Novak GTB Brushless with 5.5

[newbie816]

Hey I got the 5.5 for my tc4 runs fine in their but im thinking about getting a 1/10th scale 4wd buggy and im wondering if i should run it in it or if i should not even waste my time and get the new 7.5 which is recommended for such applications

[ElectricThunder]

Depends on what kind of track if you race, or what kind of performance you want if you just bash. The 6.5 is probably better for 4wd buggy, but still plenty fast. The 7.5 would probably be great for tighter tracks. The 5.5 would probably be a really fun bashing motor, but really, it's more of a touring car motor. I'd say 6.5 or 7.5, and 5.5 if you bash and want some crazy power.

[SpEEdyBL]

The 5.5 will run perfectly in a 4wd buggy.

Cheers!

[Tig]

I have a 5.5 in my XX-4 Graphite WE. First run today. Its pretty nutty. Runs great, handles great. Its just, GREAT. :)

[Rocksalt]

I put a 4.5R in my xxx-4. Scalded ape is the word for it. Can't seem to beat the snot out of it with high pinions... I am getting 47mph with a 16 pinion, but temps in the 160 motor and 150 ESC. With the schulze I was using a 17 tooth and speeds of 48mph. No problems at all with heat and that combination. I just went to a 13 tooth pinion and the 4.5R and the temps are sitting at 135 motor 140ESC. Much better to drive with the 13... Not that much slower on top either. I think the tire swelling has something to do with that. It just goes so damn fast the tires swell and change the ratios. I measured the tires while swelled.... something in the 5.5" range. sheesh. With the 13 I can crawl to a jump and nail it into the sky. Me likes. Having problems with aluminum CVD's though.. I don't think I can drill anymore holes in it. New steel ones are out of stock, still waiting...

[Flyojumper]

Rocksalt, I also have a 4.5r and it's in my Evader pro BX. However I don't have a temp gun or a radar/GPS.
Can you tell me your rollout using those pinions? (or the spur#, tranny ratio and tire size so I can calculate them for myself).
Also, could you tell me about how hot is 140/160/180F to the touch of the finger? Right now I have a rollout of 23mm (counting tire size at rest with no ballooning) and I can always touch my ESC/motor indefinitely but I'd like to know how hot approximately is the "3s touch" and "5s touch" in actual temperatures so I can stay under 165-175F that Novak recommends. When your motor was getting in the 160F, how long could you touch it? (neither being a sissy or a kamikaze... :) )
Thanks for the help.

Edit: BTW are you running lipos for those speeds? I don't think I'm going quite that fast (probably low 40s I'd guess) but I am using "only" matched 1.18 GP3300.

[Rocksalt]

Rocksalt, I also have a 4.5r and it's in my Evader pro BX. However I don't have a temp gun or a radar/GPS.
Can you tell me your rollout using those pinions? (or the spur#, tranny ratio and tire size so I can calculate them for myself).
Also, could you tell me about how hot is 140/160/180F to the touch of the finger? Right now I have a rollout of 23mm (counting tire size at rest with no ballooning) and I can always touch my ESC/motor indefinitely but I'd like to know how hot approximately is the "3s touch" and "5s touch" in actual temperatures so I can stay under 165-175F that Novak recommends. When your motor was getting in the 160F, how long could you touch it? (neither being a sissy or a kamikaze... :) )
Thanks for the help.

Edit: BTW are you running lipos for those speeds? I don't think I'm going quite that fast (probably low 40s I'd guess) but I am using "only" matched 1.18 GP3300.

I'm using 8000mah lipo TP battery. With schulze\pletty and 21 pinion/94 spur I get 50-52mph(overgeared). 17 tooth 47-48mph, 15 tooth-45-46mph. GTB 4.5R 17 tooth 48, 16tooth 47. I have not tested the 13 tooth on the GPS or the 15 tooth. I flipped the car accelerating with my GPS and farked up all the buttons. I hope it's under warranty, lmfao.

I would say 160 is 5-6 seconds. It all depends on how thick your fingers skin is. I used to work in restaurants and what felt hot at first was not hot anymore. The ESC is hard to determine with finger. The measurments I took were at the bottom of the heat sink. The top measures considerably less, maybe 20 deg F. Batteries are getting warm too!!! I pulled them off yesterday at 119! They make a BIG difference in power with the 4.5R. The temp probe on the ICE charger reads considerably less than with a raytech temp gun. I think about 10degF. Possible I need to check the calibration. I think a 3s touch is in the area of 190-200, 2s is like 220-240. Spit boils at 212, lol.

