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Overcrawling Buggy Design - Trail Rig

BioHazard2222

BioHazard2222

Well-known member
Joined
Mar 30, 2021
Member Number
3734
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65
Loc
Oregon
First full design and build, so flame on if you feel you must.... or better yet, constructive input would be welcomed.
I have been working on this tube frame buggy on and off for a couple of years now. Lately I have made some pretty good headway and and am getting close to being finished with the design.
It will be a 4 seater full tube frame, Chevy 350 V8 powered, TH400, D44 Front, Corp14 rear, off road exploration vehicle, a little bit of a crawler, a little bit of a overland vehicle, so a "Overcrawling" rig.
I also plan on making this street legal just to add to the fun factor.
I am getting close to having the design done and hopefully to a point I can start cutting and bending tube and welding it up.
If you are a off-roader/four wheeler/overlander/fabricator/builder/designer or experience in this sort of vehicle, I welcome any input on what could be changed or Look out for or input/help, I have never designed a vehicle or build one for that matter from scratch, but I'm making it happen.
I have done most of the design in Bend-Tech, last picture shows the different tubes I'm planning
Tan - 2"x.120DOM
Teal - 1.5"X.120 DOM
Green - 1.5X.120 HREW
Cyan - 1.25"X.095 HREW (tube doors, grab handles, and console areas)
Red - used to represent bend areas for sheet metal, (Foot Boxes, storage areas, etc)

I am still working on suspension, but planning on 4-link front and rear
Wheel base is 130"
Sitting on 37" tires
drawn with about 22" belly height

Let me know what you think and any comments
Thanks

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It's always fun to bring your ideas to CAD for tinkering even before bending the first tube. It looks like you're getting a good feel for the software. A couple notes just from an initial observation, the good ole pirate special of needs more triangulation. An X in the B pillar or X in the C pillar would add a huge amount of rigidity to keep the chassis from going parallelogram during a hard roll. The other note is with the current chassis tubes in relation to the axles, it doesn't look like you have much room for UCAs on either end of the chassis without contacting during decent uptravel. What's the height to the top of the chassis currently?
 
130" on 37's sounds overly long and the 22" belly sounds high <- just my meaningless opinion.

I don't think you'll need to have the tires at the very edges of chassis for what it sounds like you are doing. I'd encourage you to maybe try to bring in the axles a little bit and probably even look into adding some longer tube to the rear for more storage. more space is always better, especially when taking 4 people on multi-day trips

4 link is fairly easy to setup, but a 3 link might be even easier and give you just as good of performance.

Think of the chassis as 3 pieces.

bottom layer is the subframe that needs to be built around all your suspension mounts, so a rough idea of the suspension layout and travel is important to start with

middle layer holds the drivetrain and seats. make sure you have "enough" space and do what you can to keep the rear seats from being right on top of the rear axle.

top layer is everything that connects the front bumper, over/into the shocks, along the roofline and out the back. this gives you "look" and roll over protection and is where the X bracing and such and whatnot come in to play.
 
sooo i used to have a reg cab long bed truck on 38's..........yeh hard no offroad, esp east coast. Maybe moab that works. im now at 115" and 40's and it's still a big girl. Also if your design is in perspective....that looks like a H1 with the outer bars being even with the outside of the tires and the big flat trans tunnel. Thats a WIDE chassis.
 
AgitatedPancake said:
It's always fun to bring your ideas to CAD for tinkering even before bending the first tube. It looks like you're getting a good feel for the software. A couple notes just from an initial observation, the good ole pirate special of needs more triangulation. An X in the B pillar or X in the C pillar would add a huge amount of rigidity to keep the chassis from going parallelogram during a hard roll. The other note is with the current chassis tubes in relation to the axles, it doesn't look like you have much room for UCAs on either end of the chassis without contacting during decent uptravel. What's the height to the top of the chassis currently?
Click to expand...


Agitated - currently floor to roof height is like 75"... understand about adding more triangulation, I will work on adding that in to the design, thank you for the feedback... And I guess I'm having cranial flatulence and not knowing what "UCSs" are I'm guessing axle/frame clearance of some sort.


