Family Size Rat crawler build

[Earl]

I agree with you on cutting out he bottom to make the cab proportions look pleasing to the eye.That side shot with the fender on looks perfect!M brother built one and lowered the windshield base(cut and sunk into the cowl)to closer match the side window height,I just bought it made it flow better.I did the same on my PW as I thought the bottom section of the cab was too tall, took 6” off of he bottom.Looks great so far !

 

[Home_brewd]

I agree with you on cutting out he bottom to make the cab proportions look pleasing to the eye.That side shot with the fender on looks perfect!M brother built one and lowered the windshield base(cut and sunk into the cowl)to closer match the side window height,I just bought it made it flow better.I did the same on my PW as I thought the bottom section of the cab was too tall, took 6” off of he bottom.Looks great so far !

Thanks! I have a few pictures of your PW saved for inspiration, it looks great man. I have seen a Willys wagon with the cowl chop and it looks really good, it just looked really time consuming and probably beyond my skill level. Once I get the suspension mocked up and see how this thing is really going to look and feel then I will decide if I want to chop it or not.

 

[ParadisePWoffrd]

Alot of homebuilt crew cabs look like such, but this one is turning out awesome. Great job.

I agree with you on cutting out he bottom to make the cab proportions look pleasing to the eye.That side shot with the fender on looks perfect!M brother built one and lowered the windshield base(cut and sunk into the cowl)to closer match the side window height,I just bought it made it flow better.I did the same on my PW as I thought the bottom section of the cab was too tall, took 6” off of he bottom.Looks great so far !

Increasing the size of the front and rear window would be on my list for sure.

 

[Grendel]

Love this. In for the ride.

 

[Home_brewd]

I ordered a triangulated 4-link kit from Barnes4wd and the box was ripped open when I received it. I opened up the packages and found that I was missing 4- 1 1/4 heim joints with the adapters, spacers and jam nuts. So I emailed them a picture and told them what happened immediately. They sent out the missing parts right away and I had them by the end of the week. 👍
Somehow I ordered the 9/16 kit, so now have to order 5/8 misalignment spacers and drill out all the brackets to 5/8. I try to keep all my rod end hardware 5/8” on my wife and my rig so I can carry less extra bolts. I have never broken a 5/8” grade 8 bolt but I have broken 2 9/16 control arm bolts. And none of the hardware stores local to me carry 9/16” in any grade so I had to buy 1/2” hardware for mock up. 👎

I started playing around with ride height and wheel base. What do you guys think a reasonable frame height would be with 140” wheelbase? This is 17” from frame to floor so this would probably be my full compression with 7-8” of uptravel at ride height. I want to find that happy medium of LCOG and enough ground clearance to not turtle on everything.

 

[gt1guy]

8" of up travel puts the frame at 25" at ride height if that's full compression in the picture. With a 140"wb, I certainly wouldn't want it lower than that.

I'd put the tires where you want them at your 140" wb. Then start raising the body until it looks right to you. Even if the frame is 36" at ride height, the turtle will visit.

 

[Sterlingfire]

My old wheeling truck was a 00 Silverado ext cab short box. Wheelbase was 143", it was a lot to handle in tight sections... the frame was at about 20" high at ride height. That could become an issue on certain trails, but the length of the truck was the real problem... too long, but if you don't care about body damage then no biggie. I would think somewhere in the 24-26 inch range will be good frame height.

 

[gt1guy]

My JKU is at 121.5" wb, so a bit shorter. Bottom of frame is 24" at ride height and 18" with both ends stuffed. Running 45"SXII's which I believe will help keep the turtles away. Also there's 16" between the bottom of the axles and the ground and for some reason I thought not having the flat bottom of the tub ever get lower than the axles would be a good idea. I have no idea if there's any merit to that or not but, to me it made sense.

 

[Sterlingfire]

I would also add a full belly skid right away.... don't put it off. With that length you'll need it.

 

[Home_brewd]

My JKU is at 121.5" wb, so a bit shorter. Bottom of frame is 24" at ride height and 18" with both ends stuffed. Running 45"SXII's which I believe will help keep the turtles away. Also there's 16" between the bottom of the axles and the ground and for some reason I thought not having the flat bottom of the tub ever get lower than the axles would be a good idea. I have no idea if there's any merit to that or not but, to me it made sense.

I definitely agree with your first comment, I’m gonna Turtle no matter where I sit. There is no perfect number, especially with my limo wheelbase. It will probably end up at the high end of an LCOG height. I like your numbers with 45s, your rig probably performs well, I personally like the 115-125 wheel base length.