Rollout.. The internal ratio is 2.10. Final ratio with 17/94 is 11.61:1. That's a rollout of 34.34mm at 5" diameter. 24.04 at 3.5" diameter. That's 50mph at 50,000rpm with a 4" tire. Maybe it's only swelling 4", hard to tell.

[Flyojumper]

Thanks Rocksalt, very thorough answer, I appreciate.
Do you have a GP or IB nimh batteries at hand by any chance? I'd be interested in knowing exactly how many extra mph you are getting out of the 4.5r by using lipos over good quality side by side nimh packs. I know my batteries do get pretty hot, they are usually the hottest component in my setup after a run.
On the subject of temperatures, I'm not sure how the heat transfer is affected on finger to metal versus finger to liquid, but I doubt you'd be able to stick your finger in boiling water for 2-3s, no? If the heat transfer is somehow similar I would have expected the 1s touch to be lower than 212, with a 3s at maybe... 170? Is that possible? Heck, wait a second I'm going to boil some water and check how long I can stick my finger in it lol ;)
What temperature does the GTB thermal anyway? (same temperature for motor and ESC?) Is it at 175 or higher?

[billmck]

well, if you boil water and fill a standard coffee cup, and let set for 2 mins; that would be around 160. so picking up the coffee cup by the cup and not the handle, would let you feel what that temp is like.....
also, when i used to use a reg 6cell pack(i'm all about lipo, now); they would be around 120-130 when they got done charging.
hope this helps ya out some...


bill

[Flyojumper]

Hey, that's actually a good idea, thanks!
You think it cools down by 52F in only 2mn though? Maybe the surface, but I'd think the liquid deeper in the cup would still be pretty close to 200, no?

[billmck]

actually, the temp did drop that much....with a cup made of (whatever coffee cups are made of) sitting at room temp, adding water,and taking a few readings with my temp gun to give you some sort of comparison.
just trying to help a bro out....


bill

[Flyojumper]

Oh, you actually took measurements, I didn't know that, I thought you were just rough guessing that's why.
Thanks! I'm off to try that little experiment. :)

[Flyojumper]

Ouch, lol.
After some solid boiling to ensure the water was at 212F, I poured a whole cup in an 8oz glass (I don't have paper cups).
Waiting 2mn precisely, I can't touch the sides of the glass for more than 1.5s... (pressing firmly on the glass)
If sounds like good news since it would seem 160F is a heck hotter than I thought (and Rocksalt's earlier post would indicate) and the Novak's recommended 165-175 is actually pretty damn hot and would leave me a lot of room for hotter weather and/or increased gearing.
Just making sure:
1) Does the temp gun indicates 212 or close at time 0 and 160ish after 2mn?
2) Do you think me using a full 8oz glass (made of glass not paper) made a difference in the temperature I observed at 2mn?
Thanks again billmck.

[billmck]

flyojumper-
i use a ceramic cup for my coffee, and it was about 200 as soon as i poured it into the cup and took measurements from atop of the cup. then after 2 mins i temped the side of the cup. im pretty sure the highest temp from the side of the cup was around 185.
(i did it in glass and it was about the same)

just a note here: a cup of jave is a super huge comparied to novak's esc, and the esc will cool off much quicker, esp when the esc has a fan. the temp gun is a gtc (much better than the rayotec)
i just wanted you to feel what 160 was like...hope this helps

bill

[billmck]

newbie816 -
i think as long as you have the batteries to handle it, you could run any of novak's line up in 4wd buggy; just make sure you're geared correctly!! now, as for being able to control the 4.5 is something else to debate.
i have a few mf2s and was running the 6.5 for a few months. i got a 5.5 motor and now the 'trigger learing curve has started all over'


bill

[Rocksalt]

I ran it yesterday and hit 170. I could hold my finger on the motor for about 4-5 seconds.

A wetter finger will transfer heat faster! I also have callous on my fingers which enables longer holding times.

I can't test the batts now :( my front CVD is toast... still waiting on the steel ones! How long will it take, sheesh.

I ran a 15 pinion yesterday in 90 deg. weather. It took 10 minutes for the motor to say "UNCLE". I also speed tested the 13tooth.. 36.8. So the rundown is close to this. I am going to switch back to the pletty. It seems to handle more pinion, with less heat, in higher ambient temps.