Provience said:
I don't think you'll need to have the tires at the very edges of chassis for what it sounds like you are doing. I'd encourage you to maybe try to bring in the axles a little bit and probably even look into adding some longer tube to the rear for more storage. more space is always better, especially when taking 4 people on multi-day trips
Click to expand...

Province - Your probably right, I will re-look at proportions, thank you for the breakdown, makes good sense to look at frame in sections

pennsylvaniaboy said:
...that looks like a H1 with the outer bars being even with the outside of the tires and the big flat trans tunnel. Thats a WIDE chassis.
Click to expand...
Pennsylvaniaboy – yea it is “hummer-ish” it is about 6-8” narrower than a Hummer BUT it is wide and does have a good sized tunnel, which does allow to tuck up trans and transfer case to make flush on the bottom side.
 
BioHazard2222 said:
Agitated - currently floor to roof height is like 75"... understand about adding more triangulation, I will work on adding that in to the design, thank you for the feedback... And I guess I'm having cranial flatulence and not knowing what "UCSs" are I'm guessing axle/frame clearance of some sort.
Click to expand...

Upper Control Arms. It just doesn't look like there's much room to package a suspension in there the way things currently sit
 
AgitatedPancake said:
Upper Control Arms. It just doesn't look like there's much room to package a suspension in there the way things currently sit
Click to expand...

OK, that did come up in my "Google" search, but I was thinking it may have meant something else too... This is straight axle both ends, so no Control arms, but all the link system is still being worked on, and I may need to do some mods to make it all fit... thanks for the heads up!!
Not sure the best way to get more Axle clearance without raising the frame? Suggestions?
 
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LorneStar said:
A little plexiGlass some sheet metal and a few other environmental protections and it would be fine.
Click to expand...

hahaaha thanks for the confidence... I don't have it drawn, but am planning on windshield and body panels, so that should help some.
 
BioHazard2222 said:
OK, that did come up in my "Google" search, but I was thinking it may have meant something else too... This is straight axle both ends, so no Control arms, but all the link system is still being worked on, and I may need to do some mods to make it all fit... thanks for the heads up!!
Not sure the best way to get more Axle clearance without raising the frame? Suggestions?
Click to expand...

Meh semantics, links are commonly called control arms haha.

This is one of those scenarios where the bulk of the chassis is usually designed around the suspension components, versus trying to design the suspension after the chassis. You may have to raise, notch, and reroute some of your tubing to get decent geometry.
 
BioHazard2222 said:
OK, that did come up in my "Google" search, but I was thinking it may have meant something else too... This is straight axle both ends, so no Control arms, but all the link system is still being worked on, and I may need to do some mods to make it all fit... thanks for the heads up!!
Not sure the best way to get more Axle clearance without raising the frame? Suggestions?
Click to expand...

Control arms = links in this discussion
 
With a chassis this wide/ long, I would avoid the conventional “flat belly.” That is a lot of real estate to get stuck on. Taper the sides, have a flat bottom section \__/ ; gain locations for better link geometry, clear up room in the “cab.”
 
You are not listing a transfer case and you have TH400 with no overdrive. If you are overlanding, you will want to drop down your rpms for long trips. Since you have length for a 4 seater then you should be able to fit a doubler. Figure out your crawling speeds and high speed transfer speeds in relation to rpm.

It looks like the tunnel is wider than it needs to be. I decided to run the floor and seats higher over the drivetrain rather than around the drivetrain. The drivetrain is as low as it can get to the belly to keep LCG. I also pushed the motor as far forward as possible to make room for one of the longest drivetrain options. LS/4L80/241NWFDoubler/NP205
My engine compartment is 24" center to center at the rear of the block and gets wider at the front of the block. There is maybe an inch between the exhaust manifolds and the panels which my foot rests against. There will be a heat shield so it is fine. My chassis is wide and it is 60" center to center of outer tube around the front seats which are 32" center to center. The rear is a bench and the frame narrow from 60" to 42" right behind the rear bench. The roof also looks close to the seats. I've got 42.5" from top of seat cushion smashed down to bar overhead. 48" from floor to bar overhead. Seat cushions when seated and smashed are 5.5" above the floor. That model of the PRP seat is not correct either. You will also want to tilt the seat back at least 5* degrees for comfort.

