FF-02B - FWD Buggy, The 'F' is for Frankestein

[SlideWRX]

You know how sometimes something gets stuck in your head and it won't come out until you get it stuck in seomone else's head?  This FWD buggy is that.  I will build this to get it out of my head, and hopefully into yours.
I want a front wheel drive buggy, just to try out.  Tamiya never released/made a front wheel drive buggy, however a couple people on here have built them. @XV Pilot apparently made a great thread that has been lost to the ravages of time Photobucket.  This is my quest to build a Tamiya FWD buggy, using Tamiya parts. They might be from various models, hence the Frankenstein. I want to build from a front wheel drive platform, not just pull the rear axle bits out of a 4wd buggy.  That limits the chassis options.  There are the FF-01 through FF-04 chassis, and the odd numbered M chassis.  After looking at them all, I settled on the FF-02/M-03 chassis. It is cheap, and I like the clamshell design for this with how easy it is to stretch it the wheelbase - just insert more pieces in the middle!  What wheelbase do I want?  Well, 270mm-ish? Maybe?  Looking at RWD buggies, the DT-02 is ~260mm and the DT-03 is ~285, so around 270mm sounds just right.

The only concern I have with the FF-02/M-03 chassis is the gear ratio.  There is no option to put a bigger spur gear in there.  It has the option to go down to a 16t pinion, which gives it a 7.25 ratio.  That is pretty tall for buggy tires and a stock 540 motor.  The DT-02/03 are a 9.3 ratio with a stock 540, and the lightweight Hornet is an 8.2 ratio.  My solution for now is a brushless 17.5t which should handle that ratio ok.  For ESC I am using the TBLE-02s esc from my Neo Fighter.

To turn the FF-02 chassis into a buggy, the big change is the suspension arms.  That's how a TT-02 basically becomes a TT-02B, right? I picked up a set of DF-03 arms to install onto this.  If you wanted to stay period 'correct' I think the TL-01B set would be the way to go.  The TL-01 is the same clamshell style from the same time frame.  In hindsight, I think the TL-01B/WR-01/WT-01 parts will actually be the easiest way to go.  I wasn't focused on trying to keep it within a time period or anything though, and I liked the way the DF-03 bits went together. 

FF-02/M-03 chassis parts are hard to come by these days - out of production and not locally common.  Japan seems to have a steady supply of used ones though. I got lucky and got a chassis 'cheap', even with shipping.

It came with blue hexes, and ball bearings! Overall a great score.  The servo mount ended up being a bit odd/modified, but workable.

While I had it apart I put some silly putty into the diff to prevent one-wheel peel, the scourge of FWD.

I turns out the bearings in the wheel ends are 5x10, and my replacement DF-03 parts are 5x11.  The rears bits are going to get bushings for the moment as I am a bit short on my stash of 5x11 bearings.  If I had gone with the TL-01B parts, the wheel ends from the M-03 would bolt right up and use the 5x10 bearings that came with it.

I noticed what *might* be some wear/cracking on the rear suspension arm mount.  Otherwise there is very little wear/damage on the chassis.

This is where we end part 1.  The DF-03 arms fit with ~1mm of spacer added in.  I re-used the screw pins to hold the arms on.

Various parts are on their way here to keep things going!  Hopefully this all turns out well.  I still don't know what body I am going to put onto this...

[bsy2010]

Following this, as I had a similar idea a while back but never started a project.

I'm racing an ORB Forward, a fwd buggy using lots of AE and my own parts, on loose clay and it performs very, very well. So I'm curious how your car will do

On 5/21/2024 at 4:37 AM, SlideWRX said:

I put some silly putty into the diff to prevent one-wheel peel, the scourge of FWD.

You might gain a little coming out of a corner, but you will loose it going into the corner. I always preferred a very open diff to reduce understeer.

 

[Honza]

Interesting project! One more advantage of M-03 is, that it's compatible with some TL-01B parts, that can come handy - apart from suspension it's front bumper and I've also seen rear shock tower extensions, that could come handy.

On 5/21/2024 at 4:37 AM, SlideWRX said:

are the FF-01 through FF-04 chassis, and the odd numbered M chassis. 

You forgot here the cheaper version of FF-04, which is XV-01 I've always seen it as a FWD chassis with added rear drivetrain (and always wondered, if you could add rear gearbox to FF-04 to create an XV-01 TC Evo)

1 hour ago, bsy2010 said:

I'm racing an ORB Forward, a fwd buggy using lots of AE and my own parts, on loose clay and it performs very, very well.

Interesting, I remember this buggy from times when it was based around Durango and had motor in front of the axle. I should check out the development.

 

[SlideWRX]

It's in one piece!  I ordered a couple mid section pieces for the 239 mm wheel base; I figure at ~29mm each, from the base 210 mm I would end up at ~ 268mm.  I was off!  I ended up around 289mm due to the different suspension arm styles.  I took off one of the 239 pieces and installed the 225 mm piece the kit came with.  I ended up at about 274mm wheel base. Excellent!