13- 36.8
15- 42.46
16- 46
17-48.12
This is with GPS on vehicle. I would assume the extra weight would slow it down a little on top.

I am trying to remember back to nitro and testing the heat without temp gun. We used the spit method. If it boiled off in 3 seconds we were good. I think I could finger it for 2 seconds max. Guess ones 2 seconds is more than others. At 160, which is where you should run motor, is a good 3-4 seconds, 3 for tender hands, 5 for callous'd ones.

I am going to switch back to the pletty. It seems to handle more pinion with less heat in higher ambient temps.

[Flyojumper]

Thanks guys, it does help.
Rocksalt, please let me know if/when you get to GPS your 4.5r with nimh batteries.
BTW, when you say "it took 10mn for the motor to say UNCLE", you mean thermal? hehe I've not thermaled my ESC or motor yet, but I haven't driven in 90F weather yet.
If it did thermal, do you now have any idea what's the thermaling temp for the motor? I wonder if the ESC's is the same. On novak's instructions they recommend 165-175F degree safe operation, so thermaling must be set higher I'd guess.

[Rocksalt]

40.3 with a 15 pinion and NIMH. Golly... it sure took alot longer to get to 40.3! I think about 6 seconds. I have an 8th scale wing and the GPS mounted to it. I couldn't even get it to flip when I throttle it. Maybe my batts suck, but they sure have not been through much since new.. I always used the lipo. Going to the nimh was like watching paint dry in comparison. nimh came off the grill at 150! Even if I had super good nimh I don't think it will come close in comparison. Driveline drag does not seem alot, but sure heating up. 83.5 deg. here now.

With lipo, same conditions, 46.8mph. I could hear the wing hitting the rear tire a little. I couldn't take off hard without it flipping nor could I bust it open while on a roll or it would flip. I think it hit that speed in 4 seconds, but I couldn't whale on it. I think without the GPS it would definatly be faster and quicker.

I like the GTB, but it just can't take the higher pinions without heating up. I can run for 30 minutes straight with my shadow and a 16 tooth, maybe more. 19 tooth for 15 and 17 for at least 20-30 depending on how hard I drive. Still a wicked system, but I need more!

[Flyojumper]

Thanks! But you said in your previous post that lipos 94/15 gave 42.46 mph, now 46.8? (or did you merely exrapolate that earlier 42.46 value, it looks like it was extrapolated from the 94/13).
What nimh batteries do you have by the way? Side by side? GP/IB?
I'm not surprised at all by your nimh temperatures though, I think mine are getting even a little hotter on a hard run (matched GP3300, maybe 4-5s grasping the batteries firmly in my hand after the run)
What was that "took 10mn for the motor to say "uncle"" comment? Thermaling?
How is the cogging and runtime on that shadow? How does it compare in those aspects to the GTB/4.5?

[Rocksalt]

I think I calculated the 15 pinion. I think the 16 tooth was 46.8 with the schulze and pletty shadow. When I made the tests yesterday the pack(s) were fully charged. Maybe I should document on the same day the results with different pinions.

The "uncle" comment was running on a hot day. I then became suck in a drain ditch and it sat for about 10 seconds. It then thermalled and was the motor. I temped it at 175. They will get hot when running then sitting still for any period of time.

The batteries are megatech 3300mah signature series Chris something racing pack.

I can run the shadow for at least 30-40 minutes doing speed runs and a little slow section. The GTB is smoother at crawl and has more grunt to top speed. It seems alot easier to loose control with the GTB in terms of flipping. The shadow will not unless the suspension is set stiff. The schulze would be better for racing IMO. Temps were more in check with the same pinions on the schulze. Im my buddys opinion the GTB kills the schulze, but what does he know, lol. He was messing with it from a dead stop. He could stand it on end with the GTB. For me it's easier to drive the schulze, if that makes any sense. There is a price to the speeds of the GTB.. thermalling! The GTB also heats up the batteries more.. which makes perfect sense. In this heat I have to run a 13-14 tooth. Which is not much top speed. 70 deg. out and it will run on a 17. Go figure.

[Flyojumper]

Thanks for that shadow/GTB comparison.
Good to know about the thermaling temperature, it seems like it's 175F then. I'm not sure I understand this though: "They will get hot when running then sitting still for any period of time." You mean making the motor spin while the car can't move/is stuck? That would make sense since it can put quite a high load on the motor.

