Wright Stuff C

[CrayolaCrayon]

I'd agree with Lechassin. They're just banning VP hubs and stuff like that

[jander14indoor]

Haven't done this much this year, but general caveat because as some of you know I'm an event supervisor, but NOTHING I say on this forum is official. ONE opinion only.

A google search on "f1d variable pitch propeller" and "f1d variable diameter propeller" will show images of what folks are talking ruling out under these rules.

I'm disappointed (but not too surprised, unfortunately) that a three blade prop came under any question with these rules. Certainly well within the wording as I read them. The only pause I can see if an ES isn't prepared to measure a three bladed prop, takes a little more thinking.

As usual, if you think you are pushing the edges of the rules, make sure it is worth the risk of being tiered, and make sure you know the rules WELL to discuss politely and informedly with the ES. And its best if the student can lead the discussion.

Thanks,
Jeff Anderson
Livonia, MI

[bjt4888]

So I finally got some gym time. I know everyone has said a gearbox is a waste of time but I'm kind of intrigued by the idea. So I built a concept plane to test the gearbox. I put the link to a video of the first flight. I started it late since I had to launch then record. It went for 59 seconds.

https://youtu.be/Xv4Y2T5OR4c

It uses a drone prop and 2g of .125 rubber. I wound to 1.2in and had to back off to .6 or I would hit the ceiling at about 20ft.

I think this is proof of concept? I have some ways to improve from here but curious what you think about it so far?

Air coco,

Nice job. Is the gearbox self-made?

Brian T

[Airco2020]

So I finally got some gym time. I know everyone has said a gearbox is a waste of time but I'm kind of intrigued by the idea. So I built a concept plane to test the gearbox. I put the link to a video of the first flight. I started it late since I had to launch then record. It went for 59 seconds.

https://youtu.be/Xv4Y2T5OR4c

It uses a drone prop and 2g of .125 rubber. I wound to 1.2in and had to back off to .6 or I would hit the ceiling at about 20ft.

I think this is proof of concept? I have some ways to improve from here but curious what you think about it so far?

Air coco,

Nice job. Is the gearbox self-made?

Brian T

Thanks. The box I'm using is a tiny planatary box off a small robotics motor. All plastic, light weight. It doesn't work as is. Removed from motor, had to remove a set of gears, make a shaft and spacer, and put a hook on for attaching the motor, and basically use it in reverse of the design. It's made to gear down the little DC motor. I'm running it the opposite way and gearing up. 6:1 Made an adapter so it goes into the FF prop holder. The entire assembly with prop is only 1.16g. The plane is only 7g all together so I'm going to make the motor stick longer. I can also make it 28:1 but haven't been able to get that to climb in the living room so didn't bother in the gym.

[lechassin]

1:6 gearing is quite a bit higher than I expected! The prop you're using apparently doesn't need much torque, is it tiny?

To make it easier for future event supervisors to measure our 3-bladed props, we made a "go-no go" template from an empty cat food can. We just slip the plane's nose into the can to prove the prop is less than 8cm. Hopefully future event supervisors will like it.

[bjt4888]

Air,

I want to compliment your ingenuity and effort on the gearbox, but you might want to consider the “purchase preassembled” wording in the rules related to the propeller assembly. The rules appear to only allow a few elements to be purchased preassembled, including: propeller, shaft, hanger and/or a thrust bearing; with no mention of a gearbox. As one of the most challenging part of building a gearbox is the housing which aligns the gears, I’m thinking that the housing should be self constructed to be sure that it is not questioned during judging.

This is just my opinion of course, and any rules clarifications should be requested via the official SO website.

Keep up the excellent, creative work.

Brian T

[Airco2020]

1:6 gearing is quite a bit higher than I expected! The prop you're using apparently doesn't need much torque, is it tiny?

To make it easier for future event supervisors to measure our 3-bladed props, we made a "go-no go" template from an empty cat food can. We just slip the plane's nose into the can to prove the prop is less than 8cm. Hopefully future event supervisors will like it.

Yes, small. 6.5cm and about 1/4" wide

[Airco2020]

Air,

I want to compliment your ingenuity and effort on the gearbox, but you might want to consider the “purchase preassembled” wording in the rules related to the propeller assembly. The rules appear to only allow a few elements to be purchased preassembled, including: propeller, shaft, hanger and/or a thrust bearing; with no mention of a gearbox. As one of the most challenging part of building a gearbox is the housing which aligns the gears, I’m thinking that the housing should be self constructed to be sure that it is not questioned during judging.

This is just my opinion of course, and any rules clarifications should be requested via the official SO website.

Keep up the excellent, creative work.

Brian T

Dang! I knew if I put a up a 4 minute flight I'd be banned but thought I was good to try it. I can't call it the thrust bearing?

[jander14indoor]

Why would a great long flight get you banned, that IS the purpose of the event afterall!

Again, NOT official, only one person's opinion.

Before you ASSUME it is not legal, I'd recommend you request a FAQ or clarification from the NSO website, www.soinc.org
It might be considered OK under general rule 1: Actions and items (e.g., tools, notes, resources, supplies, electronics) are permitted, unless they are explicitly excluded in the rules, are unsafe, or violate the spirit of the problem. (straight from the rule book, page C1)
I don't see where it is explicitly excluded in the relevant construction paragraphs. Para 3.e lists things that "may" be part of the prop, excludes only one mechanism type, pitch change.
Doesn't seem unsafe to me, unless someone wants to claim it is because of the high prop speed.
Spirit, always subject to interpretation (personally I hate that clause, though I have used it ONCE in 20 years of event supervision). While I might not say it is against the spirit, someone else may. That's where an official position from NSO would be useful, and the only way to get that is an FAQ or clarification.

Thanks,

Jeff Anderson
Livonia, MI

[bjt4888]

Air,

Yes, I agree with Jeff. I didn’t mean to discourage your work on gearboxes. Just want to advise you to get clarification and to consider that one of the most difficult parts of gearbox construction is the housing which aligns the gears and shafts. It’s possible that a premanufactured housing might not meet rules as all the alignment is built in. Definitely submit a FAQ on the official SO website.

Also, even if the premanufactured housing is not allowed, it is definitely possible to make one from carbon plate and using small aluminum tubing for bushings. Just make a jig to align shafts and gears during construction. See examples in issues of this type of construction in Indoor News and Views or in Hip Pocket.

Not sure your current configuration will do long duration as, based upon my calculations from your data, your prop is turning at about 100 revolutions per second. However, you have a good start with an innovative idea. So, maybe a different gear ratio, or different prop, or longer rubber, or Etc.

Great job.

Brian T