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Old 11-17-2005, 05:37 PM   #1
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Default 2Spd brshless TC racing anyone interested?

I am starting this thread because I have a 2 speed electric sedan. Anyways the subject is not about what I have but about what can happen to change RC raciing. Some time ago when rc tourers were for fun, a few manufactueres made 2-speed trannies for their cars. Yokomo, HPI and Kyosho. Well it didn't take off because these were banned from racing. However, how about that we don't ban them but create a class for them.

Nowadays, we have batteries that can last almost 8 min or more. With a 2-speed you might be able to extend the run time to almost double. Add that plus the efficiency and speed of brushless motors and you might get a run time of 25 min. and a possible top speed of 50mph!! Doesn't that sound interesting? These numbers are just speculative but even within the ballpark of these its still very tempting.

Think about it. Most guys who run nitro complain about electric as not fast enough or not enough run time. Most guys who run electric don't like nitro because they don't like the messiness of nitro plus all the fumes.

So I am proposing the idea of running 2-speed brushless electric TCs with either 3800's or Li-Poly. Its clean, its fast, and it runs for a long time. This could be the thing that everyone is looking for.

Tell me what you think. Thats what a forum is for.
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Old 11-17-2005, 05:56 PM   #2
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Default Interesting

How much does a two speed transmission cost? Can you Easily retrofit current 1/10 TC cars to use them?
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Old 11-17-2005, 06:01 PM   #3
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I know HPI has one for the Pro2 for roughly 45 USD. I'm all for the idea, but I do think it should be a serparate "outlaw" class, if you will. All batteries (practically used now in TC cars- i.e. lipos, NiMH, NiCd) should be legal, non-sedan bodies optional. I think it's a great idea, but wouldn't heat buildup in the motor be a problem?
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Old 11-17-2005, 07:14 PM   #4
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The extra amps being pulled by the motor wouldn't increase runtimes at all.

2-speeds wouldn't have much of an effect on an electric motor either. Nitros benefit from a 2-speed because engines create maximum power at high rpm. The 2-speed is there to provide an easier first gear, so the car can accelerate more quickly. The transmission doesn't really increase top speed, it just decreases the time required to reach top speed. Electric motors develop maximum power at low rpm and don't need an easy first gear to accelerate well. At high rpm, an electric motor doesn't have the power to exploit an upshift to a lower gear ratio. Two-speed trannies aren't often seen in electric vehicles simply because the minor potential for performance gain is usually outweighed by the cost and complexity of a 2-speed system.
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Old 11-17-2005, 07:17 PM   #5
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ummm what is a "tc" that your talking about

i would want a 2-speed class alot

i have a old hpi rs4 sport and it has the two speed on it
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Old 11-17-2005, 09:34 PM   #6
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Sorry to burst your bubble but I see two enourmous problems.

1) No current, competative tc has room to actually fit a 2-speed gearbox. It would require a complete re-design of modern tc's to get it to work.

2) 2-speed gearbox on an electric car means NO BRAKES at all! So you end up with a mega fast car that can't be slowed down into tight corners
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Old 11-17-2005, 10:00 PM   #7
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The Alex Racing Barracuda R2 that had a hot up that you could buy from speedwaypal a 2 speed tranny that was like a spur gear it never took off because it was geared for a 23turn
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Old 11-17-2005, 11:18 PM   #8
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Most tracks are not big enough to actually take advantage of the gear shifting.. esspecially on carpet.. Tc cars are fast enough in each class as it is.. you dont need anymore top speed.. if you do just drop a faster mod in....

i had one on my play car for a while, and all it was was more maintinance..
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Old 11-18-2005, 09:07 AM   #9
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Great input guys. I really appreciate your interest. Again this is something to talk about for the sake of creating new interest in RC racing.

Team Duratrax -I hear what you say in the difference between nitro and electrics power band but would that still hold true for brushless motors running on LiPos?

Bender - You are correct the new designs on BD cars would not allow space for a 2-speed but the older two belt designs did (i.e. XRay Fk04, Tam 414, etc.). Also most people running onroad rarely use brake, but I see your point and it may be something to look into for further innovation (ie using the third channel).

Burbs - Yes, most electric tracks are too small for such a class, but they are small because it was made small to fit within the range of electric with single speed capability. Of course, you wouldn't run nitro on the same track? The idea is to run on a large outdoor track as an alternative to nitro.

Again the idea is to have an electric car run almost as fast as nitro with 20-30min runtimes (no refueling req'd!- hence no pitstops) Give it some thought.
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Old 11-18-2005, 09:20 AM   #10
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I don't think you get it, electric cars have no need for a 2-speed trasmission. A much more feasible alternative has already been discussed, which is brushless in Super electric cars.
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Old 11-18-2005, 10:03 AM   #11
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Okay, so your saying that it should be in a larger scale? I can appreciate that. So that would be.... HPI Super RS4 electric? Doesn't HPI also make a two-speed for that?

Also, someone mentioned about running a hotter wind mod motor to gain speed. But that cut short on run time?

The idea is to have great speed and long run time. Again this is a discussion, ideas would be great, problems are appreciated also.
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Old 11-18-2005, 11:50 AM   #12
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If I remember right when HPI came out with the electric 2 speed several teams tried it out. What they found was the shift point was too erratic because the power coming from the battery wasn't constant. If you look at a discharge curve for a battery pack the voltage is constantly decreasing. That means your motor RPM is constantly decreasing. With direct drive you don't notice this, but with a 2 speed the shift point would be different every lap.
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Old 11-18-2005, 12:40 PM   #13
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And applying that much load to a motor that high in the RPM range would absolutely kill the comm and brushes. Since brushless doesnt have a comm, i bet the speed control would take the brunt of the amp draw spike and put on a really pretty smoke show.
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