13T or 14T

[iba10753]

Is there a direct relationship between the number of teeth in the pinion gear and the headspeed? In other words, will the 13T get me a lower HS than the 14T? Stupid question but I need to make sure I'm getting these basics down pat.

I also keep reading about the battery choice having something to do with the pinion gear and can't really understand why. I guess for a target headspeed...a 13T is going to drain more power than a 14T?

Thanks,
Ben

[jointer]

I see you have many questions. :)
13T will gear 520KV motor (Pyro, Scorpion) in a way it will spin faster to get the optimal rotor RPM. The load will be lower on the motor, so the flight times should be a bit longer.
There might be some bogging at hard and violent full pitch loads.
14T solves this well, because the motor spins lower, so the governor have more room for work (this is the main problem), you have lower throttle curve for the same RPM.
I see in other threads you are novice in flying helis, so 13T will be optimal for you, definetly.
But when ordering the mighty TDR, get a 14T pinion also.
If you progress fast, you will be happy to have it.
Good for hard smacking, you might enjoy later.
If you have a chance and can get Scorpion 4525, get it.
I did not installed it yet, but i and my friend, we got some bearings problem with Pyro (seem we are the only ones), by only looking at the Scorpion, i believe it will be better.
Do not know the prices, but should be similar for these two.
BTW if you are not sure about my gearing explanation, learn on the web, it is one of the heli basics, just simple gearing in relation to motor RPM.
KV value is value which the motor spins if you provide 1 Volt to it.

Edit: note: for that Scorpion, only 14T is available, because 13T will not fit the oversized shaft.

[iba10753]

I've been trying to search for explanations on the use of different pinion gears and haven't had an article get through my thick skull. Even with your explanation, I still don't know if I've got my brain wrapped around it yet.

If I have a motor spinning its shaft at a certain RPM with a 13T pinion, the resulting head speed will be a certain value. If I try to hit the same head speed with a 14T pinion, the motor will be spinning at a slightly lower speed. I think I can make one good inference from the above - the motor driving the 14T pinion will have more reserve power than if it was driving the 13T pinion.

Granted, I'm not talking about the problems associated with violent maneuvers. For normal flying at a given headspeed, you would benefit from the 14T pinion in that it would allow the motor to work less, provide for more reserve power from that motor, and (again, where I must be confused) provide for a longer flight time because the motor is not working as hard for that given headspeed during the flight.

I must be missing something in the physics of how a motor works. One day, it will hit me and I'll just "get it". In the meantime, if someone just happens to know of a link to a good pinion gear primer please pass it along. It would really help. I have a feeling that getting educated on that subject will actually help me in a number of other areas.

Thanks,
Ben

[iba10753]

By the way, I may have to go for the Scorpion motor....I can't seem to find the Pyro 700-52 regular shaft model in stock anywhere in the USA at this point. I have read through all of the threads in the Henseleit forum about this motor and see that it is a tight fit inside the frame and may be rotating or torquing just a bit where it rubs against the frame sides (I may not have a good visual picture of what is being discussed, however).

Thanks again,
Ben

[helicraze]

If you plan to fly at 1850RPM then 14T it is, if you plan on 1750 or lower then 13T is better.

That is with 520KV motor.

If you use the older pyro 30-12 motor the KV is more like 560 so 13T does everything!

[Heli G]

If you plan to fly at 1850RPM then 14T it is, if you plan on 1750 or lower then 13T is better.

That is with 520KV motor.

If you use the older pyro 30-12 motor the KV is more like 560 so 13T does everything!

Agree with HC, for lower HS’s (+- 1700 or lower) the 13T is fine. I fly both (13T and 14T) in two different TDR’s and governed HS is where the difference comes in.
Also, do not confuse motor power with governor control. A governor (controlling the motor RPM to supply constant HS) needs a range to properly work in and depending on what HS you want to run, you select the required motor pinion.
As for selecting HS, it all depends on your flying style. I’m running 1700 (with 13T) on one TDR and it can do 3D maneuvers no problem. If you want a wild ride, 1850 and up is where it’s at (especially if you go 14+ pitch) and the 14T is the answer here.
As for selecting the right motor, there’s plenty of threads discussing it in this forum.

