Corrosion resistant, light weight TJ frame

[rowen01960]

The LS is ~ 5litre ... I have a Coyote 5litre model that I will “drop” tomorrow ... as well as get the Control Rods and Track Rod in ... the Prop Shaft, Transmission and Transfer Case ... then we can confirm the Travel Limits ... followed finally by the Mass Properties Table ...

 

[Mike_H]

Are the LS motors all the same? I know the 6.2L is a pretty common swap. Also, the 5.7L Hemi is making the rounds too, not so much in a TJ, but for sure in JK's. How about a SBC? If you're trying to build a Family of frames to cover a wide array of vehicles, guys like the SBC in older things like Broncos and Blazers. I'm with you on dropping the motor mounts to lower the engine...specific to a TJ, if you use the transmission mount as the "pivot" I can see it working to a certain extent. However, there is a LOT of stuff packed into a small place there, and when that axle comes up (think sharp ledge that will contact both tires) its gotta go somewhere. don't know how much you could actually drop it.

 

[rowen01960]

Are the LS motors all the same? I know the 6.2L is a pretty common swap. Also, the 5.7L Hemi is making the rounds too, not so much in a TJ, but for sure in JK's. How about a SBC? If you're trying to build a Family of frames to cover a wide array of vehicles, guys like the SBC in older things like Broncos and Blazers. I'm with you on dropping the motor mounts to lower the engine...specific to a TJ, if you use the transmission mount as the "pivot" I can see it working to a certain extent. However, there is a LOT of stuff packed into a small place there, and when that axle comes up (think sharp ledge that will contact both tires) its gotta go somewhere. don't know how much you could actually drop it.

Hey Mike! .... I guess the TJ term will refer mostly to the shape of the Body Panels in the end ...

I was not aware of Hemi swaps ... guess I need to expand my understanding of Extreme Jeeps a little ...

Your are correct in thinking “family” for the Ladder Frames ... but only in a very technical sense ... Commonality for Design/Test Process, Constituent Materials, Component Parsing/Functionality, Manufacturing Process, Inspection Processes, and where sensible ... Geometry (reduced NRC for Tooling). So Yes Broncos, Blazers, Land Cruisers, Susuki, Land Rover, and my favourite the Scout!. In fact any BOF ladder frame vehicle that is out of production could benefit .... up to a production limit of 250 Frame Types/Configuration per year. Quantities above 250/y for any one configuration type require additional automation due to the different Manufacturing Process.

Yes it will be quite “busy” up front with an engine drop ... one of the reasons for a geometry and weight revision to the Axle Housing ... same Ring/Pinion, and Shafting but increased Transverse Bending/Torsional Stiffness with Composites...

The key to available space/clearance for engine dropping, is in the Jounce Limit of the axle housing ... only rock climbers will utilize max Jounce and then on a single side ... more or less a roll rotation of the axle about the vehicle CL ... Full compression/BumpStop contact should only occurr when “dropping” the vehicle (limited to 2.5m).,. my thoughts at least.

 

[Mike_H]

Hey Mike! .... I guess the TJ term will refer mostly to the shape of the Body Panels in the end ...

I was not aware of Hemi swaps ... guess I need to expand my understanding of Extreme Jeeps a little ...

Your are correct in thinking “family” for the Ladder Frames ... but only in a very technical sense ... Commonality for Design/Test Process, Constituent Materials, Component Parsing/Functionality, Manufacturing Process, Inspection Processes, and where sensible ... Geometry (reduced NRC for Tooling). So Yes Broncos, Blazers, Land Cruisers, Susuki, Land Rover, and my favourite the Scout!. In fact any BOF ladder frame vehicle that is out of production could benefit .... up to a production limit of 250 Frame Types/Configuration per year. Quantities above 250/y for any one configuration type require additional automation due to the different Manufacturing Process.

Yes it will be quite “busy” up front with an engine drop ... one of the reasons for a geometry and weight revision to the Axle Housing ... same Ring/Pinion, and Shafting but increased Transverse Bending/Torsional Stiffness with Composites...

The key to available space/clearance for engine dropping, is in the Jounce Limit of the axle housing ... only rock climbers will utilize max Jounce and then on a single side ... more or less a roll rotation of the axle about the vehicle CL ... Full compression/BumpStop contact should only occurr when “dropping” the vehicle (limited to 2.5m).,. my thoughts at least.

