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Old Nov 14, 2008, 08:29 AM
The Kid
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Detroit, MI
Joined Dec 2007
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Oh, i figured the length was the problem...

Have you ever emailed them and told them what you're doing? They may be so inclined to sponser you perhaps?
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Old Nov 14, 2008, 10:46 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,005 Posts
Quote:
Originally Posted by Thekid3418
Oh, i figured the length was the problem...

Have you ever emailed them and told them what you're doing? They may be so inclined to sponser you perhaps?
I really havent found anyone that has longer than 60", except aircarft spruce. They have 10' lengths but the are $550.00 each .

I have thought about taking a thick walled 12" 6061 tube and truning it down to a OD of 1.2" then epoxying it into the 2 tubes and see if I could join them that way.

DAG
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Old Nov 14, 2008, 04:26 PM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,005 Posts
Here is a rendering of my main gear, the strut is 1" carbon fiber tube. I will start next week on making the parts, but first I have to pay the bills, work will have me hammered all next week. The entire right main gear should weigh 1.75 pounds.

DAG
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Old Nov 15, 2008, 07:10 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,005 Posts
The fuse is going well. I am going to get 2 48" carbon fiber tubes and see if I can take a 6061 1.5" X12" tube with a wall thickness of .25 (or a little thinner) and see if I can turn down the OD to fit the ID of the CF tube. Also I had a e-mail asking about the main gear parts, so I expoded the gear rendering.

DAG
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Old Nov 15, 2008, 07:45 AM
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Lynxman's Avatar
Troms, Norway
Joined Jan 2004
7,098 Posts
I borrowed a 6S battery from my neighbour today and am charging it now.
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Old Nov 15, 2008, 08:07 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,005 Posts
Quote:
Originally Posted by Lynxman
I borrowed a 6S battery from my neighbour today and am charging it now.
Here is how I could belt drive (with top spar and some ribs removed). Both AXI (Hobby Lobby) and Hacker are giving me great info and telling me what other people have found that works not just what a calculator says. Hacker has a huge choice of KV on their motors. If I can direct drive and keep weight and CG good I will go that way, but a smaller and lighter motor with a belt drive turning a 20" prop would be just as good if I get the RPM and amps I need.

Can't wait to see what you get with the 6cell.

DAG
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Last edited by dag214; Nov 15, 2008 at 08:52 AM.
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Old Nov 15, 2008, 08:35 AM
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Lynxman's Avatar
Troms, Norway
Joined Jan 2004
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With a 6S 2600 mAh 25C battery.

18x14" - Way too much.
68 A
20.5 V

18x10"
58 A
20.7 V
4900 rpm - That's a pitch speed of 21 m/s, or 47 mph with a 10" pitch prop.

I think the motor would be hot after landing if it was propped this heavilly in flight. The Soloprop is a much heavier prop to drive than an APC with the same diametre/pitch/number of blades though.
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Old Nov 15, 2008, 08:58 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
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Quote:
Originally Posted by Lynxman
With a 6S 2600 mAh 25C battery.

18x14" - Way too much.
68 A
20.5 V

18x10"
58 A
20.7 V
4900 rpm - That's a pitch speed of 21 m/s, or 47 mph with a 10" pitch prop.

I think the motor would be hot after landing if it was propped this heavilly in flight. The Soloprop is a much heavier prop to drive than an APC with the same diametre/pitch/number of blades though.
Thanks, that is great info. That was direct drive correct?

I have done some testing (in math) and if I belt drive with a ratio of 1.6 the AXI should be able to turn a 20-14 3blade at 4000 rpm that is a prop speed of 52mph, that is at 7 cells and the amps should be 35ish. The motor speed would be 6300 rpm. Hacker is looking at which of their motors will turn this prop set-up, but I am 95% sure that the axi with a belt drive will do the trick also. All my calcs show I need a pitch speed of arond 52-55mph.

Thanks, DAG
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Old Nov 15, 2008, 09:13 AM
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Lynxman's Avatar
Troms, Norway
Joined Jan 2004
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Yes, direct drive.

I used to fly the P-40 with this motor, a 1:1.6 gear ratio on 8S and a 20x14 Soloprop. The batteries back then didn't hold voltage as well as today but it drew ~45 A at full throttle static on 8S. I agree, on 7S the current will probably be around 35 A. I recommend you design it for a shaft diametre of at least 8 mm. I used 6 mm which works as long as you never bump into it or strike anything, but it's noticeably flexible. I'm upgrading my system to a 10 mm hollow shaft.

I buy pulleys and belts from sdp-si.com
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Old Nov 15, 2008, 10:28 AM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
8,482 Posts
Quote:
Originally Posted by dag214
The fuse is going well. I am going to get 2 48" carbon fiber tubes and see if I can take a 6061 1.5" X12" tube with a wall thickness of .25 (or a little thinner) and see if I can turn down the OD to fit the ID of the CF tube. Also I had a e-mail asking about the main gear parts, so I expoded the gear rendering.

DAG
Dag,

Are you familiar with Aeropoxy? I know CA holds carbon quite nicely but I suggest to you if you get a carbon pin sized right and glue 2 carbon sleeves together (and glue them together with Aeropoxy), they would be the last things still fastened in the event of a catestrophic event, the stuff doesn't let go, ever...

