RCCrawler Forums

DKNguyen · 02-02-2007, 04:58 PM

Hmmm. It looks like RC4WD doesn't make an 6T pinions for 5mm brushless shafts. The lowest one they have is 15T. I was hoping to reduce current consumption by gearing down a lot.

Kamikaze · 02-02-2007, 05:09 PM

You can't run two brushless motors on 1 spur gear.

DKNguyen · 02-02-2007, 05:40 PM

Quote:

Originally Posted by Kamikaze

You can't run two brushless motors on 1 spur gear.

Well...yeah....you need to two pinions and two gearboxes on front and rear. The gearboxes are fixed so I can only choose the pinion.

JohnRobHolmes · 02-02-2007, 05:53 PM

Quote:

Originally Posted by DKNguyen

Hmmm. It looks like RC4WD doesn't make an 6T pinions for 5mm brushless shafts. The lowest one they have is 15T. I was hoping to reduce current consumption by gearing down a lot.

Then choose a brushless motor with 1/8" shaft, like the hyperion z3013

I have pre-lathed shafts for them that allow standard pinions.

DKNguyen · 02-02-2007, 06:07 PM

Odd. I was just looking at the Hyperions and it said they had 5mm shafts? My preference was to use the 6T long RC4WD pinions.

sticksNstones · 02-02-2007, 06:11 PM

John is saying his are special

Are the 3025-8 motors also lathed to use 4mm pinions?

Quote:

Originally Posted by DKNguyen

Odd. I was just looking at the Hyperions and it said they had 5mm shafts? My preference was to use the 6T long RC4WD pinions.

JohnRobHolmes · 02-02-2007, 06:12 PM

They do have 5mm shafts. I have shafts that are turned down, or you could do that yourself if you have access to a lathe. The shafts are removable. Shaft...

DKNguyen · 02-02-2007, 06:13 PM

Oh, are they? It sounded like that's what he meant but there is nothing saying that for the pinions on his website (at least the ones that are showing up for me).

*drool* so much torque.

EDIT: Nvm. I thought he meant his pinions were lathed down. Now I see that he is referring to the motors themselves! I was thinking of going with the shorters versions of the 30XX like the 3007 or something- since there'a already going to be two on the robot. I don't need THAT much axle snapping. Can he get his hands on the shorter hyperion motors?

It sounds like the H3013s have more suitable mounting screws for trucks, but everyone always refers to the Z versions for planes- are they just easier to find or something?

JohnRobHolmes · 02-02-2007, 06:17 PM

I found the 3007's to stall out a bit easy with some weight on top of em. The 3013's are a good balance of power, but not too much power. How heavy is your bot?

Just about everything in this hobby has to be shoehorned in one way or another.

DKNguyen · 02-02-2007, 06:18 PM

The 3007s are stalling with 65:1 reduction? (I'm planning on using the 6T pinion).

I was estimating 25lbs, but I know that's an overestimate (I tend to do that). Realistically 16-17lbs or so. I'm not sure how high gearbox losses are. I tend to assume 50% motor efficiency and 40% gearbox losses, but that's always been with cheap brush motors.

You think everything in hobby has to be shoehorned (I have no idea what that means by I'll take it in context). Try robotics! The closest thing we have to premade is RC! Think about what we feel!

That's one of the reasons I;m going after crawler chassis- my mechanical skills sucks. Electronics on the other hand, I'll build everything up from scratch.

JohnRobHolmes · 02-02-2007, 06:23 PM

yep, same thing in Crawling but we dont have to program anything. Main stream companies are taking note though and producing stuff for us, kinda like how you can get complete bot kits now.

Even at 65:1 I think it would stall with all that weight. Thats quite a lot to haul around. It would be fine until you encountered a 90 degree ledge that was taller than the tire radius.

