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fasteddie9111
04-10-2004, 01:44 PM
Hi,
I had a few questions about a pan car's design. First, i was wondering about the steering. What are the pros and cons of the steering system that the pan car has? I know the steering rods are connected directly to the servo and this could cause bumpsteer, but what if the servo was tilted like in a pan car or even mounted upside down? Would this type of setup still provide good steering? Also, what are the pros and cons of the direct drive system? Without all the gears in a normal transmission, would it be possible to gear up more(larger pinion)? I have noticed that pan car overall gear ratios are rather low(something like 4:1) considering that the wheels are directly driven, why is this and doesnt it lead to overgearing? Any help is appreciated. Thanks!

Prelude14WRX
04-10-2004, 02:02 PM
Pan cars rock!!!! All the stuff u said makes these rockets handle like F1 cars. Brake late, nail the throttle............i love these cars :D :D

fasteddie9111
04-10-2004, 06:41 PM
so, that type of steering system is actually pretty good considering it is setup at an angle or even upside down? I am still wondering about the direct drive and gearing. Thanks for the reply!

Prelude14WRX
04-10-2004, 08:26 PM
Direct drive is great. I switched from touring to 1/12 and its so much fun and easier to work on. The run times are crazy long and my stock power 4 cell car is fast than 19t, 6 cell mod touring cars :D :D

fasteddie9111
04-10-2004, 08:51 PM
whats your rollout? could any other car thats not a pan car have similar rollout and be fine? Thanks for replying once again.

Prelude14WRX
04-10-2004, 09:01 PM
ur welcome.....anyway, i have no idea what my rollout is. Im using the trinity monster horsepower stock with 22t pinion gear and 75t spur gear. It flys :D
I dont think u should worry about rollout, just test pinion and spur gears...thats what i did :cool:

highroller
04-11-2004, 03:25 AM
Pan car have changed alot since their first introduction in the late 80's.
The servo saver position as well as the mounting point for the steering rack effect how agressiive or responsive the steering is. Mounting the servo down makes it less responsive, same as moving it in one hole on the steering knuckle. Center point was also tried-and is used on some tracks to counter act the ackerman affect - both tires would have the same turning radius. Using inline (on center) steering also makes steering more aggressive so if you use all these setups at the same time, you end up with a loose (back end break loose) the ideal setup is to have a slight push, makes the car faster. The reason direct drive is used is both from rules and what works - just like in other types of racing the gearing is determined by the size and layout of the track and motor output. In stock racing a certain motor requires a 2.14 to 2.25 rollout, in 19turn classes it may be a 2.38 to 2.50 and modified 2.89 to 3.11 rollout to get gear ratio to that area you measure tire diameter and calculate the pinion change needed as tire wears to a smaller diameter (generally going up 1 tooth). Since you have no reduction gear that equates into the calculation and it's direct drive it's a 1.1 ratio so gear ratio is normally lower than transmission cars. Since transmission cars like the B4 or Losi use different transmission ratios your gear ratio (spur/pinion) won't be the same nor can transmissions cars use the same ratios (rollout) as a direct drive car. Two direct cars may be using the same rollout but different size tires or spurs which would affect the one using large tire or spur to have slower acceleration. To get an idea of the rollout measure the distance across tire (2.25) multilplied by Pi (3.14) divided by gear ratio (spur 120/pinion-35) = rollout
2.25 x 3.14 = 7.065 (7.06) divided by (120/35) 3.4285 (3.42) = 2.058 (2.10) which would need to be change to a larger pinion 120/36 = 3.33 making the rollout 2.12 which is still below a 2.14.

Other tuning helps besides just gearing, finding what front springs work, what shock oil, springs whether tweak helps or a neutral setting makes car handle in the corners and on the straight - you want to stay on the throttle (oval) or roll off with very little hesitation and getting back on without causing wheelspin or a mishandling car or overpowering it by using a motor that's not compatiable to track surface like a 6 turn single where a 7 turn triple is about what the track can handle. In any class of pan car racing a certain motor may be easier to use than another due to the certain power band.

fasteddie9111
04-11-2004, 12:57 PM
wow, that was a lot of good info, thanks! I was wondering if you could clear up what you were saying about the steering, i did not quite understand what you were trying to say. Thanks!

Prelude14WRX
04-11-2004, 02:07 PM
The advice the guy at the hobby store told me about 1/12 scale was to make sure ur car isnt tweaked and that u have the right compound tires.....with this, it doesnt matter about all the fancy tuning things ;)

highroller
04-11-2004, 05:10 PM
Where and what point you mount the steering rods ends either slows or speeds up the steering response. The steering block has two mounting holes, the inner most can make steering more aggressive by changing the distance and angle. Like on offroad and TC by changing the position or angle of the tie rods you affect the distance and load. So how you position the steering rod and mounting point it affects how responsive the steering is.

For onroad racing you want even weight accross all tires, on some ovals (banked or flat) you start out neutral (no tweak) let the chassis setup get you around track - then tweak if needed to smooth or change the amount of weight. Tweaking just changes weight or redistributes it X ways, putting weight on right front, add more weight on left rear, take weight of left front and right rear.

fasteddie9111
04-11-2004, 05:37 PM
with the steering rods connected directly to the servo, is there enough servo movement to move the tires adequately? How come more cars dont have steering systems like a pan car? thanks for the helpful replies!

Prelude14WRX
04-11-2004, 11:05 PM
My brothers TL-01 has direct steering and handles very well with a normal hitec servo.

highroller
04-12-2004, 06:07 AM
The tie rods are connected to a servo saver that is attached to the servo.
Unless you've raced or ran a pan car then you understand where mounting the tie rod does or how it makes the car reacts. Offroad & Touring cars use a bell crank system to help reduce the shock of impact and to produce more steering power from the servo. Without it (bellcrank) you'd need a much stronger servo.

InspGadgt
04-12-2004, 03:23 PM
The other reason TCs and off-road cars use a bell crank system is because of bump steer. Since they use an independant front suspension as the suspension compresses the pivot point of the steering moves in toward the car. To keep bump steer to a minimum you need the steering tie-rod to be parallel to and the same length as the suspension arms. That way the suspension and steering all move in the same arc. Pan cars do not need this for 2 reasons. The first being that most of them use a lower front suspension arm that does not move. The second being that their suspension movement is much less then that of TCs and off-road cars. With both of these two reasons leads to a very slight inward movement of the pivot point so bump steer is negligable.

fasteddie9111
04-12-2004, 05:22 PM
thanks for the great replies again! I was wondering about that bumpsteer thing. Can't the servo be mounted on a tc or offroad car in such a way that bumpsteer is eliminated? Maybe tilting it or placing it upside down or something? Thanks!

fasteddie9111
04-13-2004, 02:54 PM
i also noticed that the stampede uses this type of steering system, so how does it work on that offroad truck? Unless, on the stampede, are the steering rods the same length as the a-arms? Thanks.

InspGadgt
04-13-2004, 04:07 PM
It has to do with the geometery of the suspension arms and steering rods. Just moving the servo around probably won't change that enough to get rid of bump steer. Though the F201 uses a single bell crank about the same size as a servo saver and there is a way to get the bump steer out using a bent steering rod from FPM. The Stampede doesn't use a bell crank true but it also has wicked bump steer.