I would also add a full belly skid right away.... don't put it off. With that length you'll need it.

Yes, I will definitely have full skids before I take it out. My grand Cherokee has a 118” wheel base with 42s and I still smash on my skid plates regularly so I’m kinda scared to run a wheelbase this long.

 

[gt1guy]

I definitely agree with your first comment, I’m gonna Turtle no matter where I sit. There is no perfect number, especially with my limo wheelbase. It will probably end up at the high end of an LCOG height. I like your numbers with 45s, your rig probably performs well, I personally like the 115-125 wheel base length.

I'll let you know when it runs

Wheel base does have an effect on where the COG ends up, just like width does.

 

[Sterlingfire]

I definitely agree with your first comment, I’m gonna Turtle no matter where I sit. There is no perfect number, especially with my limo wheelbase. It will probably end up at the high end of an LCOG height. I like your numbers with 45s, your rig probably performs well, I personally like the 115-125 wheel base length.



Yes, I will definitely have full skids before I take it out. My grand Cherokee has a 118” wheel base with 42s and I still smash on my skid plates regularly so I’m kinda scared to run a wheelbase this long.

Oh you're gonna smash on it for sure! It's fun though, and you kind of become a spectacle wherever you go. They will all be watching to see carnage!

 

[Home_brewd]

I have been mocking up the rear frame and 4-link. I don’t have enough info to put into a 4-link calculator so I went off of some general specs and things that have worked for me in the past. 38” uppers 38.75” lowers, 12” vertical separation on the axle and 6” on the frame. I need to do a lot more on the rear frame tie in, but these will work as placeholders.

 

[Earl]

Only way to deal with that loooong wb is rear steer,come on it would be bad ass!Oh and can you post full size pics so us old guys can see the details

 

[06h3]

Rear steer does wonders for rigs in the 140+ range. It does for every rig but especially that long.

Agreed on the 9/16th bolts. I broke a few and went to 5/8. Been problem free ever since

 

[gt1guy]

Do you have room to make your lower links longer? Punch what you have now into the calculator, then make the lowers a foot longer and have a look. Axle steer when articulated, fore/aft wheel travel in two wheel bump and also pinion angle change through travel.

Are you planning to have the uppers laterally locate the axle? If so, then that's what you know is "locked in" and you can't really mess with that. Has to be no less than 40* convergence, 45* is optimum. You can mess with the heights of the mounts but that's it.

And Happy New Year in 1:16

 

[Home_brewd]

Only way to deal with that loooong wb is rear steer,come on it would be bad ass!Oh and can you post full size pics so us old guys can see the details

Rear steer does wonders for rigs in the 140+ range. It does for every rig but especially that long.

Agreed on the 9/16th bolts. I broke a few and went to 5/8. Been problem free ever since

It definitely needs rear steer. Maybe later on down the road after I realize I hate driving this thing through the trails.

Do you have room to make your lower links longer? Punch what you have now into the calculator, then make the lowers a foot longer and have a look. Axle steer when articulated, fore/aft wheel travel in two wheel bump and also pinion angle change through travel.

Are you planning to have the uppers laterally locate the axle? If so, then that's what you know is "locked in" and you can't really mess with that. Has to be no less than 40* convergence, 45* is optimum. You can mess with the heights of the mounts but that's it.

And Happy New Year in 1:16

I do have room to make them longer. I had 45” lowers on my last rig and I felt like the length did me more harm than good. The longer lowers also cause the pinion to dive with down travel, not that I think it would be enough to cause a problem esp with this wheelbase. I will play around with the calculator at some point. My uppers have 50* and my lowers probably have 10*+/- but yes the uppers will located the axle laterally.

 

[Home_brewd]

Do you have room to make your lower links longer? Punch what you have now into the calculator, then make the lowers a foot longer and have a look. Axle steer when articulated, fore/aft wheel travel in two wheel bump and also pinion angle change through travel.

Are you planning to have the uppers laterally locate the axle? If so, then that's what you know is "locked in" and you can't really mess with that. Has to be no less than 40* convergence, 45* is optimum. You can mess with the heights of the mounts but that's it.

And Happy New Year in 1:16

I see what you are saying about the lowers. I added a foot to the lowers on the calculator and it changed the anti squat drastically. But I wasn’t happy with either number. So I went with the same length links I have on my WJ (38” upper 45” lower) and changed the separations a little. I think I am getting closer to something I will be happy with, but honestly don’t really know what I’m looking at, lol. Let me know what you think.

