What Size Wire Drive for 21

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AzMandella

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Oct 9, 2020
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99
I’m still gathering info but so far I can say that the wire works best will ball bearing struts. I see little or no advantage using a wire drive with a bushing strut so far.
Thanks John
I have hard time believing that the wire drive is still not better using bushings than a standard cable drive with bushings . First of all both are using bushings . Second the spine in the cable that snaps every revolution has to be using extra energy to rotate past the spine . Also if you take a cable in your hands and put a slight bend in it and rotate it you will feel it snap . At speed running 20,000+ rpms I have a hard time believing that is not taking a toll on the bearings in the engine with that constant vibration going through it and reducing rpm's du to lost energy . .
 

Danny King

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Nov 26, 2012
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The ball bearings are unnecessary for heat racing. And actually not a real good idea. More maintenance.
The lead Teflon are awesome. In .21-101 and gas.
Brent’s system is excellent and well thought out and proven in gas and 91/101 apps.
He plans on doing another size for under 91 size engines. But still working that out.

I would suggest people interested in going to wire in nitro boats do it one boat at a time. It is not a plug and play change. It changes the prop, pipe length possibly. If you changed nothing but the cable to wire you will go slower until you re-tune the set up.
changing the 21 to wire saves roughly 60% of the shaft weight plus the drag.
Changing out 1/4” cable to .125” solid saves 2.5-3 oz per cable plus drag.

With gas engines less re-dialing in is necessary. And with nitro the smaller the engine the more noticeable the change is.

wire or solid drives are less forgiving and attention needs to be paid more closely.
ALIGNMENT IS CRUCIAL or they will break.
not all boats will be able to switch over. Has to have minimal bent in the shaft log to work. It can have a bow but not a lot.
There are guys running wire and learning it. And there are some that have run em a bunch more in the time trials.
they are not as durable as a cable. But they are more efficient and clean.
 

ALLAN YUEN

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Joined
Jan 14, 2005
Messages
5,900
The ball bearings are unnecessary for heat racing. And actually not a real good idea. More maintenance.
The lead Teflon are awesome. In .21-101 and gas.
Brent’s system is excellent and well thought out and proven in gas and 91/101 apps.
He plans on doing another size for under 91 size engines. But still working that out.

I would suggest people interested in going to wire in nitro boats do it one boat at a time. It is not a plug and play change. It changes the prop, pipe length possibly. If you changed nothing but the cable to wire you will go slower until you re-tune the set up.
changing the 21 to wire saves roughly 60% of the shaft weight plus the drag.
Changing out 1/4” cable to .125” solid saves 2.5-3 oz per cable plus drag.

With gas engines less re-dialing in is necessary. And with nitro the smaller the engine the more noticeable the change is.

wire or solid drives are less forgiving and attention needs to be paid more closely.
ALIGNMENT IS CRUCIAL or they will break.
not all boats will be able to switch over. Has to have minimal bent in the shaft log to work. It can have a bow but not a lot.
There are guys running wire and learning it. And there are some that have run em a bunch more in the time trials.
they are not as durable as a cable. But they are more efficient and clean.
Thanks for info
 

AzMandella

Well-Known Member
Joined
Oct 9, 2020
Messages
99
The ball bearings are unnecessary for heat racing. And actually not a real good idea. More maintenance.
The lead Teflon are awesome. In .21-101 and gas.
Brent’s system is excellent and well thought out and proven in gas and 91/101 apps.
He plans on doing another size for under 91 size engines. But still working that out.

I would suggest people interested in going to wire in nitro boats do it one boat at a time. It is not a plug and play change. It changes the prop, pipe length possibly. If you changed nothing but the cable to wire you will go slower until you re-tune the set up.
changing the 21 to wire saves roughly 60% of the shaft weight plus the drag.
Changing out 1/4” cable to .125” solid saves 2.5-3 oz per cable plus drag.

With gas engines less re-dialing in is necessary. And with nitro the smaller the engine the more noticeable the change is.

wire or solid drives are less forgiving and attention needs to be paid more closely.
ALIGNMENT IS CRUCIAL or they will break.
not all boats will be able to switch over. Has to have minimal bent in the shaft log to work. It can have a bow but not a lot.
There are guys running wire and learning it. And there are some that have run em a bunch more in the time trials.
they are not as durable as a cable. But they are more efficient and clean.
I am going to guess the reason for having to change the prop when going from cable to wire is due to increased RPM's necessary to increase in pitch to bring engine back down in it's power band ?
 

Danny King

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Nov 26, 2012
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1,619
I am going to guess the reason for having to change the prop when going from cable to wire is due to increased RPM's necessary to increase in pitch to bring engine back down in it's power band ?
No. If you only change the shaft you will not make the same power. You will go slower. The more efficient driveline unloads the motor.
 

