Help me out a little...making my own flex shafts

[trigger]

Have you measured the concentricity between the shaft and flex (or run out). if so what were you able to achieve using this method.

Very creative idea.

[kfxguy]

Is the jig steel or aluminum? Would you give dimensions so others might make a jig?

It's aluminum. The tabs are stainless. There's really nothing special about it. I milled a .187 slot then with a ball nose mill I came back and made the slot rounded in the bottom. Then drilled a hole in one end to hold the stub in for the initial joining.

[kfxguy]

Have you measured the concentricity between the shaft and flex (or run out). if so what were you able to achieve using this method.

Very creative idea.

I haven't measured it. I chucked it up in a drill and turned it down on my belt sander. It turns smoothly in a strut and there no wobble in a drill. I've put the drill (18v lithium ryobi) on the slow speed torque setting and tried to break them. Not successful so it's pretty strong. Kind of a rudimentary test but it's better than nothing I guess lol

[kfxguy]

Ok now I need help finding flex cable to buy.

[kfxguy]

Nevermind. Rocket city had some octura flex. I bought a few stubs from ose. I wish ose carried the cable. They only carry up to .150

[T.S.Davis]

Don, you are the man.

I've been threatening to do this properly for eons. Maybe I'll give it a go myself.

We tried to weasel Ed's process out of him around a camp fire back in 2005. He wasn't falling for any of our shenanigans. Some of it I figured out but not all. It's the material I couldn't quite get a handle on. Ever notice that Ed's cable just has more flex to it than most brands? Hold them up side by side and Ed's cable will bend a tighter radius without feeling bound. And what is that gold...ish colored solder he uses? Looks more like brazing rod.

[kfxguy]

When you cut the outer layer off of the cable, do that in your lathe too. I chuck the cable up with only a little sticking out. You can use a short piece of brass tubing that the cable just fits into. Split it longways so it will close up on the cable while in the chuck jaws. This holds all the cable wires in tight. Then use the toolpost as a brace for the dremel. I use to have one of those dremel flex shafts, and made a holder that fit in the toolpost. That worked really well.

Use a fresh cutoff disc or square the edge on a stone, when you get near the bottom of the cut. Then with the lathe turning the cable, cut at the wire trying to NOT cut too deeply and score the inner wraps. I usually do not cut them all the way through, but rather stop a little shy and then break the wire the rest of the way off. You'll have to cut them almost all the way so that the wire is thin enough to break without bending. I don't want any marks on that iner wire as that's where the strength of the cable comes from. Put a little counter sink in the hole of the stub shaft to allow the non square ends of the wire to fit into. This also gives a more solder area instead of just a butt joint.

It's also important to solder the motor end of the cable too as this locks the inner and outer cable wraps together. This helps keep the cable from growing and shrinking (lengthwise) when it gets loaded and unloaded.

After terry posting, I read this again. Good info. The way I did it to cut the outer wrap of is I ran the outer layer against my bench grinder wheel, the edge of the wheel. So when it starts to cut through its chamfered and I slightly chamfer the outer edge of the stub where the cable goes in and I chamfer the inner edge going into the hole. All of this in my mind seems to have maximum bite on the outer layer. I then sand the end of stub, inner cable and outer cable with some rough sand paper. Clean it. Pre Tin the cable and drop a pice of solder in the stub hole. Heat the stub up while being vertical. Slip cable in.........

[ray schrauwen]

Don, you are the man.
Ever notice that Ed's cable just has more flex to it than most brands? Hold them up side by side and Ed's cable will bend a tighter radius without feeling bound. And what is that gold...ish colored solder he uses? Looks more like brazing rod.

Why is it good to have cable that can bend a tighter radius? Cable that does this also shortens under load more.

You are a wire drive user yes? I would think you would search out a more rigid flex cable like H&M's .130 cable that I have shown to have minimal flex and minimal shrinking under load. I don't think you even need a gap at the drive dog for that cable.
I'll be tinkering with it this season. I got my cable late last summer and never got to testing it and I'm still building that hull anyway.

Ed used those high end jeweler's torches. I think he used brazing rods or one with brass and silver in it if that exists. Maybe I'll dig his number out and call him if I can find it.

http://www.sarusilver.com/brass-bronze-brazing-alloys.html

[ray schrauwen]

An interesting video.

https://m.youtube.com/watch?v=I8zsBKvFfFs

[martin]

Most flexes are done with low temp brazing the same stuff model engineers use on their boilers etc. Around 50% silver brazing rods, melting point is around 620c, this stuff flows just like electrical solder but at a much higher temp & many times stronger.

