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Bush's for M-model 1st and 3rd gears? 66-3211, 66-3214

I finally found someone in China with a press--NOT an easy task, when you don't speak or read Chinese--and have both my layshaft and mainshaft apart, and I don't like how the bush's look for 1st and 3rd.

Does anyone know if I can find these? DeGroot doesn't show them but does have the complete gears, Draganfly shows one but not the other. Anyone have any idea where I can find both?

Also the teeth on my gears aren't exactly beautiful, so I don't really want to replace the full gears, because I understand mixing new and old gears increases the amount of 'whining' the gearbox does, but I've never worked on a g/box this old, maybe it wouldn't matter because the rpm's are lower than most of what I've ever worked on...? I don't know, I need help here...

Thanks,
Nick

email (option): nicktog@gmail.com

Re: Bush's for M-model 1st and 3rd gears? 66-3211, 66-3214

Hi Nick..from your description of pressing the shafts apart I assume you are talking about the two gears held captive by the pressed on 'double gears'
If that is the case the one on the mainshaft is 3rd gear but the one on the layshaft is 2nd., not 1st.
1st. gear is the first gear on the layshaft after the inner gearbox cover is removed.
Buying 'off the shelf' bushes may not be the best solution to excessive play due to the possibility of wear on the shafts. So the first thing to do is check the shaft diameters.
The shaft diameter for both 2nd and 3rd gears is .9975"-.998".
If the shaft is worn below these limits it is better to manufacture the bushes and bore them to finished size after pressing them into the gears.
Correct bush to shaft clearance is .0025"-.0045".
You can calculate the actual bush inside diameter required using these clearance figures and the measured size of the shafts. Aim for the lower clearance figure.
Being of a fairly advanced age now and well past their designed life span you will find virtually all gearboxes show signs of wear on the gears.
This usually takes the form of surface deterioration on the faces of the gear teeth, particularly the face that is taking the 'thrust'.
This can vary from a polished but slightly deformed surface through to longtitudinal cracks in the surface. Unless they are extremely bad I wouldn't consider replacing them, they very rarely fail in use and shed a tooth. I have handled a lot of gearboxes and have only seen one gear tooth that failed this way.
Posting a picture (or emailing me a picture) of the gears in question would enable me to express a more detailed opinion on their condition.
Unless you are planning a complete gear set replacement I wouldn't mix 'new and old' gears...better to source some more serviceable used ones if it comes to that.
One thing you do need to look at is the condition of the engagement dogs on these two gears (and all the others). If these are badly worn replacement will be required...For standard bushes (if the shaft diameters are within tolerance) the only other place I could suggest is Russell Motors...Ian

email (option): julie@wright52.plus.com

Re: Bush's for M-model 2nd and 3rd gears?

Hi Ian,
Ah, 2nd gear, darnit yes... as i said, my first time in one of these boxes, (and the first g'box in many years).

Both shafts measure .9976 (2.534 on my metric micrometer) Both visually look pretty good for their age. Which puts me barely within usable state, I guess... and right now there is about .0039 and.0042 play based on measurements. But the bushing surfaces don't look very good, and cleaning them up I think will take me out of acceptable clearances, especially since you say aiming for less clearance is better. One bushing is still smooth but shows cracking I think too...

So in this condition what would you suggest? I don't have tools to fabricate my own. Do you know what kind of clearance an off-the-shelf bush would provide?

I'm glad you don't suggest mixing gears, that would have made me pretty nervous. The gear surfaces are ugly but I think usable as I have already invested far more than I would have liked to at this point. I've never seen a fresh 'dog' so I don't know how to gauge their wear--I can see a tiny little indented step on each corner of the dogs which look factory to me, but again, I don't know.

I can't post or send any pics right now, but I will be able to soon.

Thanks for your guidance, Ian

email (option): nicktog@gmail.com

Re: Bush's for M-model 2nd and 3rd gears?

Hi Nick..These shafts are 'through hardened' so you can safely remove some material to restore the surface finish. In a perfect world this would mean a 'tickle' on a cylindrical grinder, removing the minimal amount of material to clean the surface.
An easier way, though obviously less accurate, is to mount the shaft in a lathe running at 800-1000 rpm and use a medium oilstone (and oil) to remove minor surface irregularities. Finish with some fine emery. This is an alternative if you don't have access to a grinder.
New bushes will have some excess material in the bore to allow them to be machined to finished size after fitting to the gears.
As you don't seem to have too much wear on the shafts this should be sufficient for you to carefully size the bushes to suit the finished shaft.
At worst you will end up with a better surface on the shafts,round unworn bushes and a clearance pretty close to the specified figures..Ian

email (option): julie@wright52.plus.com

Re: Bush's for M-model 2nd and 3rd gears?

Ian,
Great, I am excited to move forward on this. So I will order the bushings from draganfly. Now that you corrected me on the gears I'm working on, I see they both use the same bushing which is the one (they have 8) in stock. I will send or post a pic of the dogs soon.
Thanks again,
Nick

email (option): Nicktog@gmail.com

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