InspGadgt

My understanding is that while the off-set is similar...the hubs and bolt pattern are different. The question I have is what compound are they? If they are lilac front and rear like the WGT tires...it may not work out well for 1/12th given that the ratio of tire size front to rear is quite a bit different between 1/10th and 1/12th pan cars.

andrewdoherty

iTrader: (49)

OK, so still it sounds like 2 off sets would work then right? Yokomo and Jaco off sets?

InspGadgt

No...you would need Jaco, Yokomo, and Pro One. Pro One rims won't bolt to the Yokomo hub and vice versa.

Wedgeman

Now there are 2S lipos in the size of 1S from Trinity, LRP, Reedy, Trakpower, MuchMore, Intellect and ProTek mentioned above. I think that's a sign of good things to come.

Yesterday I was practising WGT, 1S/10.5. A friend was running 2S shorty/17.5. We had similar laptimes and were consistent during 8 min sessions. In the end my motor was 82°C/179F and used 4400mAh. My friends motor was just a little warm and used 1600mAh. The "fuel efficiency" of 1S really bugs me now, as it became clear that the most of used amps only generate heat.

When it's time to go mod speed, I'd prefer to not stress about temps so much and put one 2S slim shorty to power that 10.5.

howardcano

iTrader: (37)

You need to re-think your mathematics a bit. 1600mAh from a 2s LiPo is the same energy as 3200mAh from a 1s LiPo. That's much closer to parity than you thought. The remaining difference could easily be due to different drivers and car setups.

biz77

iTrader: (47)

The problem with moving 1/12th scale to 2s is that many are already complaining that 1s 17.5 is too fast. Some clubs are even moving to 1s 21.5. A 25.5 motor on a 2s would be roughly equivalent to 1s 13.5.

Wedgeman

Yes I'm heavier on the throttle, got older batteries and longer rollout, that explains the rest. So is it 1600mAh per cell, summing a total usage of 3200mAh? I was thinking that 2S produces the same amount of energy to the wheels with a lot less "fuel consumption". They say that when voltage is cut in half, current doubles and vice versa. It's been measured that 1S 10.5 draws 80A, while 2S 10.5 draws only 40A. That math indeed is a bit fuzzy to me now. There must be a reason to why supporters of 2S say that it is "easier on electronics". Sorry if this should be in a newbie's topic.. I just like the idea of lowering temps with more voltage and less motor, and with those new low profile batteries there's no weight penalty either.

RedBullFiXX

iTrader: (34)

I think it's a good idea for mod 12
17.5 2s

but too much punch and speed, even with 2s 25.5 for many to handle

howardcano

iTrader: (37)

Replace the phrase "fuel consumption" with "energy consumption", which is calculated as voltage x current x time. Double the voltage at half the current gives the same power, and the same energy consumption.

I don't know who says that, but they are wrong.

Again, no.

This is a valid point. All else being equal, a 10.5 on 1s gives about the same power as a 21.5 on 2s. But in order for the 10.5 to get the same power on half the voltage, the current must double. While most ESCs have no problem handling the voltage of 2s or 1s, they will heat up more with double the current.

The only component that will run cooler will be the ESC. Using the example above, the motor temperature of the 10.5 on 1s will be the same as the 21.5 on 2s if it is giving the same power output.

CypressMidWest

iTrader: (1)

Here's my take on Spec 12th tires. It will not be popular, so I have pre-emptively donned my nomex firesuit, lol.
I have been racing for a LONG time. I travel throughout my region to various tracks, and I run 12th and WGT. The lilac spec tire is awful in WGT cars, but the cars are forgiving due to their wheelbase/track dimensions. I have been to facilities where the lilac (team purple) tires work okay on WGT cars, but 12th scale cars were undriveable on any tire in the Pink/Purple family.

Some tracks run oval, spec Slash, and a horde of other classes, and those tracks tend to "fuzz up" the lilacs become sticky, and become coated in loose carpet fibers. Once that happens, no change to the chassis can make the car raceable.