Hmmm...I would argue that full jounce happens more frequently than you think. At least in Michigan and the land of the Giant Potholes. Everyday driving on the highway might be considered rock crawling in some circles!

Regardless, when I set bumpstops on a vehicle, I will check for interference in all three conditions (Driver Full Compression/Pass Full Droop, Pass Full Compression/Driver Full Droop, and Both full compression) You can bet that I'd increase bumpstop to keep oil pan clearance. I currently have about 5" of uptravel on my jeep. I should tie a zip tie around the shocks, and see how much I routinely use. I'd guess I'm into the jounce bumpers rather routinely.

 

[rowen01960]

Exellent! I was considering a 6&8” Jounce study knowing that 8” will be problematic ... need to find the boundary on this ... do you agree that a single side (Fast) compression is the worst case ie Pothole?

Keep in mind that at 8” deep x min 12” wide “gully” will “trap” most 16” wheeled vehicles ... thereby providing advance warning of a road issue ahead ...

 

[jjvw]

Exellent! I was considering a 6&8” Jounce study knowing that 8” will be problematic ... need to find the boundary on this ... do you agree that a single side (Fast) compression is the worst case ie Pothole?

Keep in mind that at 8” deep x min 12” wide “gully” will “trap” most 16” wheeled vehicles ... thereby providing advance warning of a road issue ahead ...

Don't forget speed bumps and dips in the road. Those can easily bring both sides to hard bump. I know personally.

Also, just to make sure we are all understanding each other, when we extend our bump stops, we are making sure that the hard limit to up travel is metal on metal, steel cup to steel pad. The soft jounce is designed to compress into the cup.

It may be of interest for you to know that i have over 6" of suspension up travel on both ends. I will often use most of that while daily driving on pavement. The factory up travel is about 4" before hard bump.

 

[rowen01960]

Don't forget speed bumps and dips in the road. Those can easily bring both sides to hard bump. I know personally.

Also, just to make sure we are all understanding each other, when we extend our bump stops, we are making sure that the hard limit to up travel is metal on metal, steel cup to steel pad. The soft jounce is designed to compress into the cup.

It may be of interest for you to know that i have over 6" of suspension up travel on both ends. I will often use most of that while daily driving on pavement. The factory up travel is about 4" before hard bump.

So 4/6/8” of “up travel” to hard bump stops would be 3 “limits” that I need to conform to? for fast compressions? I am trying to identify a minimum number of frame geometry variations that would maximize market usage while minimizing Spring Rate/damper variations ...

 

[jjvw]

So 4/6/8” of “up travel” to hard bump stops would be 3 “limits” that I need to conform to? for fast compressions? I am trying to identify a minimum number of frame geometry variations that would maximize market usage while minimizing Spring Rate/damper variations ...

Not sure how to answer that.

I would assume fast compression, I think. As I understand things, hard bump is the hard limit to up travel, regardless of the speed of the compression. Shocks and jounces would influence the speed of that impact.

While I would argue that no modified TJ should ever have less up travel than the 4" from the factory, the reality is that most will probably range from 2-7" of up, with 4-5" being the most common.

We set that limit to up travel based on the first point of interference. This is typically the front tires hitting the steel body at full articulation and the rear shocks reaching full compression. But there are other limitations that can happen. The correct amount of bump stop extension is variable and specific to the Jeep and it's combination of parts.

Having multiple preset bump stop extensions should be no different than the common addition of hockey pucks or spacer pucks to the bump stops. There should be nothing stopping someone from creating a custom length extension that is in between the presets.

Some additional design details to consider...

The rear extension is often added to the frame side mount. The front bump stop extension is best added to the axle pad because the travel arc of the axle will often cause the bump stop cup to pluck the coil spring due to the spring's smaller diameter compared to the rear.

 

[rowen01960]

Not sure how to answer that.

I would assume fast compression, I think. As I understand things, hard bump is the hard limit to up travel, regardless of the speed of the compression. Shocks and jounces would influence the speed of that impact.

While I would argue that no modified TJ should ever have less up travel than the 4" from the factory, the reality is that most will probably range from 2-7" of up, with 4-5" being the most common.

We set that limit to up travel based on the first point of interference. This is typically the front tires hitting the steel body at full articulation and the rear shocks reaching full compression. But there are other limitations that can happen. The correct amount of bump stop extension is variable and specific to the Jeep and it's combination of parts.

