snapped driveshaft

[ksarge91]

Snapped the driveshaft today on my superjet. I started it in the middle of the lake and it hooked up for 2 seconds then the prop started freespinning. Snapped clean in half inside the impeller. Should be fun getting it out. Just wondering what typically causes this?

Debris in pump?
Alignment?
Insane amount of arm ripping brap (just kidding, unfortunately)

Also, what other shafts will work? I'm assuming B1, roundnose, and squarenose shafts are the same, correct?

 

[Matt_E]

B1 is not the same.

 

[ksarge91]

Ok thanks. Is it gonna be a bitch to get the prop off without splines to grip onto?

 

[SJBrit]

So, what state is it in now? The shaft is broken and the front part with the splines is out, with the rear part still in the prop? You'll have to grab the rear of the shaft to get the prop off - take off the cone and you'll see the threaded rear end of the driveshaft. Clamp the shaft in a vice and the prop should spin off - don't forget to use heat (and that it is a left hand thread). You'll probably make a mess of the shaft, but I'm thinking it's already dead!

 

[ksarge91]

http://www.x-h2o.com/threads/68390-Driveshaft-carnage&highlight=broken+driveshaft

That's the same thing that happened, I'll get some pictures tomorrow. Front part with the splines is pretty much gone. If you're looking at the prop from the side you can't see any of the shaft coming out the front. I can't get it in a vise from around front because it's inside the prop. I'll pull the cone and crap off tomorrow but right now the pump out and the prop is the sitting on the bench with the wear ring and broken shaft still attached.

I'm just hoping I can save the prop

 

[SJBrit]

You may have to grind some flats, but you ought to be able to grab hold of the rear end OK. Good luck!

 

[Waternut]

Get pics. I want to see how your shaft/prop look compared to Matt_E's. Take good pics if you can.

 

[Wave Chaser]

I couldn't get anything to grab the end under the cone but the end is hollow and I found a bolt that slid right in and welded it to the shaft so I could get the prop off.

 

[Matt_E]

I ended up cutting the stator section off axis-wise to get to the shaft. Then I ground flats on it, put it in a vice, and got the impeller off.

 

[ksarge91]

Does anyone know what would cause this to snap in the first place? I'm thinking alignment maybe?

Also, will an fx-1 driveshaft work.

 

[JetManiac]

Does anyone know what would cause this to snap in the first place? I'm thinking alignment maybe?

Also, will an fx-1 driveshaft work.

No, fx1 is different length.

 

[CarterB]

jetmaniac has some custom beefy and cheap driveshafts for sale

 

[Waternut]

Does anyone know what would cause this to snap in the first place? I'm thinking alignment maybe?

That's why I want your pictures. I can only provide subjective information based on the pictures but here is what I can make out from the picture of Matt's driveshaft. Either way, it does NOT look like alignment is the issue here. It appears to be some kind of tooling damage or flaw in the manufacturing that is to blame for this.

 

[ksarge91]

Alright, thanks guys. Turns out it broke off far enough into the hub that I could fit a prop key in there. Now just gotta find the right size bolt for the cone end and I'll hopefully be able to get the impeller off.

Jetmaniac, I'll probably buy that one you PMed me in a couple days.

Waternut, I'll have pictures up tomorrow for you to hopefully give me an analysis.

Thanks guys!

 

[ksarge91]

Here's some pics of the shaft for you waternut. They're not the greatest and I'll be able to get some better ones in a couple days if these aren't good enough. Don't have a good camera right now.

Got the prop off and a new shaft from jetmaniac. Back together and good to go. Still kinda bothering me about what might have caused this....

 

[Waternut]

That looks really weird but it could just be the pictures themselves. I can't tell from those pictures. I'll PM you my email so I can get a larger version.

PS - I totally understand those things are fairly hard to get pictures of. Maybe a hand or piece of paper near the edge would help the camera focus on the shaft.

 

[ksarge91]

Alright, thanks man. I took these on a macbook but in a couple days I can get some good ones with a real camera and e-mail them to you. Thanks

 

[ksarge91]

E-mailed you teh pics waternut. Thought I'd post them up ehre as well incase anyone else wants to throw their 2 cents in on what they think might have caused it. If there's a problem I'd like to fix it before I snap another one, haha.

Thanks

 

[snowxr]

I'm sticking with it being an alignment problem. The shaft has to flex if misaligned, and that seems like the most likely area (near the point where the threads start). At 4-8000rpm that's a lot of flexing and fatigue for the metal to endure. Even a spring that's made to flex will eventually fatigue and fail. Stainless can only handle so much.

 

[ksarge91]

Would the pump alignment pins (that are currently sitting in a coffee can somewhere in my shop) have something to do with it? I was thinking no since the pump sections can't move side to side when bolted together but I don't know. How would I go about alligning my pump? Shims I guess? My motor allignment wouldn't have anything to do with it would it? Midshaft never left the hull this winter.