[T.S.Davis]

Ray, my thinking is that there would be less pressure where the radiuseseses.....s are in the stuffing with more flexible cable. No imperical data. Just my gut.

I only use wire on low powered boats. With those I have only a slight J bend. I've been moving away from the ball bearings though. Too many failures. Really frustrating.

[kfxguy]

Ray, my thinking is that there would be less pressure where the radiuseseses.....s are in the stuffing with more flexible cable. No imperical data. Just my gut.

I only use wire on low powered boats. With those I have only a slight J bend. I've been moving away from the ball bearings though. Too many failures. Really frustrating.

What bearings are you using? I use a stack of (6) r156 sealed. No less than 5 in a stack but usually 6. I haven't had one fail yet. Had a couple pop out when I was using just loctite. Now I use a snap ring. (Very important) the stub shaft needs to be turned down with 400 grit and a drill to where it can slide freely in the bearings. If not it will rip them apart from the flex shrinking under load.


I'm gonna make a flex up when my cable and subs get here and try it on my Rivercat with a sacrificial prop. Very aggressive prop at that to see if I can break it. It's in the mid 90's on 4s at this moment so it should have enough power to break it if it's weak. Boat also weighs 8.5+ lbs. be a good test if it will hold up.

[T.S.Davis]

I use all stainless and it depends on the boat how many I stack. The more the merrier if I want them to hold up. Less are faster though. I build mine so that the bearings are permanently part of the drive and not part of the strut if you follow what I'm saying. I pull the shaft and all the bearings come with it. Easier to work on. I also like to use a tail bearing with an extended inner race and flanged.

We're getting close to that "what you do vs what I do" with our boats thing again. My ball bearing setups are fantastic short term. I mean perfect. Love em. When you think about how much distance we cover you can see where our failures start to pop up. My sons Delta 29 travels about 22 miles per month. Sometimes it's only 19 miles. haha But you get the idea. On and off the throttle constantly for extended periods. They just don't hold up. You really have to pay attention to them and catch a wobbly bearing before it lets go or your hosed on race day.

[kfxguy]

I use all stainless and it depends on the boat how many I stack. The more the merrier if I want them to hold up. Less are faster though. I build mine so that the bearings are permanently part of the drive and not part of the strut if you follow what I'm saying. I pull the shaft and all the bearings come with it. Easier to work on. I also like to use a tail bearing with an extended inner race and flanged.

We're getting close to that "what you do vs what I do" with our boats thing again. My ball bearing setups are fantastic short term. I mean perfect. Love em. When you think about how much distance we cover you can see where our failures start to pop up. My sons Delta 29 travels about 22 miles per month. Sometimes it's only 19 miles. haha But you get the idea. On and off the throttle constantly for extended periods. They just don't hold up. You really have to pay attention to them and catch a wobbly bearing before it lets go or your hosed on race day.

I apologize if your taking it the wrong way. My aim was to help or give you some ideas.

I wrote a nice long post but I deleted it. I'll get to the point.

-I was just trying to help
-I don't just run straight line and neither do the customers I build boats for
-my method holds up, no matter how we run the boats
-if I'm understanding you correctly, your affixing (loctite, glue, snap ring etc) to the shaft and letting the bearings slide in the strut? Are you using a steel strut? If not, common sense tells me that a hardened outer race rubbing back and forth in an aluminum strut isn't a good idea. (Wear, galling, and if a bearing slighly cocks it will dig in the aluminum). If you closely feel the bearings, they have slack in them so they can catch on the aluminum.
-I'm not saying my method is better or that I know more than you but I am saying that in all of the types of running these boats I'm building do, I have had a failure yet except when I first did this not leaving slack inbetween the bearing and shaft, made a couple bearings pop out. Take my advice or not, just because I don't have 20 years rc boating experience doesn't mean that I don't know anything. Just be a little more open minded, sometimes you'll benefit from it. We both know how hard headed you are lol :)

[T.S.Davis]

You're too sensitive on this Travis. You asked about my bearings. I shared how I do mine. I don't have 20 years of boating experience either but I do have thousands of laps and a hand full of SAW passes under my belt. Doesn't mean a thing I know but don't assume I haven't tried umpteen different shaft setups.

I've done it a multitude of ways. From .032 wire to .098 on a gear drive. Ball bearings. Sleeve bearings. Over sized struts for bigger bearings. All kinds of stuff. I even have a strut with needle bearings. That one is really cool. Tuff as nails that one.