As you know, I currently run a 16/66 setup.

I have an 18 and a 20t pinion here, as well as an 14t. They have to be 5mm, as cou can imagine, that's why it's hard for me to get them. The 18 and 20 are good one, but the 14t looks a bit sketchy.

I don't have any other spurs as yet.

So would you suggest going 18/66? Kinda strange, but I see the point. Actually I would have thought a smaller pinion would give me lower temps. But I perfectly understand that my motor may have been undergeared.

What would be your suggestion? Do you know of any people running this gearing in a simillar setup?

Some food foryour brain;

A friend of mine geared his 6.4 kg heavy savage with a 10L like this;

(he uses 13,14 or 15 cells)

14/49 or 16/49 for high speed runs
14/49 on a Savage results in 25.61:1 in 1st and 17.79:1 in 2nd
16/49 on a Savage results in 22.41:1 in 1st and 15.57:1 in 2nd

His temps (measured on the 5 mm thick motorshaft) Highest temp he measured was 78 degrees (schulze speedo on 19khz) and on 9khz his highest temp measured is 68 (after two full runs) (outside temp was about 15 degrees)

I don't know what the timing is on the 9918 controller...

He told me, he heard that the motor may become 110 degrees on the shaft, i personally think that is high, considering that the magnet looses force when it gets hot, and it will get hotter and hotter, because it loses force (lower efficiency will result in higher temp)

Thanks for the input, Serum.

The 9918 has 15° timing, but this can be changed. Also, you can set it to Autotiming (whatever that means).

I think 110°C is a bit high. The Neodymium alloy undergoes a phase-transition at around 120°C, which may lead to instant loss of the magnetism. But I think this is a rather smooth transition, where the magnetism just fades over time. But theoretically you could kill the magnetsim by heat within a few seconds. I don't know the actual temp, though.
However, on our motors, I would say the lower the better, and I trust the guys who say everything below 80° is pretty save.

I will try the 18t and see what temps I get. I will also add a oneway to the fron end. This should reduce some brake stress on the system. Let's see. I just want a setup where I can run pack after pack without worries.

The 18 or the 20 in first gear should be plenty fast for the track you run on, and you could keep it in first gear. It wouldn't hurt to put a fan on the motor, either. It looks like you can't really get too fast on your track, so the motor gets almost no airflow to keep it cool. Let us know how the 18 pinion runs.

Today I had another test run, still on 16/66. But this time I kept it in 2nd.
Did a few laps on my small tack, some speed runs on asphalt and some bashing in the wood.
And indeed, (surprisingly for me) the temps stayed a fair bit lower.
Unfortunately I left the IR temp thingy ar home:o But I got quite good at the finger test:)

So I reckon this would be a sign for undergearing, then? At least in first gear.

I also finally had a close look at the final gear ratios. Please correct me when I'm wrong.

16/66 > 1:32.5 in 1st and 1:20.2 for 2nd
18/66 > 1:28.9 / 1:17.9

16/72 1:35.5 / 1:22.0
18/72 1:31.5 / 1:19.6

Okay, so assuming 1:32 is too low, what would be ideal?
You know my setup, but feel free to ask if yo want to know something specific.
I just weighted the Revoxx again, full RTR, and it's almost exactly 4.5kg (9 pounds)

What would you suggest for a safe gearing? Is the 18/66 with its 1:17.9 already too high for off-road bashing?

It would be great if I could use the 1rd gear without worries, but it should also be safe to stay in 2nd for a whole pack.
Am I asking too much, or do you think this should be possible.
I take it most of you guys drive your BL G-Maxxes mainly in one gear, right?

You can only descide for yourself what the ideal gearing is.

If i was put in your place, i would just try it and ask a person who had a lathe, to drill out a 3.2 bore to 5mm on different pinions. (or you could order a few from Mike) Just measure the temps on the speedo, motor and batteries.

Just measure the temps, that is a very important value. Also look at the temp on your batteries, because their lifetime will be shortened when constantly pushed to their max.

Do you think you need both gears (1st and 2nd?) i personally really fancy the G-maxx 1 speed conversion. It would shave of a little weight as well (shiftingservo, gears, one piece of the gearbox)

4.5kg RTR is very light! (9.9 lbs, for the non european.. ;) )

Hmm, I really like this ability to have 2 gears. No shift-on-the-fly, though. I just like to bash on my small track in first, without having to change pinions for something bigger.

