cosmo1974

iTrader: (3)

Hi Phil,

(1) I have a query regarding your comments about shock angle (as opposed to shock position on bottom arm).

My query is based on the theory at the site below (which I have found generally quite useful).
http://www.rccar.dk/artikler-mainmen...-handling.html
"R/C Car Handling - An Introduction To Vehicle Dynamics."

In particular, the chapter on "Suspension", section 2.8 Shock mounting locations.
http://www.rccar.dk/artikler-mainmen...g.html?start=2
It seemed (?) to all make sense (has pics and text).

Anyway, the formulae of interest is:
---- Wheel rate = spring rate * (D1/D2)² * sin (a)

a = shock angle in degrees
a = 90 degs would be an upright shock (ie: sin a = 1)
a = 0 degs would be a shock layed horizontal - not useful (ie: sin a = 0)
a = 45 degs (say) would be a shock layed down half way between the two extremes (ie: sin 45 = 0.707).

As the suspension is compressed:
-- the angle (a) gets LARGER (* this is the key observation *)
-- sin (a) gets LARGER
-- WheelRate gets LARGER
-- effective spring rate gets LARGER (harder)

(2) Therefore,
-- more angle on the shock, starts out SOFTER
-- but gets HARDER as the suspension is compressed

(3) On the surface this seems to be at odds with your comments.
What am I missing here ??

Sorry about the equations (my head hurts)

Phil C

You are correct about the angle of the shock theory, I wasn't thinking straight when writing my comment about this obviously!

I'm currently studying for a BEng Motorsport Engineering Degree and have been looking at different types of suspension recently (namely single seater/pushrod) which has obviously put me somewhat out of practice with what we use in RC touring cars! :S

Thanks for pointing out my mistake

cosmo1974

iTrader: (3)

Thats a relief, as my head could not stand any more thinking.
Enjoy your studies.

Less Thinking - More Drinking

cosmo1974

iTrader: (3)

Hi,

When NARROWING the rear track width (thin hexes), the Hudy setup book indicates following:
· Increases grip at corner exit (* I'm assuming this means rear grip *)
· Increases high-speed understeer.
· Increases front grip in hairpin turns.

I think Korey mentioned the same thing about Hara's RROC 2008 setup (ie: thin rear hexes, 72044, for more rear end grip).
REF: http://www.rctech.net/forum/6136073-post17070.html

If D2 gets less (and nothing else is changed), Wheel Rate gets larger:
---- Wheel rate = spring rate * (D1/D2)² * sin (a)
Not sure about roll centre change.

Why does narrowing the rear track width INCREASE grip at corner exit ??

Thanks in advance

jag88

iTrader: (1)

... my guess is that the narrower end of the chassis rolls more ..... (?)

goots

iTrader: (20)

so, I can never get my pro-spec diff loose enough without slipping the spur. How tight do you usually have your diff.

JKL1031

iTrader: (5)

A gear ratio is a gear ratio regardless of the relative size of the pinion/spur,, do u get the same effect if they create the same ratio?? Im curious if a smaller pinion is still easier and quicker to turn over than a larger pinion.

I ask because i was using 78/28, and now im moving to 87/32 which are fairly close to each other. Im convinced the 78/28 seemed faster and on edge towards ordering a 78t.

Korey Harbke

iTrader: (13)

For modified I run a LRP X12 5.5 or 4.5. For stock, I run whatever I have in my box. Currently I have a Trinity Duo 17.5 in my car. I also run Orca 17.5 motors, and LRP as well.

-Korey

Korey Harbke

iTrader: (13)

Track width is interesting. In my experience, narrower track widths usually give more traction. The problem is when you exceed the limit of traction, the car is really unstable. With a wider car, I typically find there is less overall grip. BUT when you go beyond the limits of the tires, the car just slides progressively. It's not an abrupt snap. It's a give and take type of situation. It's something you just have to try. Luckily its easy to change.

I sometimes go up to the driver stand, make a few laps, pull in and make a small change. I usually carry a few tools in my pocket just in case I just want to make a small change.

-Korey

Robert G

iTrader: (6)

i have a painted body for sale for a cyclone tc if anyone is interested thanks
http://www.rctech.net/forum/r-c-item...ml#post7254913

SpeedySST

iTrader: (6)

I just spent the last half hour looking for a good FDR for a low-med traction outdoor parking lot track, medium size, using a SPX (for now) and an Ion 13.5 motor. I was unsuccessful. Please help!

charlie_b

iTrader: (1)

Predating the Tekin era, 13.5's were geared between a 4.0 to 4.7.

SpeedySST

iTrader: (6)

As soon as I can get one, I plan on getting the Speed Passion 2.1 so what would the FDR be? Thank you very much!

Mark

05forfun

iTrader: (81)

When narrowing the track width,the car will have more lateral weight transfer in either direction, so with more weight being transferred to one side, that side will have more normal load on the tire, which means more traction. But as Korey stated, the car is easier to exceed the limit and then has prompt slide

charlie_b

iTrader: (1)

With the SP stuff, according to your track, 6.9- 7.6. This will also depend on the many combos you can run with the 2.1.