Relapse Buggy Build Thread

[spidr]

Originally I wasnt going to create a thread until we started cutting tube. But Ive got a lot of Cad cartoons and thoughts and processes to share, maybe I'll learn something along the way here from someone smarter than me.

For those that dont know me.....I owned a shop for around 10 years. I can build stuff all right, but I'm a horrible business man, and even worse at picking wives. I've basically stepped away from offroading other than working behind the scenes with a friend of mine, he'll come back into the story in a minute.
I had dreams of building production buggy chassis. Who doesnt right. I had a chassis that worked in my opinion. It just never came to fruition. The last thing I built for myself about 7 years ago was a single seater, rear engine IFS buggy I called 8ball. For the brief time I got to drive it, it changed my entire perspective on buggies. It was ugly, not super comfortable, and I skipped on some very important details finishing it up. eventually my life fell apart, I lost everything, and I gave up.

When my Shop shut down, my good friend opened Backdoor Fab. He recovered all my files, my thoughts and creations in digital form and asked me to help. So for the last 7 years ago I've pitched in and contributed my skill. Turns out he had a similar dream to me, and now about 12 years later, everything has come full cycle and we're working on a production style chassis again. but with the benefits of 10 more years of experience. Hes bought a Tube dragon, and the new plan has centered around creating a chassis we can cut on the dragon with minimal bends. It's been reduced to 2. I started with a Ultra 4 race style chassis. 2" DOM, with flexibility of intent. He wants a traditional front engine solid axle, I want another rear engine IFS. So we've finally nailed down most of the details. When he sells a chassis, it will be able to come with brackets, panels, motormounts, almost everythign to assemble it and go wheeling, for those that dont want to figure it out themselves. We've since spoken about a Trail style chassis. 1.75" tube, far less feet of material, lighter weight, its smaller, and wont fit everything that a good Ultra 4 racer would need, but I dont think most people need bypasses, air bumps, and all of the high dollar stuff to keep up with the Joneses.
Personally, when I managed to put my life back together i moved to the end of the world. A tiny village on a deep water ocean inlet, we live at the end of a 62km logging road, that most days you're thankful for AWD, and on bad days its 4wd and chains only. On the worst days, we've been without power for a week, and the road was impassable. One of the benefits though, the roads in our village are listed as trails, our "highway" into town is an off highway logging road, so we can drive anything with an offroad plate in town, out of town, and all the way to the next town. What I want is a bigger side by side. So what I'm building is what this thread is about. My next buggy will be similar, a race chassis, but with portals, running Inner Cs I've designed, attached to a 9" housing of my own design. This one will be much more budget friendly.
Now I have much more work into the race chassis than I do this one. It was my focus on and off for a couple of years. A lot will cross over and i'll show it off in good time.

This thread is going to focus on my Relapse buggy. I'll make another thread for my buddies version. And when I build the next ones I'll share that too. Who doesnt love internet attention

So after all that.......I present to you my partially finished in Cad Relapse.

 

[spidr]

Now to step backwards a little, the chassis are very similar. I settled one style we both liked. I've probably rendered a thousand chassis in the last 15 years. Beauty of cad is I can build it over and over again and dont have to spend the pennies I have to my name. But these im especially proud of.
Pictures show the more than I can explain. My chassis will be 50" wide, its simplistic. I'll add a few more tubes when it goes together, but the base chassis wont have them. Too many variables, and it saves everyone money to start with the basics and not undo work down the road.

 

[spidr]

So since I wanted IFS, settling on a Differential was important. And Budget is even more important.
My last buggy was based around a TTB50 center and stubs, this one I've setted on the 9.75" rear from a 2003-05 Expedition. THey're cheap, narrow, and the CV shafts are under $100 each brand new
Bonus for me, Offroad CNC Cad file sharing group on Facebook had models for both.
The diff cover mount leaves it off center. The shafts arent equal length, the pinion must be centered in the truck.
Whats nice about it though is that I can build a new cover with my own mounts. I'm not a fan of clamshell diffs, so this one is a pretty easy winner for me.

