Clutch Dog rebuild

[byacey]

I have built up with weld (7018) and re-ground the worn ears on the clutch dog for a Big twin. Is this clutch dog cast? I am concerned about the weld chipping off when under shock and destroying the gears and bearings. It seemed to weld easily enough and didn't exhibit really high carbon content like cast does when grinding. I also put a very slight negative rake on the ears so it is the tip that is in contact with the gear lobes when driving; as it wears, more of the ear will come into contact with the driven gear lobes. Anybody have any thoughts on this?

 

[Dhadley]

Re: Clutch Dog rebuild

Did you reharden it?

 

[byacey]

Re: Clutch Dog rebuild

No, I thought it best to leave it soft to prevent the driven gear lobes from wearing. Easier to fix the clutch dog from time to time. Also, I am not sure to what hardness to draw the temper for this application. 7018 is a reasonably hard weld anyways.

 

[Dhadley]

Re: Clutch Dog rebuild

Thats the problem with cutting them or welding them. Without being hardened they dont last long at all.<br /><br />Backcutting the lobes is a good idea, like they do on the outboard gears. They actually backcut the Sea Drive and Cobra gears more (5* rather than 3*) but you have to be positive the idle rpm is low and then you sometimes still need the shift interrupter to get them out of gear.

 

[byacey]

Re: Clutch Dog rebuild

I don't think the driven gears on my 40952 are raked, they appear to be a 90 degree lobe. I just may harden the ears - perhaps case hardening might be the way to go, because I wouldn't want to make the ears on the dog to brittle. I have a few worn dogs to experiment with. I am also going to drill the prop shaft and put detent balls and spring. For some reason my outboard never had it - or else in the past somebody replaced it with an older shaft.

 

[lark2004]

Re: Clutch Dog rebuild

<br /><br />This might help with the detent balls.

 

[byacey]

Re: Clutch Dog rebuild

I am ready to drill the prop shaft to add the spring and detent balls, but in looking at the drawing above for the way the clutch dog is machined, I am not sure at what point the detent balls start being compressed. By this what I mean is, does the clutch dog move fully towards the drive gear when it engages? I have really no way of determining this unless the whole lower end is re-assembled and re-installed on the motor, with some prussian blue on the prop shaft spline to determine the ultimately the amount of clutch dog travel the gear shift linkage and bell crank allow. This would determine the point where I mill the detent slot in the clutch dog; otherwise I am afraid I might mill it in such a way that the detent ball wouldn't act as a resistance stop until the dog is close to being dis-engaged from the forward or reverse drive gear. I sure wish I could see one to determine how it was milled from the factory. Could anyone provide me with a measurement of the slot depth from the outside edge of the dog?

 

[byacey]

Re: Clutch Dog rebuild

What year(s) did they start using the detent ball and spring?

 

[lark2004]

Re: Clutch Dog rebuild

I just had a look at the cluth dog from my spare parts motor, it has grooves machined into the middle and outside edges, I guess to provide the balls somewhere to go to give you the detent. I will get a photo on here asap.

 

[byacey]

Re: Clutch Dog rebuild

Thanks, I appreciate it. From the diagram it appears that it would allow the clutch dog to move some degree while in gear - but preventing it from entering the neutral position. I would think it would be better to lock it in gear with no movement available within the detent position.

 

[Dhadley]

Re: Clutch Dog rebuild

The idea of the spring and balls is to provide a quicker shift into gear. No matter how slow you shift it, it will snap into gear at some point. Hence the name -- Snap Shift.<br /><br />A lot of wear is done when folks try to shift into gear slowly. The best deal is the pop it into gear and make sure the motor is idling as low as possible.

 

[Paul Moir]

Re: Clutch Dog rebuild

The clutch dog splines are cut at both ends at an angle so the ball is constantly pushing it into forward or reverse gear when that gear is engaged. <br /><br />

<br /><br />I think you can see that in there. The left clutch dog is from a '63, and the right is from a '65. Not the added ear material as well.<br />The balls are 0.25" and the drilled hole appears to be an "F" (.257"). It's dead centre on the splines. The spring is 3/4" long. I can work out the K factor if you like, but I think just 'really really stiff' is fine.

 

[byacey]

Re: Clutch Dog rebuild

Thanks Paul. I would question if the detent really provides any kind of snap action. The dog is only going to move as fast as the gear shift on the remote control is moved, unless there is a lot of free play in the linkages and shifting fork. But I didn't realize that the detent "slot" is on an angle.<br />The fact that this constantly applies pressure towards the gears is good news to me. How much of a recess is there in the neutral position on the clutch dog? It's not evident from the photos. Again, thanks to all for going out of your way to get this info for me.<br />Bill

 

[Paul Moir]

Re: Clutch Dog rebuild

No trouble!<br />It's a little V slot cut in there. You want a depth? (bottom of the v to bottom of the v?)

 

[lark2004]

Re: Clutch Dog rebuild

nice pics Paul, saved me some time!

 

[byacey]

Re: Clutch Dog rebuild

Actually a depth from the spline 90 degrees down to the bottom of the V would probably do it, and how far the "V" starts from the clutch dog edge. Does this make sense?

 

[Paul Moir]

Re: Clutch Dog rebuild

Sure thing! I'm sorry, I should have looked closer. The neutral detent groove isn't a vee, but rather a flat groove. The splines where they're cut away are angled though. Sort of like this:<br /><br />\_/---\_/<br /><br />(I would swear they were a vee on other clutch dogs)<br /><br />The distance from the tips of the splines to the bottom of the groove is about .060" (+/- about .005 is the best I could measure it). The bottom of the flat part is .75" wide and the distance between the tips of the splines was about .135. So there a 45° slope at each side of the flat groove until it reaches the spline tips.<br /><br />The groove cuts through 3 splines deeply and 2 splines not as deep on one side, and 4 splines deeply and 2 splines hardly touched on the other side. (there are an odd number of splines I guess). <br /><br />The forward and reverse grooves are about 30°, starting about .195" away from the face of the clutch dog at the tips of the splines. As you can see from the picture, they're unnecessarily oblong. They plunge a depth of about .105". (Say, that works out with my 30° pretty close. )<br /><br />I hope that makes some sort of sense! Please just ask if you need clarification. Maybe I should just draw it. <br /><br />EDIT: fixed.

 

[byacey]

Re: Clutch Dog rebuild

Thanks paul, I am going to try and draft a cross section view of the dog and let you have a look at it; just to make sure I understand your description. Sure would be easier if I could find one locally to look at.

 

[lark2004]

Re: Clutch Dog rebuild

I'd send you mine, but I don't know how much the postage would be....

 

[byacey]

Re: Clutch Dog rebuild

I appreciate the offer Lark, but first maybe I'll check some of the dead outboard yards around here and see what I can find. It's interesting to note that my motor in 1969 didn't have the detent ball. I wonder why they dropped it, more replacement clutch dog sales??