Flex shaft between 12mm to 9mm shaft

[serc]

People,

See attachment for a picture.


I have an outrunner with a 12mm shaft and 9 mm shaft at my jet pump. I now a flex coupling but I still have vibrations. I think with a flex shaft everything totally running without vibrations ?


Does anyone has a solution to mount a strong flex shaft between a 12 and 9mm shaft ?

Rpm is about 16.000 with 10 kw power.

Thank you

[grsboats]

Probably vibrations are due to your flex coupler.....why not use non flex one....you don't need that flex!Gill

[serc]

A solid coupling would exact be in line from shaft to shaft. I thought that in fast rc boat world they use flex shaft so it easier to mount motor to jet.

[RaceMechaniX]

Serc,

The "Lovejoy" couplers usually work well when they are properly aligned. The spec is .015" parallel and 1 Deg angular. At 16kRPM, the vibration should not be too bad if everything is aligned. I have used these up to 40kRPM with a well aligned 10kW system.

Hopefully Peter Zicha will chime in here. He built a custom mount for a 3080 to go with the Hobbyking billet pump. I don't know what he ended up using for a coupler between the two.

Using a rigid coupler will only work if everything is extremely well aligned .0005 or better from my experience.

TG

[serc]

There is a bit vibration. I'm afraid it will break my bearings.
I don't have tools and experience to build it 100% aligned. I read somewhere that a flexible shaft is costing some efficiency but since it has no unaligned problems it is somewhat the best solution

[RaceMechaniX]

Yes that is correct, but you have very limited space to try and mount two couplers plus a cable. You can also consider a square drive on either side with a piece a square stock in the middle. Hopefully Peter does not mind if I post these pics of his set-up. You can see he made a top bracket to connect the motor plate to the pump housing.

19.jpgDSC01968.jpgDSC01971.jpgDSC01992.jpg

[serc]

Impressive. Maybe I need to search for a company that can build a plate like that. If it is build that. Then probably any coupling will work. I did find a company that makes flex shafts. But they do not reply.

I can mount the motor much further away so there is space for a flex shaft and 2 couplings.

[RaceMechaniX]

Serc,

Peter machined these himself. His has a small CNC in his workshop and may be able to machine a mount with bracket for you. I will ping him for you and point him towards this thread.

Alternatively, if you can space the motor further out you should be able to drive this with common parts. You can likely bore out the 10mm Lehner or MBP coupler to 12mm to suit the motor side and use a short section of flex cable to another 10mm coupler on the pump side.

Tyler

[Punisher 67]

Hello everyone

I am away from home and posting from my dinky cell I will chime in better when I get home tonight

I got my coupler from stock drive products and it resembles a telescopic coupler setup.

Will post a picture tonight

Peter

[Punisher 67]

Hello Guys

this is the coupler I used for my unit , the motor was 10mm and the pump was 8mm so I ordered the 10mm x 10mm and machined a 10mm to 8mm step down adapter .

https://sdp-si.com/eStore/Catalog/Group/844

I would recommend an upper brace much like I have on mine to cancel out any harmonics ( vibration )

Peter

[serc]

Thank you for sharing. Yours totally free of vibrations I think ? Would a flex shaft or other flex coupling have any benefits. ?

Why did you go for a telescopic coupler,instead of a straight coupler ? Is your coupler also good for slightly out of line shaft to shaft mounting ?

[serc]

http://www.sswhite.net/flexible-shaft.htm

This why I get so exited about a flex shaft

[RaceMechaniX]

Serc,

I would avoid the SSwhite flex cable and use what Peter recommended. If the flexcable is more than 2" you will have to support the cable as well to prevent it from "whipping". It may cause more issues than it solves.

Tyler

[serc]

Ok thank you. I think I will go for the coupler that Peter is using, but 100 USD for a coupler......is it that good ? Does it need to be eactly in line or is this coupler also something that can be mounted slightly out of line shafts ?