 

[spidr]

Since I had a chunk, it was time for some math.
I'll break down how I made this work, to the best of my understanding after years of pretending like I know a little bit.
If we draw an imaginary line from balljoint, to frame bushings, and off into space, the point that upper and lower arms converge should also be the point that the shaft converges, and for that matter steering. The math for the shaft is the same for tie rod to eliminate bump steer.
First thing was to make a 2 dimensional drawing to lay all that out. If anyone isnt clear whats going on there, let me know, I'll try my best to break it down.

From there I wanted to verify my work. "cycle" the 2d suspension and make sure that the numbers work. The white dots represent the center of the CV shaft. by cycling it, I can verufy that it worked, Pictures below show the differance in shaft length. and that plung was reduced to 0.04" across 21" of travel. I'd say I'm doing all right. Its already better than my last buggy.

And the last piece of the puzzle was to sort out steering arm location. I want the steering in the front. If I stuff it into a tree at speed, a front tie rod is going to try to stretch. If it was behind the knuckle it would be in compression and risk bending. I'm not planning for big tires, but I'll likely drive it fast and jump ditches. To decide where to put it, we refer back to ackerman geometry.
Drawing a line from the center of the pivot, in my case I'm running it at the same hieght as the CV, If I run that line to the center of the rear axle, my outer TRE needs to land on that line. Behind the axle it would be narrower than my Ball joints, in front, it would be wider. And if I'm designing to to be right, its entirely dependant on wheelbase. Only takes a minute to make sure its right. Mine is designed specifically for this buggy.

With those points, I could design knuckles. Which is whats pictured. My last buggy I used a 6" tube as a starting point. This time, I'm going sheet metal. I could have gone shorter. The reason my knuckle is so tall is partially to get my arm angles where I want them to control camber change through travel, but even more than that, to reduce my scrub radius to zero, on a zero offset wheel. On a 17x9, that would be a 4.5" backspace wheel, I'm trying very hard to hit all of the important improvements I wanted after my last buggy, I think its going to be a huge improvement. and somethign most buggies dont have, with deep backspacing so clear everything. wheels get a deeper offset and so much energy is waster dragging a tire instead of purely steering it. If this was a hardcore rock crawler, it could maybe help me. But for my use, and the fact that I'm planning rear steer, this is the best I can do.

 

[spidr]

Having a knuckle designed gets me where I am today. It allowed me to lay out A arms. Now my arms will likely change. I'll build high clearnace lowers, a mix of plate and tube, but these make it real easy to cycle everythign and check my clearnaces, and confirm I'm headed in the right direction. The buggy is sitting on 37" Krawlers in the rendering. I'm not planning anything bigger than 40s. I do a lot of exploring but I've reached the end of where my Silverado will take me. Theres some real good rock up here, and what looks like hundreds of miles of trail potential through the trees. I'm more "overlanding" without all the body to smash up. Honestly, I'm stupid and I'll roll it and smash things up, a simple SUV would get trashed in a weekend, and for the most part I wont be more than an hour from home. Until I have a second buggy up here to recover me, I'll have to play it safe. I dont have enough friends to count on anyone coming to get me.

I wanted to flex the suspension and make sure I was still tracking well. I went to a point I think the CV will probably be at it max operating angles. I could be over cycling. And I might have to spring for some bling to make it hold up. But I'm pretty happy with the numbers right now. Camber change is what I wanted. Have I said I like where this is going?

