Prop trust -

[Jorgen Andersson]

Hi

What are your experiencies on this area?

Square or round flex systems?

Real ball trust bearing or simple Teflon washer at the strut?

or

Letting the engine front ball bearing taking care of the prop trust?

Will it be different for different engine sizes? 21 - 45 - 90?

All experiencies on this subject appreciated!

Thanks

Jorgen

 

[Mark Anderson]

I am suprised that you have not gotten several different answers to this question. It seems that both camps are very set on there system is best. I have run most set ups over the years and saw no real performance difference. For me a square drive with a plain teflon washer works best. I have seen the hardened washers in the ball thrust bearings cut through the shaft several times.

 

[Chris Wood]

i have a bunch of RULON bushings ( not sure on the spelling ) that i got from mcmaster carr.. havn't tried them yet.. anyone try anything like that....

chris

 

[Watercadet]

Jorgen, you have the fastest model boat in the world, aren't we supposed to ask you which is better

Seriously it is nice to see that even the fast guys are willing to learn. B)

I too saw no difference on the same boat with thrust on the strut and thrust on the front bearing. I think square drive is more difficult to set up because I like to buy my shafts pre welded, and with a square drive you have to get the custom built to legnth.

 

[dave roach]

I like all the trust on the strut and not on the engine bearings.Square drive is the way to go.

Dave Roach

 

[Ken Retallick]

Anything larger than a .21 i run Square drive, ball thrust bearings and needle rollers, with a hardened shaft.

Zero wear!!

 

[lohring]

After over 10 years with both systems, I can't see any real difference. Both have their good and bad points. I currently use the collet system mostly fore ease of shaft removal with 1/4 inch flex cables. We are experimenting with ball bearing suported solid shaft drives on our straight line boats. Its surprising how much you can bend a shaft and how easily it turns. With a brushless electric motor the freewheeling propeller rpm makes a great speed indicator when the power is off.

Lohring Miller

 

[DON MAHER]

Jorgen, you have the fastest model boat in the world, aren't we supposed to ask you which is better

Seriously it is nice to see that even the fast guys are willing to learn. B)

I too saw no difference on the same boat with thrust on the strut and thrust on the front bearing. I think square drive is more difficult to set up because I like to buy my shafts pre welded, and with a square drive you have to get the custom built to legnth.

Watercadet,

Jorgen Andresson is not the fastest boater in the world. That title belongs Joerg M. (spelling) from Germany. 133 mph & he used a wire drive

Don

 

[Watercadet]

Jorgen, you have the fastest model boat in the world, aren't we supposed to ask you which is better

Seriously it is nice to see that even the fast guys are willing to learn. B)

I too saw no difference on the same boat with thrust on the strut and thrust on the front bearing. I think square drive is more difficult to set up because I like to buy my shafts pre welded, and with a square drive you have to get the custom built to legnth.

Watercadet,

Jorgen Andresson is not the fastest boater in the world. That title belongs Joerg M. (spelling) from Germany. 133 mph & he used a wire drive

Don

Thanks Don! :lol:

Sorry Joerg M.!

And congratz to Jorgen Andersson on your victory at the worlds

 

[Don Templeton]

After over 10 years with both systems, I can't see any real difference. Both have their good and bad points. I currently use the collet system mostly fore ease of shaft removal with 1/4 inch flex cables. We are experimenting with ball bearing suported solid shaft drives on our straight line boats. Its surprising how much you can bend a shaft and how easily it turns. With a brushless electric motor the freewheeling propeller rpm makes a great speed indicator when the power is off.

Lohring Miller

Lohring,

What dia. shaft are you bending?

Don

 

[PakMan]

Oh, my bad, Vespel is the Shiznit! Try it, you'll like it! Way Cool! Never wears out with Balanced props (probably even with un-balanced props... never tried that... :-o). Never changes size, is always Slippery! Don't look back! Expensive but worth it.... I've been running the same strut bearings for years and still tight!

David

 

[Charles Perdue]

Oh, my bad, Vespel is the Shiznit! Try it, you'll like it! Way Cool! Never wears out with Balanced props (probably even with un-balanced props... never tried that... :-o). Never changes size, is always Slippery! Don't look back! Expensive but worth it.... I've been running the same strut bearings for years and still tight!
David

Vespel 211 is the cats meow. NOT the graphite filled vespel, it is too brittle. This material has a lot of uses wherever you want to reduce friction. It is happy even with no lubrication and very high surface speeds.

 

[lohring]

We tried bending an 1/8 inch shaft. When supported it's as strong as a 1/4 inch flex shaft. The wire drives electric boaters use are even smaller diameter. We also found that an absolutely straight shaft that gave the prop a 2 to 3 degree angle worked as well as a flex cable in an already proven boat. We still run flex cables in the beginning to be able to change propeller angles quickly and easily. It's mostly unnecessary, but old habits die hard.

Lohring Miller

 

[Don Templeton]

Yup!

I did really like running 60s with solid shaft suported by about 13 ball bearings. Take the engine out and the prop would spin like mad in a light wind. B)

Don

 

[Tim_Duggan]

A question for you guys running square drive systems on 21s and 45 rigger's. I'm building a new 45 rigger and would like to try a square drive system on it.

