haplm's XV-01 carbon mod

[haplm]

I’ve been watching the RCCrawler Rally section for quite some time, and finally decided to get XV-01. Since I live in Czechia, land of enthusiastic XV-01 modders and rally racers, I’ve decided to modify the car so it can compete in rally races over here. Goal of the mod is to make it lighter, better balanced, and increase steering angle.

To achieve that, I’ve decided to get improved (carbon) version of the aluminum conversion kit mentioned here.
This kit features couple things that I like:

• lower weight
• freeform layout for electronics (thus better chance to balance the chassis)
• higher stiffness

But it also brings couple of features that I don’t like:

• Inability to use rear mud flaps
• Inability to mount front sway bar (or at least I haven’t yet figured out how to do it)
• Higher CG because of the servo mounting position

At the end, the only thing that really bothers me is the missing front sway bar, but hopefully it shouldn’t be a huge problem due to the nature of the rally tracks here (frequent turns, gravel/mud, lower speeds).

This is how the chassis looks like:

Servo mounting position:

Battery mount:

The battery is mounted using velcro straps, the biggest I was able to fit is the new GensAce hardcase 3200mAh 2S LiPo (semi-hard case batteries are an easy fit, eg. Traxxas 2200mAh 2S).

Steering angle:

To achieve this steering angle, caster blocks and C parts have to be modified (cut/shaved). Unfortunately I don’t have a good picture of that.

Since all the components are now exposed to elements, I have decided to put the receiver in the Traxxas weather sealed box used on Rally/Slash (TRA7424), and coat the ESC (Turnigy Trackstar 80A Turbo Sensored Brushless) with a nano protect spray. However, that wouldn’t be enough in dirt, so I have also installed Dusty Motors shroud on it:

Receiver/radio is Traxxas TQi for now, mostly because I can’t find any other system that could do traction control and telemetry at the same time.

Most of the parts are stock (except rear sway bar and TRF dampers), but tons of upgrades are on their way (carbon reinforced steering parts, long damper stays, aluminum steering bridge, slipper clutch, Gmade XD shocks, Proline springs for those shocks, etc.). I’m planning to install the upgrades during the winter season.

This is the current body:

It features Killerbody LED controller, LED cases and set of LED lights.

In progress are Toyota GT86 Gazoo Racing, and Datsun 240z bodies.

[bvrc]

I think lots of us dream of doing something like this but never get around to it (maybe that's just me).. Big Ups for the work man!

[haplm]

Originally Posted by bvrc

I think lots of us dream of doing something like this but never get around to it (maybe that's just me).. Big Ups for the work man!

Thanks! Just to be clear, I'm using a kit that other people invented. I don't want to take full credits for this work, that would be unfair. I just hope to bring couple improvements to the design that people are building on top of this.

Right now, I'm at the beginning with the car. So far, I've been able to bring it to the point when it handles really well on tarmac. With such an extreme steering angle, it requires TRF Double Cardan Joint Shafts in the front, and a lot of playing with dampers, springs and the only available sway bar.

What I want to try next is to install active traction control (TSM) to see how it will (or can) affect handling, and long damper stays with GMade shocks. To make those shocks work with the incredibly light back of the modded car, I plan to use the softest proline springs. If that is not going to work, I will probably have to get some custom made ones.

I've also spent a lot of time (and money) testing different tires. At this point, I have 10+ tires that I'm testing on different surfaces. I'll post more about that later (as well as I plan to update the thread as I progress further with replacing stock parts with what should be there at the end).

[TommyBobby]

That conversion looks grate! I was hoping you could send some photos of how the steering mounts. I see that the servo is inverted, but can't make out the bell crank placement and such.


Thanks for your help,
Tom

[bvrc]

x2

Ty and I were talking about that the other night.

Haplm, we need more picks of the steering!

[haplm]

OK, OK, here it is.

The plates are accompanied with a servo saver extension, which mounted looks like this:


Assembled steering then looks like this:


Does this help, or do you need more pictures from a different angle?

To achieve the increased steering range, you need to grind C hubs (and potentially other steering components) like this:


I thought that this is enough, but quickly learnt that other people go much further, which allows them to achieve incredible steering angles. Now when I have a spare (carbon-reinforced) set of all steering components, I will probably try to go a bit further with this (as I want the car to be competitive in local races, which it is not at the moment, solely because of steering only going to 110% :-)).

[bvrc]

Is that a kimbrough servo saver?

[haplm]

Originally Posted by bvrc

Is that a kimbrough servo saver?

Yes, it is. Works well in this setup.

BTW - I've just ordered two set of Czech made rally tires (VR Tyres):
Rally Pin BS - Yellow - VR Tyres
VR TYRES OPONY MEGA BLOK SOFT (4) FCKiT (only picture I found, these are pretty new)

I'd like to attend a dirt race next week, and I'd like to see how they compare to HPI Rally Tire (#4470 RALLY TIRE 26mm M COMPOUND (2pcs)) and Fastrax/Ripmax Rally Blocks.