 

[spidr]

Now I could leave upper and lower arms parallel. But I wanted the castor gain at bump. Add some stability for when I get a little rowdy and air it out, It'll happen, as I've mentioned, I'm stupid
Now I model In Rhino. I really should learn more about solidworks, so I can set restraints and cycle things. But I'm comfortable where I am, so sadly cycling suspension is a really complicated procedure. Its not perfect. But I've got it close.
Measuring shaft length at ride height and counting on it being approximately shortest shaft length
Increases .05" to bump, and .982 to full droop. That means that I'm using about an inch of plunge in my shaft. Im might be able to tune it better, but honestly I think the shaft will take that, and I probably cant cycle it quite as far as I have it rendered anyways. Since it gets the worst at droop, I'll just strap it where it becomes too much.
Upper Arms angled 5 degrees, Gives me a caster change from 5.73 at full droop, to 12.81 at full bump. The model is set at 8.64* at ride height.
I'm happy with the caster change through travel, but the number overall is too high, If I align it to 5 at ride height, it would be around 2 degrees at droop, and around 9 stuffed. and those are numbers I would be happy with,
I was mechanic once upon a time, and have done maybe thousands of alignments. We dont build a lot of control into our suspensions, I want to make sure I can dial this in. I cant explain why a scout is happy at zero degrees of castor, a typical Tacoma with a lift kit is around 2 degrees, and most of what I build is 5 to 7, but I know what I want to see. And if I can dial it in at all, why not. So I designed an upper arm mount to accomadate.
Toe can be tuned like any other vehicle. Camber can be dialed in by spinning the Heim joints that live as ball joints. And castor the way I have it designed can be set where i see fit purely by sliding front to rear. If I'm worried about it slipped, I can build a locking plate like many upper arms have from the factory. Set it, measure it, and cut a plate to suit, then lock it down. If i want to change it. I can.
And its far from done. No sense in gusseting a model before its final.

 

[spidr]

I've spent a lot of nights up late. Sometimes all night. I turn back to the computer when I cant go do anything else.
So I figured I'd see what it looks like slammed, Its always a cool picture. I can live with this.

 

[spidr]

And that leaves us where I am today. Mostly anyways. I have an upside down SD axle in the rear of the model. If I have to run an offset diff, why not use something production, I can get a complete front to use for a couple hundred bucks lately, cheaper than even buying custom length full floater shafts, before i recenter the diff.
And for what I'm doing, it will work well. I'm diving into the Links now to get them dialed in.
When I lost my shop I was working on a K5. 5 ton axles, cantilever coilovers on full floater hubs so I could run a sway bar side to side. It was some high tech ghetto fab, Id like to use some of the ideas on this one. I have no interest in the coilovers sitting way above the hood panel, I'd rather have them where I can mess with ratios and tuck the expensive bits out of harms way. Maybe even just use coils. Or for that matter maybe I'll use leaf springs again. That was one of the things that worked relatively well on the last buggy,.
I've spent most of my own time in the last few years working on my hot rods. I've designed a race style pedal box, individual masters, with throttle linkage built in, I'm about to be casting my own custom stainless framed steering wheels. Along the way I built a monster english wheel, and bead roller, so why not make this thing cool inside. I have a ton of fun moving metal. Dashes dont need to be flat and boring. Those southern builders have the right idea. Why not an offroad hotrod.

But thats down the road. Me And Dustin have discussed getting these going in the next few weeks. Strike while the iron is hot and all that stuff.
We're both excited about these right now, so its the right time to get into them, before we perhaps focus on something else for a while. So my hope is that within the month I've got somethign a little more real to post here. But until then, I'm guessing there should be a few people interested in whats going on. And once I get making sparks, I'm not sure I'll be bothered explaining everything. My attention span slips, like a squirrel on crystal meth.
I'm off to start laying in some off the rear attaching points now.

 

[The Freeak]

Hey, welcome back!
Plans look cool!

 

[Weasel]

Cool! I'm a nerd for CAD drawings. Haven't had time to mess with any of that recently.

 

[spidr]

Hey, welcome back!
Plans look cool!

I've had a long time to stew on this one. It should be fun.

 

[spidr]

Cool! I'm a nerd for CAD drawings. Haven't had time to mess with any of that recently.

