Alloy Tie-Rod problem.

[Devryn]

Has anyone else had a problem with the front gear contacting the alloy tie-rods?

[Murcielago659]

I remember hearing something about this. In general, the GPM parts are not that great.

[Tbird Man]

I have used ALOT of GPM alloy parts on several cars of mine and I have yet to find fault with any, when you can make the parts to the same quality as them then you can critisize them.(just think of the man hours that went into the CAD drawings alone) from what I have seen the problem is that GPM designed the tie rod for 2wd not 4wd. as such they didn't leave proper clearences. I imanine they are aware of this and are at least considering a new design. that said the only real need for it is to look good, as the plastic is lighter and strong enough for the job and flexes acting like a servosaver, if your xmod is fast enough to break tie rods then you are likely good enough at modding to alter the GPM part to fit.

[Horshu]

Yeah, I had the exact same problem. Two things you gotta do: first: take a dremel and, on those teeth that hold the servo horn, shave them to make the front look like the back (angled in). They're aluminum & the stress isn't great there, so don't worry about them being thin. #2, if you have the GPM drive shaft guide, you have to shave the bottom of that, too, so that the tie rod fits under it. It literally takes 5 minutes to do everything with the majority of that time spent waiting on the metal to cool down.

[Murcielago659]

I should have said the GPM parts for XMods aren't that great. I have GPM parts on some of my bigger RCs and they're great.

[Horshu]

After bending a couple of parts, my aura of invincibility with my GPM/texalium combo has wanted, and yeah, it really sucks that I had to grind 3 different parts down to fit in my all-GPM car (tie rods, front center shaft holder, and front deck plate all need to be shaved down), but I tell you what: I raced a friend's stock car, and all that extra weight, while requiring more torque to bring it back up to competiveness, makes for one bad hombre. My buddy had 850 mA batteries to my 700s, so he had big boost of power, and after replacing his bearings, he was faster off the line than mine with neo magnets, but almost every time there was contact, I won. I got t-boned at full speed once at the end of a drift, and my car just shifted about 2 inches then took off down the straightaway. One t-bone spun me around, but I recovered from the spinout, but every thing else was basically "Hulk go smash." My front lock plate needs replacing because a no-body wreck with a transmission lying on a shop floor permanently weakened it.
Also, during racing, my friend lost wheels on 4 separate occasions to my one time (resulting from too many wheel spacers + a hard landing on a jump). The thing about the GPM car is that it is both pretty and TOUGH. It's not invincible, and it needs power, but car vs. car, it'd be hard to beat in collisions. Also the handling is very, very nice. Given the other car's weight and later speed advantages, I still won easily most of the time, and it was due to the terrific stability of the car.

[Clint]

just ordered a whole slew of gpm aluminum parts, i am welcoming the additional weight.. as it is now..it's drift city. a little extra weight will probably make the car able to be driven controllably faster.

[Silentbob343]

My buddy had 850 mA batteries to my 700s, so he had big boost of power, and after replacing his bearings,

That only means his batteries will last longer than yours. Voltage to the motor determines how fast the car is.

[Horshu]

I dunno what the deal was with his car, but as soon as those 850s went in, his car was beating mine off the line.

FYI: For those buying GPM parts, I had to reorder the front suspension arms, and GPM *did* fix them to where you no longer have to have the front deck plate to give them full range of motion. Kudos to GPM for fixing it.

[Horshu]

Actually, are you sure the higher wattage has no effect? Power is a function of watts, not voltage, so I would figure that the true power difference is going to be voltage * amperage rather than just one of the two. Voltage is merely the force, but if the amps (actual electricity flowing) is low, then the resulting power is low. If voltage is low, but amps are still flowing, you've still got low power, but high voltage * high amps == high power.

[Silentbob343]

http://electronics.howstuffworks.com/battery9.htm

Normally, when you buy a pack of batteries, the package will tell you the voltage and current rating for the battery. For example, my digital camera uses four nickel-cadmium batteries that are rated at 1.25 volts and 500 milliamp-hours for each cell. The milliamp-hour rating means, theoretically, that the cell can produce 500 milliamps for one hour. You can slice and dice the milliamp-hour rating in lots of different ways. A 500 milliamp-hour battery could produce 5 milliamps for 100 hours, or 10 milliamps for 50 hours, or 25 milliamps for 20 hours, or (theoretically) 500 milliamps for 1 hour, or even 1,000 milliamps for 30 minutes. However, batteries are not quite that linear. For one thing, all batteries have a maximum current they can produce -- a 500 milliamp-hour battery cannot produce 30,000 milliamps for 1 second, because there is no way for the battery's chemical reactions to happen that quickly. And at higher current levels, batteries can produce a lot of heat, which wastes some of their power. Also, many battery chemistries have longer or shorter than expected lives at very low current levels. But milliamp-hour ratings are somewhat linear over a normal range of use. Using the amp-hour rating, you can roughly estimate how long the battery will last under a given load.

If using the same electronics, same load, I don't see how mah could make a speed difference. Are you sure your batteries were completly charged? LI-Ions peak cahrge to 8.4volts, perhaps you removed yous too soon from the charger?

Assume you both have cars that pull 7 milliamps under load. 750/7 is 107 hours and 850/7 is 121 hours. The car, motor/electronics, can't see that a battery has a higher mah and demand more current, both will provide that 7 milliamps. This is just an example I don't know hwat current these cars need. I know the stock FETS can handle 7 amps.

[Horshu]

Actually, and to add to the conundrum, my Radio Shack batts were charged fully in 1/2 hour. My friend's 850 Energizers charged overnight on an Energizer charger, and while his car was slightly faster than mine, it slowed down significantly within 3 5-lap races, while my much heavier car ran great for a good 10 races before slowing down. (my car is about 30 grams more than the one running the 850 mA)

[Turnination Guy]

... while his car was slightly faster than mine, it slowed down significantly within 3 5-lap races, while my much heavier car ran great for a good 10 races before slowing down.

Clearly what is happening here is that, while he has batteries that normally would give him longer life, he is using MORE CURRENT than you; which means his battery life ends up much less. As Silentbob343 quotes from HowStuffWorks.com, depending on the maximum current rating for those batteries, the 850 mAh your buddy is using can be sliced many different ways; including sacrificing running time for more current.

And as Silentbob343 tried to explain, it is not the THEORETICAL current that determines what wattage the motor can use, it is the AVAILABLE current that determines what wattage the motor can use. If the maximum possible current a battery can give at once is 0.2 mA, it doesn’t matter how many mAh the battery has; it is bad for racing.

Check what the maximum current rating (or maximum wattage and work backwards) of his batteries is, find out whether he has FETs installed, and find out what kind of motor windings he is using. He is using more current somehow; find out why.

Silentbob343, can the stock FETs really handle 7 amps? And when do you have to start using FET upgrades?

[Horshu]

We were both running stock ESCs with red stage 2s, but my stage 2 was water-dipped and has neo magnets in it.
The output rate on his batteries is 170 mA discharge rate. I can't seem to find that data on the RadioShack batteries, but I'll keep looking

[moddog]

Sounds like it's time to take the dremel to that tie rod.

On the side about batts, I run the Lenmar 850maH and they are nice. I get about 30-40 mins of runtime with my setup. I use the 15 min charger and the 2-3 hour charger and the batts seem to give better performance with the 15 min charger. Meaning they seemed to last longer when charged with the 15 min charger.