[Rocksalt]

Thanks for that shadow/GTB comparison.
Good to know about the thermaling temperature, it seems like it's 175F then. I'm not sure I understand this though: "They will get hot when running then sitting still for any period of time." You mean making the motor spin while the car can't move/is stuck? That would make sense since it can put quite a high load on the motor.

Not what I meant. If you race it, then stop.. while it sits it can go into a thermal stage. Running it allows the motor to get air past it. I am going to buy a heat sink and a fan. I see them on ebay all the time. This will stop the motor issue, but has nothing to do with the ESC heat.

[Flyojumper]

Alright, I see what you are saying, the hot air immediately surrounding the motor would not be cooled anymore and would act as a sort of "greenhouse" effect.
However, is it "healthy" for the motor to rely on a heatsink/fan to solve heat problems? It may cool the exterior substantially and "cheat" the sensor depending on where it is located but the core of the motor would be less affected and could still get relatively too hot, no?

[Philyon]

I'd like to put this gtb 5.5 in my xb8 too, but i saw the HV-Maxx.. is it suitable for it or must I put the GTB 5.5 ?

[ElectricThunder]

I'd like to put this gtb 5.5 in my xb8 too, but i saw the HV-Maxx.. is it suitable for it or must I put the GTB 5.5 ?
Neither are suitable for 1/8 scale applications.

[Rocksalt]

Alright, I see what you are saying, the hot air immediately surrounding the motor would not be cooled anymore and would act as a sort of "greenhouse" effect.
However, is it "healthy" for the motor to rely on a heatsink/fan to solve heat problems? It may cool the exterior substantially and "cheat" the sensor depending on where it is located but the core of the motor would be less affected and could still get relatively too hot, no?

Definatly not! The faster you can get heat away from the load the more you can give it. As long as you don't exceed allowable temps. If I could use a heatexchanger, water pump, cooling fan, I would loop the entire system. Ambient temps are playing a HUGE factor in gearing. If I can make a cooling system efficient it will be well worth the effort.

[Flyojumper]

Yes, but my point is that the temperature sensor may not be in the core of the motor (or wherever the highest temp point is) and the cooling provided by a heatsink/fan may not be uniform at all. If that's the case the sensor could be cooled down by a much larger amount than the hottest part of the motor, "think" that the temperatures are still acceptable and not thermal, while other parts of the motor are not cooled as efficiently and are therefore put at a higher risk than before.

[Rocksalt]

You should not rely on the temperature sensor to obtain gearing.

Heat stresses electronic components and shortens life. Cooler it is, the longer it will last. Another problem is the circuitry used to invert the DC to AC is quite small. Many lower wattage rated components are used in parallel to obtain a higher current rating. If one FET fails......they all fail at the same current. Some IGBT's and FET's have internal thermals build in. This, of course, is dependant on package size. I doubt the ones we have in our ESC have them.

The motor can is a big heat sink. The temp will transfer to the aluminum sink and the fan will blow it away. The difference in temp from the sink to the can will be minimal, it will just transfer the heat faster. This will cool the motor not only when running, but also when stopped, say from a crash. If you are running a race full out and flip.. as you wait for a corner marshall the motor could thermal if the temps were already at the 160deg. mark. Then he flips you over but the car will not drive.

I can see already the cooling needed will be just the same as it was for CPU's when they started adding fans and heatsinks. They just keep getting bigger and bigger as faster processors come out. They figured out that cooling was the only way to be able to keep the CPU's alive with the amount of transistors they kept adding to them. At one time they sold an A/C unit to cool the CPU. They could overclock the CPU more than double it's rated clock speed. Brushless will be the same because the package cannot get much bigger to fit in R/C cars.

[TunaCan Charlie]

well, if you boil water and fill a standard coffee cup, and let set for 2 mins; that would be around 160. so picking up the coffee cup by the cup and not the handle, would let you feel what that temp is like.....
also, when i used to use a reg 6cell pack(i'm all about lipo, now); they would be around 120-130 when they got done charging.
hope this helps ya out some... :)


bill
Flyo,
Fill a standard coffee cup with water, stick in your NiMh and set on high for 2 minutes and tell me what the temp is please..... :)

[GTB_USER_ERIK]

I have the 5.5 in my factory team T4, and I have too much power for my skills on the track I race on. I'm going to try the 7.5 as soon as I can afford to buy another motor.
(father of three in a single family home)

[Flyojumper]

Alright Rocksalt, points taken. On the subject of CPUs VS BL motors for cooling, maybe they can increase the efficiency of BL motors even further to decrease the heat. I'm not sure how much more efficient they can make them though.

