Quicrun 860 - understanding specs

[Westside Charlie]

Can someone explain what these specs mean?

QUICRUN 08 DUAL -BRUSHED (860 model)

2S Lipo or 5 NiMH
540 or 550 or 775 Size Motor: ≥12T Or RPM<30000 @7.2V

3S Lipo or 9 NiMH
540 or 550 or 775 Size Motor: ≥18T Or RPM< 20000 @7.2V

4S Lipo or 12 NiMH
540, 550, 775 Size Motor: ≥24T Or RPM<15000 @7.2V


I'm using a Traxxas Titan 775 motor, which is 10T. So, looking at that thrid spec, does it mean that when using a 4S Lipo (5000mAh; 14.8 v) that the ESC can tolerate motors with 24 turns or more, OR rpm < 15000 at 7.2 volts?

What if I exceed 15000 RPM?

If I'm pushing up to 14.8 volts, what does that mean? What's the significance of the 775 being 10T, when that doesnot appear to be in spec?

Any clear explanation would be helpful.

Thanks!

 

[Chumley54]

The ESC can only handle the current within those specs. The less turns or more RPM, the more current the motor draws. Your 10t motor does not meet any of those specs at any voltage. This means you will likely burn the ESC up because a 10t motor will draw too much.

You need a more capable ESC for your appliction or a higher turn (lower RPM) motor.

The 860 is a nice esc. Like any electrical component, it will fail quickly if you exceed the specs.

 

[Westside Charlie]

Thanks for clarifying what I though the specs meant. Even though I probably won't be pushing the motor too hard, I really don't want to risk burning anything out.

Can you recommend a couple ESCs that can handle my 10T 775 motor?

 

[Chumley54]

Thanks for clarifying what I though the specs meant. Even though I probably won't be pushing the motor too hard, I really don't want to risk burning anything out.

Can you recommend a couple ESCs that can handle my 10T 775 motor?

I haven't needed anything bigger than the 860, so I don't really have experience with the larger capacity you are going to use.

Having said that, if I were doing what you are attempting, I would probably look at the holmes Hobby Trailmaster BLE Pro. Holmes Hobbies TrailMaster BLE Pro - Speed Controllers - Electronics & Wiring

1. It will handle brushed or brushless, so if you decide to later choose a brushless motor (Senored or not) you already have the right equipment.

2. You can get it waterproofed for $10

3. High quality at a reasonable price.

4. It is very programmable, uses Castle Creations programming and programmer, so it is very industry standard.

5. From what I read here, HH is an excellent vendor, who is generous with warranty and problems, active in this community. Worthy of support.

So if you can afford it, You would be making a very good, very flexible choice.
When I purchase items like this, I am either looking for an excellent price (the 860 is a good example), or I will spend more if the product is excellent quality along with flexibility.

So My advice is spring for the HH ESC.

 

[Westside Charlie]

Thanks for the recommendation, Chumley54. I'll think about picking up the Trailmaster BLE Pro as you suggest, unless I completely change my mind and switch out the motor instead.

I didn't see any motor turn specs for this ESC on the Holmes Hobbies site, or anywhere else I looked. It's odd that some ESCs make a point of pecing the motor turns and others don't. Is there something I should be inferring from the other published specs?

Thanks!

 

[Chumley54]

Well, what's really nice about that particular ESC is that John Rob Holmes of Holmes Hoppy is a user of this site : Vendors - Holmes Hobbies at RCCrawler.com

You can ask him directly and get specific recommendations for your application.

The ratings are really current and voltage based (Think "Watts = Volts x Amps")

So as voltage goes up, the total amount of watts at the same current is higher.

Holmes Hobby can tell you if your motor draw at the voltage you are using will work.

You may be overpowering your truck. Besides the ability of the ESC, you also have to worry about the capability of the gears, driveshafts and axle connections.

A really large motor can result in twisted drive shafts, broken axles, stripped gears in the diff and transmission.