One of the challenges of using the DF-03 arms is making turnbuckles for the top.  The TL-01B arms are the exact same style as the FF-02/M-03 arms and use the exact same hardware, and would have made this easy.  To attach the DF-03 arms to the chassis I used some pieces from Yeah Racing made specifically for this.  I couldn't find if Tamiya had an equivalent piece.  I had various turnbuckle bits leftover from other projects that I was able to re-use to make these.

Not the greatest picture of the turnbuckle attachment, but suspension is done!

With getting the arms all setup, it was time to install driveshafts.  I was able to pull these from my DT-02 and put a different left over set in there.  They are the same as the ones for a DF-03 I think; They came with my DT-02 when I bought it used, and worked well, but maybe they are different.  They seem to be 2-4mm too short for the front axle.  I have two O-rings in the drive cup to keep the axle *hopefully* pushed in enough at the wheel end.  That is a big if, and I may have to buy a different set that is longer if it pops out.

Next up is the steering. Again I had some turnbuckle parts leftover that fit for this project.  I was easy with the installation of the ball connector, but the old plastic seems to have cracked on the steering arm.  I will see how well it holds up, and get a new one if needed.  The servo installation was a bit odd, as the previous owner didn't have one of the servo mount plates and cobbled a metal plate in its place.  It seems to work though, and this is definitely not a 'keep it original' build, so no harm.

The shocks are from an MST crawler, with barely any damping in them.  Somewhere right between a friction shock and standard Tamiya CVA...  Maybe closer to the friction shock...  Anyway, I will rebuild them later after I have got this running.  Pretty good suspension travel, just under damped. I used longer damper connectors on the bottom to clear the suspension arm.  You can see the plate used for the servo mount here too.

Some long screws and shock collars hold the shock bottom to the arm.

Anyway, I just added electronics and steering is functional.  I'm waiting for the 16t pinion to show up in a couple days.  I will throw some wheels/tires on it and take it for a spin without the body.

[SlideWRX]

15 hours ago, Honza said:

Interesting project! One more advantage of M-03 is, that it's compatible with some TL-01B parts, that can come handy - apart from suspension it's front bumper and I've also seen rear shock tower extensions, that could come handy.

You forgot here the cheaper version of FF-04, which is XV-01 I've always seen it as a FWD chassis with added rear drivetrain (and always wondered, if you could add rear gearbox to FF-04 to create an XV-01 TC Evo)

Interesting, I remember this buggy from times when it was based around Durango and had motor in front of the axle. I should check out the development.

 

I noticed after getting it all together that the bottom of the chassis at the front is VERY exposed.  I came to the same conclusion - the front bumper from the TL-01B would come in handy!  It should arrive in a few days.

[SlideWRX]

16 hours ago, bsy2010 said:

Following this, as I had a similar idea a while back but never started a project.

I'm racing an ORB Forward, a fwd buggy using lots of AE and my own parts, on loose clay and it performs very, very well. So I'm curious how your car will do

Very cool! 

16 hours ago, bsy2010 said:

You might gain a little coming out of a corner, but you will loose it going into the corner. I always preferred a very open diff to reduce understeer.

It ended up fairly loose when turning the wheels by hand; These diffs have a lot of space for the putty to get pushed away into, so I didn't put 'enough' in.  I'll get to drive it 'loose' and see how it turned out.

 

[Honza]

3 hours ago, SlideWRX said:

noticed after getting it all together that the bottom of the chassis at the front is VERY exposed.  

That picture reminded me another useful part - #3485068 U-shaped hinge pin. That will reinforce the front so it'll be able to handle some jumps

3 hours ago, SlideWRX said:

They seem to be 2-4mm too short for the front axle.  I have two O-rings in the drive cup to keep the axle *hopefully* pushed in enough at the wheel end.

I recommend using foam on the inner diff cup - this suspension geometry may cause a lot of axial movement. In the future, CVDs or DCJs would save a lot of headache

3 hours ago, SlideWRX said:

but suspension is done!

One thing I noticed here is that the front driveshaft is angled forward. You can't do anything about it due to arm shape, but be aware that this will cause it to lift the front on throttle and dive on brake. 

[SlideWRX]

IT LIVES!!!
I took it for spin on my driveway.  In general it feels pretty good.  No sharp spins when hitting the brakes - either you lift off and it will do a lazy 180 (easy to catch), or hit the brakes and it slides/understeers to a stop.  The differential ended up pretty open; I'll have to open up the gearbox and add more putty to try out the difference. It handled mostly ok, the only issue was that it wouldn't track straight.  I tried to dial out any drift on the steering adjustment, but it seemed to drift off on way or the other anyway, pretty significantly.  The DF-03 rear arms have 3 degrees of toe in - great for RWD/4WD buggy stability, but I wonder if that is too much on the rear arms for a FWD vehicle.  The sprue for the bumper comes with one set/side of the suspension arms, so since I was already buying one I bought a second in case I wanted to try the TL-01B arm setup...

Otherwise it is good!  The bumper sits flush to the chassis - that gets rid of the potential edge to crash against rocks or what have you, but I was hoping it would sit just a bit lower to be a bit more sacrificial.  I may add some small spacers to bring it down just a bit.  On a side note, the sprue that has the bumper also has a single center post, good for attaching buggy bodies...