Having multiple preset bump stop extensions should be no different than the common addition of hockey pucks or spacer pucks to the bump stops. There should be nothing stopping someone from creating a custom length extension that is in between the presets.

Some additional design details to consider...

The rear extension is often added to the frame side mount. The front bump stop extension is best added to the axle pad because the travel arc of the axle will often cause the bump stop cup to pluck the coil spring due to the spring's smaller diameter compared to the rear.

Sorry ... my incoherent train of thought strikes again! ... what I should have asked is:
1) would a TJ Frame configured for max 4” Front Jounce on a 2-4” lift frame be adequate for worst case Potholes? If yes what would the typical travel speed?
2) would a TJ Frame configured for max 6” Front Jounce on a 2-4” lift frame be adequate for worst case Potholes? If yes what would the typical travel speed?
3) would a TJ Frame configured for max 8” Front Jounce on a 4-6”” lift frame be adequate for worst case Potholes? If yes what would the typical travel speed?

Answers to the above will define axle travel arc using OE and longer Control Rods. I am not keen to raise the Spring Perch or Damper Mtg heights but will chk a lower bump stop height increase for effect at full compression ... thx!

The concept of “adding” a diagonal to support a lower motor mount has, for economics sake now been changed to a locally larger frame rail that integrates a conical cup to attach the machined mount. This also provides an increased SXN to react both bending and torsion forces/moments ... it will look like a lot like the JK frame in this region ..

 

[rowen01960]

I have been corrected the imaged engine is LS3 6.2L so the “modder bar” is now a little higher ... if I can stuff it in ....

 

[jjvw]

...
1) would a TJ Frame configured for max 4” Front Jounce on a 2-4” lift frame be adequate for worst case Potholes? If yes what would the typical travel speed?
2) would a TJ Frame configured for max 6” Front Jounce on a 2-4” lift frame be adequate for worst case Potholes? If yes what would the typical travel speed?
3) would a TJ Frame configured for max 8” Front Jounce on a 4-6”” lift frame be adequate for worst case Potholes? If yes what would the typical travel speed?..

Maybe a survey of people's bump stop extensions along with how they arrived at them would be helpful. Or talk to builders who are known to do this part of a build correctly. 4Wheel Parts would not necessarily be an example of this.

Me not knowing any better, I would suggest replicating the factory configuration and then let the end user extend them the way we already do it.

Answers to the above will define axle travel arc using OE and longer Control Rods. I am not keen to raise the Spring Perch or Damper Mtg heights but will chk a lower bump stop height increase for effect at full compression ... thx!

..

I don't see how the bump stop lengths would define the travel arc or the control arm length. Wouldn't the opposite more likely to be true?

Additionally, bump stop length is not specifically determined by lift height. That relationship is coincidental at best.

 

[rowen01960]

Maybe a survey of people's bump stop extensions along with how they arrived at them would be helpful. Or talk to builders who are known to do this part of a build correctly. 4Wheel Parts would not necessarily be an example of this.

Me not knowing any better, I would suggest replicating the factory configuration and then let the end user extend them the way we already do it.


I don't see how the bump stop lengths would define the travel arc or the control arm length. Wouldn't the opposite be true?

Additionally, bump stop length is not specifically determined by lift height. That relationship is coincidental at best.

I am attempting to rationalize the 2-6” lift desire into 3 or possibly only 2 major frame configurations .. these 3 or 2 frames will have dropped motor mounts (Low CG feature 3, 6” or 2, 4, 6”) integral to each specific frame. The dropped motor will occupy the space provided by the selected lift frame and be protected by the Lower Control Rods.

The current necessary retention of the OEM Spring & Damper Upper Mtg heights will mean the Axle is now further away from the Spring & Damper Upper Mtg Location (longer springs/dampers required) thus providing clearance for larger tires ... the max spring compression (up stroke) limit is in the same relative position as the OE unless additional stroke (> 8”) is desired which would be added (progressive spring) to the bottom of the up stroke zone (increasing further the axle offset from the Spring & Damper Upper Mtg point).

The motor mounts are “fixed” elevation points and will not be frame modifiable so ... one would need to decide the lift in advance.

User installed Upper Bump Stops (> OEM length) can be added, but will reduce Up-Stroke Travel accordingly ...

The design will hopefully provide adequate clearance between Axle Housing and Engine with an OEM Upper Stop Bumper ...

The 3 Suspension Layout Drawings will define all max travels and angles without respect to Wheel/Tire specification (thats the next stage)