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SteelRat

Post Apocalyptic Bitsa Beetle

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A month or so ago when I was clearing my loft out to sell a load of my RC gear that had sat around for about 10 years gathering dust, I never thought in a million years I'd be sat here writing a build thread for a new project!  "From little acorns... " though as the saying goes.  This project is really the product of a whole load of inspiration and ideas that have been spinning around in my head since watching some incredibly talented people put stuff together both in here and on YouTube and is really an evolution of an old car of mine, the "Bitsa Beetle", so called because it is a mish mash of various ORV based cars.  Gearbox of a King Blackfoot.  Front axles of a Frog.  Front suspension arm geometry of a Monster Beetle and the standard ladder frame that supports all generations of the ORV.

For a little while the biggest Bug bear (pun intended) that I've struggled to get around was the extra width provided by the KBF gearbox.  Obviously, it's designed as a monster truck so when you put "ordinary" wheels on it (I'm using touring car wheels with Sand Scorcher rear tyres) it looks a bit.. silly.  I'd tried to modify the arms from existing cars, or find another way to reduce that rear track width, but nothing was really coming together.  And then I discovered that the prices of 3D printers had come down a whole lot in the last few years and wondered if this might be the direction I could go in to solve that particular problem.  After some great advice by a number of people, I took the plunge with a printer (a Creality Ender 3 Pro) and have begun work.

The overall direction of this build is going to be post apoc themed car specifically based around the Fallout games.  I actually dabbled in a bit of cosplay a few years back, and made a costume of the NCR Veteran Ranger from Fallout New Vegas, so the idea here is to have a ranger as the driver, cut the roof off of a Blitzer beetle shell, build a roll cage to mount roof bits on (out of soldered brass tube, not 3D printed!).  This is certainly an ambitious project from my point of view as I've never even attempted anything like this before, so we'll see how things go!

To start then, this is  one of the pics of the Bitsa in its original guise.  The rear wheels using buggy wheels with a decent negative offset certainly helped rear track issue, but I wanted to something a bit more scale.  The shell with Willy at the helm is what became the shell for my post apoc Sand Scorcher that I posted in my showroom a while back.  I've got another beater Beetle shell that will be used for this.

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Next, the first few prototypes to get the narrowed track sorted out and first draft of the rear shock tower.  These parts are printed in PLA+ - I've got a roll of black filament coming soon so that the final parts are a more sensible colour!  I've included the original parts so that you can see how much of a size difference we're undertaking.
IMG_20211205_133305.thumb.jpg.195abe2259e77a434dbdf759f5753109.jpg

The first assembly is as below, and we already have some challenges to deal with:

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So... issues:

1 - most obviously, the length of the arms isn't quite right, so the geometry is off leading to that positive camber on the rear wheel.  Getting the lengths right using my metal rule even with everything stripped down was rather tricky and nowhere near accurate enough.  I've invested in a set of digital calipers so that I can get the measurements a bit more dialled in and we can resolve that.

2 - the narrower track and therefore shorter top arm means that not only do I need shorter suspension, but the rear wheel knuckle is fouling against the motor on full compression.  This will mean that both arms will need to be extended a notch (probably only a couple of mm).

3 - The shock tower came out pretty well (although I did have some issue with removing the supports cleanly, but I'm going to need to move the top mount holes for the suspension and also extend out where they attach to the shock tower body so that there's less flex, more strength and so that they line up properly with the lower mounts on the upper arm.

4 - Initially, I had the idea to include the body mounts as part of the shock tower, but now they've printed out, they're WAY too flimsy.  When it's finished this car is probably more likely to spend most of it's life on a shelf, but I do intend to run it occasionally.  Now I think about it, that part of the roof isn't going to be there on the finished car anyway, so they're pretty obsolete!

I think the next steps before we go any further is to sit down with a pencil and pad and sketch out some of this in more detail.  This initial discovery phase in getting used to the software to build the printed parts, and of course get acquainted with the printer has definitely been fun but as the multiple P's say, "Proper Planning Prevents Pee Poor Performance"!

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I think you'll find the upper and lower arms need to be parallel which could be achieved by a lowering of the outer top mount on the hub which might help somewhat and also reduce the fouling on the motor can

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Can you put longer shocks on the other side of the tower to the lower arm? Lower arm might take the load better?

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Fallout NV is one of the best games ever made, so I'm down with this.

I'm trying to think of a good NV themed name - Whiskey Rose could be a good un,

 

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What a cool project to take on, I will be following with interest.

I think over this holiday I need to look again at 3D printers. In a previous life I was a 3d modeller (software not physical) but had ruled out 3D printing but the more I see of what can be relatively easily achieved the more it gets me interested. Plus I love the idea of being able to prototype fairly quickly.

Good luck!

