S-Bend with Square Drive?

[BobBonahoom]

I stopped using S-bent stuff tubes with my outriggers when we burned up the inside of a radio box right at the S-bend. This was a conventional set up with the thrust load going to the engine. Years ago I tested S-bends vs. gradual bends using with an electric motor/generator set up and found the S-bend had less drag. The flaw in that experiment was probably that I didn't end load the shafts, but just let them spin free in the tube.

So my question now is about using a square drive set up, were there is no end load on the shaft. It seems like the S-bend should be re-visited and may be better. What do you all think?

 

[Elias Vazquez]

I'm all ears!

 

[mtruex]

The heat in the radio box with the s bend is because the shaft friction/heat is at the top of the shaft tube at the first bend inside the radio box .. With a single bend all the friction/heat is on the bottom of the tube outside the tub/radio box... Single bend pushes the shaft against the bottom of the tube, S bend pushes against the bottom the rear half, top the front half. All that said, i think square drive is worth trying with the S bend, afterall your test showed it was better without thrust load! Seems to me that the smaller shafts/engines this is all more significant.

 

[Jerry Dunlap]

I'll take the ease of installing a conventional drive and any additional drag over installing a S drive.

JD

 

[Chris Wood]

i guess i have not had any issues with burning up tubes in a s bend.. that i have built alot of 20 boats that way.

curious what was you using for lube on the cable? grease ? oil type ect?

i have kicked around a square drive myself. just havn't gotten dad to make one yet lol!

 

[RaceMechaniX]

I would add to the comments that the degree of friction will depend on the severity of the bends. The severity also increases with larger diameter cable.

For most of my boat including the SAW boats I try to run a single bend as shallow as allowable by the set-up. I also try to have the flexibility of allowing either square or collet in some of the boats as well.

I did try a square set-up in something like a short JAE style boat with .150" cable and the results were not terrific. Switched to a collet and the driveline was smoother. See Martin's description above.

I also did a square S-bend set-up in my 80 SAW hydro to try and get the engine more level to avoid a sharp angle between the pipe and exhaust stub on the engine. This works quite well, but the second bend closest the engine is very shallow and it is over a very long length. The driveline is butter smooth and no cable whip or temperature issues.

TG

 

[Ian Inverarity]

I have run square drive with S bend shafts in quite a few boats with no issues.

 

[Stuart Barr]

Me too.

 

[JUSTINROGERS]

Who can i go to for a shaft with a square end?

 

[Ian Inverarity]

Who can i go to for a shaft with a square end?

For 3/16" I get shafts from Kris Flynn.

 

[Anders_Martinelle]

Only time i have had problem with flexshafts is when i built my Seaduser 90 with 1/4" thrust load on the Engine.

I thought it would be good to follow the building advice from Jerry fully so i did.

Thing is that i never got it to run good and it might see odd because alot of the boats in the states run thrust load.

But after some flexshaft failures i gave up and change to Square end as i normally run and the problem was gone.

So after that i had never thought about using thrust load 1/4" again.

I have been running Square end for over 20years and had never seen any problem running S-bend or single bend when it come to Square end flex.

But this is just my experiance.

Anders

 

[JUSTINROGERS]

Who can i go to for a shaft with a square end?

For 3/16" I get shafts from Kris Flynn.

Thanks Ian

 

[dave roach]

I have try the S bend on a 3/16 cable in my hydros and all ways had problems with heat.I am using castor oil for lube in a oiler system.

So I am using 3/16 square drive in my blackjack for 15 years with no S bend and it seem fine with the castor oil..