Potatocat's 6WD/6WS E-Raminator

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One more chassis related post as I am working on the body currently (but have nothing major to show for it):

These are the battery trays that I milled up from some reclaimed aluminum- specifically Apple Mac Pro cases that were discarded...

https://imgur.com/exIp1R1

https://imgur.com/SrFNHZj

Each of these particular two trays is setup to receive four 5000mAH packs:

https://imgur.com/jDIscJv

Both trays plus accessory 2S packs fit conveniently in a .50 cal ammo can, with part of the rubber seal cut out to provide efflux venting in case something really bad happens. All I cut out was a 2" portion of the seal to prevent the ammo can from turning into a pipe bomb. The can is stored with the vent facing a bag of sand in the basement.

https://imgur.com/8DmkCTx

Battery trays charged up, mounted, and immediately prior to connection into two parallel battery modules.

https://imgur.com/Wbo9tX3

Thanks for reading!
 
Behold one of the most ghetto and janky hot wire cutting stations there is out there... I took advantage of the space between shelves of a steel wire rack and used some particle board from some furniture about to be tossed out as the basis for my hot wire foam cutter.

https://imgur.com/xPeQ0iT

I am cutting foam sheet for making the plug used in making the body. I am going to make it basically in two sections - the cab and sleeper will be separately molded, and then fastened back together.

Slow and steady progress is happening with making the body plug. I am not going crazy with detailing, the goal is just to make things functional, and as I get comfortable working with fiberglass again I'll gain confidence in making more elaborate, non-squared off designs.

https://imgur.com/K6f3qSz

A few more tweaks with the chassis were also done, and some properly thick enough antisway bars were setup for the front and rear axles. The middle axle will retain its relatively soft antisway setting.

https://imgur.com/E74LF1t

Anyhow that's all I have for now. Thanks for reading!
 
Hi all, been pretty busy but still had some time to make continued adjustments and mods for the truck. Working on the body has been a slow process since I am still sanding and forming the plugs. The first layer of epoxy and fiberglass is on, but still sanding and Bondo'ing things up. Nothing really to show yet... but in other areas:

Stanchion grind plates:
I needed some grind plates for the bottom of the truck, mainly for peace of mind when loading it on my 1:1 car. I put some Ikea cutting boards I found in the house (which I would otherwise never use in favor of my old school butcher block) and put these to work.
https://imgur.com/RZj2J4V

https://imgur.com/3iQAZd9

Onboard Electronics:
A lot of hardening of the internal systems was done, setting up the electronics to be as bulletproof as possible and integrating it with my ghetto avionics system made of a Raspberry Pi and some Arduino Nano boards. The next revision will likely feature ESP32 instead but for now I am keeping with what I know. Two compute hubs exist- one is development and looks super hacked up while the production boards will look a lot more cleaned up, mounted on slides for fast removal. They will be electrically identical though.

Here is the kiddo helping my verify and test trainer mode.
https://imgur.com/ZpefbOe

Development board set installed onboard:
https://imgur.com/55xUUCL

A first revision of some of the baseline functionality provided by these boards can be seen here. You will want to turn on closed captioning to see the notes explaining what I am doing/showing.

Not shown are a bunch of sensors I also integrated and added that all make home runs back to the avionics hub. I wired up a bunch of thermistors to grab thermal data from the motor and ESC, a ferrite core sensor to get amperage from the ESC, along with a motor tachometer made from a Hall-effect sensor. This will be processed by the compute hub and sent back to a tablet mounted on the transmitter to see all this telemetry data, which also is recorded for analysis afterwards.
 
Thanks! I almost forgot some other updates of things that were going on recently...

Truck as a software platform:
With plugging in an auxiliary wall-wart AC power supply, I can power up the onboard electronics (minus servos) for software development purposes. I know there are turnkey options for doing this but I wanted to have some fun doing this from the ground up as a learning experience but also to tailor the software to my specific purposes.

https://imgur.com/YjMyeV7

The backend is Nginx and MySQL/MariaDB serving up web pages via Flask (Python) with pages built using the Angular framework. Its my first time working with Angular but I have experience with other frameworks like Twitter Bootstrap. I think that for fun the user interface will be similar to Android Auto or Apple CarPlay via a tablet screen.

I see no reason to reinvent the horse so I'm leaning heavily on those interface designs for me to send data from transmitter to vehicle, along with a virtual dashboard screen for viewing telemetry data. I'll show more of then when I actually have something to display. Right now everything has been dirty proof of concepts and test-level code.

