Pekka L

Seems to be very difficult to find coupler for my mini hydro.
Motor output shaft is ~2,3mm and Octura flex cable is 0.098"
This seems to be the smallest Octura? http://www.offshoreelectrics.com/pro...oct-ocfhe18098

ROMA-F1

YOU CAN BUY FROM = http://towerhobbies.com/

http://www.rcplanet.com/

BACKEMF

The one worse thing than people that don't read threads or do searches are people that post USELESS links that only direct you to a hobby shop and not the item a person is actually looking for.

Tower has diddly squat and niether does rcplanet. Did supplying those 2 links get you a better discount? It better have.

Now, if you are looking for a flex hex from 2/3mm to .098 you might as well give up. There are only aluminum set screw types for that and Offshore Electrics may have what you need or Jeff Wholt can make it for you.

If you need more specifics let me know.

coriolan

The link you show:http://www.offshoreelectrics.com/pro...oct-ocfhe18098
is the perfect answer. 2.3mm is the same as 3/32" so you can use a short piece of 1/8" brass or aluminium tubing for the 1/8" Octura coupling to fit a 2.3mm shaft.
That might be hard to get in europe, everything being metric there but if you order that coupling from Offshore they also have 1/8" brass tubing in 12" length:

http://www.offshoreelectrics.com/pro...dh-ks-brass-tb

BACKEMF

That will leave about .004" of slop. Could prove to be noisey and may get hot dpepending on his rpm.

If you are stuck on a flex coupler, then you might think about a 5/32 or 3/16" to .098" Octura flex hex and have Jeff Wholt machine you a sleeve to fit down to 2.3mm. If you run any decent rpm of a mico hydro, you will want it slop free. Simplify and use an aluminum set screw type from Jeff Wholt.

Basstronics

My Feedback: (2)

I wont use another flex hex coupler again, ever.

Positive locking like set screws for me- forever.

coriolan

The difference between 2.3mm and 3/32" is actually .082mm which doesn't look sloppy to me. One can alway buy specialty reamers, buy a good small lathe and make perfect fitting bore and find out that the shaft on the motor itself has rather large variations. I run 3 cells on 4800 Kv/2.3mm shaft motors with an Octura 1/8"motor shaft> Octura .098" cable without vibrations using a 1/8" tubing sleeve on the motor shaft. Off course I pay great attention to prop balancing, my background being with larger IC boat with bigger props. I don't think anybody in Finland as ever heard of Jeff Wholt and I am pretty sure they have competent machinists there having train in that trade in Europe myself.

Pekka L

Hmm... I think that I'll try that brass sleeve.
Yeah everything here is metric so it seems that I need to make another order to OSE again.... :-)
So outer diameter is 1/8 and inner diameter is very close to 2,3mm in that brass tubing?

Planning to use small outrunners 4200-5000kv on 2s.
4200kv on 2s worked well, but my 4mm (with square end to fit 1/8 drive shaft end) flex shaft is rubbish and it seems to have lot of friction and poorly balanced.

coriolan

Are you using a 4mm tread prop? If you do http://www.offshoreelectrics.com/pro...at=Flex+Cables
has a stub shaft with .098 cable to fit that M4 but you might have to modify the strut

joeysan2

You can have one custom made by Jeff Wholt. I had one made that works great. 2.3mm by.125. The OSE site appears to be down, but you can find him there.
I think I paid $15.00 shipped

Pekka L

I'm using 1/8" props (1.4x30mm and like).
In my mini hydro (Small Bolt from HobbyKing) the original flex is 4mm that is connected to 1/8" shaft that has larger diameter head for this flex connection

I'll try to make some kind of sleeve for my octura 1/8->0,098" coupler. I hope that I can find some suitable material locallu.
Ordering only some thinn bras tube from OSE seems bit too expencive :-/

coriolan

Agreed, it would be worth it only if ordering something else too. Since you use 1/8" stub shaft with Octura prop the only problem left is the sleeve to fit inside the Octura collet or just make yourself a simple aluminium connector like this:
http://www.offshoreelectrics.com/pro...prod=cen-ws017
If you have access to a lathe it is not a big deal, just drill right trough at 2.3mm to fit the motor shaft in a 25mm length of 10mm Dia. aluminium, you can drill and tap two M3 hole as shown to lock the coupler on the motor shaft/lock the cable. The cable side might need to be a bit more than 2.3mm since you need to tin the cable at the end to prevent fraying. I use that method on small 20mm motors and lately I dont even bother with grub screws on the motor side. Instead I use permanent locktite as explained in OSE site as an alternative method to soldering .098 cable to 1/8" stub shaft. If need to release I just heat the coupler to soften the locktite
http://www.offshoreelectrics.com/inf...mble-shaft.php

coriolan

Thats what I do now for small 20mm motor with a 2.3mm shaft. the locktite hold very well.
Ignore the sub in the left picture, it just sneaked in while I wasn't looking

Pekka L

Hmm... That is good idea to use Loctite to secure the coupler to motor shaft :-)
It seems that I can find 1/8" tube from Finland, so I will use that and some loctite to connect my Octura coupler to the motor shaft.