I strongly believe that each facility could adopt a spec combo that works for that surface, but across the board one compound seems like a bad idea imho. Honestly, most tracks already have a go to tire combo. Some are Green/Blue, some Yellow/Black, some Pink/Magenta. A little research can go a long way before you ever purchase your tires for a particular event.

Rant over, lol.

RedBullFiXX

iTrader: (34)

Most tracks in essence have a spec tire, i.e. one goto combo that works on that surface

For some tracks the striped lilac spec works great, at other tracks it would kill the class

I suppose each track could use a mandatory spec combo for 17.5, but would that build the class, or be a more costly vers of what we have now ?

Spec rubber tires are great, for sedans, F1 and perhaps WGT, if that's what you're into

Wedgeman

According to electronic-hydraulic analogy, current is described as water and voltage as the height of a waterfall. The higher the waterfall, the less water is needed to produce a certain amount of energy. Just like you said with other words. But resistance plays a role in energy consumption, our wires have a limit to how much current can go efficiently through. Think about a hose at the bottom of a waterfall. If we lower the height and let more water fall down, we still have the same amount of water coming through the hose, but a lot slower. In a closed system that extra water gets stuck upon the hose and does not help in providing the desired impact at the output at the right time. My understanding is that in electrical circuits this resistance transfers to heat, and heat means lost energy.
(chemwiki.ucdavis.edu/Analytical_Chemistry/Electrochemistry/Voltage,_Amperage_and_Resistance_Basics)

Here's the post about amp differences with 10.5 1s/2s: - rctech.net/forum/9221358-post2010.html - original question was if anyone had tried to setup a wgt car with 1s/4.5t. Nobody said he's got wrong results. This is an extreme example, but how is it possible that a pan car with 4S/6T delta going about 140km/h, keeps temps below 60°C? Trying that with 2s will likely end up in burning something. Power output can't be directly related to temperatures.

howardcano

iTrader: (37)

You are correct. The ESC has the same resistance for 1s or 2s operation, but if the current doubles, then the ESC loss is four times greater.

The wires also lose some power, but for the heavy gauge and short wires and we use, it's usually insignificant compared to the ESC losses, which in turn are far below the motor losses. This, of course, depends on the particular ESC and wires used.

There was absolutely no information in that post that specified what the test conditions were, so using the test results in our discussion contributes no valid information.

Power output can be directly related to temperature if we hold all other test conditions constant-- in this case, motor power output, motor efficiency (and therefore power losses dissipated as heat), motor construction (except for turn count), and airflow.

TweakRacer

TLDR: Higher voltage and lower current of 2S setup is better, and the current 1S rules of 1/12 and WGT is keeping me from joining these classes.

Sorry if I am resurrecting an old thread. I know that the last post was almost half a year ago, however given that this thread spans 66 pages and was started in 2008, I believe it is still a relevant discussion that people have an interest in.

I have tried racing many forms of R/C cars, and was most heavily invested in running nitro TC and 8th scale onroad during its heyday in southern CA over a dozen years ago.

During that time, I also experimented with running BL motors which were relatively new and expensive tech then. I tried running Hacker motors from my planes, but the plane ESC's struggled with the heat and high current draw of repeated hard acceleration, and even worse was braking. Most plane ESC's couldn't handle braking needs, or didn't even have proportional braking, if at all. Thus, most of my early experiments involved modified nitro tourers and kept the mechanical brakes/servo. Even the car specific ESC's that started coming out at the time that could handle the high current and braking needs were bulky and expensive.

So, when Novak came out with the their first BL car setup (SS5800/ESC IIRC) I immediately installed it in a modified Nitro TC3 chassis (single speed setup, custom mount/battery tray, and finally removed the disk brake because the ESC had good useable braking) and tried it out at parking lot tracks, and at Crystal Park and Revelation Raceway. I ended up writing an article on BL motors, put it on the web, and it was republished by Mike Myers in Starting Grid magazine. Back then, we also had plenty of discussion on the topic and the future of BL racing on the SGrid forums with a bunch of the ROAR big wigs.

With all the advances in BL motors/ESC's, the only remnant I have of nitro is a shelf queen Serpent Veteq, while everything else is BL.

