yyhayyim

iTrader: (26)

John: on which side do you have your GTB and capacitor. Where is your receiver, and what are you doing to counter the surplus wheight of ESC and capacitor + wires(close to 45-50g)?

John Stranahan

iTrader: (27)

YYhayyim
Post #51 on page 2 of the thread has a full set of pics of the battery and electronics installation. Seach is not working now. I'll provide a link later. Since that pic I have added a transponder to the nose to add a little more weight there.

Your CCT has a softer front suspension due to the very thick built in front suspension sway bar. A sway bar adds roll stiffness without having to make the front springs so stiff. That's why your Lola body is probably behaving better on the CCT although good body posts help. It does have good front downforce, though. The touring car bodies are also stiffer than the Lola because of the their smooth curves. This is why those touring car bodies worked better on the stiffly sprung (solid) speed spec front end.

Thats also why a bit earlier I advocated a sway bar on any new front suspension that might come out. How about a nice wire sway bar that you can change instead of that big graphite peculiarly placed piece (or novel depending on how you look at it). Then the front springs can be a reasonable tension to absorb bumps.

Gearing-Normally 6.0 with a Novak 4.5 R (180 ft straight with a flying start) and with a good sized rear tire (31.9) rollout. Right now its 5.78 with 4.5R but the tires are down to 2.150 inch giving a rollout of 29.7 mm. I only need to make this one change at around 2.2 inch as the torque curve is good on this motor. Your speed on our straight is dependent a lot on keeping the tires planted and keeping the body off the tires and track.

I have the 3.5 R in hand now. Gearing to come later in the week.

I have also started to believe that you simplicity guys don't really mean it. You would not mind one bit a great performing car even if it has a few more pieces on it. The sound the car makes going down the track has something to do with how attractive it is for onlookers to buy it. It can be fast as hell, but if the body is flopping around and rubbing on the track from that ancient too stiff front suspesion, they won't buy one. If they see it fly, they won't buy one.

Pic shows the 3.5 R installed. Status of the tires:thin but working well. 13 tooth pinion to start.

tallyrc

iTrader: (12)

yy, depending on how bad your push is, you may want to soften up the front end a little with springs and check camber before you go to a softer tire. also check the toe.. a little toe out will yield more turn in and settle the car on corner exit... if possible, i always try to run zero toe, but if it is pushing, it may be toed in.. just thnking of ideas other than going to a softer tire...


i am afraid of how the narrow car will react to the 19T 6 cell... that is why i was asking about the wider car.. i am seriously thinking of selling the 10l3t and getting a wider car.. maybe a darkside..

John Stranahan

iTrader: (27)

I like the Darkside car as well. You will have to check with them what rear axle it comes with. I know the front is adjustable width, but it may come narrow with narrow rear axle parts. If you check or if you know give us a report.

The narrow car will have no problem with the 19 turn 6 cell with a good body on it. Your asphalt is new. When I had decent traction the narrow car handled extremely well with a hot motor in it.

Extended Pinion/Motor Bearing Wear
I am still evaluating the durability of the pinion side motor bearing. It runs quite a bit hotter with the extended pinion required with a narrow pod and spacers. I had one pinion side beraing fail prematurely, but it was from a remanufactured motor. It may not have been brand new. I think the solution will be to put a drop of mod motor bearing oil in it before each session. This is also recommended in the latest motor instructions that came with the 3.5 R.

Without an extended pinion (narrow car) I got 500 minutes of run time on a new 4.5 R motor bearing. No oil needed. That's a long long time for a motor bearing. No other maintenance needed.

I have a new bearing in this 3.5. I'll see. Will start with a 90/13 or 6.92 gear. That's a good sized spur but there is no curbing to harm it. All the barriers are at least 3 inches tall, 2 2 x 4s stacked. Nobody hits me in the back either as I am not racing. That is the smallest extended Corally pinion. A wide pod car could use a 12 tooth standard pinion (a narrow car could also). That spur in the photo up above is an 81.

SKJ

iTrader: (20)

John

A company by the name of KSG makes a front sway bar kit for the oval pan cars. Should not be too much work to get it to work on you car.

Steve

yyhayyim

iTrader: (26)

John: try switching to 64P instead. There is less play and more efficiency with this set up, less "noise" meaning more power being applied more efectively. You will notice the car run much quieter, and have a bit more acceleration. As far as which combo to go with, there is a report out on this. The best combo for wear and efficiency, is Kimborugh Spur gears, with Robinson pinion gears. This combo gets the best wear rates and has the lowest chatter and noise of all other brands when paired up. Try it and see for yourself. The car will quiet down and they will last much longer than anything else.

John Stranahan

iTrader: (27)

Steve-That's a nice looking sway bar setup. I'll think about it. Here is a link. Only thing stopping me is the price. Maybe next month. I also have only space in the position it is mounted. I'll need a new front graphite bumper.

http://www.lefthander-rc.com/catalog/product_info.php?cPath=35&products_id=533

YYhayyim - I am heavily invested in 48 pitch at this point. Will not be making a switch.
John

Pro ten Holland

iTrader: (1)

Here are some pictures of my current setup.
It's my X10
On the back I use a 2mm Tbar with its front keyed to the main chassis (no pivot ball), no Tbar brace
I use pink rear tires, jap-soft fronts (firmer than purple)
On the front I use inline axles, black tamiya F1 front springs on extra long IRS kingpins. The upper suspension arm eyelet is spaced up with a pivot ball, the inner mounting points of the upper arms are brought down 7.5mm. The servo is mounted flat on the chassis. I mounted the turnbuckles as angled as much as I got them.

The car is very forgiving on corner entry (just a hint of understeer), but starts to pick up steering mid corner. This allows me to hold a very tight line. The car is now very easy to drive fast, with plenty of traction even on a very very slippery track.