Jack
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Old Nov 15, 2008, 10:37 AM
HAL... Open the damn doors!
jfetter's Avatar
Miramar, Florida
Joined Jul 2007
8,482 Posts
Quote:
Originally Posted by dag214
Thanks, that is great info. That was direct drive correct?

I have done some testing (in math) and if I belt drive with a ratio of 1.6 the AXI should be able to turn a 20-14 3blade at 4000 rpm that is a prop speed of 52mph, that is at 7 cells and the amps should be 35ish. The motor speed would be 6300 rpm. Hacker is looking at which of their motors will turn this prop set-up, but I am 95% sure that the axi with a belt drive will do the trick also. All my calcs show I need a pitch speed of arond 52-55mph.

Thanks, DAG
High amperage and very low efficiency (heat) is exactly what I was saying a few pages back, that motor is simply not the correct choice. I'm not trying to tell you I am the expert, only that I have quiote a bit of experience with 6S setups and the Axi/Hacker options, in this case, the KV rating is all wrong for what you want. If you want to design a belt drive I am sure that will work but it really shouldn't be much more than an excercise in electric fundamentals to size the motors appropriately here...

Jack
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Old Nov 15, 2008, 11:45 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,005 Posts
Quote:
Originally Posted by jfetter
High amperage and very low efficiency (heat) is exactly what I was saying a few pages back, that motor is simply not the correct choice. I'm not trying to tell you I am the expert, only that I have quiote a bit of experience with 6S setups and the Axi/Hacker options, in this case, the KV rating is all wrong for what you want. If you want to design a belt drive I am sure that will work but it really shouldn't be much more than an excercise in electric fundamentals to size the motors appropriately here...

Jack
Thanks Jack and you are most likely more an expert than I, The AXI info shows the 4130/20 with an 18-10 prop. That is where I was going with attempting an 18-10. I am now starting to understand the whole amp/KV rating thing. The reason I am trying to be careful of the actual motor size is weight. Hacker has some motor with really low KV that could easily turn an 18", or 20" prop well, but they are heavy motors, and lots of $$$$. Hacker does have some very cool inrunners with planetary drives that are a lot lighter and can turn a 20" prop, but again lots of $$$, but I may end up going that way. In the end with all your help and Hacker/HobbyLobby I will find what will work. But the P-40 with a 3blade 20" prop has the power I need, especially when I would take 6 set-ups like the P-40.

The big battle is:
1st-Weight
2nd-Scale prop 20" or 18"
3rd-$$$$
Or should I say $$$$ is what will making me belt drive 305Kv type motor if all other options are just to expensive.

Thanks for your input and keep it coming.

DAG
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Old Nov 15, 2008, 11:52 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,005 Posts
Quote:
Originally Posted by jfetter
Dag,

Are you familiar with Aeropoxy? I know CA holds carbon quite nicely but I suggest to you if you get a carbon pin sized right and glue 2 carbon sleeves together (and glue them together with Aeropoxy), they would be the last things still fastened in the event of a catestrophic event, the stuff doesn't let go, ever...

Jack
Aeropoxy-Yes it GODS glue.
Just finding a CF OD to fit the 1.5" ID is the hard part, but I am going to get some 48"X1.5" CF tubes and turn a 1.5 6061-T6 tube down to the ID of the CF tube the Aeropoxy the tubes together. After messing around this morning with some scrap CF tube I bet it will work, but boy is it going to get expensive. First I need 4-48"X1.5" for the fuse, then 5-36"X1" for the wing spars, and 2-36"X1" for the H-stab. About $600.00 worth of CF.
Thanks, DAG
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Old Nov 15, 2008, 11:54 AM
It only takes one good idea
dag214's Avatar
Fishers, Indiana
Joined Oct 2004
6,005 Posts
Quote:
Originally Posted by Lynxman
Yes, direct drive.

I used to fly the P-40 with this motor, a 1:1.6 gear ratio on 8S and a 20x14 Soloprop. The batteries back then didn't hold voltage as well as today but it drew ~45 A at full throttle static on 8S. I agree, on 7S the current will probably be around 35 A. I recommend you design it for a shaft diametre of at least 8 mm. I used 6 mm which works as long as you never bump into it or strike anything, but it's noticeably flexible. I'm upgrading my system to a 10 mm hollow shaft.

I buy pulleys and belts from sdp-si.com
Thanks Lynxman, what does the P-40 weigh????

DAG
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Old Nov 15, 2008, 01:58 PM
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Lynxman's Avatar
Troms, Norway
Joined Jan 2004
7,098 Posts
It weighs 6 kg (13.22 lbs) with a 4270 mAh 8S battery and has a wingspan of 73".

A benefit of belt drive is that you can adjust the gear ratio to get the rpm/torque you need. That was one of the things that made me try it on my P-40 instead of rewinding another motor as I often had to rewind over and over to get the desired result. I recommend using a idler pulley on the belt to wrap the belt around the pulleys on the slack side of the belt. It isn't showing in the picture I posted because I added it later. I made it from two ball bearings.

I'm sure Hacker or MM or Scorpion can supply a suitable custom wound motor though.
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Last edited by Lynxman; Nov 15, 2008 at 02:05 PM.
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