I use it pretty much daily. I'm all self taught, but when I'm not programming for my buddies shop, I'm generally working on something for the hotrod, its just too easy to model everything as I go, so that I can add brackets when I need them. Pretty much takes cardboard out of the equation

 

[chaplinfj60]

very cool very cool, so where are you located that you have a 60km drive slash road wow...

 

[posford]

8ball was 7 years ago?? Holy fuck.

Looking forward to this, been following you on the insta and youtubes

 

[Tech Tim]

Good to see you still at it spidr! Looking forward to this build.

 

[mobil1syn]

I have no interest in the coilovers sitting way above the hood panel, I'd rather have them where I can mess with ratios and tuck the expensive bits out of harms way. Maybe even just use coils. Or for that matter maybe I'll use leaf springs again. That was one of the things that worked relatively well on the last buggy,.

what about airbags?

 

[posford]

what about airbags?

Stupid thought, a lot of my buddies have gotten away from using airbags on their trucks, and went to Timbren springs. I wonder how those perform compared to an airbag

 

[spidr]

very cool very cool, so where are you located that you have a 60km drive slash road wow...

West coast of Vancouver Island. Tiny fishing village that used to be a booming mill town.

8ball was 7 years ago?? Holy fuck.

Looking forward to this, been following you on the insta and youtubes

Yeah. Time flies man. And thanks

Good to see you still at it spidr! Looking forward to this build.

Thanks Tim.

what about airbags?

I've got vehicles I'm finishing the bags on right now. I want to be able to tune it, changing pressures messes with spring rates, it's bulky and unpredictable. Ive spent so long messing with geometry that the idea of not being able to drive it to its potential just doesn't make any sense.

Stupid thought, a lot of my buddies have gotten away from using airbags on their trucks, and went to Timbren springs. I wonder how those perform compared to an airbag

I've thought about that, I used timbrens as bumps on the upper arm last time. Super impressed with how well they work, and If I can find another affordable set I'll probably do it again. But for the travel I'm shooting for I'd need to run them in a 4 or 5:1 ratio, which feels super excessive, and I'm not sure they have a high enough spring rate to support that.
I've got a little time to sort out what I want to run, I've got some pictures in my head and a direction I want to head, it may just come down to what I find on the market for a decent price.

 

[PurfsMcGurfs]

This looks rad man. Cant wait to see it get going.

 

[chaplinfj60]

BC is awesome in the late 90s we surrey for day trip. nice area... cool man...

 

[pennsylvaniaboy]

Looks impressive. It also looks like the chassis could be used with front motor and a solid axle up front?

 

[spidr]

Looks impressive. It also looks like the chassis could be used with front motor and a solid axle up front?

Yup. The other one that's getting built at the same time is going that route.

 

[spidr]

This is the "race" version of the chassis I've been working on much longer. The point from the beginning was that we wanted a chassis that we could use for front or rear engine relatively easily, and IFS or solid axle. My chassis will purely be getting a Double triangulated 4 link, the solid axle chassis will be getting trailing arm rear, double triangulated front. One day if we do sell a few chassis, this will simplify being able to provide brackets, mounts and panels, but right now, if we only ever produce our own, then I still get to let my ego revell in the fact that I made it possible.
The CNC press brake should show up soon, which means we can start smashing plate into the shape of an axle housing, and form some inner Cs

 

[HYDRODYNAMIC]

Looks super cool! But unless your sitting on phone books you're not going to see over the hood. Figure out how to drop the hood so you can see over it. If your are 6'-15" then figure out how a short person will see over it.

 

[spidr]

Looks super cool! But unless your sitting on phone books you're not going to see over the hood. Figure out how to drop the hood so you can see over it. If your are 6'-15" then figure out how a short person will see over it.

