Here are a couple of pics of the Cam grinder and the Crankshaft grinder that I built last year. Used both to complete bits of the little 4 cylinder.
By the way, the Engine is water cooled (block) 4 stroke, 25cc, runs on methanol/oil mix of 5 percent, and gets to 10,000 rpm real quick. Water is circulated via magnetic drive water pump to heat exchange tank. Anyhow, here's the pics.
Very nice work on the cam grinder, is the crank grinder incorporated in the same machine? How about elaborating on the design. I have been searching for some time for a grinder to build to support my model engine work.
Very nice indeed.
I can see a small grinding wheel which looks like it is for cams and also a large cutoff type for the deeper throws on a crankshaft. It would be nice if you enlightened us on the design or where you can obtain it. Us small engine nuts would be happy to know. Nice clean installation.
Would be happy to give more detail on both machines which are of my own design. There are no plans as such, mainly as each machine is purpose built to my requirement and from many recycled materials and parts from old photocopy machines, computer bits etc. Maybe best to start a new section???? See what I can do in the next few days.
Decided to build this machine when the need to came to construct the crankshaft for a 4 cylinder 25cc engine (now up and running). To describe the grinders operation I will refer to the 4 cylinder crankshaft which was "flat" construction i.e. big ends for 1 and 4 spaced 180 degrees from 2 and 3. This can be seen in the snapshot below taken from a small video of the grinder in action. The flat blank for the crankshaft was milled up from round bar (only way I can get 4140 steel here) and 3 centres were marked up and centre drilled each end. One each end for the main bearing centre and the other two pairs for the big ends. The crank blank is then rough sawn to remove most of the unwanted material and the blank is then ready for the grinder. Two old computers are used for the grinder. One follows the position of the two axis of travel and shows measurements on the monitor. The other keeps a track of the on or off status of several optical switches on various parts of the machine and, via a small plc program, control the whole grinding operation through to final shutdown. The optical switches (from old photocopy machines, printers etc.) are very accurate (0.5 thou) and the position of these are adjusted prior to grinding to a particular diameter for the journals and for the axis motors to drive to certain limits on each end of the journal. To grind, the blank is fitted to the centres (say for the main bearing journals) and a drive dog engages to the spindle drive. (again as seen in the photo) With the grind diameter and the width of the journal pre-set, start-up will see the main grind wheel and the spindle running. After a short “settling time” delay, the feed-in motor advances the grind wheel a pre-set amount (from 0.5 to 3 thou per rev of the spindle) Then after another small delay, the axis motor kicks in and starts feeding the grind wheel along the journal axis till it reaches the optical limit. It then feeds-in once more and then the axis motor returns the grind wheel back to the starting point. This continues back and forth until the pre-set diameter is reached ( again sensed by optical switches) and after a small delay the grind wheel backs out of the journal and the machine shuts down. The photo shows the narrow grind wheel fitted (3mm) as the journals here were only about 0.25” wide. There is provision to fit the wider 6mm wheel if required. Also, the drive motor is and old auto-washing machine motor (about 0.3hp) and the wheel runs fairly close to 1450rpm with no problems. (so long as feed-in speed is kept to the above limits) A “dresser” bar is available to give the grind wheel a “touch-up” now and the to keep it “true” however there seems to be a very low wear rate on the wheel (which is great) An attachment to the bed enables the machine to be set to a “no-axis travel” for the crank webs to be ground. In this mode the blank is stationary in the attachment and on each rotation of the spindle drive (just a simple timing reference in this case) the grind wheel advances in by the pre-set amount in a straight-in cut, trimming the sides of the previously rough-cut web. Photo shows webs already cleaned up. …………………… Jeff
interesting machine - being able to grind cranks is nice. TP grinder on lathe would be more typical, I'm wondering if you can share some of your thinking on why you didn;t go that route or why you think its superior. as i understand the description, the axis that determines the dia (y?) is computer controlled via the optical switches. I'm curious why you went this route vs a manual feed screw or even steepers on a feed screw. Also, is the chrome moly prehardened or did you heat treat it? what are you using for the spindle/grinding wheel.
Yes, I can see your point however ....Don't like grinding on a lathe.Good lathes such as my Myford cost big bucks and grinding can make a real mess of things.
Grinding machine once setup is fully automatic carries on grinding while I'm doing other things. Using optical switches fits in with the plc controller and DC motors I had on hand that are simpler to set up. When changing from one crankshaft design to another, simple parameter changes are all that is necessary.... no programming changes required.
The 4140 steel was used as is ... it requires no hardening ... thats the reason why I used it. In any case, most forms of hardening can create all sorts of problems (bending)
The grind wheels I used are simple cut-off wheels ...cost about A$3.00 and work fine. They are made here in Aus but no doubt you would have similar where you are. 180mm dia with 22 mm bore .... two thicknesses .... 1 @ 2.7mm and the other @ 6.8mm ... max speed of 8600rpm so I'm well within the limits at 1450 rpm. Just took a look at the one I used for the 4 cylinder crank and the wear on it is about 40 thou diameter. Not bad considering this was for the journals and the crankwebs as well as a light touch with the "true-up" stone
Yes, I can see your point however ....Don't like grinding on a lathe.Good lathes
best place to use a tool post grinder is in a completely different room than the lathe, with airlock between. . I rarely use the TPG and put a lot of time into protection and cleaning. lots of paper towels held down by magnets and a clean up boarding on disassembly. if you were doing this a lot it would increase the appeal of a separate machine.
nice work on the machine, and look I forward to seeing the cam grinder