wtcc5's TT-02 race development and race reports: Version 5.2 release

[wtcc5 5899]

The preparation continues.




I removed excessive slop from the rear retainers and also from the hub bushings. Then I optimized the seating of the top plates to make sure they hold all bearings down without pressing them or adding resistence to the drivetrain.

Without the top plates the dampers are much better visible. Otherwise they are nearly perfectly hidden.




For the indoor season I will drive without the dust caps. The chassis looks much better without them, in my eyes.






Then I removed the electronics from the KRv2 chassis and made some pictures with both chassis:












The v2 looks more athletic with the v3 looking lower and a little fat. So lets check on a scale how much more all these arms and turnbuckles weight:

KRv2




KRv3




So 46gr more seems to be OK for that amount of added parts including the two heave damper.


Last for today. The electronics went over from the v2 to the v3 chassis:




The coming evenings are for the body preparation. Managing this chassis is like having a second job. 

(4 february 2020)
 

[wtcc5 5899]

Many ideas on the suspension are experiments and like when the KRv2 was new, I really doubt if the the v3 will be fast. The preload idea and the sway bars will work either combined or seperated (having one or the other). The heave damper is a big question mark. I will definitly need time to sort it out.

Step by step I am working to make the v3 ready for the maiden run. Today the Exotek J-Zero body was cut and adapted to the chassis. The bumper lost some material. The horizontal bodypost holes are new for me and of course I doubted if they function properly, but they do! No excessive body movement under load. I also prepared the color scheme. Who can guess what it will be?

I wanted to relax on saturday, but no chance. The body took the whole day to finish. That is not the way to enjoy the hobby... Even the installation of the redesigned bumper brace happened in a hurry. Normally I enjoy adding a new designed part.

Well here is the RtR car:












The car gained weight and is now very close to the standard weight of 1350gr.:

(5-8 february 2020)

[wtcc5 5899]

The way this day went, was a big relief.

I put on old racetires for the first run. The feeling of the car is definitely different, but I managed to find a rhythm and a first trust in the behavior of the chassis. For the second run I installed the transponder, put on tire additive and had a solid run, ending with a 9.7s as fastest lap. That was a very welcomed surprise. I thought achieving laptimes of ten seconds would be a good start.



After two more runs, the tires had holes everywhere and I switched to a fresher set. The run was inconsistent, but I had much more grip and ended up with 9.599s as fastest lap. This brought up a wide smile on my face. It was a sign, that this design has potential.
In the following runs a lot of other drivers were also on track, which disturbed my rhythm. The car is fast, but not easy to drive. I also have a change in the behaviour for the time the tire additive wears off. My guess here is, that the spring is too soft. Oh, and I need to use thicker oil. 500cst feels like water with the rtr car. On top of that I found all camber measurements were different, so I cannot trust my setup system anymore. After the latter one was corrected, the car was easier to drive. I managed to achieve the same pace of the v2 in the last race. That was very encouraging.
Motivated by this pace I played around with the length of the heave damper. The other damper and springs were too soft, so this could help, was my thought. For this special situation the length of the heave damper significant changed the behavior and how much speed was scrubbed in this high grip conditions. I found if the heave damper is starting to work as soon as the car gets a load, it feels just ok, but is fast. In the end I could do 9.6s even after 50 laps. The fastest lap of the day happened on lap 44 and was a 9.58s. That is faster than I ever was with the v2 in that late stage of a run.




This was an awesome first practice day for the v3. I somehow cannot believe my luck. A new car and it is immediately on pace... that is the „Gordon Murray McLaren MP4/4“ dream every designer dreams of. I need to write down the setup, put new oil in the rolldamper (1000cst or better 2000cst ?) and install the harder leaf springs.
What a day...

(9 february 2020)

[wtcc5 5899]

And another video of one of the early runs:

https://youtu.be/M9tG7nehLEA

 

Here a short video of the suspension:

https://youtu.be/2HtENKnPBXc

[wtcc5 5899]

Time for some work on the suspension. Last weekend the track was closed for the Tamiya Euro Cup event. I didn’t participate, as I didn’t like how my Gentleman class car felt on track and also, because many parts went to the v3. Well I used the weekend for other important stuff, too. This friday and saturday will be used to change the oil on the shocks, check the suspension and try a new suspension configuration.

