Eagle Racing M06 custom

I've started a project converting my Eagle R31-16fm into a rear-motor M chassis.....just because  :lol:

At first, I was calling this a M31-16RM, but I figured I might as well call it an M06 custom.

First off, the R31-16fm is a front motor chassis, which isn't really that ideal for RWD drifting since there ends up being less weight over the rear wheels causing the chassis to struggle to get up to speed and drift with others, unless you put grippier rear tires.....and front motor chassis are more suited for CS drifting (from my experience). I also want more variety during drift sessions so drifting an M-chassis would at least provide that.

Now, Tamiya's M-chassis in particular have adjustable wheelbases since they make bodies of different wheelbases (210, 225 and 239mm). I will also make the wheelbase adjustable. It will pretty much be a 2-piece chassis where the upper and lower decks overlap and mount using hardware. This way it will maintain rigidity. The front half will mount below the rear half to prevent snagging on track curbs and debris. And making it rear motor putting all the drivetrain in the rear makes this possible since there's no long any drivetrain parts that span the length of the chassis.

Ok, enough babbling. Here's some pics.


Comparing the chassis to a Tamiya MX-5 body to get an idea of how much I need to shrink the chassis.




Checking clearance with motor assembly. Clears the spur gear and the rest just fine.




Here's a pic of the motor assembly separate. I'm using the stock 18t center pulley with a TA05 36t diff pulley, and the belt is a 50t with a tensioner. 


I thought I was gonna have to custom fab my own lower control arms, but after digging around my spare parts and looking at parts online, I discovered I can use some existing parts and modify them. The rear arms are Tamiya TA04/05 front arms. I plan on using Sakura D4 front arms for the fronts.


The C-hub area is where I can mount a rear upright. There was already a tiny hole right where I needed it to be to insert the pin so I used it to drill out. 

Shaved the rest of the arm for clearance for upright.

Test fitted the Eagle upright. Will be using Tamiya 2 degree uprights.

Assembled on chassis.



I just so happened to have 30mm cvds in my parts bin (lucky). I know the diff cups are damaged. Might grind them out so I can use cushions.

I'm using the stock deck just for mock-up. I will be making a custom adjustable deck. And if you're wondering about the O-rings for the turnbuckles, they're simply there just to reduce wiggling since they do move quite a bit.

Both arms done and mounted.

Test fitting body. 






Nice and flush. I actually lucked out on the arm length. Those are HPI Cup Racer MX60 6mm wheels.



In short, this proves that it's very doable to reverse this chassis into a rear-motor layout. I'm just taking it further with doing an M conversion.

More updates to come  :=):

Awesome job man [THUMBS UP SIGN]. Really impressed

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Looking good. This is an interesting build.

Thanks guys.

For the front I utilized the various pieces of the rear bulkhead. I wanted to try to use as much of this chassis' components as possible. I came up with this configuration to mount the upper control arms. The bulkheads are reverse mounted and the arms are connected to small braces that normally connect the bulkhead pieces together.




Right now the arms are only being braced at one point. I will be making a custom brace at the other end to better hold it together. Otherwise it works really well for what I'm trying to achieve.

Here's pics of the whole mock-up so far.






Test fitting the body for the front end.






So far things are coming together well. I plan on doing a monoshock for the front so no damper stay is needed. Still waiting on the carbon plate and a few other parts. Updates to come.

DDJ what a awesome project! Your creativity never ceases to amaze me! Can't wait to tandem with this beast!

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Yeah can't wait to drift this too.

Long awaited from China, my carbon plate arrived.

It's a 2mm plate, 200x300mm. Perfect size for this M chassis project.

Used masking tape to draw out the deck pieces and hole locations. I used the stock chassis as a template.


Cut and drilled out. This is the front half piece.


Here is the rear half with the parts mocked up. It had to have a diff hole since the 36t I'm using needed clearance. And yes I will countersink the holes.




Gives you and idea of how it will be adjustable. The front half will mount below the rear half.




Chassis temporarily set to 225mm wheelbase to test fit Miata body. Looks pretty sick  :B):



Front suspension is mocked up using 3Racing TT01 rear adjustable arms for now.

Things I'm still waiting on:
- D4 front arms
- Short case lipos
- Stealth magnetic body mounts
- 3Racing diff cushions
...and I still need to make some custom pieces for the upper deck, some bracing, and for the monoshock. Other than that, it's going quite smoothly.

Did a little more work. Countersunk the holes.