Sticker Fun:
I had been experimenting with printing stickers out on photo paper, covering them with a topcoat of clear vinyl, and then applying them with a backing of spray adhesive. This was more fun than I expected...
https://imgur.com/slO3XKz

Alternately printing on sticker vinyl also worked well but it remains to be seen if the color will fade. These were also given a top cover of clear vinyl adhesive.
https://imgur.com/Zy0hb6q


Pneumatic tire conversion:

This one unlocks the only serious (or at least somewhat annoying) performance problem of the truck. I put inner tubes inside two of the tires, and will hopefully finish off the rest as soon as the tubes arrive. The reason for doing this is no fault of the original design. Because I am putting more ground pressure per tire down and they are carrying more weight than intended stock foams are just not going to cut it.

https://imgur.com/iyc8lMV

The secret for making this work is taking in some compromises. There is no inner tube that is going to fully fit inside this tire, short of rotocasting your own inner tubes. I decided to try out a hybrid approach of putting the inner tube inside the centerline of the tire, but surrounding the tube with cut tire foams just like a sandwich. Imagine a chocolate donut being the inner tube. Now make it a sandwich with two halves of a sliced bagel. Now put this whole thing inside a tire carcass and now you know how I made this fit. I used 11x6x5 inner tubes and they fit perfectly for what I needed.

https://imgur.com/yYXoC5N

Here you can see an inflation pressure holding test where the front axle has noticeable crowns on it, but the rear four tires are unmodified. I belted up the inside of the front tires using nothing other than fabric athletic tape. I think if that holds up well I will leave it alone, but if it doesn't then I will move to stainless steel wire mesh impregnated with rubber paste and stretch tape.

So far I can see that I have sacrificed a bit of braking distance when driving on very smooth indoor surfaces. I don't think this will translate into a performance hit when outside on pavement which will grip the tires more and just generally have more bite. I'm interested to see if any changes offroad occur.
 
Awesome work the entire way. Dedication and attention to details is on point. Inner tube idea is interesting, curious to see how it holds up. I'd think it could be weaker in my mind with 3 separate pieces in one tire, but not sure.
 
John Parks said:
Awesome work the entire way. Dedication and attention to details is on point. Inner tube idea is interesting, curious to see how it holds up. I'd think it could be weaker in my mind with 3 separate pieces in one tire, but not sure.
Click to expand...
Thanks man! I have not been able to drive the truck very hard but I had similar concerns as you. I'll share what I discovered so far:

  • I had similar worries about this setup being more delicate but the foams on the sides end up "armoring" the inner tube, effectively protecting the sidewalls and edges of the tire carcass from damage.
  • The worries I had about the tube "drifting" inside the tire and causing the valve to go out of alignment - like you see with underinflated bicycle tire tubes did not occur at all. I forgot that this is because the tire is effectively beadlocked, so the tube is not being "dragged" inside the wheel under hard acceleration for this to be a real problem.
  • The carcass of the PrimalRC tires are a bit on the thin side though, so I am looking at getting some 4" to 6" wide Kevlar fabric and some rubber adhesive plus some rubber backing to make a sleeve or sleeve. This is not really to inhibit pizza-cutter expansion, though it work for those spinning their tires fast enough. I am doing it mainly for better puncture resistance.
  • Balancing these tires gets to be a royal pain in the neck because of so many moving parts basically inside the tire making some extra wobble inevitable.
  • Inflation pressure in my case on a 10 x 6 x 4 inner tube works out to just be around 3 psi. Is enough to create a slight crown on the tire, but not enough to stretch out the tube so it "evens" out along the tire carcass. Unfortunately Primal never intended the tire to be used in this way so even if I had a fictional inner tube like a 10 x 8 x 4, the tire would likely still be lumpy.
Overall I am very happy with how this performs. I've only been able to drive the truck for very short periods but its a very clear difference especially on pavement. I sacrifice a bit of braking performance because of less contact patch on the ground, but driving performance is really noticeable.
On another side note, I have learned the hard way why there are not likely many outrunner sensored motors. I saw that my motor tachometer started giving INSANE weird glitches once I went beyond half throttle. This is not information which reveals itself from "clean room" indoor basement testing. The Hall-effect sensor I used in my tachometer was getting ___flooded___ with spam hits and I was trying to figure out why.

