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50-size.belt drive

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Old 09-14-2019, 10:46 AM
  #1  
ini
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Default 50-size belt drive

Hi,

Influenced by OS belt drive, contra systems and lately AR Single drive, I made my own for Sebart Miss Wind 50E:
At least as powerful as Hacker A50-16S but lighter. Runs very smooth and cooling is easy to arrange.

Shaft and prop fastening are spares from Hacker. Belt and larger tooth wheel are from ebay. Motor and smaller tooth wheel are helicopter components from 380 size (Goblin 380 etc.).
Design and cf plates are my own.



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Old 09-14-2019, 11:00 AM
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Old 09-14-2019, 02:13 PM
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Jeff Worsham
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Good job! How many grams? What prop are you turning? I was looking for an alternative to Hacker A50-16 but only found the 50 Products drive. Hard to justify the price on that one.
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Old 09-14-2019, 03:58 PM
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Please forgive my total lack of knowledge. I understand the contra drives, I am trying to figure out what the advantage is to a belt drive on a non-contra setup. Of course you can change gearing, but you can get a different kv motor for that.

Adding a belt drive or gears has to add inefficiency and heat, compared to a direct drive, add to the weight and complexity (more things to go wrong), or at least thats why my little brain is telling me.

I'm sure there is a reason, I just can't figure it out

What am I missing?
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Old 09-14-2019, 04:30 PM
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Default Very nice, INI.



I like the way you think, I too couldn't justify costs of the current reduction motors so, like you, I was inspired to do my own. It's a bit lighter that Adverun Single and using the Competition Pyro with a little different reduction, a bit more powerful as well. Still awaiting the airframe for the moment but bench tests are very good with the D3Motors ESC/Governor I had Adam set up for me. Contra is next on the agenda but still searching a nice benchtop lathe. Awesome that you've done this for a 50-size! I was thinking a contra for 50 size just because it would be cool to have but had no idea what to do about props. Good luck.

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Old 09-15-2019, 12:29 AM
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ini
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This drive was actually designed for 5S as I have plenty of those, half of 10S used in 2-meter planes.
Prop is APC-E 16x10, 16x12 is also possible.
Measured RPM in bench is a tad over 8000 1/min w. 16x10 with full pack.
Weight is 301 grams in configuration of the picture. Without prop drive (40 g), rubber insulators and back support it is 247 g. Bigger wheel could be made lighter but didn't bother, with this total weight.

I do not have actual weight of Hacker A50 but on web site it is stated to be 345 g. It is unclear whether that includes propdrive or not.

Starting point for all this was cooling. I used to have an AngelS 50E w. Hacker A50-14S. That was prone to overheating. A new slotted spinner could be the answer. Heat is also a symtom of lesser efficiency. My drive runs very cool indeed.

The above question of justification for all this is good. Why bother when the belt has friction and it becomes more complex?
The answer is in the nature of electrical motor, especially outrunner. A direct-drive motor has to be built heavy to provide enough torque and it still suffers when it is run at lower speeds with heavy load. A motor that runs faster works with significantly better efficiency and behaves better. This gives more benefit than is given away with belt. For me it is also an engineering challenge that is interesting. So, more power and longer flight times is the answer.
As an example a small RC heli Goblin Fireball has direct drive. The motor weighs 200 g. Similar sizes other helis use gearing and the typical motor weighs 70-80 g. Gearing is ~ 50 g or less.

I also have a bigger one in the works. Just wanted to test the concept with a smaller one first.
​​​​​

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Old 09-15-2019, 12:43 AM
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Good work Ted. That looks very good too.

Something you could consider, and this also applies to Adverrun SD:

​​​​​In my tests I found that in sudden change of direction, the prop alignment tends to change as rubber isolators flex. Because of this I had to bring the back support further away from prop to keep alignment decent and to make plane more stable.
Also, I put the back support in the center so that the torque of the motor will be handled by front rubber isolators, not the the back ones. This is not a big issue but need to be considered when installing the drive in the plane. If you keep it like that the back support of the plane need to be strong and stiff enough to cope with vertical forces induced.

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Old 09-15-2019, 12:48 AM
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One benefit in this concept is that if you end up in situation where you want/need to change kV or behaviour of the drive, it is possible to change gearing. Normally you just change smaller tooth wheel and cf plates and the rest is kept as is.
There are more choices available than with current outrunners (+Plettenberg).

