haplm's XV-01 carbon mod

[stormridersp]

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...

Imo, you dont need to add that much anti-dive anti-squat to the suspension. When books say that you need to focus the upper-bottom a-arms into the center of gravity, that's only an allusion. Just a couple of minutes of a degree are enough to accomplish that. On the other hand, the compromise of adding 6 degrees of caster to yet 10 degrees is too great. Caster is always more important than anti-dive/anti-squat and should be adjusted first. In fact, I never saw any rally or race car running more anything closer to 10 degrees of caster; 9 degrees is usually considered the very maximum.

Until I moved back to Europe earlier this year, I used to make car physics into Assetto Corsa racing simulator, for rally & race teams and track day enthusiasts. To make the car physics, one needs to perfectly draw the suspension geometry and behavior of the car, by perfectly measuring all the suspension components. Most of the cars that I made, never exceeded 4.5 degrees of caster: Lancia Delta S4, Impreza WRC 98, Clio Rally, Ferrari 288 GTO, Impreza 22b, Citroen DS3 WRC, Alfa Romeo 155 DTM '94, Ferrari 330 P4...

Imgur: The most awesome images on the Internet
Lancia Delta S4 Group B

Regarding the front ARB, I think that you can already mount it using stock parts. Check the parts NN15. You can attach them to your upper deck plate and run the front arb from there.

Cheers

 

[haplm]

Imo, you dont need to add that much anti-dive anti-squat to the suspension. When books say that you need to focus the upper-bottom a-arms into the center of gravity, that's only an allusion. Just a couple of minutes of a degree are enough to accomplish that. On the other hand, the compromise of adding 6 degrees of caster to yet 10 degrees is too great. Caster is always more important than anti-dive/anti-squat and should be adjusted first. In fact, I never saw any rally or race car running more anything closer to 10 degrees of caster; 9 degrees is usually considered the very maximum.

Until I moved back to Europe earlier this year, I used to make car physics into Assetto Corsa racing simulator, for rally & race teams and track day enthusiasts. To make the car physics, one needs to perfectly draw the suspension geometry and behavior of the car, by perfectly measuring all the suspension components. Most of the cars that I made, never exceeded 4.5 degrees of caster: Lancia Delta S4, Impreza WRC 98, Clio Rally, Ferrari 288 GTO, Impreza 22b, Citroen DS3 WRC, Alfa Romeo 155 DTM '94, Ferrari 330 P4...

Imgur: The most awesome images on the Internet
Lancia Delta S4 Group B

Regarding the front ARB, I think that you can already mount it using stock parts. Check the parts NN15. You can attach them to your upper deck plate and run the front arb from there.

Cheers

I absolutely agree that more than 10 degrees is way too much (and thanks for sharing your reasoning for that). The reason why I use the kickup is that other racer kind of insist that it really helps with the bumpy track. However, most of them is running mid-motor XRays, so IMO they may need it more than my XV with motor in the front.

However, for the last race, I have already decreased the kickup to 4º, and it certainly helped with the steering.

So now I can do two things - either remove the kickup altogether, and have 10º with the standard hub, or get (print) new hub with 0º, and use up to 6º of kickup with that custom hub. As a temporary solution, I will try to remove the kickup completely, but ultimately I want to test 6º of kickup + 0º custom hub, which IMO might be the best combination.

Regarding the Front ARB - you will have to believe me that there's no space for it with the current steering configuration. Look at how much I had to cut the upper plate to clear steering links in full lock and full suspension compression. However, the steering rack should solve this, as long as I will be able to find one that will allow me those 45-50º of steering angle...

 

[stormridersp]

I absolutely agree that more than 10 degrees is way too much (and thanks for sharing your reasoning for that). The reason why I use the kickup is that other racer kind of insist that it really helps with the bumpy track. However, most of them is running mid-motor XRays, so IMO they may need it more than my XV with motor in the front.

However, for the last race, I have already decreased the kickup to 4º, and it certainly helped with the steering.

So now I can do two things - either remove the kickup altogether, and have 10º with the standard hub, or get (print) new hub with 0º, and use up to 6º of kickup with that custom hub. As a temporary solution, I will try to remove the kickup completely, but ultimately I want to test 6º of kickup + 0º custom hub, which IMO might be the best combination.

Regarding the Front ARB - you will have to believe me that there's no space for it with the current steering configuration. Look at how much I had to cut the upper plate to clear steering links in full lock and full suspension compression. However, the steering rack should solve this, as long as I will be able to find one that will allow me those 45-50º of steering angle...

