The T bar acts as a suspension component. It acts as a torsion bar type suspension to control roll in a car and it also acts as a spring to support up and down movement of the chassis. Because it is acting as a suspension component, it must have outstanding memory characteristics meaning that the T bar must always return to its original position. Fiberglass has been used since the inception of the T bar car first introduced by Associated in the 12L many years ago. There have been numerous variations of the T bar car by many manufactures over the years but it still continues to be the design of choice for many reasons. Simplicity, compact and low cost is probably the primary reasons a T bar car is so popular and it does work well, to a point. Because the T bar acts as a spring, placing a coil over shock on the car is redundant. You now have two springs on the car trying to control up and down movement. This also happens when you place coil over shocks on the side to control roll. The ideal thing to do would be to use only the shock without the spring. But this does not work because to get the T bar to support the car fully loaded with all its components, batteries, motor, ESC, etc. the T bar would have to be very thick. So thick that the side to side movement to control the roll of the car would be severely hampered. The only design variation that I have not experimented with is to have a T bar thick enough to support the weight of the car, remove the tweak screws, and place a center shock on the car without a spring and then place coil over shocks on the side to control the roll. I have experimented with over the counter T bars and no tweak screws and three coil over shocks with limited success. There are some BMI guys that are having some success with a three coil over shock application but I found it did not suit my driving style.

Fiberglass T bars will begin to loose their memory due to the constant flexing at the high stress points, especially if you crash and cause the T bar to move past it's designed limits of movement. This will show up as tiny white stress lines in the T bar where the T bar makes the tight radius to connect to the lower motor pod plate. Once a T bar begins to develop those stress marks, your car will not maintain proper tweak and therefore the handling will be inconsistent. Time to replace the T bar. Thusly, the spring steel T bar offers the best of everything. Extremely high memory and extremely high durability. Kevlar has always intrigued me due to its toughness quality and its possible ability to minimize stress fatigue. As for the use of titanium as a T bar material, I would think that the cost of titanium and the additional cost of a treatment process to make it have the same or greater memory than spring steel would make it cost prohibitive for the average racer. While I would never discourage anyone from experimenting, I think if you want to make something out of titanium, make some wheel hubs and or motor pod plates. You would have racers lining up to buy those types of components. Or better yet, make those same pieces out of magnesium!!

I have to agree that magnesium is a great material, but it's very difficult to work with. Though titanium pod plates and wheel hubs would be great! :sneaky:

Another thing, can someone give me a average gear ratio for a 19t motor?
It doesn't have to be for a specific motor or track, just an indication so I know where I have to be.

Crashby, thanks for the very detailed explanation of Tbars. Couple of things though.

Associated for sure did not come up with the idea, long before Associated had the 12L, Deltas were runing Tbars on Super Phasers, there may have been others before this, but to my knowledge Delta was first about 5 years before Associated. No big deal.

FWIW, not all Tplate cars use the Tplate for a torsion spring. You mentioned this in referencing triple shock setup cars. Also the CRC cars have a floating Tplate setup where the tweak is set by preloading side springs. For consistancy, my L4 is moving away from a Tplate for centering chassis roll.

In regards to the use of Titanium for a Tplate, just as in making most RC parts from Carbonfibre or Glassfibre, you start with a flat sheet. Titanium sheet is readily available in a heattreated condition, so it becomes a matter of just "cutting it out", and installing. Titanium also has excellent memory and fatigue life, plus is extremely strong. I wouldn't be suprised if instead of bending or breaking a Ti tplate, it rather sheared the scews that secure the pivot ball sockets to the T plate.

The idea being to run a thin Titanium Tplate and place more control into the shock spring, similar to a linkage car AND not use the Tplate for any springing of roll control. Hopefully I can make the setup where the Tplate is having almost no effect on the chassis setup other than keeping the rear secured to the front. Then again I may just get lazy and not bother.