DKNguyen · 02-02-2007, 06:24 PM

Really? Good to know. You are talking about running it on 14.4V right? I would be running into curbs and stairs (which I use as a climbing benchmark) a lot more than somewhat sloped rocks. Oh...did I mention I'm using 7" tires? Was the 3013 reccomendation for 5" tires?

What runtimes do you get with the 3013? The thing I'm starting to worry about is current draw. (Although, I doubt it will be going cruising at full speed the entire time, or climbing the entire time for that matter.) What kind of cells do you typically use on the crawlers? I'm used to using 4mAh-8mAh on my things.

JohnRobHolmes · 02-02-2007, 06:32 PM

3013 for 7" tires. I am talking about running running 7.2 volts actually. If you want to run 12 cells the 3007 could work with proper gearing. On 12 cells the wheelspeed can be a little much.

DKNguyen · 02-02-2007, 07:47 PM

I've been taking a more careful look at the numbers and with the 3013, I'll get the speed and torque I want and for sure make up for all the losses. With the 3007, it's pretty close. It would work in a perfect world, but it won't make up for the gearing or motor losses. But all I would lose is a bit of top speed...so I dunno. Lose a bit of top speed for better run time or get the performance I want and lose a bit of run time. I'm pretty sure I can just run the 3013s slow if I need to.

The biggest problem is that the way the data is given, I have no idea where the motor is on it's efficiency curve. It looks like I'll probably go with the 3013 since I'm pretty sure brushless motors for airplanes (that's how the data is given) are operated nowhere near stall, but the motor efficiency probably an average of 60% on the speed curve? Or are the airplane motor normally operated even closer to no-load than I thought?

JohnRobHolmes · 02-02-2007, 07:59 PM

The efficiency of the hyperion outrunners is in the low 80s, with efficiency climbing as you get a longer and longer motor profile. Running it near stall will cause heat like any other motor. As long as you dont overdo the duty cycle the motor will not overheat. Going to a larger motor gives extra overhead for power and lets the motor run with less strain- at a weight and runtime penalty of course. The 3013 motors are only 4 ounces vs a standard brushed 540 motor of 6 ounces.

Planes can run near stall on the motor. Ever heard of F5B? Short bursts of power get those planes a few thousand feet in the air.

As you tax the motor harder the efficiency drops, just like any other motor. The highest eff points will be under low load situations.

DKNguyen · 02-02-2007, 08:10 PM

Well I realized I had the speed constants for the motors and since I had the RPM, I used the efficiency curve of a 550. Efficiency curves look pretty similar anyways, I think they just scale differently depending on the motor's max efficiency. It puts it pretty much at the top of the efficiency curve for what I want when it's going full blast (err actually, at my desired max RPM, the power is 2x as much as I need).

They're pretty much even right now. One can put out more power when needed and the other puts out just the needed power. There also seems to be barely a difference in current draw under the same conditions, at least as far as I can tell. But I get the impression that the 3013, at low speeds/voltage will run more slowly for a given voltage and have more power (more torque I guess) which is more suitable. So that's that! THanks for your help.

I suppose I can get HolmesHobbies to get a couple HP-H013-16 ordered in?

sticksNstones · 02-02-2007, 08:59 PM

You've been talking to the man this whole time.

Just click his link in his sig and e-mail him

JohnRobHolmes · 02-02-2007, 09:09 PM

Gonna have more shippable on the 10th

DKNguyen · 02-06-2007, 02:52 PM

Is it safe to lathe down a 5mm shaft to 3.17mm? Isnt the shaft 5mm for a reason?

Right now it's either:
-get a lathed down shaft and use the 9T long gear
-or use the 15T gear with a 1.5:1 portal axle

POrtal axles sound good for the lessening of torque on the drive axle and ground clearing, but I don't like the efficiency loss or the twisting that I think could happen since the shafts are offset.

JohnRobHolmes · 02-06-2007, 02:55 PM

It is easy to lathe down a shaft as long as it is removable. If it is not, you will have to rig up a lathe to turn it down. Being an inrunner, the shaft is probably not removable. You might get away with removing the entire "armature" and lathing it down, but the overhang of the workpeice might be too long to get a good cut on.