Not going to lie. Style matters to me on this one. Lets not kid oursleves. The 8ball buggy was ugly.
But for the sake of argument, I dropped a model of me in (pardon the crude nature, i never figured out how to model me better), measured line of site, and then did the same for a silverado, becuase I drive one, a camaro, to give an actual cars perspective, and a super duty, because it seems like everyone drives one nowadays. And of course those lines get worse for every leveling kit, lift kit, tire size upgrade, or bed with 1500lbs of fire wood in it.
I'm not saying its great. But in my case. I'm going out of my way to run little to no firewall in the front, and will have visibility below the "hood" line, and while i will have a blind spot in the middle of the measurement, I'll be able to see close. With an engine up front, That hood isnt actually too bad, and in a conventional buggy, I've built a few that had a hood essentially straight out from the cowl bar, and the blind spot would be the same, the high spot on the hood would be equal to the end of an actual hood.
I grabbed a picture of a random buggy off google images too, I guessed the wheelbase is around 112, because that still made the tires seem a little small, but included it as well since it had a drive in it and gave me a reaslistic line of site im not guesstimating on.

All of that being said. If i'm calling this the trail chassis, and the other one the race chassis, the race chassis it bigger in every concievable way, including head room. I'm building the smaller chassis because Its cheaper, smaller,.lighter and I want to see it happen. All the excuses aside, thats why I'm building one before anyone even gets the chance, because real life trumps CAD every day of the week except Saturday night, and if it isnt just right, I can change it. The buggy is designed so that the roof is easy to change, it can be cut down to cowl and belt bars and replaced above that, and I can redraw it a few inches higher if I need to. I'd like it to work this way if possible though.

And I hope that it doesnt sound like I'm shooting you down. But i have put some thought into it. The other chassis visibiltiy and head room both improve. This one it isnt my highest priorty, just in case I havent maken that dreadfully clear.. And I do enjoy the conversation.

 

[YotaAtieToo]

I've always enjoyed your "all in and then some on every aspect but budget" approach. Will be following this.

I'm not sure I follow the logic behind trying to design a chassis that works with front engine and solid axle, but also a rear engine and ifs though. Unless I missed something, it just seems like it would have to many compromises.

 

[spidr]

I've always enjoyed your "all in and then some on every aspect but budget" approach. Will be following this.

I'm not sure I follow the logic behind trying to design a chassis that works with front engine and solid axle, but also a rear engine and ifs though. Unless I missed something, it just seems like it would have to many compromises.

Possibly. In reality this chassis shares quite a few similarities dimensionally between both of these buggies I built.
I realize that if we burn a few of these, that virtually none will be rear engine, even fewer will be IFS. But I haven't found anything specifically shortcoming about using this chassis for the setup that I want. If I had purely posted drawings of a solid axle chassis, it never would have been considered to run it this way. The changes I needed to make was minor, watching where the X in the back landed to allow for the engine to reach through the rear firewall. Making sure I have enough "frame rail" on both ends to contain a drivetrain. And for the Ifs, making sure I had square mounting points to hang the entire subframe. If you can see something I shorted in order to make sure it worked both ways, my ears are open, but I don't think that one is sacrificed for the other here.
The advantages to making sure it did though, where high. Every suspension bracket, panel, engine mount, it's all universal. If we burn 10 of these this year, I could pre cut a builder's kit to go with it. Designing it with only 2 bends, makes replacement tubes easy. I can label every single bar and just hit print on B17 and E3, the roof can be cut back to dash height and fully replaced, thus chassis is just the evolution of designing it over and over again for close to 15 years.

 

[YotaAtieToo]

Makes more sense. Basically it's designed to be a solid axle front engine, but you made minor changes to fit your needs.

Carry on

 

[Pickuptrucker]

Can’t wait to see it start coming together

 

[HYDRODYNAMIC]

Looks like you will need CV front and rear on the T case with the rear being a 2 piece with a mid shaft so the rear driveline joints can cancel out. The front IFS pinion can be aligned with drive line so only the CV sees angle.