Today I build four small plates, that will connect the outer anti-roll-bar mount and the heave damper mount, to stiffen up the arm. Unfortunately the front half will be tweaked a lot by the leaf spring and the heave damper. I dislike that very much. And while I am working on an v3 mk2 already, I will also try a new outer anti-roll-bar mount configuration.


This is the front unit as it was up to now:




The new anti-roll-bar mount configuration will renounce the upper plastic brace and the lower carbon plate. Overall the whole assembly will sit lower on the arm:




A new carbon plate will be mounted on the outer screw of the assembly and connect to the heave damper arm:






Like this, the arm gains a lot torsional strength. The parts for the v3 mk2 will be more effective with the carbon plate directly mounting behind the heave damper.

 

I finished all preparations for tomorrow. The stiffening of the arms is a clear improvement. Especially the front axle is now as smooth as a Awesomatix. The rear could be better. I will need to look, what takes away the smoothness there. The same goes for the dampening. The front is near perfect with 2000cst. The rear is still underdampened and will do another movement after the first dip. Tomorrow will be interesting: How will the car feel and behave? After tomorrow I will implement all made experience into the upgrade package. Looking forward to it.

(21-22 february 2020)

[wtcc5 5899]

It was a interesting sunday practice in Senden. The conclusion of the first run two weeks ago, was, that the car is fast, but needed thicker oil in the rotation damper and that the driving feels kinda off. So I put 2000cst in the damper housing and tried different damper and spring combinations, leaving all other setup adjustments untouched.





The first run was the initial setup plus 2000cst oil. And the car had an awful rear end. No grip at all, just oversteering. I tried to drive it for some laps, had some high speed accidents and decided to give up on this damper combination. Well, it wasn’t just the rear heave damper, that caused the lack of grip. Last time out, I said the oil was too thin and the leaf springs too soft. Now with 2000cst, the springs felt just right and the dampening, too. I adjusted spring rate, ride height and tire loads. The spring of the rear heave damper had to leave the chassis and the guided end was attached to the damper arm with a ballstud. It made the rear just a little better. Much better was to leave the whole rear heave damper on the pit table. Finally an acceptable balance in the car. Up to this point I was very happy, that the v3 seems to be as chrash save as the v2.





I started to work through the heave damper combinations and found the car to be fastest with one heave damper in front, without spring and attached ballstuds on both sides to the arms. Like this the car felt exceptional in carrying speed through fast corners, but lacking in feel and handling in slow corners. The laptimes with the heave damper in front were in a 9.5-9.8s range, with the faster laptimes in the early stages (not like last time). Negative was the inconsistent pace through the lack of feedback. The front liked to wash out easily and didn‘t allow me to push.



Leaving both heave damper off the car, gave the wanted feedback and behavior after increasing the spring rate in front. The car felt great and did all I want, resulting in a series of laps within a tenth. That was great. With fresh tires, this would have been the fastest run of the v3. In comparison to the runs with front heave damper, the ultimate 9.5s laps were missing and also the late 9.6s. So using a heave damper has an advantage, even though it takes away feeling for the car...

(23 february 2020)

[B.RAD 240]

I'm obsessed with this thread! Incredible stuff. Love the mix of race reports and car development, so cool.

[wtcc5 5899]

I went to Senden again last saturday. Unfortunately a good days work with the car fell apart due to a (my mistake) faulty set of tires. I fought the car for most of the time. The setup changes helped just slightly. When I put on an old set of Sorex 28, suddenly everything was fine again. The car became easy to drive and the times fell by two tenth on average. So this day was kind of wasted a little bit.

Now after three days and several hours of working with the car off track, I put all new experience into an upgraded cad version. Today I want to show the upgraded damper design:



It looks very much like the first version, but except for the ballbearings, o-rings and the piston rod, every part changed. Lets take a look inside:




The end cap will get another tap to get rid of the leaking through the o-ring pushing the cap open. Also the end cap will be made from aluminium or (varnished) carbon fiber to be stronger and not getting tweaked that easily.





