haplm's XV-01 carbon mod

[4roller]

Originally Posted by haplm

And here we go...

Sexy

[zzotta]

Originally Posted by haplm

To check it a "scientifically", I have started measuring all the aspects of the car and creating RC Crew Chief model.

Dear haplm,

great thread, I am following it since the beginning.
I am planning to buy RC Chief Crew, so I am very interested in your experience with the software.
Is there any way to share models?

Thank you for your thread,
Marco

[haplm]

Originally Posted by zzotta

Dear haplm,

great thread, I am following it since the beginning.
I am planning to buy RC Chief Crew, so I am very interested in your experience with the software.
Is there any way to share models?

Thank you for your thread,
Marco

Hi zzotta, thank you. I really hope that this will help at least few people to turn their cars into better racing machines...

RC Crew Chief is definitely interesting piece of software, and I'm pretty sure it worths the price. It (at the moment) doesn't allow you to model all aspects of the car (like pro-dive / kick-up), but everything important is there, and you can get a lot of insight into your setup. But I need to warn you - you need to understand the car physics before you use this. Without that, I believe it is useless.

However, once you understand things like roll center, gravity center, weight transfer, shock natural frequency, and others, than this program is a great tool to understand their values/position/behavior on your car. You just need to be ready to interpret those values somehow, and turn the insight provided by the software into set of tuning actions to get the desired setup.

I still have a pretty basic model, because quite early on, it revealed to me that my roll center was all messed up because of a design flaw of the carbon plates I'm using. Since then, I'm working on fixing that, as you can see in my previous posts. Once I have fix for the camber mounts, I'll redo the upper plate, update the model, and I will move on to look at other parts of the car.

Sometimes I tell myself that I should just abandon the XV platform, and get some XRAY T3, Tamiya TB, or even XRAY XB4 chassis, and start working with that, but for now I'm sticking with it. There's simply too many converted T3s that are very capable rally racers :-). For me it is a challenge to create an ultimate XV-01 mod for rally racing...

And yes, one can share RCCC models with others. However, my model is going to be good only with my plates, camber mounts, and whatever else I will machine/print. I was thinking about turning all of this into some sort of kit once I'm good with the design, so if somebody is interested, I could ship it to them.

[zzotta]

Thank you for your deep analysis.

Originally Posted by haplm

I was thinking about turning all of this into some sort of kit once I'm good with the design, so if somebody is interested, I could ship it to them.

Good news, keep us updated.

[haplm]

Well, the thing is mounted now:







To fit the part to the car, I've had to cut out the mounts on the upper plate, but I don't regret it :-). It allowed me to rollback the mod that I had to do on the rear hub (post #29).

Upper inner hole is the original camber link mount position (I mean on the original plastic kit - links are parallel with a-arms), and all the other holes allow either shorten the link (thus make the camber change be more aggressive), or increase height of rear roll center. After trying different positions, I have now settled on inner middle hole (the pictures above were taken during the tests, so they show the link in lower inner position, which generated too much oversteer on the corner exit). This setup pushes the car closer to being neutral through the corner. It can still oversteer if throttle is applied at the right moment, but generally it goes through the corner very well and stable. Long links mean very little camber change, so the rear tires keep in touch with the ground most of the time.

Part of the setup is also some taming of the ESC and throttle. 0 turbo, 0 boost, 90% drive frequency, 0 punch, 50% neutral brake, 20% neutral brake drive frequency, 70% throttle, 40% exponential curve on steering. Nothing for speed runs, but great for constant turns.

For those who care about the material for the 3D print:

• Prototype was printed using PLA. Not exactly what I want to mount on the car (feels too brittle).
• Current "production" batch was printed using 3 different filaments: HIPS, PETG, Ultrat (Z-Ultrat)
• HIPS is nice looking, but feels too soft and flexible
• I'm going to keep experimenting with Ultrat and PETG, both seem to be good for such kind of components
• M3 holes are created using 2.85mm holes without thread, which is then created by slowly screwing in M3 screw (it gets really hot during the process, and it requires significant force, so I do this using very slowly turning electric screwdriver).
• The screw can't be pulled out even using huge pliers, so the method above seems to work well

[haplm]

There's one more Datsun to the team:



In the first race, the car worked better than it ever was. Still not perfect, but definitely going the right direction.

I have also finished BMW M3 Evo body for the second of the two cups that I'm racing in this year (and most of the credit for how it looks goes to my wife, who designed and painted it):

[4roller]

Dude that's a lot of rally cars.

[haplm]

Originally Posted by 4roller

Dude that's a lot of rally cars.

Wait, this was a small race, just 24 people :-). First big one attracted some 80 racers .

Right now, I'm looking forward to the first outdoor one, which is happening at the end of the month...

Sent from my SM-G935F using Tapatalk

[Natedog]

Originally Posted by 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.

Thanks for comparison pic with tire names and brands! Do the Fastrax Rally Block tires come with foams, do you use foams in them, are they strong enough to not roll under in corners? Have you tried Tamiya Rally Block tires soft compound (looks same) and can you compare the two?

Almost forgot, but what about the Chiner Rally Block tires on the bay?