 

[Home_brewd]

This was hard to do but it was time. I started tearing down the old family wheeler. I pulled the front axle, tires and struts for the Willys.

Earl, let me know if these pics are big enough.

 

[AgitatedPancake]

Awe man sad day for the old dub. But I just can't be mad with how cool this new one is . Just a couple notes to help make sure ya get the most accurate results with the calculator -

-The axle end of the lower links will probably end up like ~4" in front of axle centerline, so as drawn they may be a little shorter than you're thinking
-The unsprung weights may be a little higher than you have listed, because they're not only accounting for the weight of the axles, wheels, and tires, but half the weight of the links and coilovers too
-Right now you have the CoG for the sprung mass 15" above axle centerline. If you end up running with a belly in the 25"+ height range, I wouldn't be surprised if the CoG went up to 40" or beyond, which should change your anti squat numbers a bit

 

[Treefrog]

Some other input on the calc. I would count half the link weight but not the shock weight with the axle. The CG is probably about right if the belly is at 20". The inputted value is for the entire vehicle. And down travel needs to be a negative number.

 

[AgitatedPancake]

Some other input on the calc. I would count half the link weight but not the shock weight with the axle. The CG is probably about right if the belly is at 20". The inputted value is for the entire vehicle. And down travel needs to be a negative number.

Is that because the body of the shock where most of the mass is stays with the chassis, where only the rod and piston move with the axle? That would make sense I suppose, hmm

 

[gt1guy]

One thing I noticed right out of the gate was that your front drive bias is set to zero. So the calculator is thinking it's 2wd and only the rear axle is receiving any torque. It is thinking that all of the drive torque being reacted to is all happening at the rear axle only. That 106.3% anti squat would be half that (53.15%) in 4wd, because in reality, both axles are reacting to a drive torque. Setting the front bias to 50.00 will tell the calculator that both F&R axles are driven.

Also, the front brake bias should be 60.00ish , right now the calculator doesn't thing you have front brakes.......or at least really rally bad ones.

 

[Home_brewd]

Awe man sad day for the old dub. But I just can't be mad with how cool this new one is . Just a couple notes to help make sure ya get the most accurate results with the calculator -

-The axle end of the lower links will probably end up like ~4" in front of axle centerline, so as drawn they may be a little shorter than you're thinking
-The unsprung weights may be a little higher than you have listed, because they're not only accounting for the weight of the axles, wheels, and tires, but half the weight of the links and coilovers too
-Right now you have the CoG for the sprung mass 15" above axle centerline. If you end up running with a belly in the 25"+ height range, I wouldn't be surprised if the CoG went up to 40" or beyond, which should change your anti squat numbers a bit

Some other input on the calc. I would count half the link weight but not the shock weight with the axle. The CG is probably about right if the belly is at 20". The inputted value is for the entire vehicle. And down travel needs to be a negative number.

One thing I noticed right out of the gate was that your front drive bias is set to zero. So the calculator is thinking it's 2wd and only the rear axle is receiving any torque. It is thinking that all of the drive torque being reacted to is all happening at the rear axle only. That 106.3% anti squat would be half that (53.15%) in 4wd, because in reality, both axles are reacting to a drive torque. Setting the front bias to 50.00 will tell the calculator that both F&R axles are driven.

Also, the front brake bias should be 60.00ish , right now the calculator doesn't thing you have front brakes.......or at least really rally bad ones.

Awesome feedback, thank you all. I definitely don’t know what I am doing with the calculator but I will learn. I’m going to punch more numbers in tonight and see what I can come up with. I have read that 70-120% anti-squat is general numbers to shoot for, above 100% being more rock crawler friendly and below 100% for go fast. If that sounds correct, is there anything else I need to shoot for?

 

[Treefrog]

Awesome feedback, thank you all. I definitely don’t know what I am doing with the calculator but I will learn. I’m going to punch more numbers in tonight and see what I can come up with. I have read that 70-120% anti-squat is general numbers to shoot for, above 100% being more rock crawler friendly and below 100% for go fast. If that sounds correct, is there anything else I need to shoot for?

As far as I know the current trend and preference is lower anti-squat. The numbers for rwd being 20-40% for go fast and 60-80% for crawling. The big thing to look out for is you want to avoid crossing the 100% line (rwd). With the more modern approach being to stay below it. On taller belly rigs this can be tricky, and it's probably okay to cross it at the limits of travel.