AzMandella

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Joined
Oct 9, 2020
Messages
99
No. If you only change the shaft you will not make the same power. You will go slower. The more efficient driveline unloads the motor.
So what direction have you found in prop change ? I'm a little confused . I understand what you are saying but seems to be what I am thinking . Since the driveline is more efficient and unloads the engine wouldn't rpm's go up using the same prop ? Kinda like driving a car and slightly pushing in the clutch without changing gears or letting off the gas . The engine will unload some and rpm's will go up and speed will be reduced .
 

Danny King

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Nov 26, 2012
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A 2 stroke engine, especially a high nitro burning 2 stroke engine is nothing like a car engine.....they need load
 

dr gary turner

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Dec 25, 2004
Messages
2,300
I have been running wire drive 21-101for about a year

There a lot of details that must be followed or they will fail.

Unless one has pretty much maxed out all other performance options, any gain with wire will be negligible
 

Brad Christy

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Jun 24, 2002
Messages
1,218
Doc, Danny

How do they fail. What gives out?

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC
 

Danny King

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Nov 26, 2012
Messages
1,619
If alignment is the issue they break at the collet. If poorly spaced bushings are the problem they can break anywhere. If oiling is a problem the stub shaft can let go.

if you get the .125” drive from Brent he has them dialed in. You just have to be sure
The engine alignment is perfect.
The failures I had were on the 21 and 45 boat and both were mistakes and learning.
 
Last edited:

timwhalen

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Joined
Oct 25, 2015
Messages
704
Ball bearings, the stub shafts are soft and won’t support needles running on the surface. I buy ball bearing by the dozen. The balls are really small and if you run them dry at all the little grains of sand disappear quick! I buy mine from McMaster Carr, class 3 I think.
John, looking at Buckshot's photo, if wanting to setup a wire drive for a D rigger using a 3/16" stub, are there

bearings available that fit the 45 Speedmaster struts?.... or is it required to use a .150" stub/wire drive, and use a sleeve

inside a 3/16" bore prop?...

Thanks-

tim
 

ricwally

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Jan 21, 2018
Messages
106
Tim, you can use a .078 wire with a 1/8" stub and a 3/16" adapter for the props. Then 1/4" bearings will fit in the Speedmaster struts. I have been doing that for a couple years.
 

John Beardslee

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Apr 20, 2011
Messages
1,538
John, looking at Buckshot's photo, if wanting to setup a wire drive for a D rigger using a 3/16" stub, are there

bearings available that fit the 45 Speedmaster struts?.... or is it required to use a .150" stub/wire drive, and use a sleeve

inside a 3/16" bore prop?...

Thanks-

tim
Tim, I had to modify the strut for the ball
bearings, if you opt to try lead Teflon, that’s an easy change.
If you’re an “S” bend advocate, you probably will break wires. I do soft the edge of the collet with Cratex to keep from breaking at the collet. I also use aluminum tubing to sleeve down for the wire to run in as well as a delrin bushing half way. I approached my testing by making up a cartridge type set up so I could pull the whole drive line and exchange it back to cable easily.
 

Brad Christy

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Jun 24, 2002
Messages
1,218
Doc, Danny,

How is the wire connected to the stub shaft?

Thanks. Brad.
Titan Racing Components
BlackJack Hydros
Model Machine and Precision LLC
 

timwhalen

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Joined
Oct 25, 2015
Messages
704
Tim, I had to modify the strut for the ball
bearings, if you opt to try lead Teflon, that’s an easy change.
If you’re an “S” bend advocate, you probably will break wires. I do soft the edge of the collet with Cratex to keep from breaking at the collet. I also use aluminum tubing to sleeve down for the wire to run in as well as a delrin bushing half way. I approached my testing by making up a cartridge type set up so I could pull the whole drive line and exchange it back to cable easily.
Thanks for the direction, John..... yeah, I understand the stress an 'S' bend would but on the wire,

and how a support mid length would keep wobble in check, to whatever degree. I do put a very

mild 'S' config in the cable drives, but haven't put a mild bend in the stuffing tube passing through

the tub floor, like someone had suggested.

Your 'modular' test setup sounds like a good way to go.

Also, I understand what you're doing at the collet- getting rid of any sharp stress initiators.

Again, thanks, John-

tim
 

timwhalen

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Joined
Oct 25, 2015
Messages
704
Tim, you can use a .078 wire with a 1/8" stub and a 3/16" adapter for the props. Then 1/4" bearings will fit in the Speedmaster struts. I have been doing that for a couple years.
Great, thanks!
 

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