seankyew

iTrader: (1)

Since when did Jorn TQ the 2wd buggy at the worlds?

fredswain

iTrader: (1)

I didn't like the gullwing arms for the same reason. They were too aggressive in shape so yes they could scrape.

micholix

Fred, could you sum up, what for you would be the ideal dex210, or any other 2wd buggy?

Like, A chassis, with the possebilaty to run saddle packs side by side, or an shorty pack parallel, any changes on the chassis about the front kick, or Generaly changes on the gometry of the chassis, or the suspesion itself!?

Cain

iTrader: (294)

alright in short to get my "V1" Dex210 to be more on point, I should look into:

- V1 shocks but remove the rubber grommet
- V2 towers front and rear
- V2 lower shock collars

Is that correct or should I still use V1 dimension rear towers?

71schaeffer

iTrader: (10)

Yep on point! I got my Protek shorty lipo in today and almost forgot how small it was compared to my stick lipo lol gotta love this hobby

fredswain

iTrader: (1)

This is going to get VERY long so I hope you realize what you are asking!

I used to think that a one design fits all was possible. I don't really feel that way anymore although I still won't rule it out. If you try to do lots of things, you'll usually only be good at most of them but truly great at none of them. I do really like the DEX210 gearbox and that it can easily go rear motor or mid motor in one package. What I don't like is their chassis. While it may technically allow any style of battery to be used, it doesn't necessarily allow them to be used in the orientation or location in which they would be best served. Saddle packs being a good example. You currently can only use saddles on very high grip since they are lined up like a stick pack rather than side by side in mid motor where they would be better utilized. A feature for the sake of having a feature, isn't a useful feature in my opinion.

I actually think the B5 and B5M are done well in this regards even though I disagree a little with their suspension geometry. What I like about that car(s) is that they realized that while most of their parts can be used for nearly every track, not all can. That's why they didn't just do the convertible. I guarantee they'd have done the one gearbox idea if Durango didn't have a patent on it but even that isn't that big of a deal. I like that they realized that in rear motor, a different battery orientation or options was probably necessary from mid motor. They were smart to offer two chassis here rather than one. I also like that they kept the number of screws on the bottom of the chassis to a minimum and kept the servo as low as possible. These are good design attributes that I'd certainly follow on a car.

I've stated many times that I'm big on fundamentals. I want the geometry to be correct. Once it's correct, I see no reason to change it. Then you tune around the geometry. I think too often we change geometry as a way to tune. That's backwards. Shock location being a great example. Why do we need more than one shock mounting location on the arm? Where is the optimal location? If there's an optimal location, why do we have multiple options?

Let's look at the shocks. Changing their location on the arm changes their motion ratio. The motion ratio is the amount of shock travel vs the amount of wheel travel with suspension movement. On a real car, a motion ration of 1:1 is considered ideal for comfort and handling. They've also got other considerations such as the flex in the suspension system to worry about. In rc we've got much stiffer suspension arms so flex in the arm isn't much of a concern for us. The farther out on the arm the shock is, the longer it needs to be. Look at the lengths of our front and rear shocks and then look at where they are mounted on the arms. If we move a shock mount point inwards on the arm, we give the spring less leverage. In order to maintain the same wheel rate (effective spring rate accounting for leverage), we need to run a stiffer spring. Front spring rates on our buggies are higher than the rears even though the rears hold up a heavier end of the vehicle. This is because of the difference of leverage. There's no reason why we couldn't run short rear shocks closer in on the arms as long as the springs are stiffer. It comes down to available space. The longer the shock and further outward it's mounted, the higher and wider the average weight distribution will be which affects the center of gravity and other things like roll resistance.

The other thing that happens with shock mount locations on the arms is that pack changes. Pack increases as the shock is moved outwards on the arm. This is the single least understood thing about tuning. Shock pack isn't only determined by hole size and quantity and oil viscosity in a shock piston. The main factor is piston speed. If the wheel travels a certain amount, a shock mounted further out on the arm has a piston that has to travel a further distance than a shock mounted closer in on the arm. That means it has to cover a longer distance in the same amount of time. It has to go faster to do it. The piston travels through the oil faster further out which increases pack. Balancing effective pack front and rear is difficult and nearly everyone gets it wrong. If it's correct, on a vehicle that has a longer shock in the rear than in the front, a larger piston (more and/or larger holes) will ALWAYS be used in the rear and a thinner shock oil will ALWAYS be used in front. My 210 currently has 20W up front and 40W in back. You should never have thicker oil in front than in the rear. Look at any setup sheet from any pro and tell me if anyone understands that. I forget the pistons in mine at the moment but my spring rates are also balanced. My entire car is very neutral.