The height of the drivetrain looks about 12" too high. The whole drivetrain should drop down and a subframe added to the chassis. The lower links will attach to the bottom of the subframe. Upper links will attach to the subframe where it meets the main chassis. This will lower the hoodline as the engine will drop down giving better vision. This will also change the radiator mounting.

Wheelbase is 119.5" with 40"s

The front and rear seats need to move back towards the rear tire. There is not enough leg room in the front. The rear seats should be side by side or a bench and have the headrest straight above the rear axle tube. My rear headrest is 4.5" behind the axle tube. You are better off to extend the rear of the frame past the rear axle than to have a longer wheelbase. The shorter wheel base helps for steering and high centering. The rear frame hanging past the axle has been proven to be a non issue by most all the KOH cars running spare tires way out back and dragging them through the rocks. Diagonal tubes in the rear will help slide of ledges and drops rather than a squared off tail like a Hummer or Jeep. The diagonal tail will also lower the approach angle while still giving room for storage.

More triangles. The windsheild needs a ../\.. instead of an ...I... Same goes for the rear right after the seats ../\.. not ./...\ .

Really decide if the doors are worth the hassle. They are compromising strength. If you put in a X instead of a door it can still be easy to get your foot over while not having to deal with a door that jams and will not add any strength in a rollover. If you really want a panel half door then make a thin one out Lexan or UHMW that is minimal and will not smash your finger getting in and out of when off axis.

Take the rear of the cage out further back, before it runs downhill. You want to protect the gear you put back there and the passengers heads. I see so many people run the tubes down quickly for looks and then once loaded out for race or camping all the extra gear and parts are past the tubes and it doesn't look cool or practical anymore.

Plan for panels now. It will be much easier if you have a plan and tubes in the correct planes and locations so the panels can attach. Otherwise you will have some complex panels with no good way to end them or stop and start the next panel.
 
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I agree that there is no room for proper length upper and lower suspension links, the bottom of the chassis needs some redesign to accommodate those.

Where will the fuel cell and spare tire live? Cargo space looks very slim.

This is definitely a WIDE beyotch at the bottom of the chassis, boat sides would help for sure.

And since you're investing the time, effort, and money into this there is no reason to not spring for a D60, shave the 14b, and run 40s. No matter how you go about this, you're going to be spending many tens of thousands of dollars to end up with a decent product. The extra $1k for a D60 is negligible.

OR...

Go buy a Chevy Avalanche 2500, SAS it with a D60, add a doubler, and be done.
 
Everyone said it already, but I believe your chassis has no provision for any kind of suspension mounts. That's the main drawback to your design.

If I were you, I'd engineer and draft the suspension first then position the drivetrain, then the passengers and tubes. You will quickly realize that there is a reason why none of the "good" full tube buggies look like your design.

If you want to overland in a buggy with an engine screaming at 3000rpm at 55mph, while your friends are hanging out in comfy JKs, that's your problem. But if the ultimate goal is just to have a capable multi-purpose rig, I'd go with one of the suggested options above and focus on improving driving skills.
 
Bebop said:
Everyone said it already, but I believe your chassis has no provision for any kind of suspension mounts. That's the main drawback to your design.

If I were you, I'd engineer and draft the suspension first then position the drivetrain, then the passengers and tubes. You will quickly realize that there is a reason why none of the "good" full tube buggies look like your design.

If you want to overland in a buggy with an engine screaming at 3000rpm at 55mph, while your friends are hanging out in comfy JKs, that's your problem. But if the ultimate goal is just to have a capable multi-purpose rig, I'd go with one of the suggested options above and focus on improving driving skills.
Click to expand...

i think the suspension issue could be fairly easily resolved by simply building down from the current "floor"

consider the current floor as the max top for the upper link mounting point, then drop about 6" or whatever you need to make lower control arm mounts. put the suspension where it wants to be to keep the lower links nearly flat at ride height. 30" long would probably be plenty to save some space in the cab.

