Are people thinking about rc performance all wrong today?

[fredswain]

I had a bit of a brainstorm with my friend Chad yesterday. We both started racing when many of you did back in the mid 80's. Back then due to a lack of battery power and motor efficiency we'd strip the cars down as light as we could get them in the hopes of being as fast as possible with the available power. Today power and run time are not an issue. Motors are more powerful than ever and many of the brushless motors have tons of low end torque compared to the brushed motors. We are also seeing people add weight to their cars for better handling. It sounds weird but I've seen it work. Is this mentality backwards? It seems counter to what we always did. Even in the real world of racing, cars are as light as possible. The real question of course is how light is too light?

Chad and I have always been Mazda RX-7 guys. Historically Japanese cars have typically been lighter in weight than their American car counterparts. They have also been lower in power. Their engines are smaller with less low end power but more rpm. It has always balanced out fairly well. You'd have the Japanese sports cars that were light and nimble with their small motors and less overall power and then you the American cars which were heavier with larger engines that had more power but at a lower rpm. Both designs had their advantages and disadvantages and were good in different ways. Times are changing of course and this doesn't necessarily apply anymore but then we got to thinking about the same idea in rc.

It seems like modern rc is turning more into the old American car template. It's more powerful but heavier. People are adding weight in the name of handling. The 2 heaviest things in our rc cars are the motor and the battery. The rest of the electronics have gotten to be very small and very light. Battery life is also so great today that you can typically run for a couple of qualifying runs on the same pack and keep in mind these heats are typically longer than what we used to run back in the day. What I'm getting at is we have more battery life than we need to race. A race car carries enough fuel to get the job done and no more. Why not in rc?

So you may have some idea of where I'm going with this so I'll finally get to it. Why not get the cars back down to as light as possible? I don't mean as light as the rules allow I mean as light as POSSIBLE! Keep in mind that a lighter car takes less abuse in a wreck than a heavier car does. It's physics. We can only get the chassis down so light though so the savings need to come in other ways. Now lets say we power our light cars with 1 cell lipos. Half the size and weight of a 2 cell depending on your mah rating. I know you're thinking that we've just slowed down to a crawl due to half the voltage but here's where the Japanese car mentality takes over. Run a very low turn motor like a 3.4T or 4.5T brushless. You won't have any low end power of course so will require higher rpms. As an example if we have a 3300kv motor on 7.4V, you get 24,420 rpm. Theoretically. Now if we ran half the voltage at 3.7v but on a hotter motor such as a 6600kv motor, we'd still theoretically get 24,420 rpm but with a narrower usable power band of course. The reality is that we'd want a hotter motor than this still. If you think this won't work then take a look at 1/12 scale on road. Yes those cars are lighter and on smoother tracks but the point is to get our off road cars down as light as possible. Modern tracks are pretty high grip and slipper clutches can be adjusted. Sure you are still going to have less power available but then again it would need to push around less total weight. It doesn't need to be the fastest on the track. It just needs to be competitive. The idea being that the lighter weight will equal a more nimble car with the hopes that the chassis would make up the rest of the time.

I'm not saying this is a valid idea but it is an idea that I feel could potentially work. We won't get 30 minute run times anymore but if they could get 8-10 minutes then it should be enough to get the job done. The cars would be lighter which would make them more tolerant of wrecks and with less weight the suspensions could be setup softer which would make it quite nimble over rough sections of track.

Maybe it's a stupid idea. Then again, maybe it could work. I'm curious nevertheless. Discuss...

[Charlie don't surf]

The weight issue is mostly an off-road handling issue and it basically boils down to the lighter car being unable to keep power down in Its current configuration. Also most weight added is for weight transfer not just " sprung weight" I do forsee some really radical changes in off-road designs in the near future. And I don't mean redesign, I mean rc10 type game changing designs. Real car physics, and their relations to track and driver inputs are kind of a moot point in the RC world though, as the car reacts 100 times faster in the rc world.

[fredswain]

That's the thing. They are unable to keep the power down due to having an excess of it. A lighter lower powered car would take lots more technique to hold speed so I'm not saying it would be easy. We wouldn't have as much tire melting power available to require all that weight. It still does come down to traction though. As I said, we were brainstorming. It could be an interesting experiment.

[tamiyadan]

.

[Coelacanth]

Here's another consideration: with power and acceleration always on the rise--and one could say that the speed of 1/10 and 1/8-scale RC vehicles is beyond ridiculous if one wants that--comes the need for a stronger chassis. In order to survive the rigors of racing & running that only required nylon, plastic & a few alloy parts back in the day, the power of cars today requires thick carbon fiber & alloy practically everywhere. Typically, stronger means heavier--unless cost is no issue, then carbon-fiber would be used in every part. But not many people would be affording that, especially with the economy being what it is.

[fredswain]

We wouldn't necessarily have to have a flexible chopped to bits car just to have it be light. Remember lots of weight savings could come from modern electronics and a 1 cell lipo battery. In many ways the vehicle design would be a throwback to the RC10. A lighter chassis that needs a softer suspension will need to have higher roll centers for good cornering. This means shorter arms than modern cars. We could actually go back to the core of racing in the 80's but with modern electronics doing what we never could back then.

[bearrickster]

I agree with a lot of what you said, but I dont agree about a lighter car being stronger? I have run my Pro se in a lot of races and its a brick. I got hit by a Kyosho 4wd car going wide open with a brushless down the straight, it knocked mine off the track 12 feet into the parking lot, not a scrach picked it up tossed it back on the track to finish the race. the new lighter Kyosho didnt fair so well, it was a mess. I have never worried about weight so much and never really broke anything other than small parts. I have always built my cars with strong parts weather they were light or not. but this has just bin my experences.

[fredswain]

I'm not saying that a lighter car is necessarily stronger. What I am saying is that less weight tumbling down the track should require less energy to dissipate. I'm not proposing that we start building everything as light and thin as possible in the name of weight savings. Most of the weight savings would be the electronics and through efficient design. I'm actually a fan of sacrificing a little rigidity in some places in the name of strength. Using RPM type arms is a good example. They are heavier than graphite arms but also won't snap in a hit.

[bearrickster]

I'm actually a fan of sacrificing a little rigidity in some places in the name of strength. Using RPM type arms is a good example. They are heavier than graphite arms but also won't snap in a hit.

Thats what I ment I Run RPM arms on all of my Losi's

[RC10resto]

We could actually go back to the core of racing in the 80's but with modern electronics doing what we never could back then.

Just come up with a good brushless / lipo combo that would equal a nice vintage 7 cell / mod motor and toss them in some RC10's and JRX2's. There are plenty of runners and parts out there, I would love to go back to the old cars with great power (not crazy) and long run times. Only problem is the tracks would have to have "roost-able" dirt on them

[fredswain]

If these could be made to hit 30 mph I'd be happy. It's what we measured my RC10 at with a 19 turn Trinity modified on a 2 cell lipo. We mounted a small gps on it and ran up and down the street.

[Charlie don't surf]

30 is nothing, you can hit 50+ with a 21.5 and a 2s

[fredswain]

Boosted to high heaven maybe but a nonboosted 17.5 won't even touch 25. They are like old stock motors. 30 mph is fast enough for any track.

[Charlie don't surf]

So in this discussion, what are you trying to "design" or debate? What type of car/truck for what type of battery, and what type of motor, what type of course and what type of tires?

[fredswain]

I'm trying to figure out if it would be possible to design a decently competitive car that is lightweight using half the power that is purpose built purely for the race track. Offroad, 2wd buggy, 1s lipo. The rest is what would need to be worked out. Thanks to modern technology I think it's doable.