[iba10753]

If you plan to fly at 1850RPM then 14T it is, if you plan on 1750 or lower then 13T is better.

That is with 520KV motor.

If you use the older pyro 30-12 motor the KV is more like 560 so 13T does everything!

Well, at first I'm sure I'll be at lower HS simply because I will not have the experience to perform aggressive maneuvers with the TDR. After that, who knows?

Thanks,
Ben

[iba10753]

I see you have many questions. :)
13T will gear 520KV motor (Pyro, Scorpion) in a way it will spin faster to get the optimal rotor RPM. The load will be lower on the motor, so the flight times should be a bit longer.

Jointer, I wanted to get back to the statement you made above if you don't mind. I just can't get my head to accept the fact that if a motor has to spin faster...that your flight time would be a bit longer.

I want to make sure there's not a miscommunication here. I'm beating my head against the wall trying to understand the logic in the statement you made.

I have a feeling that this subject is so elementary that I should be discussing it somewhere else. I just don't know where to look.

Thanks,
Ben

[iba10753]

Agree with HC, for lower HS’s (+- 1700 or lower) the 13T is fine. I fly both (13T and 14T) in two different TDR’s and governed HS is where the difference comes in.

Okay, got my brain around that one.

Also, do not confuse motor power with governor control. A governor (controlling the motor RPM to supply constant HS) needs a range to properly work in and depending on what HS you want to run, you select the required motor pinion.

Ahhh, okay. So, the choice of motors we have available for the TDR probably all have plenty of reserve motor speed or power available. If you want higher HS, then it might be necessary to go to 14T in order to get the reserve power from a motor that the ESC is trying to control. Man, I hope I'm starting to get the concept here.....a very small lightbulb might have just gone off in my head.

As for selecting the right motor, there’s plenty of threads discussing it in this forum.

Agreed, but to my very new and very inexperienced eye almost all motor discussions end up with some manner of friendly disagreement with wide-ranging opinions. For example, I had great hope that Jan's recommendation of the Pyro 700-52 would work out but now I read threads about the shaft diameter being too small and bearing and heat problems. Granted, these problems might be in discussion from people who have a MUCH more aggressive flying style than I might ever have. Hopefully, you can see what I'm talking about....I sure want to see positive consensus on the Pyro but then I begin to wonder if it's a time bomb about to go off inside my TDR.

Again, from an inexperienced eye, the only motor I've seen discussed that didn't generate some type of negative points is the Align MX motor. It won't be too long before I have to make my own mind up about the motor I'm going to go with but, so far, the excellent discussions have provided me with nothing more than confusion.

Because of being a beginner and because I'm positive that my flying style is going to be much more sedate than most of you....I'll bet I simply rely on the word of Jan that the Pyro 700-52 is a good choice (unless he's changed his own mind by now). As my experience grows (and with my 2nd TDR), I might be able to explore the possibilities. Heck, I'll be ready for more aggressive flying and I'll be a lot "smarter" about equipment options and possibilities at that point.

Of course, the Pyro is very hard for me to find at this point but I'm hoping that's not the case by the time I'm ready for my TDR build. That's still six months down the road so a lot can happen in that period of time.

I'm not trying to generate sympathy here. If my own experience level was higher I'd probably have my own strong opinions with regard to motor choice, pinion choice, HS, ESC model, etc. I'm just trying to suck as much information up from you guys as I can to get me up the learning curve as quickly as possible. You can probably already guess that I'm a bit detail-oriented and I absolutely hate doing something without really knowing what I'm doing. :)

Man, I hope I'm not wearing out my welcome!

Thanks,
Ben

[iba10753]

Jointer, I wanted to get back to the statement you made above if you don't mind. I just can't get my head to accept the fact that if a motor has to spin faster...that your flight time would be a bit longer.

I want to make sure there's not a miscommunication here. I'm beating my head against the wall trying to understand the logic in the statement you made.

I have a feeling that this subject is so elementary that I should be discussing it somewhere else. I just don't know where to look.

Thanks,
Ben

Hey, I think I've made a breakthrough after thinking about this. Just because a motor is spinning faster doesn't necessarily mean that it is using battery power faster. It's the amount of "load" that the motor is under in order for the ESC to maintain a given HS....that means the battery is going to discharge faster.

