Wire Drive Experiment

[BobBonahoom]

I have always wondered if a wire drive really has an advantage over a flex cable so I did an experiment. I made both a 0.062 wire drive and a 0.150 flex cable for my JAE 12 rigger. This boat has an OS T1202 engine and weighs 2.0 lbs. The strut runs 4 ball bearings with each shaft type and the shaft lube is castor oil. Fuel was 65% nitro with 15% oil, 3% of which is castor and the prop was a 1516-17-45. I have a Futaba GPS inside the radio box.

The water was flat with no wind. The first run was with the wire drive and the top speed was 73 mph. Then I put the flex cable in with no other changes and the top speed was 68 mph. Then I went back to the wire drive and again got 73 mph. So the conclusion is that with this boat and engine, the wire gives 5 mph over the cable. The advantage would probably be much smaller on bigger boats with more powerful engines. In the case of the 12 engines, every bit of weight reduction and friction elimination pays dividends.

 

[PaulHail]

Thanks for sharing your results. Another consideration with wire drive is it has less angular momentum and less mass, so it will accelerate more quickly. Same effect as a lighter flywheel.

 

[Terry Keeley]

73 mph is haulin' the mail for a .12 boat!

 

[Brian Spitzer]

Bob,
Where can one source the wire drive components?

Brian

 

[longballlumber]

Bob,
Where can one source the wire drive components?

Brian

Hey Brian,

There is a couple ways to attack this... Octura makes 3/16" stub shafts for both .062" and .078" and those can be found at OSE.

https://www.offshoreelectrics.com/proddetail.php?prod=oct-oc6062ps
https://www.offshoreelectrics.com/proddetail.php?prod=oct-oc6078ps

Octura also has a selection of couplers the compliment the stub shafts. Ron Shaw keeps those in stock from what I recall.

I think most guys are buying K&S Piano wire off the rack

Others have simply built up the stub end of the wire assembly by telescoping brass (again K&S) tubing to the appropriate size. In this case they start using ball bearings in the strut.

 

[Grimracer]

Its also worth noting.. one uses a sleeve retainer to attach the wire to the stub. Solder does not work well.

Grim

 

[Ron Zaker Jr]

I have always wondered if a wire drive really has an advantage over a flex cable so I did an experiment. I made both a 0.062 wire drive and a 0.150 flex cable for my JAE 12 rigger. This boat has an OS T1202 engine and weighs 2.0 lbs. The strut runs 4 ball bearings with each shaft type and the shaft lube is castor oil. Fuel was 65% nitro with 15% oil, 3% of which is castor and the prop was a 1516-17-45. I have a Futaba GPS inside the radio box.

The water was flat with no wind. The first run was with the wire drive and the top speed was 73 mph. Then I put the flex cable in with no other changes and the top speed was 68 mph. Then I went back to the wire drive and again got 73 mph. So the conclusion is that with this boat and engine, the wire gives 5 mph over the cable. The advantage would probably be much smaller on bigger boats with more powerful engines. In the case of the 12 engines, every bit of weight reduction and friction elimination pays dividends.

Very stable fast boat ,have seen it run. How much deflection is in your driveline?

 

[Charles Perdue]

I use thick walled stainless steel tubing for the stub shaft, tin the wire and run it completely thru the tubing and use Stay-Brite solder. I drill the hole that retains the drive dog thru one side of the SS tubing so that the drive dog screw secures the wire also, just for insurance. Never had a problem with them coming a loose even in a 45 rigger. To eliminate more problems the wire needs to be supported in the center to prevent the wire from oscillating which will cause the wire to break.

 

[Grimracer]

OMG.. thats signature is a pip...LOL.... good one

 

[brad nichols]

Some great info Charles!!

BraD

 

[BobBonahoom]

Bob,
Where can one source the wire drive components?