once that base is added on there, cut out your current "floor" and see how low you can model the drivetrain into the new suspension mount subframe, there is probably a good bit of gain to be had there. if you want more interior space, you can keep the seat mounts high as well. you may be limited on how low you can drop the drivetrain though to keep the axle out of the oil pan.

i think you would be better served by giving up some "low COG" by having the front axle under or near the crank pulley though. shortening the wheelbase overall will significantly help turning and stability.

then add more trunk space, cut off the cage/passanger area, redraw the A-C roofline and fill in with bracing
 
I think "Overcrawling" is really just trail wheeling. They're doing similar stuff in the mountain bike world, down country and enduro are ultimately just trail riding.

IMO, 37s, Dana 44, and Chevy 350s are antiquated. Going 40s, Dana 60, and 5.3 is nearly no additional cost in the scheme of things and is much more futureproof.

My rig has a bunch of rear overhang, I hit it on stuff. The new build will also have a bunch of rear overhang, because beer takes up a bunch of space.
 
My Jeep is at 122" wheelbase, 18" belly height, on 42's, 59" wide body, and it wheels like a bus. I'm not mad, that's just how it is (my prior rig was a comp crawler, 106" wheelbase, 42's, 51" body wide body). Rear steer either way, whole lot of similarities between them. I do think 22" belly on 37's is pretty tall, but at 130" wheelbase, not out of line. But a 130" wheelbase is huge. If your roof height is 75" with a 22" belly, your chassis is 6" shorter vertically than mine, my roof is 77". I could lower my roof by probably that much and still fit height-wise, but I ran with what I have in no small part to match Jeep hood/cowl/windshield/grille dimensions.

I'll also +1 on the fuel/spare/cargo questions, it looks like you can fit a tank or cargo, but not both. If you choose to go belly tank... well... I'm in the process of trying to make that work. I do not recommend. I wanted specifically to be able to fit camping gear for 3-4 for a weekend, minimum 20 gallon tank, and not have to load onto the roof to do it. I don't know if you can presently match those; I realize they're my goals not yours, but it sure sounds like you're after a lot of the same as I was when I built mine. I don't care about a spare, I run steel beadlocks and liners, so I can run on a flat primary tire for a long time, and on a rim for a good way too if I waste a liner, but I'd had enough of roof-loading "Clampetts go to Moab"-style on my buggy.
 
HYDRODYNAMIC said:
Take the rear of the cage out further back, before it runs downhill. You want to protect the gear you put back there and the passengers heads. I see so many people run the tubes down quickly for looks and then once loaded out for race or camping all the extra gear and parts are past the tubes and it doesn't look cool or practical anymore.
Click to expand...

I ended up de-cool-ifying my Jeep with just this point. I had it drawn up as a fastback, it looked so cool on the computer screen, I really wanted to build it as a fastback, my kids liked the fastback look, I liked it, and I was pondering the camping gear in it, the soft-top bow over the back anyway if I did a wagon top, as long as it was being driven around with no top and no gear in it it'd look so sweet... and I listened to my wife, who also liked the fastback look, but said "think of where you're going to put sleeping bags and a tent", and I built the wagon cage. And the first event out, I smacked it in the very back top-left corner on a rock wall, knocked off a bunch of paint, scratched the cage up. Still happy I did the uncool wagon cage. Much more practical for a camping rig. And Home Depot has more rattlecans of cage paint, I specifically rattlecanned the chassis for that reason.
 
So many great responses here to my post, it looks like I will be reworking the bottom area as I finish up the suspension, Also sounds like maybe re-evaluating axle placement, and cargo area...
I appreciate everybody’s input and may contact some of you directly with some additional.
I continue to welcome ideas and suggestions.
I will also post some pictures/ideas as I make a few chages, of course it will be a couple of days before I get a chance to work on the design more... dang work is getting in the way this week
 
Here are some screen captures with some of the updates you folks recommended. Also added 4-link's represented in drawing without 4-link mounts or link ends
Wheel Base: 125"
Belly Height: 20"
Over All Length: 157"
Over All Height: 76" (I think I stated wrong height in earlier comment)
Floor to ceiling: 48"
Still drawn with 37" (likely will run 40's with next set of tires)
Also included is the 4link calk screen shot. (do the numbers look acceptable?)