Luckily I am looking for tachometer data as opposed to motor sensor orientation data. You can't easily get orientation direction from the many magnets that are now epoxied to your endbell as opposed to a single magnet fixed right to your rotor like an inrunner. I had a pair of magnets encased in a Delrin plastic cylinder mounted on my motor where the propeller would be, if I used this like an airplane motor.

https://imgur.com/QXUAavr

The problem with this arrangement is that once enough power from the throttle is fired up, there's enough electromagnetic field chaos to mess up the Hall-effect tachometer sensor even though it is a few inches away from the endbell magnets and motor coils. Explaining this problem is like trying to rely on verbal communication when inside something like a warship's engine room. All that noise drowns out any attempt to shout no matter how loud and even in close range.

Inrunner brushless motors don't have this problem because the Hall-effect sensors are mounted right next to the rotor magnet. They are pointed right at the source of the single largest electromagnetic fields within the motor and are being told to measure that. There is no ambiguity about the sort of signals they are receiving. My solution to this problem will have to be something like an optical encoder instead of something that relies of magnetism... i.e. using hand signals through line of sight instead of trying to out-shout a pair of gas turbines, hah.

https://imgur.com/p5A38V0

In the meantime I am making serious progress in the software used for the truck, and waiting for the warmer weather when I can start working with epoxies outdoors to finish the body. I now have my telemetry data all being written to a USB drive inside the pictured enclosure. The data is meant to be an "expendable" filesystem since I don't want to use the same MicroSD card as my Raspberry Pi to control wear leveling.

Thanks for reading!
 
Last edited:
Wow! All I can say is I joined this site because of the wealth of information and have been browsing all the threads when I have questions. 99% of the time I don’t even have to ask a question because the answers are already there. With that being said, your posts so far have blown my mind. I can’t wait to see the end result bro. Cheers!
 
Siscokid7 said:
Wow! All I can say is I joined this site because of the wealth of information and have been browsing all the threads when I have questions. 99% of the time I don’t even have to ask a question because the answers are already there. With that being said, your posts so far have blown my mind. I can’t wait to see the end result bro. Cheers!
Click to expand...
Thanks! I have been pretty busy lately so progress has been slow. Also this process of making the body plug really showed to me the limited talent on smoothing out even a simple set of shapes. This sort of work on a smaller mold is not my forte. The analogy here would be someone who realizes their limitations with carpentry and can do framing work just fine, but is not really ready for fine cabinetry etc. I am almost done fairing out the body plugs and will work on making the molds soon hopefully... then laying up some fiberglass to crank out some finished bodies.

This is the rough profile of what I am trying to make.

https://imgur.com/BmYdhnM

This is where I was with the body plug a few weeks ago... lots of Bondo was involved and the foam was not as flat and smooth as I thought it would be. It's not the foam's fault though.

https://imgur.com/DMol1nT

About midway through the fairing process...

https://imgur.com/RpsW2lh

Closing in on finishing up the fairing. I gave a coat of primer so I could spot imperfections easier.

https://imgur.com/xnynqGl

I'm basically going to accept some small imperfections because i'm sort of on a race against time- some bad decisions I made in the beginning of the plug making process means the foam I am using is steadily deteriorating, so I might just accept leaving some defects in the plug as-is so I can hurry up to make something functional, even if it is not perfect.
 
Hey all, after a bit of a break mainly dealing with other responsibilities, I finally am taking some time to try and finish off this project. The bad news is that my first attempts with making the body molds from the plugs did not go so well. After thinking about spending time to repair the molds versus starting off with brand new plugs I decided to just try it all again.
On the good news front I built up a new gantry to make it easier to lift, store, and work on this truck. The old way I was doing this was ugly... deadlift the truck up and stand it on its back bumper, then lift it up on to a wire shelf where I would be able to carabiner it in place so it doesn't fall. This was not an ideal process and the wire shelf was not that stable except when the truck was just perfectly balanced on it.
https://imgur.com/HGXTATo
The solution was to keep the original frame but re-do everything with rigid conduit, angle, corner, and tee brackets. Much more stable, and lifting the vehicle up is a simple process of hooking up a boat trailer winch and cranking.
https://imgur.com/YXWQJnE
https://imgur.com/cEK5xd5
I'm also machining up a pair of battery trays so I can add these packs up, making the jump from 8S composite packs up to 12S.
https://imgur.com/memvMOt
Thanks for reading!
 
I managed to take some time over the weekend for myself and get some R/C stuff done. Not a whole lot, but it was slow and steady progress.