The piston works well and is surprisingly strong, even though it is just 1mm thick plastic. Also just screwing in the rod didn't cause any problems. Nevertheless, for the thicker oil I want to use, I want the piston to be stronger. I increased the thickness and also changed the damperhousing to have two piston stoping surfaces and to have some millimeters of oil between housing and piston, with the piston full turned.




The housing also got a bleeder. And this is funny, because Awesomatix just announced their updated damper cap with bleeders. Ever since I built my rotationdampers and had to glue on the endcaps, because of the extensive leaking, I wished I had listened to Nerobros suggestion (given in summer last year), to add a bleeder to my design. Well I didn't and now are forced to use a syringe to press the thick oil into a small hole in the housing. That sucks! So right after building the first dampers, I added a bleeder in my cad model. With my housing design, I now can refill oil without having to disassemble anything, and also have the air directly below the bleeder opening (a full oil change of course should happen from the endcap side).




One good visible change happened on the rodside. I will now have two ball bearings in oil, securing the rod in its position, then the o-ring and another (not absolutly necessary) ball bearing defining the position of the rod end bit. All these parts will be secured in place by 0.5mm plates

(1 march 2020)

[wtcc5 5899]

Saturday and sunday are RC days!


I got a nice compensation for another RC project and got a new radio. My first since 2013 or 2014:




Then, I finally bought harder leaf springs and the PSS system (front only):







The installation went on without obstacles. The car is pretty good to handle. My way to secure the leaf spring with a screw is manageable without seeing the inner end of the leaf spring. Only downside is, that I have to move away one side of the anti-roll-bar ballbearing plus holder. I also like the way to setup the tire load with a 1.5mm wrench and a little turn.



The chassis is an eye candy and I always want to drive it as soon as I have it in front of me. But as I wrote earlier here, many parts need a redesign to reduce the bending under load, especially the arms with their attached parts. Like with the damper caps, I will evaluate if I replace Nylon with aluminium...

(7 march 2020)

[wtcc5 5899]

Again no improvement laptime wise. At least I find the car more easy to drive with the changes I did today...



Well, it started in an opposite way. I bought RCK shop tires some weeks ago and wanted to test their performance. They seem to have a lot of grip, but drive strange and give no cornerspeed at all. Still the car will grip roll. So something is wrong with the combination of rubber, insert and wheel. From the outside they look like Volante, but drive differently. After some runs I felt too old to drive slow tires that cause setup problems and put on Sorex 28 rubber with Sorex black insert on Tamiya dish wheels and was instantly 2 tenths faster and after some more runs was back in the 9.6s and 9.7s.



I also needed some runs until I adapted to the Sanwa M17 radio. After three runs I had the crossover point when I got used to the hardware difference and felt a gain in precision and control. The latter two aspects are very slight in comparison to my first generation Sanwa MT-4 and not worth the pricetag of a Sanwa M17. Also with the MT-4 I could race months without charging, while the M17 gave a low battery warning after just one day... This just as feedback if anyone wants to know some pro and cons.

Back to the KRv3: One more thing, that I need to change, are the rear active toe links. Like the steering links, these tend to change their length on a hit or crash. In front I changed to longer thread rods already and it worked very well, now I need to do this for the rear also, to prevent a change in toe after every incident.
Today I tried to find the good feeling, nice behaving setup and ended up with a heave damper in the rear without spring and 1.5 degree camber in front. Until last time 2.5 degree gave the most grip. Today this was too much and the car didn’t respond well. Maybe this is because of the Tamiya wheels.
Also the car didn’t bite as good as two practice days ago. The hard spring was also much too stiff. Soft is the best option and the PSS in front feels good. Right now I am convinced, that 2000cst is too thick. I will definitely try 1000cst next time. My hope is that the car will connect better to the surface.
I am still searching the sweet spot of this conversion...