Increasing the steering angle is really a problem that I could never solve myself. I also tried scrapping the hubs, but that resulted in premature wear and breakages of the shafts parts in particular, the cups. The thing is that messing with the steering requires a lot of work in order to keep the same steering geometry, or at least one that doesnt cause too much bump steer due to a poor steering geometry. I assume that you are familiar with the principles of steering geometries.

Btw, how did you cut the carbon plates? Did you used CAD to design it?

 

[haplm]

Increasing the steering angle is really a problem that I could never solve myself. I also tried scrapping the hubs, but that resulted in premature wear and breakages of the shafts parts in particular, the cups. The thing is that messing with the steering requires a lot of work in order to keep the same steering geometry, or at least one that doesnt cause too much bump steer due to a poor steering geometry. I assume that you are familiar with the principles of steering geometries.

Btw, how did you cut the carbon plates? Did you used CAD to design it?

Yes, steering angle is tricky one. This is how my steering looks like (a lot of milling was involved):

Although I'm using double cardans, you can see that the steering (hub/knuckle) is not at their (modified) limit (45º roughly). It is the double cardan which is not allowing it to go further. Some of my fellow racers overcome that by milling even the DCD or CVD, but that is churning through pins and cross joints like crazy. Basically one race, and either the pin or joint (or both) are gone.

I don't like that, so I'm trying to find better shafts. So far, I found double cardan from Active Hobby (50º) and also Square TGE-542SP CVD (55-60º). I've just ordered both, so let's see if they really work when they arrive.

However, you are absolutely right that the steering requires tons of work to keep it operable with such extreme angles, and also super long shocks (75-85mm). Everything has to be repositioned (even suspension mounts), milled, extended, etc. And yeah, bump steer is a problem, but to solve it, I would have to reposition upper links, which is nearly impossible. Because of this, I believe that there's not much more I could do with this car (although I will try), so for next season, I'm switching to a different platform.

For this car, I have CAD model for both the plates, hubs, ESC box, and rear camber link holder.

It shows my attempt to reposition front mounts for camber links, but most likely I will scrap that effort, and will focus on placing the steering rack on the bottom plate and adding ARB holders to the bottom of the upper plate.

And yes, at this point I know a lot about steering, and car physics in general. I'm even using software to simulate it. But I'm sure I'm nowhere close to what you have learned, as I started learning it like 6 months ago (and had to learn CAD in between as well )

 

[stormridersp]

Yes, steering angle is tricky one. This is how my steering looks like (a lot of milling was involved):

Although I'm using double cardans, you can see that the steering (hub/knuckle) is not at their (modified) limit (45º roughly). It is the double cardan which is not allowing it to go further. Some of my fellow racers overcome that by milling even the DCD or CVD, but that is churning through pins and cross joints like crazy. Basically one race, and either the pin or joint (or both) are gone.

I don't like that, so I'm trying to find better shafts. So far, I found double cardan from Active Hobby (50º) and also Square TGE-542SP CVD (55-60º). I've just ordered both, so let's see if they really work when they arrive.

However, you are absolutely right that the steering requires tons of work to keep it operable with such extreme angles, and also super long shocks (75-85mm). Everything has to be repositioned (even suspension mounts), milled, extended, etc. And yeah, bump steer is a problem, but to solve it, I would have to reposition upper links, which is nearly impossible. Because of this, I believe that there's not much more I could do with this car (although I will try), so for next season, I'm switching to a different platform.

For this car, I have CAD model for both the plates, hubs, ESC box, and rear camber link holder.

It shows my attempt to reposition front mounts for camber links, but most likely I will scrap that effort, and will focus on placing the steering rack on the bottom plate and adding ARB holders to the bottom of the upper plate.

And yes, at this point I know a lot about steering, and car physics in general. I'm even using software to simulate it. But I'm sure I'm nowhere close to what you have learned, as I started learning it like 6 months ago (and had to learn CAD in between as well )

You have already done quite a huge great job there. Very professional. How did you learn CAD? Now that I'm back in Europe, I'd be interested in giving my XV-01 carbon conversion another try, but I know nothing about CAD modeling.

Cheers

 

[haplm]

You have already done quite a huge great job there. Very professional. How did you learn CAD? Now that I'm back in Europe, I'd be interested in giving my XV-01 carbon conversion another try, but I know nothing about CAD modeling.