Changing the upper shock mounting point changes the spring rate progression through travel. A spring has the most leverage when the arm is completely perpendicular to it. It is effectively softer everywhere else. I prefer to have my shocks oriented perpendicular to the arm, as measured in reference to an imaginary line drawn from the inner hinge pin to the shock mounting point on the arm, at full suspension compression. That means it effectively gets stiffer as it gets closer to bottoming out. That's where it needs it the most. This may not always be desirable though.

Basically I told you all of that to tell you this. I'd only give one lower shock mount option on an arm. Then I'd give you probably a max of 3 options for the upper mount with the center allowing that perpendicular location with full compression. I'd set the location so that the front and rear used the exact same shocks. Simple. At least for a mid motor. You do what you can in rear.

I like varying levels of front kick. This is what I like about Losi and now Associated I guess. I like that Losi gives you the option of 20°, 25°, or 30°. For modern high traction tracks, I'd probably run 20°. I don't like having this particular thing being fixed.

Suspension geometry is where things get tough since this is where I don't believe one size fits all. In order to keep the effective change in roll center the same between the front and rear of the vehicle when a front kick is present, the front arms have to be longer than the rear. The greater the front kick, the longer the arms. That would mean that a 20° kick would want shorter arms than a 30° kick but still both be longer than the rear. This is where I like the Losi design. I already stated that I'd probably run a 20° kick if I could. Their front arms are longer and if you do the math they are the perfect length for their 20° kick, which is what the chassis is actually at. Of course there are certain compromises for the other front kick amounts but you can't always do everything. They can't really go longer than they did which would only mean going shorter in the rear. That might not be a good thing so compromise is always going to be present somewhere. Their suspension geometry is about as good as it can get.

I've also stated that I don't believe in chassis flex as a tuning option. If you do need it, and that's a big if, I'd support lateral flex only with no flex being possible front to rear. I could potentially see this on very rough tracks but many today are smoother but with jumps such as most indoor clay or carpet tracks. It's not a jump that would need chassis flex. You definitely don't want it at all on smooth tracks.

I also like carbon fiber as a chassis and tower material. I know some say that aluminum is necessary to maintain reliability but that's not really a statement that can be made with any certainty since any design revolves around material selection and vice versa. Certainly the accounting department has a say in things to though.

Camber link locations get complicated for most people when they don't have to be. I'd probably give only one location on the outer hub but have this one vertical for subtle roll center adjustment and then have two inner locations but facing sideways for only shorter or longer options. That's it. You'd never hear another person asking if they should raise the inner location or lower the outer. You'd eliminate the confusion.

I'd leave antisquat ability in the rear and I'd leave rear toe adjustability but in that instance I'd only adjust rear toe at the hub. I'd leave the inner arm mount at 0° always and only adjust it's pitch for antisquat. By adjusting rear toe on the inboard side, you change the sweep of the arms which is a geometry change to the suspension when the only goal is a toe adjustment.

If I designed my ultimate car, it would be on a platform that was modular. Every possible feature wouldn't be built into one complete do it all vehicle. I'd have different front kick options built into different bulkheads that can be swapped and each bulkhead would only be compatible with a certain suspension arm. Then again the shock tower would change and the bellcrank offset would also have to change so that's probably not a good idea after all. It would almost just be easier to take the Shumacher approach and just design a different car for a different race surface and then use the Traxxas approach to as much part sharing across the product line as possible. Realistically that could probably be as simple as 2 different cars in 2WD or basically the Associated approach with the B5. In 4WD, the car is so different from a 2WD that one design can be made to work just fine. The modern trend of changing motor sides on shaft drive cars to use shorties or saddles is probably a good and versitile one.

The answer is tough but I'd probably pick a track type and design a car around it. Then I'd take away most tuning features and would leave only what is necessary, eliminating those which are unnecessary. People today are convinced that more features equals a better car. The reality is that more features just equals a more complicated car that is harder to figure out if you don't understand the fundamentals. I'd standardize wheels to be the same across the product line. That means the exact same front wheels in 4WD as in 2WD and obviously with the rear. ROAR may be about to completely ruin that chance this year though with their new wheel spec we'll see. Sometimes good intentions lead to unintended negative consequences. Above all, after I had a car design, I'd do everything I could to teach people how to tune them and use them properly. I'd completely eliminate any sharing of setup sheets which only serve to confuse. Here's a way to tell if you are looking at a good setup sheet or not. Ignore whose name is on it. Name doesn't override good sound fundamentals. If the front shock oil on the sheet is heavier than the rears, ignore the sheet. If you can't trust part of the setup, why trust any of it?