Flying with lower headspeeds (and with a 13T) probably means you're not flying aggressively so the ESC is not having to really push the motor to maintain your HS. Hence, the motor will not discharge the battery as much and longer flight times are the result.

Flying aggressively with higher headspeeds would probably require a 14T just so that the ESC has more reserve motor power to work with in order to maintain your higher HS. It's the aggressive flying that means you should probably move to a 14T so that you can actually fly the way you want to fly with and that the ESC and motor can support that flying style.

Somebody please tell me that I've finally gotten it! :)

Thanks,
Ben

[ZuvieleTeile]

Hi Ben,
you are at the beginning to see a light at the and of the tunnel. . .:noteworthy

Every electric motor has a RpM where it delivers its best torque, but this is not as pronounced as with car engines, but still there.
Also there is a efficiency curve.
That's the amount of amperage the motor uses for turning and not for heating up.
If you run a motor with a 85% efficiency at 25000 Rpm on 17000 Rpm, you might run it at 70% efficiency.
To put this in numbers:
You are heating up the atmosphere with 30% of your available energy.
If you are drawing 80 Amps, that 30% is 24 Amps times on average 48 volts resulting in a heat distribution of 1150 Watts.
That's a nice room heater isn't it?
And that heats up your bearings, which lose the grease, it heats up the copper winding which increases its resistance, it heats up your shaft which expands and puts pressure on the bearing's inner race, it heats up the pinion which makes the intermediate gear soft and finally you have less flight time, because your battery drain is huge.

Therefor it is important to get your ducks in a row and use a pinion where you run your motor most of the time as close to it's best torque and as close to it's best efficiency as you can.
When Jointer says, that the motor runs faster but you have longer battery life, then that's what he meant.
It is not always like this with every motor, but in this case it all fits together.

If you run your motor at it's best efficiency RpM, which is not necessarily a lower RpM, then you have more power/torque and less amperage draw.
Don't worry about the RpM reserve. There is plenty of it with a 13t or a 14T pinion.

The reserve, we are talking about here, is the ESC reserve.
The governor needs about 30 % of its range to be able to govern high demand situations.
Meaning, at your highest RpM setting from the transmitter side, you ESC should be about 70% "open". (Like in open throttle)

Hope, this gives some juice to the discussion.;)

[iba10753]

Perfect, ZT, that was a big help. Knowing that the power drain is not a linear curve necessarily associated with pinion shaft RPM is what I was missing. Also, hearing that it is actually ESC reserve that we need to worry about was another breakthrough for me. Thanks for expanding on the subject.

Jointer, I stand completely corrected! Please forgive me for doubting you!

Thanks,
Ben

[jointer]

No problem. :) Since my last post, it seems all written here by others is true.
Anyway it is difficult with the eficiency and 13T/14T.
With 13T, it should be more effective also because the motor spins faster, cool itself better and have "lighter" load.
But please do not worry, basically, 13T is general purpose pinion, from 1350RPM to 1850RPM.
14T is useful if you want to have RPM in range 1850-1900 and use high pitch values.
It is related to governor function as ZT described - there might not be enough headroom from which you will "take the power" if you have 13T.
Because governor mode is trying to keep the RPM constant and in high motor load, the gov need that headroom to compensate.

[iba10753]

Thanks, Jointer! Despite this subject probably being first-grade level stuff I'm glad I asked the original question. Maybe there were others lurking who needed a little refresher. Every time someone has added to this thread, it's helped me bit by bit to start getting the hang of it.

Now, if I just knew what the heck "P and I" stood for....:lol:

Thanks again,
Ben

[jointer]

You probably should invite me to Texas for visit and i will explain it. :)
For start, try to search the web for PID regulators, ESC governor is one, Vbar or any flybarless electronics also.
I fly around 3 years and still learn new technical stuff.
I guess it is part of the hobby.

Edit: there are pilots who just fly and do not care about the background.
Then there are some people who try to learn something more, try different things, tune the available stuff to perfection... i am one of them, but it is probably best to be somewhere in between.

[iba10753]

That's just what I wanted...some words to search on. I didn't know what the letters stood for.