All the numbers I just mentioned are for rwd or 100% rear drive bias. To get a rough idea of 4x4 performance, the drive bias is 50%. This multiples anti squat and front anti lift by .5.

I just went to take a quick look at roll stuff and noticed you have all your Y (width) values really large. The Y value is distance from centerline, not between the points. That said, your roll values seem alright for a crawler.

 

[06h3]

Agreed on what tree frog has said. I am in the high 60s to low 70s on anti squat but can’t comment on it yet because I haven’t wheeled it yet.

With that said, I made my decision to be in that ball park running link numbers for friends. The ones under 100% seem to work noticeably better. One was over 100% and just changed his setup to be under 100% and was very happy with the changes.

If your drive bias is 50% you want your AS to be under 50% if the drive bias is 0% you want it under 100%.

 

[gt1guy]

Guess the easiest way to understand why you want certain AS numbers is to fully understand What AS is/does.

2wd explanation here. When you hit the gas, there is a torque moment that acts on the axle housing at the same time there is a longitudinal load transfer of weight to the rear. ( I would love to discuss which happens first) If your geometry is setup for 100%AS, 100% of that longitudinal weight transfer will be held through the links. The shocks will not have compressed at all. The suspension still work, it's not locked up solid, it is still free to move and absorb bumps. The links are just holding the amount of weight that transferred to the rear wanted to squat the ass end.

Now if you go above 100%AS, say to 125%. When you hit the gas in the same rig with the same amount of longitudinal weight transfer, the links will be trying to hold 25% more weight than is being transferred to the rear and the rear end will lift.

At 50%AS, your links are holding 50% of the Longitudinal load transfer. So if you had zero% AS and the rear squats 5", at 50% the squat would only be 2.5".


Where it gets fuzzy for me is while the suspension can still move while the links are holding X amount of load, there's still a fuck ton of force loaded in the links.

 

[Penetrode Offroad]

Sweet build!

 

[Earl]

This was hard to do but it was time. I started tearing down the old family wheeler. I pulled the front axle, tires and struts for the Willys.

Earl, let me know if these pics are big enough.

much better for us vision challenged people

 

[Home_brewd]

As far as I know the current trend and preference is lower anti-squat. The numbers for rwd being 20-40% for go fast and 60-80% for crawling. The big thing to look out for is you want to avoid crossing the 100% line (rwd). With the more modern approach being to stay below it. On taller belly rigs this can be tricky, and it's probably okay to cross it at the limits of travel.

All the numbers I just mentioned are for rwd or 100% rear drive bias. To get a rough idea of 4x4 performance, the drive bias is 50%. This multiples anti squat and front anti lift by .5.

I just went to take a quick look at roll stuff and noticed you have all your Y (width) values really large. The Y value is distance from centerline, not between the points. That said, your roll values seem alright for a crawler.

Haha, yes, I couldn’t figure out why my mounting points looked so wide, I guess I didn’t spend enough time looking at the graph. I will fix all the obvious stuff and start over, thanks.

Agreed on what tree frog has said. I am in the high 60s to low 70s on anti squat but can’t comment on it yet because I haven’t wheeled it yet.

With that said, I made my decision to be in that ball park running link numbers for friends. The ones under 100% seem to work noticeably better. One was over 100% and just changed his setup to be under 100% and was very happy with the changes.

If your drive bias is 50% you want your AS to be under 50% if the drive bias is 0% you want it under 100%.

Guess the easiest way to understand why you want certain AS numbers is to fully understand What AS is/does.

2wd explanation here. When you hit the gas, there is a torque moment that acts on the axle housing at the same time there is a longitudinal load transfer of weight to the rear. ( I would love to discuss which happens first) If your geometry is setup for 100%AS, 100% of that longitudinal weight transfer will be held through the links. The shocks will not have compressed at all. The suspension still work, it's not locked up solid, it is still free to move and absorb bumps. The links are just holding the amount of weight that transferred to the rear wanted to squat the ass end.

Now if you go above 100%AS, say to 125%. When you hit the gas in the same rig with the same amount of longitudinal weight transfer, the links will be trying to hold 25% more weight than is being transferred to the rear and the rear end will lift.

At 50%AS, your links are holding 50% of the Longitudinal load transfer. So if you had zero% AS and the rear squats 5", at 50% the squat would only be 2.5".


Where it gets fuzzy for me is while the suspension can still move while the links are holding X amount of load, there's still a fuck ton of force loaded in the links.

Thanks for the input again. I will play around with the calculator more this evening and try to understand it better.