Great loooking off-road dirt rally track too!

IIRC these are same tires that came on Tamiya 1/12 scale Porsche 959 and few other models and they didn't have foams, but can't recall for sure.

[haplm]

Originally Posted by Natedog

Thanks for comparison pic with tire names and brands! Do the Fastrax Rally Block tires come with foams, do you use foams in them, are they strong enough to not roll under in corners? Have you tried Tamiya Rally Block tires soft compound (looks same) and can you compare the two?

Almost forgot, but what about the Chiner Rally Block tires on the bay?

Great loooking off-road dirt rally track too!

IIRC these are same tires that came on Tamiya 1/12 scale Porsche 959 and few other models and they didn't have foams, but can't recall for sure.

Fastrax Rally Blocks usually come pre-glued with foam inserts, but VR is selling them without rims, including inserts. I do run them with inserts, without they wouldn’t be able to keep shape.

I wasn't aware of soft version of Tamiya Rally Block. So I did some googling, and found that some sites (like TowerHobbies) really sell a tyre labeled as Tamiya Rally Block Soft Compound, but it has the same catalog number as the standard one. So I’m kind of confused. Is it really a soft variant of the standard Tamiya RB, or just misleading label? Do you have one? Is it really softer? The standard version is way too hard, which makes it unusable for racing.


I've go some more tires (and experience) since my last post on this topic, so I have decided to create a comparison table here. It lists all relevant tires I own, and my experience with them. N/A means that I haven't used the tyre in the given context, or I don't have enough experience with it yet.

[Natedog]

Great info, very nice spreadsheet thanks for sharing! Been looking at Traxxas rally, Tamiya etc. saw Headquake built his rally on Traxxas Mini Slash, I've got one of those currently. Running it with stock SCT body and found some slightly larger tires and wheels combos on the bay, stock tires and wheels are good on tarmac and long lasting but skates all over in dirt especially on hardpack. I don't know anyone racing rally nearby.

[haplm]

Originally Posted by Natedog

Great info, very nice spreadsheet thanks for sharing! Been looking at Traxxas rally, Tamiya etc. saw Headquake built his rally on Traxxas Mini Slash, I've got one of those currently. Running it with stock SCT body and found some slightly larger tires and wheels combos on the bay, stock tires and wheels are good on tarmac and long lasting but skates all over in dirt especially on hardpack. I don't know anyone racing rally nearby.

I have regular 4WD 1/10 Slash LCG, which can be easily converted to Traxxas Rally. IMO that is a perfect car if you just want to do some crazy driving (bashing), and you don't care about scale bodies. If you buy some shroud (Dusty Motors, etc), you can run the car in pretty much anything (except water) without any problem, and it will be tons of fun.

However, it is completely unsuitable for scale rally racing. The car is too big, overpowered, not scale, and doesn't have enough steering angle. That to some extent is true also for the 1/16 version...

You may want to look at MST XXX Rally as well. Seems to be a really nice rally car...

Speaking of racing, here is the link for second race I have attended this year.

[Natedog]

Do you have a picture of your scale rally car(s) next to your Slash LCG? I think Slash Rally is probably too wide and kinda longer than scale?

Yes, MST XXX looks pretty good too.

Nice ramps, bridges and course, looks like lots of fun! Wish we were closer, I'd come check out the races.

[haplm]

Originally Posted by Natedog

Do you have a picture of your scale rally car(s) next to your Slash LCG? I think Slash Rally is probably too wide and kinda longer than scale?

Yes, MST XXX looks pretty good too.

Nice ramps, bridges and course, looks like lots of fun! Wish we were closer, I'd come check out the races.

I'm sorry it took so long, I've been a bit busy sketching new upgrades for the car (I'll post some update about that soon). In the meantime, here is the picture of two badly beaten bodies... :-)

[stormridersp]

Really nice build, I'm thrilled reading through it.

One question, regarding weight, how much could you shave off in the last version of the carbon convertion?

Cheers

[haplm]

Originally Posted by stormridersp

Really nice build, I'm thrilled reading through it.

One question, regarding weight, how much could you shave off in the last version of the carbon convertion?

Cheers

Well, I'm not targeting weight. IMO it is not necessary the have the most lightweight car, but rather the most durable (so you finish every single single stage - ie. no penalisation) and the one with best handling. But of course you should stay within some reasonable limits . To answer your question - the latest version of the car without body weights 1350 grams (including shorty LiPo - 140g). Weight balance is now 57/43 F/R. Both ends have shock towers for 85mm shocks, but front is still 75mm, just mounted a bit lower. I'm also using XJ one piece mounts in both FF and FR positions to help steering links to clear the FR susp. mounts when the wheels are fully turned and the car is sitting high.

Speaking of latest version - here it is:




It has a 3D printed box for ESC, which perfectly fits the carbon chassis, and is easy to open/close. There's also mount for ON/OFF switch, and holes for wires. I've put it through some serious mud over the weekend, and it worked perfectly.