My electronics all seem to have comically long leads for this build with the compact chassis setup.    I know this may hurt your eyes if you love to trim the wires down to perfect length.  Long term I may trim the servo/esc wires down, and maybe make a second set of motor leads that are a lot shorter.

[SlideWRX]

Steering Straight
I decided to try out the TL-01B rear arms to see if 0 toe-in for the rear could keep it straight.  I had the arms from the bumper sprue; I bought two sprues because I suspected this might happen.  They bolt right up using the original M-03 screws I had.  You can see the difference in the wheelbase from this picture halfway through the change - I went down to ~261mm wheelbase.

I took it out for a spin and it seemed to help.  It wasn't quite perfect but it was better.  I took it back in and kept looking at the rear wheels - they seemed to be toed out, not straight.  I took a look at the uprights that I thought were stock, and sure enough they showed a '2R' & '2L' on them.  I had gone from 3 degrees toe-in to 2 degrees toe-out, because I had them on the wrong sides.  Gee, I am sure glad I can tell the difference in 5 degrees of toe on my RC car...  Anyway, I corrected them to 2 degrees toe-in and I'll take it out after these thunderstorms roll through, probably tomorrow.

I took the time to fix the shocks so they were less bouncy.  These are from MST - originally on a CMX crawler.  They are very similar to CVAs - the same arrangement with two o-rings on the bottom and no extra guide pieces.  They are a 9mm internal diameter vs 10mm for Mini CVAs which are similar length. There isn't a bladder to separate air/oil though. The piston for these had a lot of big holes, so I started with Blue 600 oil, and some Tamiya X-rings.  That was a good improvement in damping, but still a bit under damped.  I could probably go to 900 for best/optimal results.

Meanwhile, I decided to fit an old Falcon re-pro shell from TBG on it for now.  It was already chopped up for a different project that never happened, so it got re purposed for this.  I've started on a gunmetal grey base color.  The rest of the painting will get done after the rain.  The shell sits really high with the high mounted servo getting in the way, so it has been chopped to expose the servo a bit and let it sit lower.  I am tempted to chop even more away (kinda like an engine sticking out of a hood) and try for a bit lower - I suspect I could get maybe 5-10 mm, cover half of the battery. For Better or Worse, let me know what you think...

[TurnipJF]

Re-purposing shells is often a challenge. I'd vote for a more aggressive trim to get the shell lower. Possibly trim the rear straight too?

[SlideWRX]

9 hours ago, TurnipJF said:

Re-purposing shells is often a challenge. I'd vote for a more aggressive trim to get the shell lower. 

It will definitely give it a 'big engine in the front' feel. maybe I should find something like this for effect?  

9 hours ago, TurnipJF said:

Possibly trim the rear straight too?

Take off the original falcon wing posts in the back? or just a trim around the bottom?

 

[TurnipJF]

4 hours ago, SlideWRX said:

It will definitely give it a 'big engine in the front' feel. maybe I should find something like this for effect?  

Take off the original falcon wing posts in the back? or just a trim around the bottom?

 

I think a blower would look cool up front!

As for the rear of the shell, I'd lose the Falcon wing mounts and use the Racing Fighter as inspiration for the cutline.

[SlideWRX]

It is "Complete"!

Well, how complete are these things ever? Some things to consider when creating a FWD buggy:

- That servo sticks through a LOT.  The front mounts for car body posts also get in the way - I'll have to get a close-in shot.  The steering arms are high as well, which also need carve outs on the body. This all meant the body almost couldn't be used - it was perilously close to being cut in half to clear various things.

- None of the front upright/steering arms are made with regular rear wheels in mind (obviously).  This means that normal Tamiya rear wheels sit too deep and interfere to the steering arm, unless you put a 12mm thick 12mm hex on there to push the wheel way out.  The wheels I initially put on and ran with are Kyosho Scorpion wheels that have much less offset.  Comical wheels also seem to work, although I have to take them for a spin.

- I don't have any protection for my motor & battery, sitting right behind those tires that are going to be throwing a lot of debris at them.  I really want to work something out here.

[SlideWRX]

Here is what the combination of body post mounts, servo & steering arms caused to be trimmed from the body.  A bit of material could be recovered on a fresh cut of a new body, but not much.

On full compression I decided to let the steering arm hit the body instead of trimming away more, and having nothing left...  On a fresh body I could recover some of this, but not much!

The left front tire will be throwing a lot of stuff at my motor, and both wheels with pummel the battery with stuff.

CAUTION!!

[TurnipJF]

I think that looks brilliant! The combination of big front tires and servo sticking out makes it clear that this is something different to the norm.

I shall look up the part number this evening for the front steering thingies that I used on my Fiat 500 to accommodate a wider range of wheels and tires. I seem to remember there the same ones as used on the manta ray.

[TurnipJF]

The uprights I used on my Fiat 500 are p/n 0445572, although looking at your photos more closely, they may not provide much improvement if any. 😔