Cheers

Thanks. I'm using Fusion 360, which is free for non-commercial use like this, and they have tons of great Youtube tutorials. I've had some basics from school, so it wasn't that difficult to learn the basics quickly...

 

[haplm]

Caster is always more important than anti-dive/anti-squat and should be adjusted first. In fact, I never saw any rally or race car running more anything closer to 10 degrees of caster; 9 degrees is usually considered the very maximum.
Cheers

Well, this really caught my attention ;-). So here I am - 0º 3D printed hub plus 4º kickup = 4º caster:

I have tried them on the pavement, and they held well. So I hope they will survive at least the next race, before I can get better prints . And BTW the handling definitely feels better .

 

[stormridersp]

Well, this really caught my attention ;-). So here I am - 0º 3D printed hub plus 4º kickup = 4º caster:

Sent you a pm

 

[Dims]

Hello guys,

Haplm... The ground clearance of your car looks very high. How much is it exactly?

I want to have a similar height but I'm not an expert and more hobbiest than you. At the moment I have the xv-01 as normal Version with the normal damper stands and damper.

Can you recommend Damper or at least tell me the length of them?


Greetings from Germany Berlin

 

[haplm]

Hello guys,

Haplm... The ground clearance of your car looks very high. How much is it exactly?

I want to have a similar height but I'm not an expert and more hobbiest than you. At the moment I have the xv-01 as normal Version with the normal damper stands and damper.

Can you recommend Damper or at least tell me the length of them?


Greetings from Germany Berlin

Hi, the car can do up to 27mm ride height, however I'm typically not using that. My usual ride height is around 21mm for gravel, if there's a really rough track, I go up to 25mm. For tarmac, I set the car at 10-15mm.

To get that flexibility, I'm using custom shock towers that allow you to mount 85mm long shocks. I'm using them if I need those ±25mm. The easiest way for me how to lower the car (because I don't have down stops) without compromising something is to use 75mm shocks with that custom tower. So I have two sets of shocks (85mm and 75mm).

However, one drawback of that 85mm tower is, that some bodies don't fit that well in the front (basically those with low hood) - like my Datsun. Subaru and BMW are mostly fine.

You can achieve similar ride height with 75mm shocks (and long damper stays), but the chassis will bottom out together with the shocks, so you don't get any extra movement of the suspension. This should be good enough unless you are racing, so IMO you should be good with the optional long damper stay (shock tower). However, you will have to do some milling on the c-hubs, and perhaps also on the chassis (under a-arms).

If you are racing (or want to), I really suggest to perform conversion similar to mine. Otherwise you should be good with 75mm shocks, long damper stays, and some milling. IMO you don't even need to go higher than 20mm, which shouldn't be that difficult to achieve.

Are there any rally races around Berlin, BTW?

 

[Dims]

Thank you for your quick reply. I have to admit I wasn't carefully reading your posts as I should be but a summary as you did is something I really appreciate.

I will consider to buy a couple of damper and maybe the long damper stand as well as soon as I can spend some more time.


I'm not a professional and don't want to be attend a race. I don't even have enough time to drive around with my cars right now.

I don't know about rally races around Berlin but If I pick up something I an let you know. If you consider to come around if there is a race don't hesitate to reach me out. We can probably work something out in case you need a place to stay.






Btw.

I pick up your idea with the dusty motors shroud and that was/is a really good idea mate.
(took the version of the Traxxas Rustler)


P.S.

How long are the damper coming as standard with the XV-01 and how long are the long damper versions? Tamiya is selling them but I couldn't find a description of the length.

Do you know that? I'm not into it and don't know how to measure damper in a correct way.

 

[haplm]

Thank you for your quick reply. I have to admit I wasn't carefully reading your posts as I should be but a summary as you did is something I really appreciate.

I will consider to buy a couple of damper and maybe the long damper stand as well as soon as I can spend some more time.


I'm not a professional and don't want to be attend a race. I don't even have enough time to drive around with my cars right now.

I don't know about rally races around Berlin but If I pick up something I an let you know. If you consider to come around if there is a race don't hesitate to reach me out. We can probably work something out in case you need a place to stay.






Btw.

I pick up your idea with the dusty motors shroud and that was/is a really good idea mate.
(took the version of the Traxxas Rustler)


P.S.