Plus one of the bodies is now equipped for night races

[stormridersp]

Originally Posted by haplm

Well, I'm not targeting weight. IMO it is not necessary the have the most lightweight car, but rather the most durable (so you finish every single single stage - ie. no penalisation) and the one with best handling. But of course you should stay within some reasonable limits . To answer your question - the latest version of the car without body weights 1350 grams (including shorty LiPo - 140g). Weight balance is now 57/43 F/R. Both ends have shock towers for 85mm shocks, but front is still 75mm, just mounted a bit lower. I'm also using XJ one piece mounts in both FF and FR positions to help steering links to clear the FR susp. mounts when the wheels are fully turned and the car is sitting high.

Speaking of latest version - here it is:




It has a 3D printed box for ESC, which perfectly fits the carbon chassis, and is easy to open/close. There's also mount for ON/OFF switch, and holes for wires. I've put it through some serious mud over the weekend, and it worked perfectly.

Plus one of the bodies is now equipped for night races

Truly amazing!

Have you managed to fit the front and rear anti roll bars?
Talking about 3d printing, have you ever thought about printing a rear diffuser?


Edit. A few years ago, I tried cutting myself a carbon chassis, but due to parts that I couldnt find, I was limited to a 1 plated chassis, so it did flex quite a bit. Back then, I was using the Carbon version of the FF-04 as a guide for the project. Both cars are very similar.


Tamiya XV-01 - Page 38 - R/C Tech Forums

Nowadays, with 3d printed parts as an option, I would go even further as to completely redesign the bottom carbon plate to make place for aerodynamic ducts and diffusers, sort like the Traxxas XO1



Cheers

[haplm]

Originally Posted by stormridersp

Truly amazing!

Have you managed to fit the front and rear anti roll bars?
Talking about 3d printing, have you ever thought about printing a rear diffuser?


Edit. A few years ago, I tried cutting myself a carbon chassis, but due to parts that I couldnt find, I was limited to a 1 plated chassis, so it did flex quite a bit. Back then, I was using the Carbon version of the FF-04 as a guide for the project. Both cars are very similar.

....

Nowadays, with 3d printed parts as an option, I would go even further as to completely redesign the bottom carbon plate to make place for aerodynamic ducts and diffusers, sort like the Traxxas XO1

...

Cheers

Ah, it is you who made this for the first time :-). I saw your post in RCTech, but I didn't connect the dots (names) :-).

I have mounted the rear ARB, that isn't a problem. Front is much more difficult. Due to the omitted steering bridge, the steering links are quite long and at some point, they are pretty much everywhere in between the servo and front diff housing. So mounting the bar in between the plates isn't much of an option. You can't put it on top, because there's the belt. So I'm thinking about mounting a steering bridge, to get better steering geometry, and also some space for the ARB. I will either extend the original one (to get higher steering angles), or I will implant the bridge from some other car (I already have Sakura D4 bridge to start with).

For my racing, I don't need ducts or diffusers, because our racing is quite low speed (but a lot of turns) - check out the videos at the bottom of this album. What I really need is ground clearance (around 20mm), high steering angles (around 50º), and good suspension - both geometry and shocks.

What I'm currently trying to achieve is custom caster block with less than 10º caster angle (which is the default). That's because the my car has around 6º of kickup (like buggies), which means that combined with 10º of caster in the block, the total caster is 16º, which is IMO too much for my racing (kind of deaf steering).

I already have to CAD drawing,


I even have a 3D print, but FDM printing technology is probably not good enough for this (it breaks under stress). So I will try Laser Sintering (SLS) and see how it goes :-).

[stormridersp]

16 degrees of caster is too much!
I didnt understand how you managed to add so much caster, can you explain?

Regarding the steering block, I was thinking about using FF-04 as seen below. Its a perfect match for the XV-01 and it allows the use of the standard steering geometry and stock parts. The bad thing is that it seems pretty difficult to find any FF-04 EVO parts these days.



Very nice pictures btw! Lots of very customized chassis running in there.
Cheers

[haplm]

Originally Posted by stormridersp

16 degrees of caster is too much!
I didnt understand how you managed to add so much caster, can you explain?

Regarding the steering block, I was thinking about using FF-04 as seen below. Its a perfect match for the XV-01 and it allows the use of the standard steering geometry and stock parts. The bad thing is that it seems pretty difficult to find any FF-04 EVO parts these days.

...

Very nice pictures btw! Lots of very customized chassis running in there.
Cheers

Well, the standard XV-01 caster block (which is actually DB-01 / TRF501X hub) has 10º caster.

Then I have 6º of kick-up, which basically means that I have spacers under my FF suspension mount, which are angling the front a-arms. 3mm of spacers adds roughly those 6º. The trick is, that kick-up is additive with Caster - for explanation see "Caster" section here. This page also explain what kick-up does in the section "Kick Up and Anti Squat".

If I mount some steering rack, I will solve the from ARB similarly to FF-04. I will mount it underneath the upper carbon plate, using mounts that I will probably cut from standard XV-01 front ARB mount (unless I will find that FF04 component). Thank for mentioning this, it might be helpful...

And yes, there's a lot of either very customized chassis, or even custom chassis. Couple guys simply started designing their chassis from scratch, and they are just using components from various cars to complete them. Definitely interesting to watch and learn...