(9 march 2020)

[wtcc5 5899]

Well, last sunday I was comparing the performance of the KRv2 vs. the KRv3. And the KRv2 is a little faster and a lot easier to drive. I made a big step with the v3 in terms of control last time, but the v2 is still better. In a discussion with Florian Botzenhart, we think that the active preload could cause an unpredictable behaviour, because of the always changing preload. We have a combination of a fast to slow to fast corners, that is very difficult to drive with the v3 (no matter what setup). With the v2 it is much better to control and implement line correction. So right now, I am thinking of deleting the active preload.

The aluminium caps for the new damperdesign are in production. I also plan to relocate the leafspring to a centralized position to reduce the effect of bending the arm.

So much thoughts are in my head. One of my visions is to build an F1 chassis with the dampers hidden under the small nose. Another vision is to do a 4wd LeMans chassis for my Toyota Gazoo TS050; middle motor and very low. I would also love to have a full carbon chassis KRv3...

(16 march 2020)

[wtcc5 5899]

Oh well, I maybe wanted to much for my limited skills. The v2.5 (yes not v3.5 as it is a step backwards in complexity) will have a reduced complexity, to help me understand the rolldamper layout better. In this version I eliminated the active preload and the heave damper arrangement. The leaf spring is now located next to the damper and the anti-roll-bar will sit very low in front of the suspension arms.




The outer leaf spring retainer is a small 3mm carbon pin to reduce friction and increase stiffness. The springtip is guided by a small plastic arm. Look closely:




The anti-roll-bars changed from Xray to the Awesomatix wire. Still not perfect, but like this I have the wire out of the way and can reach the leaf spring preload and spring rate parts much better. The wire is also much wider which is good and bad. Good is the more efficient function due to the increased uptravel, bad is for my car, that the c-hub is so close. That caused the problem, that the ballend-guide-design won't fit and collide with the wheel. A new outer assembly was needed. I will use two small carbon pins as guides that can rotate via two small bearings.





Another weak part of the v3 was that I couldn't attach the droopplate in front, like I could with the v2. The new arrangement allows that. The very complex block of the v3 is reduced. The anti-roll-bar mounts are separated and the spring mounts are located slightly more to the outside and thus allow for the block to be attached to the tub chassis original threads (you guys recall, that I am not allowed to modify the tub or use a reinforced tub).


The car really looks "empty" without all the arms and levers. With these layout changes a lot of parts changed: new arms, new damper housing, new mounts, new droopplates, new topplates... It is crazy, but kind of fun. I honestly don't care much about the costs  I want to see it race successfully  Not right now, because of corona, but in may or june. <-- Oh boy was I wrong...

 

(20 march 2020)

[wtcc5 5899]

Bernd from Raceberry was very nice and produced my dampercaps in between his tight schedule.
With these in my hands, I will prepare the other parts for production.

(2 april 2020)

[wtcc5 5899]

I hope you guy are healthy from wherever you read this!
The numbers in the USA are crazy high. Europe seems to stabilize a bit. China is on its way back to a normal living. The weather in Germany is fantastic ever since we are asked to stay at home. My wife and I are enjoying the home office and now the easter holidays together. I just came in from working in the garden (yeah, I don't like it). Then updated the FF thread and now are doing virtual small talk with you guys. I just hope you all do fine, both regarding health and financially.

Just a little update on this project: To save the unnecessary high shipping costs once, I did the KR-MF Shapeways order together with the parts of the v2.5.
The pure number of parts is crazy, with 54. A lot of small stuff for the damper end retainer and the outer anti-roll-bar mounts. I am excited how the new damper design will turn out. If it won't work proper this time, I quit roll dampers 

Plastic parts arrived:



I also ordered some small stuff like ballbearings and a 2mm carbon rod.
 

Parts are slowly gathering:



Now I am just waiting for the small stuff.

(11-21 april 2020)

[wtcc5 5899]

The chaos phase 

I started building. The Shapeways quality differs a lot. This time the small holes are nearly perfect and the large diameter are off by 0.5mm, but not constant, but elliptical... Luckily nothing that would reduce the part function. The front went together well up to now.



