go-devil drive shaft problems

J

jburn25

New member
Hi, I'm new to the forum and hoping to get advice on my go-devil motor problems. I've got a home made "go-devil" longtail 9hp honda. The drive shaft set screws kept shearing and the shaft would spin freely in the motor coupler so we keyed out the shaft the the coupler. This worked great for a while, but still eventually if you hit a stump or something on accident with the prop, the shear key will shear out of the shaft. The most recent time it actually tore out a piece of the shaft whenenver it ripped out.

Does anyone know of a better material than stainless steel to use for the shaft? I was under the impression that these motors should still perform even if you hit a stump.
 
This home made motor you have, the rear end does pop up easily out of the water when you something, right?

Ed.
 
jburn,

There will always be forces to contend with when a spinning object hits a immovable object. That is why Ed asked if your motor was free to pivot away from the point of impact. If the whole mud motor is balanced and built correctly some of those forces will not be transfered to your drive system but be absorbed by the pivoting away and/or up and over the source of impact.

Some of the cost of a commercially built motor is the design cost you are experiencing now. With out knowing the specs on the type of stainless material you are using or the size and length of the shafting, it would be hard to advise what to change. What ever you decide, keep in mind that given enough outside force, there will always be a weak link. You have to decide if that weak link will be a shear key or,,,,,,,,,say for instance a piston rod or bent crank. Hit something hard enough, something else is going to give.

BTW, You might consider giving us your real name and location so we can all get to know each other better. :>)
 
Thanks for the reply, and sorry about the "scree name". I didn't realize it until after I registered that this was one of those "friendly" forums where people use their real names lol. My name is Jordan Burnham and I'm in Baton Rouge, La.

To your reply, yes the motor is designed to pop out of the water. In fact, upon inspecting the entire rig you will notice that it is designed almost exactly as a real go-devil motor. To the untrained eye it looks exactly alike. Obviously, it's not a real go-devil and after I looked a a few real more real ones I can now tell the differences. Nonetheless, it's a center balanced long shaft mud motor that my cousin picked up for a steal of a deal.

I understand that there is always a problem whenever a spinning object (with a lot of torque) hits an immovable object, but it is my understanding that the real deal go devils don't have this problem. And since the weak link in our rig has consistently been the shaft shearing, I was wondering if anyone knew what kind of shaft the real go-devils use and what we should look for to put on this rig. If I can get some pictures on the web in the next few days of the shaft and coupler I'm sure that would help too.

Thanks again
 
huh 16 years of Go-devil only motors for me and never had that happen. and I have hit PLEANTY of stuff!

the shaft never rusts on the prop end so id guess at SS (but it also says if rust is present on the shaft to replace it) of some sorts the spec sheet in the manual just shows a long square key to the U-joint and another to the motor. gives no spec sizes sorry to say.

It does say that the key is a PRESS fit and should be extremely tight with no play at all.
 
I had a home-built mudmotor for a few years. Had to make a number of modifications to get it running reliably.


A few questions:

Do you have a bushing in the center of the shaft housing to reduce wobble when you hit an obstacle or apply a lot of torque?

Is the shaft diameter the same as on the Go-Devil?

Is the skeg long enough to protect the propeller when you hit a log?

Are you using a large enough shear pin?

Rick
 
Thanks for the responses everybody. No there is not a bushing in the center of the shaft that I am aware of and the diameter of the shaft is the same as on Go-Devil's from what I am told. The skeg does protect the prop from things that you go directly over, but I think our problem is whenever the prop hits something from the side. There is no protection if you are turning and thats usually when we have the problems. As to the size of the shear pin, I'm pretty sure its the right size because its always the shaft that strips, not the key breaking or anything like that.

I did notice the most recent time we took the shaft out that it does have a considerbable amount of rust on it, however, so maybe it's not made of stainless. Or maybe its just time to replace this one with a new stainless steel one. I don't even know where to get one because go-devil won't sell you parts unless you own a go-devil.
 
You could take the old shaft out and have a new one machined from stainless.

Also, consider putting a bushing in the center. That made a big difference in mine.

Rick
 
I don't know for sure. But I had one made for mine, and along with a center bushing, it solved the problem I had with wobble from applying too much torque.

Rick
 
Well I'm still in the same position as before... I don't want to/ can't afford to spend money on another fix that isn't going to last at least this duck season so I'm trying to figure out my best option.

I passed a "go-devil" type motor being pulled on the highway the other day and followed the guy long enough to notice that his u-joint connected to the shaft (prop side) with some sort of pinch bolt or clamp collar thing that just tightened down around the shaft real tight. The idea has obvious problems, but seems like it might be my best option. No keys, or set screws to break, and I can always carry around a wrench and tighten it if I need to. Only problem is that I've searched everywhere for a u-joint with the pinch bolt mechanism and can't find it.

Can someone please help me find one of these u-joints? or at least the yolk/coupler that attaches with the clamp thing....

Thanks!
 
Check out ag or industrial supply places. Farm implements and industrial machines have all sorts of interesting bits that can be re-purposed. I've noticed a trick is often finding what a thing is called and the searching for it by the proper name.

You could also just browse/search Northern Tool and McMaster-Carr for some ideas.
 
Jordan,

Maybe these guys can help.

http://www.mudmotortalk.com/

Or here

http://fisherbeavertail.com/kitsintro.html

I would start with a micrometer or a good dial caliber and get your shaft diameter and call mudbuddy or Beavertail to see if their u-joints are for the same size shaft you have. You can get u-joints with either a set screw or a hole for a roll pin. I would personally use a u-joint with a square head set screw to tighted the joint to the driveshaft. You want to spot drill a depression in your shaft to seat the set screw into to keep it from slipping. DO NOT thru drill. This only weakens the material. You'll need to measure very carefully the contact point where the set screw will contact the shaft then set up in a drill press so you can get true center of the shaft. It doesn't take being off center much more than a few thousands of an inch to set up a wobble that will destroy your bearing. If your shaft quailty is in question you might measure your shaft length and purchase the shaft, u-joint and bearings from Beavertail. If your shaft housing is fashioned like the manufactered units the shaft housing is actually 1" schedule 80 pipe. The dimensions are 1.315 O.D. with a .179 thk wall. This holds true if it's steel pipe or aluminum.

Hope this helps...oh and use something like Loctite red sealant to lock the set screw threads. Don't use the blue, you'll never get the set screw loose!

Ed L.
 
Ed,

I thought the red loctite was the more permanent stuff. I used a lot more of the blue on my recent waterpump/timing belt job on my tundra per the factory manual.

Charlie
 
Charlie,

Your right. I had a brian fart....Blue is the one to use. Red is the heavy duty stuff and will require heating to break the bond

Sorry for the confusion.

Ed L.
 
thanks for the responses. I have tried mudmotortalk.com and I have searched all kinds of industrial and agricultural supply companies with no success.

Ed, thanks for the response. We have actually tried everything you have mentioned and the set screws would always shear off whenever we hit the smallest obstacle. Whenever we used the keys, it seemed to be absolutely perfect, we used set screws with lock tight on the keys, etc, etc, etc but it still sheared. The only thing we haven't tried is buying a new shaft and if i can't find a good pinch bolt u-joint then I might have to buy one.
 
I've checked out those u-joints before and contacted a company about them. They said that they are made for steering columns for automobiles and most likely wouldn't stand up to the pressure of our PTO type application. I was told that if they weren't stainless it might be worth a shot.

Thoughts?
 
I'm tempted to just try one of those couplers. It seems like the cheapest option. I mean, if stainless steel shafts are being used for these applications I don't see why stainless steel u-joints can't be used.
 
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