First off was the 6S battery modules are ready. I made a last minute decision to stick with two 6S2P modules instead of trying to make a tight fit with all three in 6S3P configuration. We will see how this holds up. This will give me 12S2P of power. My gut feeling is that it will be fine. The current motor handles reasonably well with 20AH of battery safely behind it, and the cells don't get too hot.
https://imgur.com/WDNYqlA

With the 6S modules mounted up, it was time to see if my calculated center balance point was close enough... and it was! Though the body will tip the mass slightly forward this was right on the mark of what I was hoping for.
https://imgur.com/uwTGZsz

I had a suspicion the truck was a bit heavier than what I had originally thought- and my guess is that the methodology I used to weigh it by standing it up on end on top of a digital bathroom scale had some deficiencies. A cheap crane scale definitely shows that the truck suffers from "electric vehicle disease". It comes in unloaded about 30 lbs heavier than I thought! 154.72 pounds... that is almost my weight.
https://imgur.com/lqJbT82

...with the 6S battery modules loaded up it comes in at 167.50 lbs!! I am actually not upset, but actually relieved. I had my suspicions the truck was a bit heavier than I thought considering how much I handled it and I am used to moving around heavy objects on a regular basis. I have to give kudos to the folks at Primal, since even divided by 3 these axles are holding up far more mass and potentially impact stresses than they were originally released on the Raminator/Digger...
https://imgur.com/Injlt0R
https://imgur.com/G5Wm9Sl

Thanks for reading!
 
John Parks said:
That's an awesome job, that weight will be fun to load. I assume you're using that lift to move it in a pickup also?

What kind of body are you going with? Honestly a big yellow school bus would be sick
Click to expand...
Thanks! ...and yes this thing is ...fun... to move around ahaha. The gantry is useful for me to lift the truck upright so I can put it on a dolly vertically. Then I can squeeze it through the basement and garage door and load it up on the 1:1 car. Getting it from the garage back into the house is easy because I already have a similar crane to stand it up when in the garage.
As for the body I am looking to build up a semi truck like this:
https://imgur.com/x23o6L6
The school bus seems cool but I have also seriously considered the M142 HIMARS missile truck...
 
I took a small side quest which at first seems like it has nothing to do with this truck, but the pictures should explain it all...

https://imgur.com/t0lPjvV

This is a tiny little truck using Tamiya TLT-1 axles that follows in the same general layout as my large scale. It is also powered by an outrunner, in this case a 4250 with 710kv. Battery power is a conventional 2S LiPo hardcase. It is going to be configured in terms of handling as similarly to its larger brother as much as possible.

https://imgur.com/zOVsAw4

https://imgur.com/jq21kTF

Here's a short clip of it running. One of the major goals with both trucks is to have the center of gravity nice and far back. This little truck is the first time I was able to achieve a full level of relaxed dynamic stability where under normal throttle conditions the vehicle handles very stable and tracks straight... but if you blast the throttle a tiny bit, it becomes very willing to slide out or even drift a bit.

https://imgur.com/lQuQNUT

A few things are left to do before these become more similar in handling, such as adding antiroll bars and limiting straps. But now that I have two trucks that need bodies hopefully this will push me forward to get all of that done for both of them at once!

Thanks for reading!
 
Hi all,
Its been a while but I've been able to restart work on the body recently. The original mold has been fixed up but its still far from ideal. Knowing what I know now I will try a version 2 after I finish this initial set of parts, as it seems better to have something to run with even if it isn't perfect.

https://imgur.com/eNdnND2

De-molding this was tricky but compressed air helped a lot. The version 2 mold will be multipart so its easier to manage.

The defects in the surface finish should be clearer here, but I'm still going to push ahead since something 70% of the way is better than nothing at all.

https://imgur.com/iD8tNvB

Window frames are styrene sheets with the edges painted, with some foam construction adhesive to mount to the body.

https://imgur.com/Tm2YasB

The windows themselves are airplane covering- I had to use Ultracote instead of the Monokote I am used to but they feel similar enough. Headlights and grille are decals that I printed out on vinyl.

https://imgur.com/oXw8qgV

At this point only the sleeper cab remains...
 
potatocat said:
I managed to get some time to drive the truck this weekend alongside my daughter. She was driving it most of the time in trainer radio mode and shot some video of the truck just driving along outdoors:
Click to expand...
My lord, that thing drives way too smooth for the beast that it is. Very, very cool!
 
tacky187 said:
My lord, that thing drives way too smooth for the beast that it is. Very, very cool!
Click to expand...
Thanks! Despite its size it is pretty easy to drive with no real gotchas in handling. There's a few little tweaks I need to do (like replace a chipped sprocket and some bearing whine) but its mechanically pretty dialed in for the most part. There is also the issue of the seals on the V3 Primal shocks not being the greatest as they leak quite a bit. I'll look to addressing that soon hopefully. I can't be too critical on them since the shocks are handling more weight than intended and they were getting several hours of straight up work like this:
 
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