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10 hours ago, KEV THE REV said:

I think you'll find the upper and lower arms need to be parallel which could be achieved by a lowering of the outer top mount on the hub which might help somewhat and also reduce the fouling on the motor can

Yes, they do need to be parallel, but there isn't any scope at all to modify the hub (and to be honest, I'm not really sure I want to do that if I can get away with it.)  Really the only way to achieve that is by making sure that they're the correct length.  If I measure what the distance needs to be between the two holes on the lower arm, I can calculate what the length of the top arm needs to be to make it parallel.  I was thinking last night that as I have a 3D CAD program to model the bits I want to print, I could actually use it to model the whole gearbox casing if it came to it, and that isn't as difficult as it sounds, believe it or not.

 

 

9 hours ago, Nobbi1977 said:

Can you put longer shocks on the other side of the tower to the lower arm? Lower arm might take the load better?

That is a really good idea!  The only problem with that would be that the coil would then foul on the upper arm.  I've thought about this further and because I'm going make this a convertible beetle with an exposed roll cage, that shock tower is going to be more or less obsolete in that guise anyway, and isn't going to look very good on the final car.  I'm going to look at a way to incorporate the fixings that mount the cage to the body of the car as a way to mount the shocks.  With that, could be the possibility of moving the top of the shock mount forward which would get over that problem.  Definitely food for thought though!

 

9 hours ago, Nikko85 said:

Fallout NV is one of the best games ever made, so I'm down with this.

I'm trying to think of a good NV themed name - Whiskey Rose could be a good un,

 

Haha.. that's a really good name - and to be honest I hadn't thought what I might call it.  "Benny's Basher" might not be very popular.

 

 

7 hours ago, GeeWings said:

What a cool project to take on, I will be following with interest.

I think over this holiday I need to look again at 3D printers. In a previous life I was a 3d modeller (software not physical) but had ruled out 3D printing but the more I see of what can be relatively easily achieved the more it gets me interested. Plus I love the idea of being able to prototype fairly quickly.

Good luck!

Thank you!  What 3D software were you using?  I'm using the free version of Fusion 360 by AutoDesk, having previously done a little work in Blender, but I'm by no means an expert in either.  I would heartily recommend looking at 3D printing again, because the prices have absolutely plummeted in recent years.  I've been looking at them for a little while, but I always came back to, "do I really want to spent £6-700 on one" - which is the sort of money I was looking at when I'd considered it previously.  Now that figure is £2-300 so a whole lot more viable.

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@SteelRatI mainly used Lightwave and Maya but could also work my way around 3D Studio Max and Cinema 4D. Blender and other software were only just appearing as I was leaving the industry. I’ve also used AutoCAD a bit.

The issue will be having enough time to get my head around learning software AND the printing. I do have a contact nearby who has all sorts of 3D printing gear so I could just create the models and get her to do the printing.

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Honestly, if you've already had some experience with 3D modelling, you'll pick up the software side really quickly.  Fusion360 has its quirks, but it's really easy to get to grips with, certainly for generating relatively simple pieces like I have above.  Like most design work, I've found that the real secret is being able to identify the simple shapes that make up a more complex whole.  F360s modular nature in terms of putting pieces together as a collection of "Components" that are those simple shapes make it pretty easy to build the design up.  This is why I'm considering using it to draw a CAD of the gearbox casing, and potentially even the whole model so that I know exactly how things are going to look before I start bringing it in to the real world, whether those pieces are going to be 3D printed or not.

In terms of the printing side of it, the biggest struggle I had was getting the bed levelling (which apparently a misnomer, and it's more accurate to refer to it as "tramming") - more particularly getting the distance between print head and bed right.  Too close and you don't get a clear print.. too far away insufficient adhesion to allow the printer to layer the print properly.  I found that the problems were really a combination of me working out the best method to do the adjustments, but more crucially the state of the printer when it left the factory.  I had to tighten some of the bolts on the bed runner bearings, to stop it wobbling and also completely remove and reseat the springs used to adjust the bed height, once I did that and the springs were sat properly, it actually wasn't that hard.  I've also bought a set of upgraded springs (only about £7) which are stronger and give greater range and control of the adjustment.

I'll definitely say that YouTube is your friend for both of these elements of the overall "discovery".. there's a ton of tutorials, reviews and what have you on all bits of the process, so you want be short of a good resource for help if you run in to problems.  It's worth it too.. it's so incredibly satisfying a process - on a personal note with lock downs and what have you, it's definitely lifted me out of a bit of a mental rut!

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3 hours ago, SteelRat said:

Really the only way to achieve that is by making sure that they're the correct length

And parallel , shortening or lengthening will not produce parallel . The distance between inner and out points top and bottom need to be similar . You can also use 3mm threaded rod as the upper wishbone , you don't need an actual made part , the rod can also be adjusted insitu (or use turnbuckles) The lower damper fixing point could be made in the lower arm and use a longer damper . The damper top mount can be spaced out using bushing to prevent foulling on the rear bulkhead

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That's a good point re the upper wishbone and using metal rod.. I had tried that initially with some rod ends I have for crawler links, but the body of the rod end itself was too long pushing it out further than I wanted.  May have to look at other options.