With that said, on to the 1S versus 2S discussion. Higher voltage and lower current is better, period. For the same amount of power output (watts from the motor), it is more efficient, runs cooler, stresses electronics less, less power sag with rapid power demands, and cheaper.

On the "cheaper" factor, which is always good for everyone and the sport, there are several considerations:

1S brushless systems are uncommon outside the 1/12 and WGT circles, thus making them more expensive. Look at even the micro planes/helis/multirotors which only have BL on 2S or up. The cost of a booster or an ESC with a built in step up, is added cost that we shouldn't need or have to pay for. Not to mention that ESC's with higher current handling simply cost more, period. While there is an argument that ESC's that handle higher voltage and cell counts also cost more, I do not know of any ESC that costs more because it can handle 2S in addition to 1S. There just aren't many (or any) 1S BL ESC's for any R/C application outside of use for 1/12 and WGT.

Battery wise, you can run a smaller capacity Lipo, so generally it would be a wash price wise. Then again, 1S batteries for the two classes are a niche product, thus expensive. Not to mention the high capacity and high discharge rate or C rating needed. All that means more cost. Dumping such batteries also means more heat, which means less battery life, and even more cost. This doesn't even factor in the increased costs of high current chargers and power supplies needed to charge a high capacity lipo (needed because of low voltage)! Even from a safety perspective, higher voltage is still safer for humans than higher current, given our use case. Also, while not an issue anymore, a receiver pack in an electric R/C vehicle is extra cost, redundant, silly, and bothersome.

Performance wise, higher voltage can produce much stronger performance, either in acceleration or sustaining of high speeds. See examples in electric planes F5D/F5B, helis, pattern/unlimited F3C, helicopters, or multirotor FPV racing. Heck, look at bashers, or 1/8 scalers, especially with on road going from 4S to 6S. The higher voltage allows the potential for higher performance, cooler temps at the same performance, or you can always tone it down with cheaper lower Kv motors, even the very high value outrunner motors.

If concerned that the small motors are too light for traction/driveability on low traction surfaces like untreated asphalt/concrete, then set a higher minimum weight limit. Easy to stick lead on the pod or chassis. Plus, I could even run my porky fiberglass RC12i from the 80's or other new but cheaper chassis.

Which brings me to the last point. There is no reason for the fascination and fixation on 540 size motors, which are based on the performance and limitations of outdated brushed motors. That's like thinking that 5 liter pushrod V8's are the bee's knees, and thinking that all future engines should either be 5 liter, pushrod, or V8, even in the face of cheaper, smaller, more efficient, but newer engine technologies. If the a 380 size BL on 2S is more than you ever need, great because it is cheaper and lighter than a 540 on 1S. Or better yet, just run cheap outrunner motors. Great torque, much cheaper, and lower Kv so no issues with pinion sizing.

Also, the argument that it is impractical for hobby stores to carry smaller BL motors doesn't make sense, as even car specific retailers often carry motors for smaller scale cars. If it is hobby store that caters to other forms of R/C, smaller motors and outrunner are very common. On a related note, for the argument that it is better to have motors you can use between your stock class 1/12, WGT, and TC, I am confident that racers would have purchased a motor for each vehicle, rather than swapping between heats and reprogramming the ESC. Maybe you couldn't use your 380 motor from your 1/12 as a backup for your TC, but that isn't critical at the club level. At regionals or the nats, a backup motor is a necessary cost and is a drop in the bucket all things considered. Especially if the motor already cost a lot less than a 540 size.

Therefore, unless 1/12 and WGT start using cheaper and commonly available 2S lipos (many more applications across many R/C disciplines), other/smaller BL motors, and cheaper ESC's (blinky is a nice concept, but no booster/stepup/high current capability/cost), I will not be running these two classes.

[Jumps off soapbox....]

DesertRat

iTrader: (2)

Tweak, most of these ideas are daft.

For all its faults, the truth is that pan car racing has never been cheaper or easier. It costs $500 to build a spec-motor winning pan car from all new parts and a budget radio.

I think that instead of coming to an informed conclusion, you psyched yourself out when it comes to 1/12 pan car racing.