TunaCan Charlie, I'm not sure I understand where you are going, but I take from the smiley that it's a joke on how hot my Nimh get? You can't be serious with the nimh in water part that's for sure. :)

GTB_User_Erik, you can always "tame" the 5.5r via ETA and Expo settings if your radio has those.

[tcolesen]

Alright Rocksalt, points taken. On the subject of CPUs VS BL motors for cooling, maybe they can increase the efficiency of BL motors even further to decrease the heat. I'm not sure how much more efficient they can make them though.

Just wait. There might be something on the market soon that will offer this.

[SpEEdyBL]

It's best just to use higher voltage and a lower kv motor.

[ElectricThunder]

It's best just to use higher voltage and a lower kv motor.
If you're racing by ROAR rules, that's a no no, but for now, I agree.:D

We need 99% efficient motors...that'd be pretty cool. :eek:

[GTB_USER_ERIK]

Flyojumper yes my radio has those features, though I wish the ESC had a program to 'TAME' the motor

[Flyojumper]

With those two features on the radio (especially if the expo offer curve points settings) I'm pretty sure you can effectively "tame" the motor much better than anything the ESC could offer. Play around with those settings and I'm sure you'll find something that will suit your track well.

[Rocksalt]

That's not always possible. When you 'de-tune' via radio you run out of the 'efficiency' range. You also are running a lower frequency and lower voltage at lower speeds. This draws more current and makes more heat. I was able to program some acceleration rates on the GTB4.5R. It tamed the car but I always felt the controller or motor didn't like the pulsing from the radio. I never proved it, but it would act strange at times and seemed to generate more heat and less runtime. It's just a feeling at this point, nothing proven. The radio IS pulsing the signal... so in effect it's like grabbing throttle, backing off, giving throttle, but at a higher frequency than our fingers can oscillate. I'll do a more scientific test and see what I come up with.

I don't know if the GTB's higher currents are affecting my radio, but I don't seem to have problems with glitching with the schulze. The GTB will do it at slower speeds while turning. Every now and then it will dart forward.

[Flyojumper]

Definitely let us know about your "more scientific" tests later, I'd be interested in seeing your findings.

[djbodies]

Can you run difference Brushless ESC on it? Many thanks

[raytracer]

Since I dont see an official Novak GTB brushless thread here goes.
If ever I brake the brushless motor that comes with the GTB, how well does the esc alone compare to brushed esc like qc2, atsushi vf, etc?

[nicholcgn]

Not sure what you are asking but here is a shot at it.

If you kill the brushless motor just buy another. I just do see you killing one that often. I have been running a 5800 motor for over 1 year.

2nd - Running a brushed Motor. Yea it is good. It will not be quite as good as a specialized brushed only esc but I doubt more than 5% of the rc community could tell the difference. Biggest thing will be that there are less profiles for brushed.

[raytracer]

Not sure what you are asking but here is a shot at it.

If you kill the brushless motor just buy another. I just do see you killing one that often. I have been running a 5800 motor for over 1 year.

2nd - Running a brushed Motor. Yea it is good. It will not be quite as good as a specialized brushed only esc but I doubt more than 5% of the rc community could tell the difference. Biggest thing will be that there are less profiles for brushed.

Thanks. I'm just concerned about the brushless motor getting killed and I'm stuck with an average esc.
I was going to buy a quantum comp 2 which costs over a $100 but if the gtb is good enough I'll just add extra money to get a dual purpsose system.

[CharlieS]

Well, actually as a Brushed ESC, the GTB is better then Most regular brushed ESCs. It's big and all, but if you are looking for the "ultimate" foward only racing ESC, The GTB is the way to go... For sure.

This may not be true for all Dual purpose ESCs, but for the GTB we use the ENTIRE ESC.

THanks
Charlie

[ElectricThunder]

Well, actually as a Brushed ESC, the GTB is better then Most regular brushed ESCs. It's big and all, but if you are looking for the "ultimate" foward only racing ESC, The GTB is the way to go... For sure.

This may not be true for all Dual purpose ESCs, but for the GTB we use the ENTIRE ESC.

THanks
Charlie
Are you allowed to run more voltage in brushed mode because the FETs are in series then or anything like that? Or is the 6 cell limit still applicable?

[CharlieS]

Limit stays the same. Sorry. :)