BTW, this is very silent. You can only hear the prop.
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Old 09-15-2019, 03:38 AM
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Interesting point. I suppose one could opt for a longer motor shaft and use a soft mounted bearing from the back of the motor. I have already changed the motor shaft for a longer one so I guess I can do it all again. Thanks, Ted.
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Old 09-15-2019, 03:45 AM
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Or you just put another two aluminum spacers in place of those back mount rubbers and connect back of those with a simple plate. Then install a rubber in the center of the plate.
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Old 09-15-2019, 07:44 AM
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Yes, that might be the smart approach. Lately, I'm organizing a new build and somehow I've gotten stuck in this "weight saving mindset". Can't seem to shake the urge to over analyze every little thing to perhaps save a gram or two. Silly, I know, but there is that hope that I'll be pleasantly surprised by the total weight when finished and of course, by extension, I'll miraculously fly better, LOL. I flew F3c for twenty years and hardly ever gave a thought to increments of weight so this is a new challenge for me, for sure and I like challenges. When I see what some of the top pilots' models weighed at WC, it just drives me a little harder. I can't have their fingers or brains but at least I can strive to have some of the other advantages.
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Old 09-24-2019, 11:36 PM
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Hi Guys
INI I think we spoke off this at the Nordic Champ i Finland this summer?
I have started to collect parts for this!
I'm going to make one for a 2M airframe and are going to use the 3GT belt from a OS belt drive.
What I have troubbel to find a good selction off is the gear wheels that are first cheap and light weigt , where do you find this ?
I have thinking to use parts that are mostly already made (as I dont have a lathe in my workshop) the frame for this I plan to make out off 3mm carbonplates
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Old 09-25-2019, 10:33 AM
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Exclamation Gears and sprockets

Originally Posted by RuneG View Post
Hi Guys
INI I think we spoke off this at the Nordic Champ i Finland this summer?
I have started to collect parts for this!
I'm going to make one for a 2M airframe and are going to use the 3GT belt from a OS belt drive.
What I have troubbel to find a good selction off is the gear wheels that are first cheap and light weigt , where do you find this ?
I have thinking to use parts that are mostly already made (as I dont have a lathe in my workshop) the frame for this I plan to make out off 3mm carbonplates
Rune, be aware that sprockets have different toothing which require belt suited for the special type of sprocket.
Take a look /at this web siteand you will see different types of sprokets and belt sices/toothing..
https://www.gearsandsprockets.co.uk
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Old 09-25-2019, 10:51 AM
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Default Gt3

Originally Posted by DagTheElder View Post
Rune, be aware that sprockets have different toothing which require belt suited for the special type of sprocket.
Take a look /at this web siteand you will see different types of sprokets and belt sices/toothing..
https://www.gearsandsprockets.co.uk
i know that Dag, i will use GT3 both in belt and sprockets AS this is the type Thats used on the OS and I know it will do the job , in fact what I thinking off is more or less to remove one Stage off the gear on the Os. I think I found some from some Heli parts today
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Old 09-25-2019, 10:54 AM
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That'sright Rune, we did talk about this earlier in July.
I will gather some information and come back to you.
I have a larger unit ready for bench testing and the air frame is also ready to accept it. Current weight is just under 500 g with prop drive & rubber grommets.
The tests may cause some modifications.
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Old 09-25-2019, 01:02 PM
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RuneG, all you have to do is go to the heli market. SAB and others all use 3mgt belts in their top level machines. Belts can be bought online from various sources if you need another length [which you will unless you plan to incorporate an idler]. These parts are dirt cheap and well machined. Typically they are designed for 10mm and larger shafts but that's an easy mod to accomplish. Motor pulleys are also available from industrial sources at reasonable prices although the number of teeth are limited in selection so ultimately, you will have to carefully select your motor Kv.
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Old 10-15-2019, 11:04 PM
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@ted32776 which propshaft did you use for your custom drive?
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Old 10-16-2019, 03:27 AM
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Tomas L.....Mike at F3A Unlimited has a "front mount conversion kit" made by MAXX products for mounting a Himax pattern motor from the front rather than standard rear mount. This kit will have a very nice hollow 8mm shaft with very light prop adapter included.
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