Check steering angles. Steering right will make contact with the turnbuckle so I will have to make some kind of limiter to prevent it from touching. Otherwise looking good.




Determining servo location. I outlined a cutaway area on the rear deck to clear the servo.






Both deck parts with the rear deck cutaway.


A better idea of how it will be adjustable.

Short

Long


Servo mounted and chassis temporarily set to 225mm.








I will be able to determine the screw locations to connect the decks once the D4 front control arms are installed to actually determine the wheelbases. Also, the upper deck has a chance of being just one piece instead of 2 like the lower deck. The rest of my carbon piece seems long enough to cover it. I should be getting the D4 arms today so I can continue. The front tires do make contact with the body so I might reshape them for better clearance and for that stretched tire look  :B):

Going great so far. Stay tuned.

Yay parts came in. Sakura D4 arms and diff cushions.


Gens Ace short lipos.

95mm length. Despite their size, they're quite dense. Must be due to being 60C.


Shortened arms to "M" size.



Mounted.


Here's the deck with its 3 mounting setup for 210, 225, and 239mm wheelbases.




Here's my mock-up of the monoshock. The upper arms have grub screw holes to lock the camber arms in place. I used the holes to mount posts to hold the shock brackets. Pretty simple.......oh, and my stealth mounts came in too. The bumper mount is off a TA05 I believe, I just happened to find it in my parts bin.




I used these parts that mount to the bulkhead that normally hold the center pullies on the stock chassis to help extend the mounting location for the upper deck so now it's possible for it to be one piece instead of 2 like the lower deck.


Drawing out the upper deck.


The upper deck with battery mount. Hole locations drilled for the 3 wheelbases.






The reveal. Here's the chassis put together with electronics (minus battery). Wheelbase set to 225mm.






So this is generally what it's gonna look like. Pretty simple. I do wish my drill holes were cleaner. Let me know what you think.

So I was able to do some test runs just to see what issues there were. It would spin out easily, even on gentle weight shifts. Here's a list of issues:

- Front monoshock mounting method stresses the upper arms causing them not to move properly which caused spin-outs.
- Steering link makes contact with tire when steering to the right, which also caused spin-outs.
- Lots of weight in the back and not much up front.

I rounded the front tires for more consistent contact patch and body clearance. I mounted them to an axle end and used my drill press to turn them with a file and sandpaper.




The position of the shock caused the arms to be stressed and angle backwards thus causing friction and not moving properly. I came up with a new setup that places the shock right over the arms for better and proper movement.

Before

After




For the steering issue, I made a simple steering stop out of a HPI rear wing riser. I just cut it to length so that the tire comes really close to the steering link and it doesn't limit the steering overall. Before, I had stops for both sides but it limited the steering too much and caused spin-outs, so I just kept the side that needed it.




Finished the Miata body. I plan on doing body lines so it doesn't look so solid and plain, and block out the holes.



Fits quite well  :=):


My current setup is as follows:
Front
- 35wt oil
- Unknown spring (sorry). I'd say it's in between Eagle blue and green springs.
- 5-6 deg camber
- 5 deg caster (estimate)
- About 4-5 deg toe out for parallel steering
- At least 140g of added weight (body has 21g up front making a total of 161g with body mounted)

Rear
- 10wt oil
- MST Extreme soft springs pink/gold
- 1 deg camber
- 2 deg toe in
- damper sponges

Power
- Mamba Max 4600kv motor & esc
- Spektrum DX3.0 tx/SR300 rx
- Futaba S9452 servo
- Stock Eagle gyro
- Gens Ace shorty 2s lipo 5000mah 60c

Gearing
- 89t spur
- 18t pinion
- Stock 18t center pulley
- TA05 36t diff pulley

Rollers
- HPI Cup Racer T-drift
- HPI MX60 6 offset 8 spoke wheels

After all these mods, it's drifting quite well now. It still has a low limit meaning spin-outs are still easy but overall control is increased. At first, it was a bit hard to break it into a drift since all that rear weight provides so much traction so I stretched the gearing a bit for more wheelspin (ran a 90/14 spur/pinion but now is a 89/18) and messed with springs, preloads, camber, toe and weights (all the normal stuff). At one point, I stuck a Masterlock up front and it actually drove great. I also increased the front track a bit to help give the front end a bit more strength. I have yet to test it on a track layout since garage testing doesn't tell me everything. But right now I'm overall pleased with it.

I'll be experimenting with a brushed setup as well, especially since the motor and esc will be a bit lighter.

Looking good, and this was/is and excellent write up. There's a lot of good information.