How long are the damper coming as standard with the XV-01 and how long are the long damper versions? Tamiya is selling them but I couldn't find a description of the length.

Do you know that? I'm not into it and don't know how to measure damper in a correct way.

I'm not a "pro" either. I'm attending the races just for fun, pretty much as everybody else here does. So I wouldn't be afraid of this, if you can find some race around you. It is great to meet the people there, and they can give you a lot of useful info.

I'm currently not thinking about going to Berlin to race, there's much more races than I can attend here or in Poland (however, I do come to Berlin from time to time for business, and I really like the city).

XV-01 long dampers are 75mm. Standard are 61mm. You take the measurement eye-to-eye, ie. from the middle of the hollow balls. If you plan on getting the 75mm shocks, consider big bore (12mm internal diameter). There should be enough info around that in my thread.

And I'm glad you liked the shroud idea, I really love them, although I'm not currently using the one I have for XV (but I'm using them on two other cars).

 

[haplm]

I've done couple more modifications to the car over the last two months.

First, I have replaced the FDM 3D printed caster blocks with SLA prints (laser sintering). The quality of those parts is awesome compared to FDM. Very precise holes, much better tolerance, and most importantly, the material seems to be really durable (the one I have selected is called PA2200).

Next, I've got some DCJs and CVDs allowing higher steering angles than the standard Tamiya DCJ. Specifically, those I've got are:

• Active Hobby AC420 DC Drive Shaft Universal Set for TA05/06
• Square TGE-542SP Universal Drive Shaft Set 42mm

AC420 doesn't seem to be manufactured any longer, shops are just selling what's left, and I can see why. The double joint is very tiny, which might be OK for drift car (for a while), but I broke both joints (pins) after just one race (around 40 minutes run time). Unfortunately there are no replacement part available, so I can write off $30. When it worked, it was awesome, however. 50º steering angle, and no wheel shake.

TGE-542SP is much better in terms of durability. It survived two races so far, and I can't see any damage visually. It provides even higher steering angle (55º), however it isn't that smooth obviously. But good enough for rally, especially in gravel.

However, there come a problem with such steep steering angles (and long shock travel range). Front uprights are hitting camber links really bad, binding and damaging the steering (including servo saver and the servo itself). So there was a need for a radical solution:

I've cut the upright arm off, and created a new one from 3mm carbon sheet. This arm has a much better shape, avoiding contact with the upright (and suspension mount). It is mounted using two M2 screws to the original upright (there are two predrilled holes that are just perfect for that).

Another modification that is kind of necessary is replacing the FR separate suspension mounts with one piece variant. One can use the same holes, and the advantage is, that the one-piece mount gives you some extra space previously occupied by the separate ones (which were hit even by the modified upright arm).

With these two modifications, 50º steering angle combined with 85mm shock is no longer a problem:

In tight turns, this modification gives me cushion when I don't get the turn perfectly right from the beginning. It will not win the race, but it definitely helps when one doesn't get as much practice as he should .

BTW - this is what the drive shafts have to survive...

 

[kongluc]

Do you have a one-way?

Sent from my LGAS375 using Tapatalk

 

[reg]

Hi haplm,
Awesome thread buddy and amazing work,you mention in this post bellow that most use a mid motor Xray,would it be possible to get them to start a thread up on here of all the tips,tricks and build processes they put into the cars?

I absolutely agree that more than 10 degrees is way too much (and thanks for sharing your reasoning for that). The reason why I use the kickup is that other racer kind of insist that it really helps with the bumpy track. However, most of them is running mid-motor XRays, so IMO they may need it more than my XV with motor in the front.

However, for the last race, I have already decreased the kickup to 4º, and it certainly helped with the steering.

So now I can do two things - either remove the kickup altogether, and have 10º with the standard hub, or get (print) new hub with 0º, and use up to 6º of kickup with that custom hub. As a temporary solution, I will try to remove the kickup completely, but ultimately I want to test 6º of kickup + 0º custom hub, which IMO might be the best combination.

Regarding the Front ARB - you will have to believe me that there's no space for it with the current steering configuration. Look at how much I had to cut the upper plate to clear steering links in full lock and full suspension compression. However, the steering rack should solve this, as long as I will be able to find one that will allow me those 45-50º of steering angle...

 

[haplm]

Do you have a one-way?

No, I don't, as I'm really not sure about rear wheels only braking.