I don't understand about the length of the part not being relevant though.. surely if the  the top arm is too long in relation to the lower one, it's going to increase the camber of the wheel, assuming you use the same mount points on the gearbox casing and wheel hub?  I mean the ratio of lengths between the existing parts make for parallel upper and lower arms and so the only other variable that is in play is the lengths of the printed ones?

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The length of the upper rod is relevant,  so an adjustable upper arm is good to have to achieve the camber you want  , but in order for the hub to move in set camber motion the arms will need to be parallel to begin with otherwise the hub will move in and out at the top causing + / -ve camber changes . The wheel hub should move up and down with the suspension motion and remain constant in camber

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Thanks for the tips @SteelRat definitely worth exploring. Glad too that you seem to get so much enjoyment from it. 

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1 hour ago, KEV THE REV said:

The length of the upper rod is relevant,  so an adjustable upper arm is good to have to achieve the camber you want  , but in order for the hub to move in set camber motion the arms will need to be parallel to begin with otherwise the hub will move in and out at the top causing + / -ve camber changes . The wheel hub should move up and down with the suspension motion and remain constant in camber

Exactly.  The top arm as it stands at the moment is too long in relation to the positions of the holes on the hub and the length of the lower arm.  As the top of the hub is pivoted from the where it attaches to the lower one, it means that when it extends out depending on the length of the top arm, its trajectory is curved, not a straight line, that's why it's not parallel.  In order to prevent the fouling, I'll need to lengthen the top arm (probably only by a mm or two), and lengthen the lower arm so that it brings the hub to directly vertical.  To do that, I'll need to extend the lower arm by more than whatever I extend the upper one.

If I line up gearbox and hub on the bench so that the top of the hub doesn't foul the motor and measure between the two holes.  Make the top arm.  With the top arm in place make the same measurement for the lower arm, but that length will be greater due to the position and shape of the axle hub.  Also if I mount the top arm behind the fitting instead of in front of it as it is stock, I can then mount the longer suspension leg to the bottom arm and get around the problem of the coil fouling against the top one.

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Pity the motor is in the way or you could put a top arm on the other side of the upright. A threaded bar one would be thin and give clearance for a shock off the bottom arm. 

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2 hours ago, Nobbi1977 said:

Pity the motor is in the way or you could put a top arm on the other side of the upright. A threaded bar one would be thin and give clearance for a shock off the bottom arm. 

And that's exactly what I've done.. I'll post pics tomorrow.  I realised that the stock KBF has the upper arms on the front side anyway, so I'd not fitted it correctly in the first place.  The top of the upright / wheel hub / whatever it's blummin called still snags on the motor, but i don't think it'll be enough to cause a big problem, particularly as the springs on there at the moment are from a TA03, so quite stiff.  I have some softer ones and theres the option to fiddle around with the shock length.

Threaded rod a couple of crawler rod ends with the bottom of the shock between them mounted on the upper arm.  With all of that assembled, I now know that my bottom arm has to be 3 mm longer - who'd have thought it would have made that much difference - aaah the joys of suspension geometry.

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On 12/6/2021 at 11:36 AM, SteelRat said:

I don't understand about the length of the part not being relevant though.. 

I did something similar with a DT-02 front and have some pictures about the effect of arms being parallel or not.

 

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Update.. after a LOT of faff and hair pulling with my 3D printer, I've finally got it set up properly and printed out the lower suspension arms and modified shock tower.  Also put together some 3mm rod with rod ends to make the top arm and mount the suspension legs.  I'm pretty pleased with the result!

* Narrowed the rear track successfully with very little camber on the rear wheels, although still does snag at maximum compression.  Room for tweakage though.

* The modified shock tower doesnt need to be anywhere near as tall as the stock KBF and the body will be mounted on a brass tube / steel rod cage that is fixed to the chassis.

* I'm in two minds whether or not to make it a convertible as I originally intended.  The ORV chassis doesn't lend itself very well to that configuration because of the big lump in the middle of it.  I have some ideas about though, so we'll see where that goes.

* The ground clearance and sag in the suspension I'll need to correct to lift and stiffen it a notch.  It just needs wider collars or longer springs.

Pics:
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IMG_20211211_115833.thumb.jpg.1186a39d0094a78b5c8ff1f78f42d63d.jpg

IMG_20211211_120053.jpg.d5d83e418661b105939755ebcb59383e.jpg
 

With the body just roughly laid on the chassis as is, I'm pretty pleased with where the rear wheels are.  Obviously it'll sit a little higher once it's done.

IMG_20211211_120144.jpg.fce98a67c12bcc8edfb6384a9fb3c623.jpg

 

Next steps are the cage.  Just waiting for the steel rod and brass tube to arrive, then it's drawing board and soldering iron time!

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