Brian

Brian, I get the wires with stub shaft attached from Jeff Wohlts. I think he attaches the stub shaft with some kind of retaining compound, but he does not say how he does it, just that it took many tries to come up with his method. They do not appear to be soldered. Wohlts is at: http://rcraceboat.com/Storewiredrive.html

 

[BobBonahoom]

One thing that I don't like out the wires is that they break at the engine collet. During the last 5 years I have had 3 break there. It seems to happen after a lot of running. I think it is due to putting stress on the wire during engine starting when I pull up on the flywheel with the starter. I now try to hold the engine with my left hand to try and keep the wire straight when starting.

I was hoping the cable would give the same speed so I could go back to it and not risk wire breakage, but the 5 mph added speed from the wire is too much to give up on. I am also going to put small piece of silicone tubbing on the wire at the collet so it if breaks it won't wind up in the lake with my prop. I keep an extra wire drive on hand as a spare when racing.

 

[Charles Perdue]

One thing that I don't like out the wires is that they break at the engine collet. During the last 5 years I have had 3 break there. It seems to happen after a lot of running. I think it is due to putting stress on the wire during engine starting when I pull up on the flywheel with the starter. I now try to hold the engine with my left hand to try and keep the wire straight when starting.

I was hoping the cable would give the same speed so I could go back to it and not risk wire breakage, but the 5 mph added speed from the wire is too much to give up on. I am also going to put small piece of silicone tubbing on the wire at the collet so it if breaks it won't wind up in the lake with my prop. I keep an extra wire drive on hand as a spare when racing.

 

[BobBonahoom]

Very stable fast boat ,have seen it run. How much deflection is in your driveline?

Ron,
I don't have any bushings in the drive line, just 4 ball bearings in the strut tube. There is no traditional strut, just a piece of brass tube glued to the ski that extends back to effectively lengthen the boat. You can see from the pic the angle to the engine.

The drive dog runs inside the strut tube. I assume that there is no shortening of the wire like there is with a cable, but if there is that is why the dog can move wherever it wants. The strut tube telescopes down to the size you would run with a 0.150 cable from the tube to the engine. That means the wire is much smaller than the ID of the stuff tube and I center it in the tube at the engine end.

 

[Charles Perdue]

I lost a few props when I first began to play with the wire drive, but that got old.

I use the 3/16 X 5/16 ball bearings in my struts and I solder a very short piece of brass tubing (about 1/8 inch long) on the 3/16 stub shaft just in front of the front bearing. I then drill and tap a 4-40 size tapped hole in the strut tube side just BEHIND the front bearing and put a VERY short button head screw in that hole. Make sure that the screw does not touch the stub shaft.

When the wire comes aloose for any reason, the short piece of tubing on the stub shaft and the stop screw in the strut prevents the stub shaft from sliding out of the rear of the strut.

As I mentioned earlier when the wire oscillates, it will cause the wire to break at the engine or the stub shaft. This usually only takes a few seconds when it does occur.

I think that he oscillations are primarily caused by the wire having flat sides where it has been ran between rollers to straighten it and when it is spinning in an arc, or the pulses of the engine firing or the pulses of the prop blades striking the water but without a center bearing of some sort to stop the wire vibrating, they usually break.

 

[Dave Grote]

Charles how sale the ball bearing that you us in the strut

 

[dr gary turner]

Charles, doesn’t everything that spins produces a sine wave down the rotating mass

Many years ago the thing was to run a Mr G hardened solid shaft in a tube of many ball bearings

Well a well known boater many years ago was making passes at Huntsville record trial

He hit the throttle and in the middle of the pass came to a sudden stop
When he got the boat the shaft just in front of drive dog was BENT AT A RIGHT ANGLE

He replaced the shaft and the same thing happened 3times

We decided that the shaft was being ridgidly restricted and thus restricting the SINE WAVE AND THE ENERGY WAS DISSIPATED at the end of the shaft LIKE A BULL WHIP and snapped the shaft bending to a right angle

So I would expect the wire drive would sine wave also

 

[Brian Spitzer]

Thank you for the information and links, very helpful.

 

[dr gary turner]

Is there a wire drive for a 101?

 

[RaceMechaniX]

Doc, Brent Beyers on Jim's RCBD is selling 3mm wire with 1/4" stub shafts pre made. You can easily adapt one of those kits, however the coupler is challenging. I am working on those with the Germans who made really nice collets.