What I'm doing instead is, that I'm overdriving front of the car, which helps to pull it out of the turns, and it also helps with steering. Disadvantage is, that front tires wear quite quickly.

That's why I want to try one-way pulley in the back of the car while keeping the front overdrive as described here. That should solve the tire wear, however I'll have only front brakes, which will cause oversteer during braking. How much it is a problem for racing is to be seen, so I'm building a second car to test this (and couple other things).

BTW - I have found out, that 3racing Sakura pulleys are generally compatible with Tamiya, which enables some interesting modifications.

 

[haplm]

Hi haplm,
Awesome thread buddy and amazing work,you mention in this post bellow that most use a mid motor Xray,would it be possible to get them to start a thread up on here of all the tips,tricks and build processes they put into the cars?

Thanks.

Regarding the mid-motor X-rays - I'm not sure that I can make somebody to post stuff here, but most likely, I'll have one for the next season. So sooner or later, I'll start a thread about it myself.

In the meantime, I suggest you check out this document: http://embieracing.com/en/wp-content/uploads/sites/3/2016/02/RC_Rally_Car_Rebuild_Manual_1.1.pdf

It describes what needs to be done to turn a TC car into a rally car (and Xray is being used as an example). It was written by one of the guys here, who is building these cars for others (and of course racing them), so if you are interested, let him know, he can do this for you if you want...

You can also check this thread to see how to cover it, which is the most essential thing (IMO).

 

[kongluc]

No, I don't, as I'm really not sure about rear wheels only braking.

What I'm doing instead is, that I'm overdriving front of the car, which helps to pull it out of the turns, and it also helps with steering. Disadvantage is, that front tires wear quite quickly.

That's why I want to try one-way pulley in the back of the car while keeping the front overdrive as described here. That should solve the tire wear, however I'll have only front brakes, which will cause oversteer during braking. How much it is a problem for racing is to be seen, so I'm building a second car to test this (and couple other things).

BTW - I have found out, that 3racing Sakura pulleys are generally compatible with Tamiya, which enables some interesting modifications.

Rear wheel only braking allows you to sort-of kick the rearend around...what i've noticed with my pro 4x4 is the need for a front one-way bc the front wheels lockup when i only just want to kick the rear around...

But that is an interesting set-up... I think i get it... do the front wheels barely disengage when braking or not at all...or no rear brakes at all which is more what it sounds like...you must use a Low brake percentage if so..

Sent from my LGAS375 using Tapatalk

 

[haplm]

Rear wheel only braking allows you to sort-of kick the rearend around...what i've noticed with my pro 4x4 is the need for a front one-way bc the front wheels lockup when i only just want to kick the rear around...

But that is an interesting set-up... I think i get it... do the front wheels barely disengage when braking or not at all...or no rear brakes at all which is more what it sounds like...you must use a Low brake percentage if so..

With the simple front overdrive (front pulley is smaller than the rear one), you get full time 4WD braking (there's no element allowing either end to disengage).

With the part-time 4WD setup linked previously, rear is engaging only when front is spinning faster than rear. Which means that during braking, rear is disengaged. That shouldn't be such a huge issues, as most of the braking is done by the front wheels anyway (but the rear might be a bit twitchy).

One thing that the 3racing pulleys allow me to do differently compared to the fyrstormer's setup linked above is, that I don't need to put smaller pulley to the front (ie. I can keep the standard 18T pulley), as I can put 19T one-way pulley to the rear (Tamiya doesn't produce 19T one-way pulley, which forces you to find something smaller for the front if you stick with Tamiya parts).

What you say about rear-end braking is true, and theoretically it should help around the corners. Only problem I can see is, that the braking power might be too weak, but that is exactly what needs to be seen in a real race...

 

[reg]

Wow thanks haplm that's awesome info,looking forward to seeing the thread to start.

Thanks.

Regarding the mid-motor X-rays - I'm not sure that I can make somebody to post stuff here, but most likely, I'll have one for the next season. So sooner or later, I'll start a thread about it myself.

In the meantime, I suggest you check out this document: http://embieracing.com/en/wp-content/uploads/sites/3/2016/02/RC_Rally_Car_Rebuild_Manual_1.1.pdf

It describes what needs to be done to turn a TC car into a rally car (and Xray is being used as an example). It was written by one of the guys here, who is building these cars for others (and of course racing them), so if you are interested, let him know, he can do this for you if you want...

You can also check this thread to see how to cover it, which is the most essential thing (IMO).