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View Full Version : Excavator Drive Sprocket making



boslab
07-13-2009, 03:03 PM
Hi, I was looking at my drive sprockets on a 3 ton mini excavator, they look really worn and i have lost a track recently, i was wondering if making new ones was possible having never tried sprocket or gearcutting before.
i have a Cinncinatti toolmaster and a large dividing head as well as a big rotary table.
how accurate should sprockets be and what would be the preferred matirial
[i have access to Hardox and suchlike.
also can a metal track be re-pinned if worn? i know it sounds like i want to re-manufacture the whole track bed but any advice [including go buy a new one] would be welcomed.
thank you
mark

Mark Hockett
07-13-2009, 03:35 PM
You don't state what brand of machine you are working on and I am not that familiar with the mini excavators but on my D3 Cat the track pins have bushings on them. When they wear it is common practice to press the tracks apart and rotate the bushings 180 degrees and press it back together. The rear sprockets are usually fairly cheap and not worth making, plus they are a very very hard metal. The rear sprockets on my Cat are less money than the rear tires on my last sports car. For parts I would call Kent Baugh, who is a member of this forum (ktbaugh)
, and see what his prices are,
http://www.ktbaugh.com/

hardtail
07-13-2009, 04:31 PM
Unless your machine is obsolete it's usually not even worth considering making your U/C components.....years ago they would build up with weld sometimes.......if your rails are coming off there maybe more things going on.........

boslab
07-13-2009, 06:55 PM
Thank you for your reply, the beasty is a Nissan N300, old, but a good little machine, i have been considering rubber tracks but they seem to be very expensive, she has metal tracks on at the moment, i will have a close look at the pins to see if theres a bush, perhaps i should raid the piggybank [ a set of rubbers complete with sprockets and idlers over here is about $2-3k judging from the quotes i had today, if its not careful its going to get wheels!
probably more acceptable to the police who dont take kindly to metal tracks on the highway!
once again thanks for the reply, it is appreciated
regards
mark

Limy Sami
07-14-2009, 02:39 PM
Boslab, if it's on steel leave it on steel, rubbers can be a pain - like tearing,....... have you tried firms like Digbits etc.

If it's only your time?........ I'll put it this way;- you can do a lot with a welder and angle grinder.

FWIW 1 don't over think it, it's an old machine and the first thing you'll do is run all your nice shiny new parts in mud:D

FWIW 2 Use mats on tarmac;-)

boslab
07-14-2009, 03:12 PM
Thanks limy, illleave the steel alone and maybe get some navi mats or track pads, ive checked digbits out lots of good stuff on thier site, prob is i get carried away, ended up looking at thumbs [the old girl is hammer plumbed so i suppose a hydraulic thumb is possible]
talked to a local yokel and ther is a firm in bridgend called dragon laser, it seems they can cut up to 16 MM with thier CO2 cnc laser, problem is getting the drawing of the sprocket as a DXF file or whatever.
anyway thanks for the imput, it is appreciated
best wishes
mark

doctor demo
07-14-2009, 05:33 PM
You used to be able to buy weld in liners for drive sprokets, they looked like a large bearing shell . But even that is time consuming compaired to just replacing with new. It is surprising how cheap they realy are compared to other parts.
Now as far as a thumb goes , once You get used to using one, ya almost can't run a machine without one. Building a thumb would be a realy nice project and far less expensive than buying one.After years of bitching My previous employer finaly gave in and let Me put a thumb on the back hoe.

Steve

boslab
07-15-2009, 09:35 AM
i watched a couple of vids on youtube of excavators useing one, i'm sold on it now, next design it and make it, that might be the hard bit as i'm not sure how to hook up the hydraulics to the hammer circuit, there appears to be two pipes on the boom, a flow and return that are coupled to a footpedal in the cab, might need to have a DC valve i think?
regards
mark

kf2qd
07-15-2009, 03:42 PM
Thanks limy, illleave the steel alone and maybe get some navi mats or track pads, ive checked digbits out lots of good stuff on thier site, prob is i get carried away, ended up looking at thumbs [the old girl is hammer plumbed so i suppose a hydraulic thumb is possible]
talked to a local yokel and ther is a firm in bridgend called dragon laser, it seems they can cut up to 16 MM with thier CO2 cnc laser, problem is getting the drawing of the sprocket as a DXF file or whatever.
anyway thanks for the imput, it is appreciated
best wishes
mark


Worked with Plasma and Oxyfuel machines inthe past - Find a good flame cutter and they can cut those sprockets any thickness and much cheaper than Laser. Laser at that thickness is going to be rather slow. A good flame cutter can go from your drawing to 30 or 60 thou over and then you can finish and flame haeden for longer life. 1030 or 1045 plate.

doctor demo
07-15-2009, 04:17 PM
i watched a couple of vids on youtube of excavators useing one, i'm sold on it now, next design it and make it, that might be the hard bit as i'm not sure how to hook up the hydraulics to the hammer circuit, there appears to be two pipes on the boom, a flow and return that are coupled to a footpedal in the cab, might need to have a DC valve i think?
regards
mark
Depending on the machine and the hammer, the return line may have some back pressure or it could be straight to the tank.
If I remember what I did was to take the return line and put a tee in and then a check valve so while the hammer is being used the thumb circut does not see any back presure from the hammer.
On the presure side of the circut I teed off to a sol. valve then to an adjustible pressure relief valve that goes to the return side . You have to have the relief valve set to just below the bucket force so that You can curl the bucket and the thumb will be pushed back but still hold without having to fidle with any controlls. Also without the relief valve ya can bust something, usualy the most expensive part in the string or at least the hardest to replace.
I used the same triger switch to hammer or use the thumb, so ya have to add an on-off switch in line with the thumb sol. or the thumb tries to grab the hammer.
The company bought a complete thumb (kit) but after seeing it we made major mods to make it work for us, so I would suggest starting from scratch.

Steve

boslab
07-15-2009, 04:33 PM
thanks a lot, the old girl is going to get a makeover asap, the thumb might turn into a saga but life is all about new expiriences, good and bad, i like the chinese curse, may you have an interesting life, i think that one got me, ill go with the thumb and flame cut sprocket, keeping the steels on the wheels,....onward and upward [ish].
thanks gentlemen [any other advice will be welcomed]
regards
mark