By the way, you've got a standing invite to Houston anytime! :cheers

[jointer]

I know, the basic problem of searching, how the ask the Google. :)
This is great hobby, where you can learn some things about mechanics, gears, various materials and also electronics.
If you want.

It is totally off topic, but i sometimes (like today) have a feeling i am living in the wrong country, full of corruption, stupid politicians, terrible state services and court results... and trapped in boring work.
Nevermind, there is no paradise on Earth and it seems these problems are everywhere.
(yes, i have really bad mood today, sorry for sharing it)

[iba10753]

I know, the basic problem of searching, how the ask the Google. :)
This is great hobby, where you can learn some things about mechanics, gears, various materials and also electronics.
If you want.

If I stop learning, I don't think I'd last much longer than a month or two before wanting
to put a bullet in my head. I'm fascinated by all of the technology wrapped up in this sport.

It is totally off topic, but i sometimes (like today) have a feeling i am living in the wrong country, full of corruption, stupid politicians, terrible state services and court results... and trapped in boring work.
Nevermind, there is no paradise on Earth and it seems these problems are everywhere.
(yes, i have really bad mood today, sorry for sharing it)

Well, there are a lot of people in the US who also feel that they are living in the wrong country, full of corruption, stupid politicians, terrible state service and court results. I'm one of them - so don't feel too bad. I am fortunate that I am very happy with the work I perform. I have a one-man computer network consultant firm and I'm constantly challenged every day. I'm just now giving up one great hobby (extreme long-distance motorcycle riding) for RC heli flying and I am very excited about what the future will bring and how much progress I hope to make.

The state of Texas is the only state in the United States that has legally reserved the right to secede from our union. I wish it would happen because then I would be able to keep my eye on crooked politicians who are only 150 miles from me (Austin, TX, the capital of Texas) rather than 1500 miles away in Washington, D.C.

It's becoming a strange world - I hope that honest, cooler heads begin to prevail soon.

Ben

[aussiemick]

an easy analogy with the 13 and 14 tooth pinion is a bike.

a 13 tooth pinion is like pedalling in first gear, it is easy to turn the pedals but you will run out of speed with your legs before getting the bike to full speed.
A 14 tooth pinion is then 5th gear, it requires more energy from the pedals to get up to speed (and for low speed riding) but once up to speed it seems easier to keep that speed constant.

Mick

[iba10753]

Great analogy, Mick. You should teach for a living!

[dswitkin]

Edit: note: for that Scorpion, only 14T is available, because 13T will not fit the oversized shaft.
Can someone confirm that this is true, that a Scorpion 4525 cannot take a 13T pinion?

Daniel

[helicraze]

I am not 100% sure, but 2 problems 1) not much pinion to bore 10MM hole. 2) the bearing block will hit the motor so that needs to be ground a little.

A lot of work for a pinion that will only give about 1600-1700RPM

[spdntckt]

Daniel

You can make either the 13T pinion or the 14T pinion fit the 4525.. here are the gotchas

a) because of the 10MM to 6mm tapering at the end of the shaft, you either have to counter-bore the pinion so you can get it all the way down the shaft OR use two motor mounts stacked so that the tapering does not interfere with the pinion seating in the correct position.

b) 14T pinion gives enough clearance on the intermediate shaft bearing block. 13T does not. If you run 13T you will have to mill out a bit of material on the intermediate shaft block so that the motor case does not rub (ask me how i know this ;)

Personally, i do not see why you would use 13T with 4525.. you will not be able to effectively use most of the power it is capable of. the 4525 can pull 15 Deg pitch at 1900- 2000 headspeed all day long. if you only wan to run 1700-1800 head-speed there are other motor options

[dswitkin]

Thanks, great info. What I wanted was a very efficient motor with milder headspeeds for long flights. Maybe I'll discover I'm a speed junky and 14T will be great, but I would prefer to start at 13T if it was easy. I'll ask Jan when my kit is ready in May.

[Edvard R]

You'll be OK with a 14T pinion. If you are using a Jive120, it performs well even at low throttle %.
Should your HS still be a bit too high for your liking, you can adjust the timing of the motor in the Jive program. A timing value of -5 gives you about 45-60 less RPM on the head.