Is there a particular brand of 3/16 squared end flex cable you would reccomend?

I've only ever used collets in the past and only used Hughey or CMD cables with welded stubs as they were reliable.

Thanks in advance!

Tim.

 

[Jim Allen]

Oh, my bad, Vespel is the Shiznit! Try it, you'll like it! Way Cool! Never wears out with Balanced props (probably even with un-balanced props... never tried that... :-o). Never changes size, is always Slippery! Don't look back! Expensive but worth it.... I've been running the same strut bearings for years and still tight!
David

Vespel 211 is the cats meow. NOT the graphite filled vespel, it is too brittle. This material has a lot of uses wherever you want to reduce friction. It is happy even with no lubrication and very high surface speeds.

Charles,

All of the Vespel polyimide resins contain amounts of graphite by weight except SP-1 & SP-3. SP-211 has 15% graphite by weight. I use SP-22 which is 40% graphite by weight and has the lowest cofficient of thermal expansion. SP-211 does have the lowest coefficient of friction & the lowest wear rate up to 300 deg F.

Jim

 

[Charles Perdue]

Oh, my bad, Vespel is the Shiznit! Try it, you'll like it! Way Cool! Never wears out with Balanced props (probably even with un-balanced props... never tried that... :-o). Never changes size, is always Slippery! Don't look back! Expensive but worth it.... I've been running the same strut bearings for years and still tight!
David

I stand corrected. Are you ready to adopt me now so that you can teach me about all of these goodies?

Vespel 211 is the cats meow. NOT the graphite filled vespel, it is too brittle. This material has a lot of uses wherever you want to reduce friction. It is happy even with no lubrication and very high surface speeds.

Charles,

All of the Vespel polyimide resins contain amounts of graphite by weight except SP-1 & SP-3. SP-211 has 15% graphite by weight. I use SP-22 which is 40% graphite by weight and has the lowest cofficient of thermal expansion. SP-211 does have the lowest coefficient of friction & the lowest wear rate up to 300 deg F.

Jim

 

[Jim Allen]

Oh, my bad, Vespel is the Shiznit! Try it, you'll like it! Way Cool! Never wears out with Balanced props (probably even with un-balanced props... never tried that... :-o). Never changes size, is always Slippery! Don't look back! Expensive but worth it.... I've been running the same strut bearings for years and still tight!
David

I stand corrected. Are you ready to adopt me now so that you can teach me about all of these goodies?

Vespel 211 is the cats meow. NOT the graphite filled vespel, it is too brittle. This material has a lot of uses wherever you want to reduce friction. It is happy even with no lubrication and very high surface speeds.

Charles,

All of the Vespel polyimide resins contain amounts of graphite by weight except SP-1 & SP-3. SP-211 has 15% graphite by weight. I use SP-22 which is 40% graphite by weight and has the lowest cofficient of thermal expansion. SP-211 does have the lowest coefficient of friction & the lowest wear rate up to 300 deg F.

Jim

Charles,

One of the obivious problems with the very expensive Vespel materials such as SP-21, SP-22 & SP-211 is their high rates of thermal expansion when used at surface feet per minutes of 1,500 to 2,000. For a .250 diameter shaft these shaft speeds equate to 22,900 to 30,600 RPM. I found in tests that a normal sleeve bearing clearance of .0005 would be insufficient to prevent some shaft lockup. When using the SP-22 material in struts it was necessary to add an angled water inlet in the bottom of the strut to prevent shaft lockup.

I found a better strut & stuffing box bearing material in Bearium Metal grade B-8. This general purpose bronze is non-seizing, non-scoring, has unusual wear resistance, is self lubricating, has a low coefficient of friction, has a high shock resistance & a high compressive strength. B-8 When used with a small water inlet in the bottom of the strut & a shaft of Rc-45 hardness lasts forever!

Jim

 

[Geraghty]

[quote name='Jim Allen'

I found a better strut & stuffing box bearing material in Bearium Metal grade B-8. This general purpose bronze is non-seizing, non-scoring, has unusual wear resistance, is self lubricating, has a low coefficient of friction, has a high shock resistance & a high compressive strength. B-8 When used with a small water inlet in the bottom of the strut & a shaft of Rc-45 hardness lasts forever!

Jim

Jim,

Where can I buy it.

I checked MatWeb but they don't list any vendors.

Rod Geraghty

 

[jnissen]

I found that the 1/4" square drive was a don't care in the mono running surface drive but did make a difference when I ran it in the rigger. The stub shaft provided a much smoother transition into the strut on the rigger and this was good for about 1-2MPH on the GPS. The larger solder on ferrule in fornt of the strut also is spinning in the water (more drag). For different riggers with the stuff tube enclosed then it's a don't care again. The way I see it is in a surface application where you don't want a cable break or collet let go to ruin yopur day then the square drive is hard to beat.

I also agree that the steel washers between the teflons or other material are a no no. They eat the shaft quickly. I just run a stack of teflons and replace as necessay (every three or four years!).