02-02-2007, 06:13 PM	#28
DKNguyen Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada Posts: 308	Oh, are they? It sounded like that's what he meant but there is nothing saying that for the pinions on his website (at least the ones that are showing up for me). drool so much torque. EDIT: Nvm. I thought he meant his pinions were lathed down. Now I see that he is referring to the motors themselves! I was thinking of going with the shorters versions of the 30XX like the 3007 or something- since there'a already going to be two on the robot. I don't need THAT much axle snapping. Can he get his hands on the shorter hyperion motors? It sounds like the H3013s have more suitable mounting screws for trucks, but everyone always refers to the Z versions for planes- are they just easier to find or something? Last edited by DKNguyen; 02-02-2007 at 06:17 PM.

02-02-2007, 06:18 PM	#30
DKNguyen Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada Posts: 308	The 3007s are stalling with 65:1 reduction? (I'm planning on using the 6T pinion). I was estimating 25lbs, but I know that's an overestimate (I tend to do that). Realistically 16-17lbs or so. I'm not sure how high gearbox losses are. I tend to assume 50% motor efficiency and 40% gearbox losses, but that's always been with cheap brush motors. You think everything in hobby has to be shoehorned (I have no idea what that means by I'll take it in context). Try robotics! The closest thing we have to premade is RC! Think about what we feel! That's one of the reasons I;m going after crawler chassis- my mechanical skills sucks. Electronics on the other hand, I'll build everything up from scratch. Last edited by DKNguyen; 02-02-2007 at 06:23 PM.

02-02-2007, 06:24 PM	#32
DKNguyen Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada Posts: 308	Really? Good to know. You are talking about running it on 14.4V right? I would be running into curbs and stairs (which I use as a climbing benchmark) a lot more than somewhat sloped rocks. Oh...did I mention I'm using 7" tires? Was the 3013 reccomendation for 5" tires? What runtimes do you get with the 3013? The thing I'm starting to worry about is current draw. (Although, I doubt it will be going cruising at full speed the entire time, or climbing the entire time for that matter.) What kind of cells do you typically use on the crawlers? I'm used to using 4mAh-8mAh on my things. Last edited by DKNguyen; 02-02-2007 at 06:27 PM.

02-02-2007, 07:47 PM	#34
DKNguyen Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada Posts: 308	I've been taking a more careful look at the numbers and with the 3013, I'll get the speed and torque I want and for sure make up for all the losses. With the 3007, it's pretty close. It would work in a perfect world, but it won't make up for the gearing or motor losses. But all I would lose is a bit of top speed...so I dunno. Lose a bit of top speed for better run time or get the performance I want and lose a bit of run time. I'm pretty sure I can just run the 3013s slow if I need to. The biggest problem is that the way the data is given, I have no idea where the motor is on it's efficiency curve. It looks like I'll probably go with the 3013 since I'm pretty sure brushless motors for airplanes (that's how the data is given) are operated nowhere near stall, but the motor efficiency probably an average of 60% on the speed curve? Or are the airplane motor normally operated even closer to no-load than I thought? Last edited by DKNguyen; 02-02-2007 at 07:49 PM.

02-02-2007, 08:10 PM	#36
DKNguyen Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada Posts: 308	Well I realized I had the speed constants for the motors and since I had the RPM, I used the efficiency curve of a 550. Efficiency curves look pretty similar anyways, I think they just scale differently depending on the motor's max efficiency. It puts it pretty much at the top of the efficiency curve for what I want when it's going full blast (err actually, at my desired max RPM, the power is 2x as much as I need). They're pretty much even right now. One can put out more power when needed and the other puts out just the needed power. There also seems to be barely a difference in current draw under the same conditions, at least as far as I can tell. But I get the impression that the 3013, at low speeds/voltage will run more slowly for a given voltage and have more power (more torque I guess) which is more suitable. So that's that! THanks for your help. I suppose I can get HolmesHobbies to get a couple HP-H013-16 ordered in? Last edited by DKNguyen; 02-02-2007 at 08:15 PM.