During a tarmac race last week, I was able to compare performance of HPI V-Groove Super Radials (#4541 V-GROOVE SUPER RADIAL TIRE 26mm PRO COMP (2pcs)), HPI X-Patterns (#4790 X-PATTERN RADIAL TIRE 26mm D COMPOUND (2pcs)) and HPI Pirelli Chinese knock-off made by Austar. Being very soft wet tire, V-Groove was the one with most grip (but presumably fastest wear), X-Pattern followed (slightly worse times, but nothing horrible). That Austar tires are joke. They turned the car into a drift machine, which amused all the other racers, but I've ended up last in that round. So I'm tempted to buy and try the original to see how bad the knock-off really is, but I already feel like owning too many different tires :-). I'll post some pictures later, once I have those VR Tyres at home.

[bvrc]

Those mega block tires look insane!

[haplm]

So, to make the car competitive, I've pulled out my proxxon grinder out of its box, and mutilated C and D parts of the steering:





I hope I haven't weakened them too much, but only time will tell (carbon reinforced spares are ready). Anyway, this gives me 120%+ steering angle. Unfortunately my Traxxas radio can only set epa/trim to 120%, so I can't really use it (so I guess time for a new radio).

There's one steering details that I have forgot to mention last time - I'm using carbon fibre extension when attaching steering rod to C hub:



And finally, Toyota GT86 body is finished, including LEDs:





Interesting on this body is, that it is combination of Tamiya (body + decals) and Killerbody (plastic parts, chrome parts, LED buckets, LEDs, LED control system). Surprisingly, everything fits very well together (one just needs to use Mode A on LED controller, as recommended Mode B doesn't work well with selected LED colors)

[bvrc]

looking good man!

[haplm]

Originally Posted by bvrc

looking good man!

Thanks!

Next on the list are the Gmade shocks and long damper stays. Then it should be ready to race next weekend...

[haplm]

So the Gmade shocks are finally mounted.

Unfortunately all the Gmade springs are way too hard for gravel rally (even the green soft ones). Fortunately there is Spring Assortment for Pro-Line PowerStroke Front Shocks (6063-00). All of these springs are too hard as well, except one - blue. That one works well in the front. I haven't been able to find soft enough spring for rear (and this is probably only problem of my carbon mod, which is super light on the rear). So I've got some custom made ultra soft springs, which seem to work well.

Front setup:
Oil: 250 cps
Piston holes: 3
Pressure: medium-high
Spring: Proline PowerStroke Blue

Rear setup:
Oil: 200 cps
Piston holes: 4
Pressure: low
Spring: Custom made ultra soft

[haplm]

VR Tyres finally arrived (2 left most ones):

20160915_202819_001

BTW one can typically choose from 3 different compounds when buying them, which is nice. They also have their own version of Rally Block tire: XT BLOK BS - Silver - VR Tyres

HPI Rally tires are next on that picture, followed by Fastrax Rally Block, Ripmax Rally Block, and chinese knock-off of HPI Pirelli.

[haplm]

So, I've just finished a dirt race, where I have tried 4 leftmost tires from the previous post.

Fastrax rally block doesn't really work as is (too much sliding). What other people say is, that if you cut it, performance should be better. I will try that for next race.

Those "tractor" tires have impressive traction when climbing uphill (there was a part of the track with really steep climb), but otherwise they don't provide enough traction (in dirt).

Both HPI Rally and VR Pins work very well in dirt, but after one race is hard to say which are better. My feeling is that pins have more side traction, but they are extremely bad when climbing.

This was the track:





Cars:







Timing:

[Robbob]

Any videos of you guys running?

[haplm]

Originally Posted by Robbob

Any videos of you guys running?

I don't have any video of my car from the weekend, as people haven't posted much yet. I have couple more pictures and slow motion videos of others here: https://goo.gl/photos/dwTNsG57vkYxGv2L8

Next week, I'd like to attend this race: https://www.youtube.com/watch?v=HMQtOmUEml8

From there, look at related videos (or you can use this one as another starting point)

[bvrc]

I'd love to know more about the timing system you guys use... Got any details on that thing? What transponders?

Sent from my SAMSUNG-SM-G890A using Tapatalk

[haplm]

Originally Posted by bvrc

I'd love to know more about the timing system you guys use... Got any details on that thing? What transponders?

Sent from my SAMSUNG-SM-G890A using Tapatalk

The way how the lap times are taken is actually pretty simple. No transponders.

Into each stage, cars are starting at predefined time, same as in the real rally (usually with 30 seconds or 1 minute gap between them). Typically, you have a monitor (or tablet) which tells you where the starting procedure is - who is starting now, and who's next. It usually beeps somethign like 10 sec before you should go, and then when is the time. Early start is penalized (late is your problem).

End time is precisely measured by an IR/laser gate, and transferred into a timing software.

The whole thing is running on some arduino box (HW), and some guys wrote the SW (I believe there's more than one system, but I'm not sure).

If you need to know more about some part of this, let me know, I will ask. I'm just talking to one of the guys operating this, because I'm asking him for source data from the timing system, so I can analyze them (turns out it is bunch of XMLs).

[Robbob]

I gotta say it definitely looks funner then I originally thought. Easy way to make a fat guy skinny too lol.

FPV with a spotter chasing the car for ya would be sick