More testing to come when the weather clears up (if it ever does).

John Stranahan

iTrader: (27)

Pro-ten Holland-thanks for the setup and the pics. I have two different small servo savers coming. Which is the one on your car. I probably could use a slightly harder tire than purple as well on the front when the track is high traction. Link please to those jap tires. I have Magenta rears coming for this high traction condition as well. You might have some bump toe in that is increasing steering mid corner.

Steve-I have the blue sway bar kit on the way. I see that left hand RC also offer .060 inch shortened lower A-arms (IRS modified associated pieces) and the kingpins that Pro ten Holland is using. I think I will do this lowering mod to my lower arms. This will actually lower the roll center. It will also give me some more ride height if I need it. My silver front springs are not letting the front of the chassis bottom on the track as evidenced by lack of new scratches on the 8 x 32 screw heads, so I think I am still a little on the stiff side. That sway bar will let me soften the springs and take advantage of the full ride height. The goal is to keep the front wheels planted off the bumps.

3.5 R gearing
I had a few short bursts on the track today with the 3.5. They are patching the track in preparation for the RC Pro-Series Nationals. It looks like I'm going to need about a 7.38 gear to have adequate acceleration on the short straights. (23.2 mm runout). The bottom end is softer. Should be a good motor for slippery conditions. Could not test top speed as some work was proceeding on the straight. If you are using this motor in a wide pan you could post your gearing.

Pic is of that KSG front sway bar slightly doctored to get a better look at that sneaky extra steering link. I imagine this is to reduce slack or maybe to produce perfect ackerman like on a TC3 as it is constant length. Spy shot stolen from KSG or Left Hander RC.

John Stranahan

iTrader: (27)

Roll Stiffness

I mentioned roll stiffness so I thought I would discuss it a little. A car that is cornering will tend to roll. The chassis force that tend to resist this rolling action is the Roll Stiffness. In the photo I am aplying a 6 ounce-inch torque (simulating a turn) with a torque wrench (screwdriver type) which is trying to roll the car onto its left side. The left side depresses some and the right side rises .025 inch. The car rolls. The roll stiffness is 6.3 in-lb/degree. You never need to calculate this number, but if you were building a sway bar spring system for a new car you might use this number from a good handling car, which this one is, and save a lot of track testing.

There is a good roll stiffness on a car that will give you good handling with a particular level of traction (say high grip asphalt) and a particular tire. Stiffer sway bars as well as stiffer front springs give the front a higher roll stiffness. When the roll stiffness is right the car is supple, but responsive and has good grip. If the roll stiffness is too high, the car is responsive but lacks grip and slides too much. If the roll stiffness is too low the car is sloppy handling. It may stick then slip, then stick on a high speed turn.

If the front roll stiffness is too high (relative to the back) the car will understeer (push). If the front roll stiffness is too low the car will oversteer (hook)

Roll center
Another handle on roll stiffness is the roll center. If the roll center is low the roll stifness will be lower. Centrifugal force will have more leverage. You will have more grip, a more supple car. If the roll center is higher (like on our front ends) the roll stiffness will tend to be high for a given spring.

tallyrc

iTrader: (12)

can someone explain to me the "shortened lower a arms" ... i have to put about a .25" spacer under my lower front arms (between the lower arms and the chassis) to ge anythng remotely like low enough ride height.. without raising my arms i had like 7/16" ride height... why would you want "lowered arms"? my owners manual even calls for a thick shim in there.... the pros in touring oftem simply bend their own swaybars out of hard piano wire.... for about one tenth the cost of that heavy thing you could make 10 yourself...

John Stranahan

iTrader: (27)

I'll give it a shot. Say your ride height is 5 mm with a 2.4 inch tire. You could use lowered arms and a shaved tire and still be at 5 mm ride height. You would have a lower roll center with the shaved tire. You would have less roll stiffness and more grip with the shaved tire than you would otherwise.

I have not made any yet. Right now my front tires are very short. If I used lowered arms it would raise the chassis up where I want it. You could just use a smaller spacer.

Most touring cars have a nice ball built into the suspension arms to mount the pianno wire sway bar to. You still need links and sway bar pivots. When you make it yourself it may not have the best appearance. Bling. Touring car sway bars are cheap compared to this one for the pan cars. I alway buy a set for the touring car and then never use them in the final setup as the springs are about the right stiffness already. I don't need to soften them to go over bumps. This pan car front end is really stiff.

I raced touring cars many years and attended big races. Never saw a homemade swaybar. It is so much easier to buy the factory part.

tallyrc

iTrader: (12)

looking at your book collection, which is your hobby, photography or engineering? "fundamentals of physics"


some roll stiffness is dictated by suspension geometry also, which is unfortunately much harder to calculate.. for example shorter and lower inboard links create greater amounts of camber gain throughout the suspensions motion range (roll or bumps). when created by cornering forces, some of this roll is offset by the traction of the tires. as the car corners, the force the ground is applying to the lower half of the wheel is in affect trying to lift the chassis and resist the roll.. the closer the links are to parallel, the less leverage they have to resist the roll..

tallyrc

iTrader: (12)

ahh so as my tires wear i will be needing to lower and lower my arms to compensate.. i'm still on my first set of pancar tires so this is all new to me..

John Stranahan

iTrader: (27)

I have corrected this post from new information that I gained on page 20.

The suspension geometry and roll center is easy to calculate on a twin active A-arm car. I have a program that does it. The angles you speak of simply change the instant center which affects the roll center. Parallel active arms always have the roll center at the ground.

On our pan car raising the outer upper A-arm with shims will raise the roll center. Lowering the inner A-arm pivots with a special mount will raise the roll center. See page 20 for a pan car roll center sketch.

Roll center Schematic