02-02-2007, 04:58 PM	#21
DKNguyen Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada Posts: 308	Hmmm. It looks like RC4WD doesn't make an 6T pinions for 5mm brushless shafts. The lowest one they have is 15T. I was hoping to reduce current consumption by gearing down a lot.

02-02-2007, 05:09 PM	#22
Kamikaze I wanna be Dave Join Date: Oct 2005 Location: Columbia TN Posts: 6,154	You can't run two brushless motors on 1 spur gear.

02-02-2007, 06:07 PM	#25
DKNguyen Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada Posts: 308	Odd. I was just looking at the Hyperions and it said they had 5mm shafts? My preference was to use the 6T long RC4WD pinions.

02-02-2007, 06:12 PM	#27
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	They do have 5mm shafts. I have shafts that are turned down, or you could do that yourself if you have access to a lathe. The shafts are removable. Shaft...

02-02-2007, 06:17 PM	#29
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	I found the 3007's to stall out a bit easy with some weight on top of em. The 3013's are a good balance of power, but not too much power. How heavy is your bot? Just about everything in this hobby has to be shoehorned in one way or another.

02-02-2007, 06:23 PM	#31
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	yep, same thing in Crawling but we dont have to program anything. Main stream companies are taking note though and producing stuff for us, kinda like how you can get complete bot kits now. Even at 65:1 I think it would stall with all that weight. Thats quite a lot to haul around. It would be fine until you encountered a 90 degree ledge that was taller than the tire radius.

02-02-2007, 06:32 PM	#33
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	3013 for 7" tires. I am talking about running running 7.2 volts actually. If you want to run 12 cells the 3007 could work with proper gearing. On 12 cells the wheelspeed can be a little much.

02-02-2007, 07:59 PM	#35
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	The efficiency of the hyperion outrunners is in the low 80s, with efficiency climbing as you get a longer and longer motor profile. Running it near stall will cause heat like any other motor. As long as you dont overdo the duty cycle the motor will not overheat. Going to a larger motor gives extra overhead for power and lets the motor run with less strain- at a weight and runtime penalty of course. The 3013 motors are only 4 ounces vs a standard brushed 540 motor of 6 ounces. Planes can run near stall on the motor. Ever heard of F5B? Short bursts of power get those planes a few thousand feet in the air. As you tax the motor harder the efficiency drops, just like any other motor. The highest eff points will be under low load situations.

02-02-2007, 08:59 PM	#37
sticksNstones Pebble Pounder Join Date: Jun 2006 Location: Flagstaff Posts: 181	You've been talking to the man this whole time. Just click his link in his sig and e-mail him

02-02-2007, 09:09 PM	#38
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	Gonna have more shippable on the 10th

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02-06-2007, 02:52 PM	#39
DKNguyen Quarry Creeper Join Date: Jan 2007 Location: Alberta, Canada Posts: 308	Is it safe to lathe down a 5mm shaft to 3.17mm? Isnt the shaft 5mm for a reason? Right now it's either: -get a lathed down shaft and use the 9T long gear -or use the 15T gear with a 1.5:1 portal axle POrtal axles sound good for the lessening of torque on the drive axle and ground clearing, but I don't like the efficiency loss or the twisting that I think could happen since the shafts are offset.

02-06-2007, 02:55 PM	#40
JohnRobHolmes owner, Holmes Hobbies LLC Join Date: Nov 2004 Location: Volt up! Gear down! Posts: 20,290	It is easy to lathe down a shaft as long as it is removable. If it is not, you will have to rig up a lathe to turn it down. Being an inrunner, the shaft is probably not removable. You might get away with removing the entire "armature" and lathing it down, but the overhang of the workpeice might be too long to get a good cut on.

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