The leaf springs snuggle well into their place. The short carbon rod sits nice as well (below the tip of the spring). A good start 

 

 

Front unit completed:

(22-25 april 2020)

[wtcc5 5899]

It is done. It is a rolling chassis now. Enjoy the KRv2.5:




















The weight came down to KRv2 values:

(26 april 2020)

[wtcc5 5899]

The KRv2.5 is rtr now. I took the electronics out of my TC7.2 (a beautiful chassis) and put them into the new car.
A big hobbyshop in Germany owed me a set of Yokomo B10 shocks for a little project I did for them. These arrived last week and look stunning on the KRv2!






I did some detail work on the v2.5. The droop plates didn’t fit right and bend as I attached them. Today I recognized and removed a little material on hidden places and now they sit flat on the chassis. Also I found 500cst oil too soft and changed to 1000cst. This feels and behaves more like a standard shock.

With both cars so clean and beautiful I pulled out the scale to see how heavy they are rtr without body:





They are pretty equal  even with different servo and esc.

(29 april 2020)

[wtcc5 5899]

Tamiya came up with a new steering rack design (54965). It looks neat and lighter than the current blue one. Another plus is the changeable Ackermann setting and the long tie rods. My competitive customers of the KR conversions already bought the new Hop Up and now demand a new design of the topplate, because it won’t fit with the current one. Michael Koos sent the new steering rack to my home and I took the time to build it virtually in CAD.
The new rack has longer arms and the steering brigde in front, causing several collisions.



The new design topplate has the camber links brought 2mm to the front and makes space for the longer steering arms. The conection that holds down the center ball bearing also lost material to allow for up to 2mm Ackermann change. I 3d-printed a topplate to check the CAD model. And it nearly fits. I had to take away 0.5mm more material in the middle.

 

(2 july 2020)

[wtcc5 5899]

The outdoor season is almost over and I didn’t visit a track up to now... Thanks to Covid and all the restrictions for the clubs.
This will change this weekend. There is one more RCK race (the series I designed this car for). I somehow stumbled over this date and now are really looking forward to it.
I pulled out the KRv2, checked it, changed some worn parts and now felt the need to install the new steering arms that were mentioned some posts earlier (my customers have it already for some months now):





(10 september 2020)
 

[wtcc5 5899]

Back from the race...
It was a near perfect weekend. Perfect weather conditions, nice people, a lot of tracktime, runs without technical issues and not much mistakes.
Saturday practice was nice. I did a lot of laps, 15 minute runs and then 10 minute breaks. That was really cool. The track was low grip and my car and setup were still from Senden indoor high grip carpet. A few tweaks with springs and anti-roll-bars brought the car in a good window.





On raceday I switched from Volante Hybrid to Volante 36r. The car was a tenth slower that way, but much more consistent to drive and reacted smoother to direction changes. I could sweep all qualifiers and later all finals, too. Most of the front runners didn’t attend or cancelled their participation, so it was easier for me this time. I still had a great time with all the nice folks around. It was a perfect end to my holidays.

(14 september 2020)

[ThunderDragonCy 8903]

Fabulous stuff Kevin. I do fine RCK rules really funny though. They allow yoy to build these crazy modified ends to the car, but you must only use the stock tub. Not even reinforced! Seems strange to me, but i love that they are like this for your ideas to evolve. 

What was the idea behind the Heave damper on the V3? I thought F1 only used these to carry the suspension when the extreme downforce fully compressed the softer regular suspension?

One note on bodies: i have a Zooracing Zoozilla body and a Protoform Spec6 for my touring car. Everyone says the Zoo is a bit too aggressive, but i find the Spec6 a bit lacking. Do you have experience of regular touring car shells too? You seem to find Exotek shells a good middle ground for GT. 

[wtcc5 5899]

@ThunderDragonCy: The rules are the rules  Yeah, the are strange. Made for every TT-02 driver to have fun on raceday, not for a guy like me who exploits them to make the fastest race TT-02 and doesn't care what the costs are (that was a lie, I do care a little bit). Still those rules are the most fun to work with.