That's my little design rant.

Cain

iTrader: (294)

Correction to my V1 "on Point" list:

- V1 Front and Rear shocks but remove the rubber grommet
- V2 A-arms Front
- V2 towers front and rear
- V2 lower shock collars front and rear (these? TDR330600)

Dino or fred or anyone else, how does that sound?

fredswain

iTrader: (1)

I personally always run bladder shocks. By removing the bump stops, the piston would hit the bladder and that's something I don't want to happen. That means I'll always run bump stops. If you aren't running bladders, and you really always should be, check to see if the piston is capable of moving above the actual shock body at all and into the cap. If it doesn't, running without a bump stop should be fine. If it can do that, leave the bumps stops on. I'm at the point where I've decided to never run a V2 rear tower.

13Maschine

iTrader: (1)

A really short note after my day at the track yesterday. I was at SCVRC in Santa Clarita, CA, which is a nice new indoor clay facility near Hot Rod Hobbies. (Just in case people wanna check it out...)

I have yet to get my V2 to handle like my V1. I ran my V1 with both the shorter chassis and the longer RDRP. Given the new suspension geometry being the main difference I suspect this is the culprit. I just haven't really nailed down exactly what it is.....I suspect fred is onto most if not all of it already. It does seem a little more stable high speed wise. The worst part is that it pushes (lack of steering) and it hooks a bit. Hooking meaning I tend to spin out come out of a corner at times. ....

more on this later today

fredswain

iTrader: (1)

If the shocks bottoming too soon is in fact a problem, and I haven't verified that it is, then the way it would manifest itself would probably be on high grip tracks with sudden understeer during hard braking on corner entry and a back end that sometimes washes out suddenly during on power corner exit. Straight line handling and jump landing probably wouldn't be affected. It would mostly be limited to corners and even then most likely in scenarios where a lower amount of droop is run. I'd rather have too much suspension travel in either direction and then limited than to not have enough.

aeguy

iTrader: (4)

so fredswain, when do you start production? just kidding but i do love to read your posts thank you for all your insights

fredswain

iTrader: (1)

I'm working on my dirt oval design right now. It's very simplistic compared to others.

Dino_D

I do agree the the B5M has a better battery layout and the option of running a square pack in the mid motor will definitely help on lower grip situations. Also running a shortly sideways all the way to the rear is great on high grip tracks - especially for mid-motor.

Also your explanations are very detailed and spot on.


We don't have smooth tracks up north. In fact they are mostly all outdoors, sun baked dirt with a bit of clay, and sometimes a bit rutted with some dust and loose stuff on top, hence why we run the Dimec +8 over the aluminum chassis. We almost always have to run either impacts, or blockades. Mini pins won't last, and barcodes slide everywhere. Even the indoor ones are not that smooth and still cool indoors, so the grip is low. In fact, to be honestly, we hardly ever have a track that can run a mid-motor setup regardless of manufacturers, except for the canadian national race in which enough rubber is laid down. Even still, conditions favor either car, and the A main is still mixed between both mid and rear. Morning and evenings are better with rear, afternoon mid is quicker. You can get an idea with the video.

+ YouTube Video

https://www.youtube.com/watch?v=wMEyaHpvOHc




If you compare the current v2 chassis with the carbon chassis currently available, I can tell you that the carbon chassis flexs more than the aluminum.


I hear you, that a straight arm is more efficient, but in testing, 3 degree inboard toe feels more locked in a corner vs outboard. Outboard is better when there is enough grip as it allows the car to rotate more in a turn, and inboard is better on low grip. Then again you can adjust anti squat add more to alter the rotation mid corner with inboard toe. Durango has static 3 inboard, and adjustable outboard. Adding extra outboard rear toe will help with exit stability and doesn't really take away that much steering in corners.

A lot of good points you mentioned in the design of a future car, but not everyone has the luxury of those Cali style tracks. I am jealous of you guys already.

fredswain

iTrader: (1)

Keep in mind that the current carbon chassis is 2.5mm thick. I'd prefer at least 3mm and even then would have some additional carbon bracing. I used to have an Atomic Carbon Cr2 and I loved the way the chassis was done on it. It was very rigid.

Again, I'd probably just design a car for a certain type of surface and if it didn't work on a different surface would either offer upgrades if possible to meet those or would go after an entirely new car. Maybe not quite to the extremes of Schumacher though.

wileycat

iTrader: (62)

Anybody know where i can find motor pinion gear ratio set ups for this buggy, i cant find it on the web site?