Back in the 70's, on a 1:1 car, an acquaintance put a 427 rat motor in a Chevy Vega (They were a light, subcompact car). Think Corvette motor in a Toyota Corolla. The power to weight was awesome. It only tried racing once. The torque and weight of the engine actually twisted the Unit body such that after the first acceleration test run, the front wheel was help off the ground. Just because you can do something, doesn't mean you SHOULD do something.

So if you are going for massive power, make sure the whole drive train is beefed up for it.

In addition, the torque twist on the chassis will be difficult to control, resulting is poor handling.

 

[Westside Charlie]

As it turns out, I've already written to Holmes through their site to ask about compatibility.

Of course, I know the formula Watts = Volts * Amps but I'm generally clueless about how to apply that to various RC matters. Probably I'm stymied a bit by their being no consistent standards about which specs are published and which aren't. But that's all part of the fun, right?

As for overpowering my truck -- that would not surprise me. I'm not really going for super speed or even power, exactly. Let me explain a bit more.

I decided I didn't like my gas Traxxas 2.5 because I just plain didn't like gas. So, instead of selling it, I looked into converting it to electric. There's plenty of information out there about this, including a nice site that had some how-to videos along with brackets they make for motors - including a bracket for 775 motors (expecially the Traxxas Summit motor. So, I figured what the heck, let's try that bigger motor.

Once I got that, I realized that the ESC I was planning to use (A QuicRun 60) couldn't handle the likely draw. After poking around, I was pretty sure that the 860 could do the job.

But, as you've confirmed -- not quite. This 775 must really be a beast! But unlike that 427 rat motor in a Chevy Vega cautionary tale, I think the Traxxas 2.5 frame and gearing would accommodate the 775.

But do I really want to do that?

I mostly enjoy hi-torque crawling and I'm starting to think that I should get another 540 motor after all and keep the ESC 860; maybe that sweet-looking Holmes CrawlMaster pro with 13T -- specced at 2250Kv. With a 2S 7.4 5000mAh lipo, that would probably generate 15,000 rpm - and it's in spec.

And I can save that big old 775 for something else.

Anyway, I'm thinking motor swap now.

Let me know what you think.

And thanks for all your illuminating insights.

 

[Chumley54]

Didn't know thew application.

The essence is power and heat. More watts = more power and heat.

The problem is that all motors are not exactly equal. So a 10 turn motor from one manufacturer can draw different power than a motor from another. Even different models from the same manufacturer with the same number of turns can be different.

So faster = less turns, slower =more turns. Contruction of the motor also affects current draw. Magnet strength, wire gauge on the rotor, etc.

So there are a lot of variables, and while turns give a general idea of the speed and current draw, it is quite a bit lacking.

The other part is gearing and application. low gearing (a large ratio) will allow faster motor speeds and better torque multiplication. Generally you will draw less current and run cooler. High gearing (a small ratio) will generally draw more current because the motor is running slower.

Application is another factor. Long speed runs demand different current than slow heavy rock crawlers.

So there are many variables to consider. Your case is a little clearer, as you are using a larger, high draw motor the the 860 is just too low a rating for the voltage and current you will likely need.

It is confusing. I deal with electric motors at work, but not so small ones (up to 6000 HP), so torque curves and current draws are familiar to me. Fortunately, large motor manufacturers give very complete information on RPM/current draw, inrush current, etc. These little motors are more difficult to ascertain. Some have specs showing maximum current draw and RPM curves, but most don;t seem to.

Funny (ironic funny, not humorous funny) how much science is in these "Toys" of ours.

 

[chopfather]

I've converted two t-maxxes to electric using the 775 motors and evx2 esc's but they are just used as backyard bashers for me and my son. We usually go wfo so no experience crawling with this set up.

 

[Westside Charlie]

Thanks for your thoughtful feedback on motors, specifications, spotty standards, and general overall mystery around out "Toys". It's actually helpful for me to read your summaries of some fundamental principles so I can better formulate the questions I need to ask to do what I think I want. I'm more convinced than ever that I should move to a smaller, and slightly less powerful motor that my 860 can handle. But I will see what else I can learn about current draw from these motors.