The idea of making other components from Ti is novel, but offers no real gains. For general comparison, steel being the reference, ti is about half the weight of steel and similar strength, aluminum is about one third the weight of steel and about one third the strength. These are just general comparisons as aluminum can vary widely depending on alloy and heat treatment.

So in regards to rear pods, aluminum is good and if the makers of the pods used a better alloy they would be able to make them stronger with no weight penalty, or make them more compact at similar strength. Somehow I was lead to beleive that most companies, other than niftech, used 6061 while niftech used 7075 which is a substantial difference in strength.

PK

Your correct about the Delta cars I had several versions of that car. How could I forget?!?

As far as using ti for motor pod plates, you state that ti offers superior strength over aluminum so why would you not make them out of ti? Rear axle hubs bend very easily so again, why would you not make them out of ti? You are also correct about the Niftech motor pod plates. They are the only company I have found that makes their motor pod plates out of 7075 but Ray is not making them anymore. OD and I contact him on a regular basis, trying to get him to make more but even with a promise of buying all he could make, he still has no interest in making more.

You did not address the possibilities of using magnesium. What say you about that material? I had a magnesium right side clamping hub that I got from a company called Dialed Racing many, many years ago but it is for a two bolt pattern and no longer applicable to modern wheels.

What's the thermal conductivity of titanium vs. aluminum?

7075 Aluminum is 130W/m-k
6Al-4V Titanium is 6.7 W/m-k

information courtesy of www.matweb.com

-James

What do you guys use to lubricate the damper plate?

Everything!! :lol: YOu'll need a good selection from 50 wt shock oil, 100wt shock oil to something really thick like Losi thick hydra fluid. Also a good way to get different thickness lubes is to buy different weight OFNA silicone oil like 5,000 to 50,000. Three distinctly different weights should do. Thin, med and heavy.

The first t-bar car was the delta phaser. This was before the super phaser. It was introduced at the 1981 worlds, which it won. (yes, I was there) Art Carbonel won the race with Kevin Orton (Tekin) also in the A main. On ther phaser the t-bar was bolted to the chassis unlike todays cars that are articulated.

Wow! You must be really old! :D

What? What? We are all old...he, he...But, WE know how to have fun...

I wasn't sure if the Phaser did or did not as I got my first Delta circa 84 and it was a Super Phaser.

Crashby, Magnesium is good in many applications. It could be used for several things on the 1/12 chassis, like Associateds right side pod they offerand even the opposite pod and standoff spacers. As for Ti pods it could be done, but for any savings of weight they would need a Jenny Craig program compared to aluminum. The 6061T6 series most aluminum components are made from is not very exotic and is typically a non aerospace and more industrial alloy. Pods made from 2024, 7075, or better still 7050 are more reasonable choices for upgrade. They are quite a bit stronger, basically the same weight, good thermal properties, and easy to machine.

I did a little looking in some leftovers I had kicking around and found a small peice of Ti. A friend that also runs 1/12 was talking about it with me today, we both agree this is something that just needs to be tried. Time will tell.

PK

AE made a right side magnesium pod plate awhile back for one of the 12L series cars.

Yokomo had L & R lowered lightweight magnesium motor mount plates listed for the YRX12 about 2-3 years ago


as for titanium it is unique, TI weights more than AL. TI made items require alot less material to equal the same strenght as AL. thats where the weight savings come in.

Yokomo
 

Hey Guys,

I was in the market to go 1/12 and heres my option list so far

Yokomo YRX-12 WE
CRC V3.2
Associated 12 L4

I really like the yoke and i know they are quick, my only problem is finding the worlds edition with al the blue alloy parts. If anyone knows a site that sells what im after at a reasonable price can u let me know

Thanks in advance

Stormer Hobbies have them in stock for $239.00 and you will probably not find a better price anywhere else.

Click on the link below.

http://www.stormerhobbies.com/cgi-bi...umb=on&smode=0