The heave damper should reduce/limit the overall chassis movement in high load situations, like throwing the car into a high grip u-turn and heavy braking. And looking back to the first v3 runs, I guess it worked, with compareable thin oil and soft rolldamper settings. Overall, the damper layout with active preload setting had the intention to have a soft setting (oil and spring), that only hardens in cornering or load situations. It was connected with the steering angle and that is not consistent to load increase...

Speed wise the v3 worked not bad. Just the feedback and feeling was somehow disconnected and I lost trust, because in fast direction changes with little steering input, I experienced a chaotic behaviour of the car.

For my competition tc I prefer aggressive steering and a lot rotation (on the edge to drifting). So the Mazda shells were always too planted for my liking. Unfortunately not many shells have both, aggressive steering and a predictable rear end. The PF Dodge Dart was not very popular, but suited my setup and driving style very good. The Bittydesign 410R was nice, but still too planted for my liking. The PF Type-S was very good on the TC7.2, but also not very popular and then very fast replaced by the actual high downforce shells.  I have the Zooracing Baybee, but didn't test it, yet, as all the tracktime was used for the TT-02KR versions and FF-01 schoolyard racing...

The Exotek GT shells have a good balance and a very low silhouette. They could however have more downforce overall. But that is the price for the look. I don't like the Zooracing Zoodiac look...

[ThunderDragonCy 8903]

2 minutes ago, wtcc5 said:

@ThunderDragonCy: The rules are the rules  Yeah, the are strange. Made for every TT-02 driver to have fun on raceday, not for a guy like me who exploits them to make the fastest race TT-02 and doesn't care what the costs are (that was a lie, I do care a little bit). Still those rules are the most fun to work with.

The heave damper should reduce/limit the overall chassis movement in high load situations, like throwing the car into a high grip u-turn and heavy braking. And looking back to the first v3 runs, I guess it worked, with compareable thin oil and soft rolldamper settings. Overall, the damper layout with active preload setting had the intention to have a soft setting (oil and spring), that only hardens in cornering or load situations. It was connected with the steering angle and that is not consistent to load increase...

Speed wise the v3 worked not bad. Just the feedback and feeling was somehow disconnected and I lost trust, because in fast direction changes with little steering input, I experienced a chaotic behaviour of the car.

For my competition tc I prefer aggressive steering and a lot rotation (on the edge to drifting). So the Mazda shells were always too planted for my liking. Unfortunately not many shells have both, aggressive steering and a predictable rear end. The PF Dodge Dart was not very popular, but suited my setup and driving style very good. The Bittydesign 410R was nice, but still too planted for my liking. The PF Type-S was very good on the TC7.2, but also not very popular and then very fast replaced by the actual high downforce shells.  I have the Zooracing Baybee, but didn't test it, yet, as all the tracktime was used for the TT-02KR versions and FF-01 schoolyard racing...

Thanks for the feedback. To be honest i prefer a slightly more planted feel myself. I think possibly the Zoozilla is too aggressive, and i have been wondering whether the Baybee might be better. A bit less on the nose and also physically smaller. The Zoozilla has big overhangs which actually makes it harder to avoid kerbs and other cars. 

[wtcc5 5899]

If you have read this thread up to now, I just want to say thank you!

With this post this thread is back to the present. Covid definitely had an impact on my work and motivation. If there are no races and no allowance to visit tracks, then why and how make the car better? So in summer 2020 I got the FF-01 fever and did schoolyard racing with @Quincy.

The rolldamper topic is still on. As the damper are right now, they are not leaking and ok to work with. BUT! I underestimated the impermeability of the print. The oil sweats slowly through the housing walls. So after a while i got air in the damper... It was once my goal to realize a 3d printed damper housing, so now I need to decide which way to go. Should I use another 3d print plastic or go aluminium (milled not printed). The latter would be my favorite choice, but that requires a new housing design. And that is what I am working on at the moment:

I have a lot less freedom in design than I have with a 3d print and that is a tough challenge...

 

[ThunderDragonCy 8903]

@wtcc5 Can i ask what the advantages of the rotational damper and leaf springs are? Especially now the heave damper is not included?

Could you paint the inside or outside of the printed plastic damper body with clearcoat to seal it instead?