I begin to believe that the difference in the 2 speeds gearing ratio is already to wide for being save in both gears over a long time. Well, at least for my setup.

Of course I have to find out for myself. I just never thought there might be something like under-gearing. (hotter in 1st than 2nd)
Apparently 1:32 is undergearing on my Truck (maybe I should add a bit weight:L: )

However, I would still like to ask the same question: Would 1:18 be overgeared?

Yes, I plan to get the proper pinions from RC-Monster.
My batts stay surprisingly cool, barely hand warm. And the controller is also rather cool. It just get's warm when I drive in second.

I had a full run in second only: ESC 60°C, 9L 75°C

Yes, the Revoxx IS very light, even with shifting servo and all. Everytime I have to pick it up without batts, or even without wheels, I'm like: whoa, babe's a lightweight. :) But I might add some stuff to make it better, though, and heavier too, for better of worse.

Double post, I know:o But I have a (more sensible) question this time.

Look, heat is about the only indicator we have on how our systems is actually doing. Apparently you can tell by the different temps if a system is struggling or somethings wrong.

For example, a hot motor can either be due to under- or overgearing. Agree?

Hot batteries are a sign of a too high current draw, I think.

And a hot controller means ....uhm, maybe someone can help me there.

My experience on my 9L shows that it's obviously undergeared on 16/88. When I stay in first gear, the motor gets hot, but the controller stays exceptionally cool, and vice versa in second gear. Motor stays a bit cooler, but the controller is like 80°C.
The batts always stay cool, like 30-35°C.

I have heard from other guys that their batts get hot. I only ever had hot batts on my brushed Maxx.

What do you think on this. Some input would be great. I like to understand things, and it drives me nuts when something won't make sense.

I also had a close look at the literature on NdFeB magnets, and found out about all the different grades and the maximum temperature they can handle. It's an interesting matter, and I look forward to test some other combos.

Thanks for reading
DAF

The higher the quality of the batteries (read; lower internal ressistance) the colder they stay.

The controller on 80 degrees, why don't you use a fan?

It depends on how the controller is developed/designed.

Let's say a transistor/fet can deliver 25A on 20 degrees, when the temperature rises till 70 degrees, that same fet/transistor can only deliver a 5A So it depends on the amount of fets/transistors that the controller has got in it, how much A it can handle when it is 80 degree, but it is always less than when the contoller is cool.. A fan might be handy for you right now.

Hmm, there seems to be no getting around a fan for me, then.
I have a fan on my brushed ESC, and also have a few fans lying around, those 12V computer fans, 4cm and 8cm, I think.
I'm just hesitant on the Revo bacause I don't really have space and I like the clean look it has now.
But you're right, I'll have a look at this.

80°C on the ESC is the extreme case, after 2 sets of packs back to back.

Wait, just got an idea: How about taking one of those 4mm fans and put it under the shrink wrap? This would look clean as well.
And then I would power it with the 18V from my packs.
Think this would work?? Could I just wire it to the input leads of my controller (which is a warrior 9918, btw)??

Just make sure the air blowing from the fan has somewhere to go.

Sure! Have to think about a nice flow.

I already found some 25 x 25mm or 30 x 30mm fans at an electronic supplier.

Is it possible to wire them directly to the input leads of the controller? Or will this have an impact on the performance??

I think I will mod my warrior. If it can be done clean I'll give it a try.
Expect pics when I'm done. I'm thinking of two small fans directly on the heatsink, covered with shrink. With some proper inlets as well as outlets, f'course.

It would be nice to get a real clean way to mount a fan to the speed controller. Its hard to make a fan look clean and also function correctly.

You probably have seen this, this is how i mounted the fan on the 9918.. (2X M3 screws)

http://www.serum.demon.nl/BL%20lightning%20PRO/21.JPG

http://www.serum.demon.nl/BL%20lightning%20PRO/18.JPG

and that's the frame i use for that 9918 It would gain a little bit of weight, but that a small sacrifice to make for a descent speedoholder®

Looks good, I like this frame thing. Thanks for the pics.
Is this a 4 x 4cm van??

How about the wireing? Can I wire it directly to the input leads of the esc?

I will get two smaller vans, have to take the exact measurement tonight, and then shrink them on. Let's see how it works.

I thought about wireing two 12V fans in series and feed it with the 14 cells. What do you think?