parallelogram for up and down movement?

[Satamax]

Hi Satamax, interesting project you have here.

I'll weigh in on the discussion, as long as you keep in mind that I don't have the saw parts in front of me and have never seen a grape picker other than the picture in your link.

My first thought about the parallelogram is that it puts the saw head further out of the grape picker and would magnify any change in the difference in the height of the front to back wheels as it is going down the track causing the blade to rise or dip and also make it hard to keep the blade (front to back) parallel to the track, I also think that Brucer brought up some valid points.

I think that a pair of sturdy post with a cross piece at the top and fastened to the inverted U shaped frame would be the easiest and would be more sturdy, a lift system like Bandmiller2 had described to me once that has a hyd. cylinder with a double pulley on the rod end that pushes a cable in order to shorten it and cause the saw head to lift. (think fork lift, for every inch of cylinder lift you get 2 inches of saw head lift). One piece of cable to each side of the saw head with a eye bolt for adjusting side to side height.

Thanks Hilltop. Well, i see your idea. Pretty much like a four post car lift cablewise. I'm not too keen on cables. The U shape is quite backwards in the frame. And the wheels extend in front of the frame.  Ok my saw has a pretty deep footprint of nearly three feet at the puley. Plus the lengh of the parallelogram, and the lengh of the machine, i would lose something like 20 feet of cutting. But it's soo easy, atach the machine, the four rail wheels, and off i go. The hydraulics are already all there. Forward and reverse movement. Enough power. I already found the hyd motor for it in the garage of a builder frend.

And if they weren't people like me trying to adapt, refine, modify and all this. You would still be hunting with wooden spears, may be with a stone on the end. But in it's time it was already a revolution! 

I'm not trying to offend you, but your tone comes accross a little defensive toward criticism of your design ideas. You did ask the members 'why not',

Anybody can see a point why not?
Max.

so they (we) are responding as such.


I commend your thinking outside the box, I too, like to stray away from mainstream, but when something works, it works and you go with it. I feel that the guys here want you to succeed in your project are just trying to keep you from setting yourself up for failure.
On that note I say just go for it. If you pull it off it will be one bad ass and unique mill, for sure.
I just know from experience that redesigning something that doesn't work after putting many hours into it really sucks.

EBC, well, i take constructive criticism well usualy. And i try to shut my mug when realy needed. Totaly agreed about building and rebuilding and adjusting and tinkering, and tweaking. It can get tiresome sometimes.

As for the ram, i don't see what can do any harm to hydraulic rams! I was thinking one each side, exact same ones, slaved to each other,  i mean paralleled.

When the ram is fully extended, the backward force on the sawhead will be magnified considerably when it reaches the ram. This will apply much higher forces on most of the rotating joints. This in turn will magnify any "play" in the various joints.

When I'm trying to drive a linkage with a hydraulic cylinder, I determine the midpoint between the two extremes of motion. Then I try to arrange for the cylinder rod to be at right angles to a line between the pivot point and the end of the cylinder rod.

Still, the pivoting points bug me. Ball bearing pillow blocks are costly. ...

Ball bearings may not work well in that application. They will only be rotating through part of a turn and will eventually wear unevenly. Lubricated bushings may do a better job.

Brucer. You mean downwards force on the joints? Because, backwards, i don't see it. Ok, so pillow blocks it would be. I understand the idea of having the cylinder perpendicular to the line of motion. It's no quary machinery. >But still it would have to raise and lower the saw, on it's full stroke, si it would need to be near enough to the support side pivoting points. 

I think the parallelogram idea has to many joints, you're going to have a hard time dealing with the lateral movement for one. When the blade hits the wood, it pulls pretty hard to the side. It just seems like you are doing it the hard way, but I don't doubt you could make it work. I'm all for innovation ;)

Ok Bartender. 8 main joints too much. Plus the four for the rams. I thought it was simple, because there's no sliding parts. I like the up and down screws, like in a two post car lift. It doesn't have much play in the up and down movement. Tho it doesn't hold any lateral movement, and has to have precise slides. I see the two posts and four posts homemade mills, with PET bearers on the square tubing. Well, four, no way. Two might be considered. Still not convinced by the chain up and down.

