G: Gearbox (Single - Burman) Burman Drive Sprocket Loose

vibrac

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Having looked at the tab washer and the face of a sprocket today I can see the interference with the curve of the sprocket recess however the washer is of a thickness that I can compress it to the sprocket face with my thumb so a little tweek on the tabs or just tightening the nut overcomes the interference. I do think that the nut needs a spacer sometimes as it can run out of thread and finally it does look like the gear with the splines is unobtanium
 

Martyn Goodwin

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Vic and others,

I have been able to locate a second hand Driving Gear (the one with the splines) and am now waiting on the postal service to deliver it - fingers crossed that they don't loose it AND that its in serviceable condition . But it was only 10% of the Spares Co new old stock listed price. Then again the Spares Co have nil stock.

Considering the apparent unobtanium status of any further replacements I'm considering investigation of having the old damaged splines reclaimed as Vic suggested. Now to find a shop who can do the lazer welding then another to recut the splines and lastly - a heat treater.

Today its strip the box completely to see if / what else needs attention.

SHMBO tells me I need to cut down on the use of the Comet, that covering around 10,000 miles on it each year is just too much for the old thing. Changed her tune when I agreed and said that maybe I should have a second one to 'spread the load'

Martyn
 

Martyn Goodwin

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Finally, Thinking of the impact loads on the driving gear splines seems to me that the ESA is just not doing its job in absorbing transmission shocks and there seems little that can be done about that.

M
 

greg brillus

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I'm guessing the gearbox spline was worn all along, just not so noticeable with a new sprocket slid over the shaft. Movement in the spline will hammer away at any sprocket combination. My machinist has repaired the spline on the input shafts welded up and re machined........It is not cheap as it is time consuming........Probably around the $300 dollar mark in our money, maybe a touch more.......
 

brian gains

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for the record I replaced the output gear during my recent Burman Box Debacle, see tagged on end of Melt Down thread, I thought the dogs appeared worn and may have been contributing to my problems.
I bought a second hand item from Draganfly a s used but serviceable, they did have NOS items at multiples of the price I paid. The dogs I had seen on output gears of the comparable though different ratio Ariel box seemed far beefier leading me to think my dogs were worn. Once I received the replacement, the dogs were not appreciably different in profile to the item being replaced. Having given consideration to the latter if the dogs were appreciably worn would the profile have not been biased as wear would have been just on one side; it wasn't which leads me to think that for whatever reason. meshing, revs that is the way the dogs were designed. As for the damaged splines and sprocket fitment issue. I would suggest that the sprocket nut was not tightened down initially then consequently run, hammering the splines to death.
 
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Cyborg

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Now you could add up all side contact faces of the slots to find a total for Honda and Burman or Vincent that has to bear all loads from chain pull. The Japanese splines look a lot deeper than the very flat type of the Burman - or Vincent as well. I suspect to see very high specific loads in kg per square millimeter or in imperial units if you like, in that old design, that takes all the wear and will be difficult for lubricants to prevent fretting. Still I think all you can do is to care for a perfect fit in the spline plus EP grease or MoS2 paste when assembling. Any extra high torque on the nut is wishful thinking. That is why there are designs with push fit and circlip , no nut and thread as not helpful at all.

Vic

Good point and yes the Japanese are likely deeper. Again, I don't have a Burman sprocket to compare, but just a quick comparison to a Norton shows the Japanese splines .5mm deeper. In this case the splines (on the Norton) are just over 7mm wider, but some of the extra width is due to the shoulder that the output seal runs on which the Burman sprocket doesn't have. (Japanese shaft is about 6.75mm smaller in diameter). Not that any of this matters in the grand scheme of things...just find it interesting.
The splines in Martyn's photo look odd to me. Probably just the photo, but the groove shown by the top arrow doesn't appear to be in the spline indicated by the lower arrow. In any event, when welding up the splines that groove or whatever it is ( perhaps from a washer fretting away) looks like it should be filled in to maximize the load bearing area, making sure the threads don't go any deeper than necessary.
Martyn, if your new sprocket has good splines, but worn teeth, you could always do as Robert does and graft new teeth on it. He is our resident orthodontist.
Burman.jpg
 
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Martyn Goodwin

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Good point and yes the Japanese are likely deeper. Again, I don't have a Burman sprocket to compare, but just a quick comparison to a Norton shows the Japanese splines .5mm deeper. In this case the splines (on the Norton) are just over 7mm wider, but some of the extra width is due to the shoulder that the output seal runs on which the Burman sprocket doesn't have. (Japanese shaft is about 6.75mm smaller in diameter). Not that any of this matters in the grand scheme of things...just find it interesting.
The splines in Martyn's photo look odd to me. Probably just the photo, but the groove shown by the top arrow doesn't appear to be in the spline indicated by the lower arrow. In any event, when welding up the splines that groove or whatever it is ( perhaps from a washer fretting away) looks like it should be filled in to maximize the load bearing area, making sure the threads don't go any deeper than necessary.
Martyn, if your new sprocket has good splines, but worn teeth, you could always do as Robert does and graft new teeth on it. He is our resident orthodontist.
View attachment 30337
The 'groove' erosion is in every groove! Good fortune has it that replacement sprockets (the dogs in the old one are buggered as well) are available from the Spares Co at a reasonable cost.
 

Martyn Goodwin

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Loctite 660 is touted as the go to solution to ensure a 'perfect' fit on splines. Has anyone tried using it? What was the result? I am also wondering about subsequent disassembly issues if it is used.

Thinking of using it as part of the rebuild.
 

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Vincent Brake

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Or use n style such a thing as wedge keys. I learned one had double set at 120 deg over the axle and flange.
Very very good fixing

Well 6 here yes.

In fact not a bad idea.

Make them from Toolox 44 steel
45 hrc, super stuff
 
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