Thank you in advance for your comments

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BioHazard2222 said:
Here are some screen captures with some of the updates you folks recommended. Also added 4-link's represented in drawing without 4-link mounts or link ends
Wheel Base: 125"
Belly Height: 20"
Over All Length: 157"
Over All Height: 76" (I think I stated wrong height in earlier comment)
Floor to ceiling: 48"
Still drawn with 37" (likely will run 40's with next set of tires)
Also included is the 4link calk screen shot. (do the numbers look acceptable?)


Thank you in advance for your comments
Click to expand...

Regarding the link numbers, sorry to do this to you, but do you mind using version 6.1? https://drive.google.com/file/d/137uQlrHcfcW3S6E4BiWtB0JDc9DB8ArH/view?usp=sharing
There was a pretty big mistake in a few of the equations that got patched out.

The rear anti numbers seem like they may be a bit high. You may want to flatten that upper link some. Also run the numbers with 100% rear drive bias because of weight shift when climbing. It may be a little tricky to put the rod ends directly at the nodes, you may want to offset them some. Also in the rear, you don't need that much convergence angle. The lower the combined total, the less articulation steer there will be.

The suspension as a whole will have some oversteer tendency. Just something to be aware of.
 
Treefrog said:
Regarding the link numbers, sorry to do this to you, but do you mind using version 6.1? https://drive.google.com/file/d/137uQlrHcfcW3S6E4BiWtB0JDc9DB8ArH/view?usp=sharing
There was a pretty big mistake in a few of the equations that got patched out.

The rear anti numbers seem like they may be a bit high. You may want to flatten that upper link some. Also run the numbers with 100% rear drive bias because of weight shift when climbing. It may be a little tricky to put the rod ends directly at the nodes, you may want to offset them some. Also in the rear, you don't need that much convergence angle. The lower the combined total, the less articulation steer there will be.

The suspension as a whole will have some oversteer tendency. Just something to be aware of.
Click to expand...

Thank you, I have downloaded 6.1 and entered in the values, now I will work on getting the rear anti numbers down, by setting the rear bias to 100%, the dropped the Antilift way down, so ill play with the numbers to see if I can get the antisquat down too.
The issue you are referring too on the convergence angel is on the rear upper links? they don't need to be that close at axle end?

Also, can you tell me, the link length in the calc just represents pivot to pivot correct? meaning, it represents the length of the joint as well, so you just need to make sure you deduct joint length from link (eye to eye) length to get actual link length
 
BioHazard2222 said:
Thank you, I have downloaded 6.1 and entered in the values, now I will work on getting the rear anti numbers down, by setting the rear bias to 100%, the dropped the Antilift way down, so ill play with the numbers to see if I can get the antisquat down too.
The issue you are referring too on the convergence angel is on the rear upper links? they don't need to be that close at axle end?

Also, can you tell me, the link length in the calc just represents pivot to pivot correct? meaning, it represents the length of the joint as well, so you just need to make sure you deduct joint length from link (eye to eye) length to get actual link length
Click to expand...

Technically there is no anti-lift in the front since it doesn't have any force with 100% rear bias. That's something I forgot to have a check for in the calc.

The rear links in general. I believe that the rule of thumb is 40* combined upper and lower to keep the axle from shifting side to side, but a bit more doesn't hurt. You can play with both to get the roll slope behavior you want. So yes, they don't need to be that close.

Yes, the link length is pivot to pivot.
 
Treefrog said:
The rear links in general. I believe that the rule of thumb is 40* combined upper and lower to keep the axle from shifting side to side, but a bit more doesn't hurt. You can play with both to get the roll slope behavior you want. So yes, they don't need to be that close.
.
Click to expand...
Thank you TreeFrog.

I have updates the Calc and adjusted the links where ends could be added and I THINK maybe have numbers looking OK?
I'm not 100% sure what the "Good Numbers" should be on all the different areas. Does this look reasonable?

Also, any input on frame overall design is appreciate

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Screenshot 4-Link Calc-V2.jpg


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