Guys, i think this is simple. No complicated geometry. Few joints. Doesn't have tons of moving parts, or things to assemble.

What bugs me is the lengh, and the fact that travel will be uneven, being faster near horizontal, and slower at top and bottom.

[eastberkshirecustoms]

As for the ram, i don't see what can do any harm to hydraulic rams! I was thinking one each side, exact same ones, slaved to each other,  i mean paralleled.

FYI Satamax, here is a little indication of what can happen to hydraulic  rams. This is on my FEL with grapple installed. Hydraulics produce a lot of power and take as much punishment. I hope this helps... -EBC

[Old Hilly]

Well, I don't see what all the problems are. Take a look at the rear end of a coil-spring suspension car, then copy it. Motor car's suspensions take a fair sort of pounding and will work for years without problems. The "panhard rod" (if that is the corect term for the bar that keeps the rear wheels in line with the chasis?) keeps things in line sideways. If the mill head is rigid enough it will not flex or twist and provided the 4 linkage arms are of equal length then the head will be maintained perpindicular to the mill track. If there were to be another frame above the mill head that would carry the hydraulics then the lifting forces would be almost perpindicular.
Personally I rekon you could get almost all the parts you need from a car wrecking yard. Tie-rod ends and ball joints would do the job as pivot points, after all, that's what they were designed to do and they are cheap and readily available.
Good luck with the project,
Dennis from "Down Under".

[Satamax]

As for the ram, i don't see what can do any harm to hydraulic rams! I was thinking one each side, exact same ones, slaved to each other,  i mean paralleled.

FYI Satamax, here is a little indication of what can happen to hydraulic  rams. This is on my FEL with grapple installed. Hydraulics produce a lot of power and take as much punishment. I hope this helps... -EBC

Ouch!

Well, that's small rams compared to what i can scavenge.

Dennis, thanks for the encouragement. Yep it's similar to two triangle or four link car suspension. The only problem, car suspension would be too short and not give enough travel.

[Old Hilly]

Right, you got the idea. Now start looking at what is available from the scrap bin or wrecking yard. As most suspension and steering components are made of some sort of steel they can be cut and welded. I admit that there are potential problems with welding heat-treated steels but steering rods are not heat treated and are usually hollow. You could also consider finding some heavy-wall tube and using that as your arm with the threaded part of the tie-rod welded into it. This way you have an arm as long as you need with the ability to adjust it's length to the exact distance needed. You might care to look at truck steering components if you are worried about the strength of the assembly.
If you get the design right you can make a perfectly safe chair from folded and glued newspaper, all you need is the engineering knowledge to get all the folds in the right places. Get it wrong and you end up sitting on the floor.
Your mill head idea is no diferent to the paper chair idea and probably an improvement on what is in common use on bandsaw mills at the moment.
Keep thinking outside the square,
Dennis.

[Satamax]

Thanks a lot Denis.

Well, for the moment i'm in need of a cold exhaust exhaust smokeless stove. So i'm after that.

http://www.permies.com/permaculture-forums/10367_0/alternative-energy/a-cyclone-in-a-rocket-

I've found the motor for the machine tho. Hydraulic OMT 500 from danfoss. 40kw from 0 to 1500 rpm.

Bye.

Max.

[Satamax]

Hey Dennis.

Aparently, i'm not thinking that much out of the box! Look in front of this wineyard tractor.

[Old Hilly]

Mate, that is a wild bit of gear! Too tall and narrow for this part of Australia but it's an interesting machine. I asume it's for spraying the Grapes?
With the hydraulics to lift your mill head, if you construct another arch somewhere near the head assembly and hang your ram from that so that your lift is pretty much vertical you will put a lot less strain on the pivot points than if the rams were pushing upward and outward at a 45 degree angle. If you design the arch so that it has some "rubbing strip" material on the inside face so that the linkage arms can rub against it then you will reduce the potential for the mill head to move sideways considerably.
What was the idea behind the heating stove you mentioned? It looks so well insulated that I am amazed that any heat escapes at all. Or is it more of an incinerator to burn waste than a device to heat a building, thus needing to stay "cool" on the outside?