had been running a skid plate that was tied into the motor mounts, causing the engine to break free and fly through the front windshield. Unfortunately a small wiener dog and a bunny were hurt. That is all. Good night"


"I didn't get a harumph outa that guy"

[NAILER341]

lol. your skid tie in needs some testing chris. i think it cause your knuckle to fail.

[Chris L]

It damn near caused a catostophic failer. Ok, so the wheel was crooked. Damn rocks.

[mrblaine]

Originally posted by Jays89YJ


mrblaine, I've seen TJ motor mounts. I also know about jacking up an engine. I would not jack up the front end of my YJ using a board under my engine. If you notice, the complete structure of the frame mounted motor mounts is designed for downward force applied to them. The weight of the engine for example. If a mirror image of the existing motor mount was made for this installation and put beneath the motor mount, that would be MUCH better for mounting purposes. I also believe a cross member should be put between those pieces of square tubing. I would put a rib down where the obtuse angles are.

I disagree strongly that they are designed to withstand only downward force or that is designed as the primary function.

They need to withstand dynamic loads from torque transmission to the drive wheels, rotational both lift and compressive at opposite sides.

They need to withstand centrifugal forces from the weight of the engine assembly at speed around corners.

They need to withstand lifting forces generated when hitting abrupt elevation changes at speed.

They need to withstand forward tension forces when restraining the weight of the drivetrain under heavy braking.

And, there are times when they withstand combinations of those forces in rapid succession in a very short period of time. I have never seen or heard of an instance where the frame mounts have been damaged in any manner.

They are substantial both in design and material selection as well as the formed and welded clamshell structure. I'd venture that any skid will fail long before the mounts do.

[Darrell C]

Chris, I want to know if sparks flew when that knuckle busted?

[Chris L]

Originally posted by mrblaine
I disagree strongly that they are designed to withstand only downward force or that is designed as the primary function.

They need to withstand dynamic loads from torque transmission to the drive wheels, rotational both lift and compressive at opposite sides.

They need to withstand centrifugal forces from the weight of the engine assembly at speed around corners.

They need to withstand lifting forces generated when hitting abrupt elevation changes at speed.

They need to withstand forward tension forces when restraining the weight of the drivetrain under heavy braking.

And, there are times when they withstand combinations of those forces in rapid succession in a very short period of time. I have never seen or heard of an instance where the frame mounts have been damaged in any manner.

They are substantial both in design and material selection as well as the formed and welded clamshell structure. I'd venture that any skid will fail long before the mounts do.

Ok, but what about the bunny?

[mrblaine]

Originally posted by Darrell C
Chris, I want to know if sparks flew when that knuckle busted?

nope, but there will be a few getting the new inner welded back on

[Chris L]

Originally posted by Chris L
Ok, but what about the bunny?

Hey Darrell, did you know that when you break a CTM that sparks fly out from under your jeep? Oh, wait you were there

[Darrell C]

Originally posted by Chris L
Ok, but what about the bunny?

Are you telling me the rabbit died? You know what that means, right?

[Chris L]

Originally posted by mrblaine
nope, but there will be a few getting the new inner welded back on

That was supposed to get done tonight. Damn rain! Now it looks like thursday. Still have to build some new rockers.

[Darrell C]

Originally posted by mrblaine
nope, but there will be a few getting the new inner welded back on

Come on now...we all know you can't weld cast.

You have to glue it!

[Chris L]

Originally posted by Darrell C
Are you telling me the rabbit died? You know what that means, right?

You mean the rabbit done died?

[Darrell C]

Originally posted by Chris L
Still have to build some new rockers.

Need a set of those myself.

[Chris L]

Originally posted by Darrell C
Come on now...we all know you can't weld cast.

You have to glue it!

I have this new Gorilla glue for wood. I am sure it will work...harumph!

[Chris L]

Originally posted by Darrell C
Need a set of those myself.

I am going to make some out of 6", 3/16th's plate, side and bottom, and then some 2"-2 1/2" dom tubing for the slider. I will zip a 1.5" out of the radius with the palsma fuser and glue that together with the plate. I will also use that expanding spray foam in a can to seal up any loose ends. Should look sweet

[mrblaine]

You know, me and Jay was having a perfectly fine engineering/practical experience conversation and ya'll are messin it up, now cut it out. Go mess with yates or something.

[Chris L]

How bout we mess with Brian