Preliminary Grapple Rake Design for 422

[scarg]

Please advise comments on the preliminary design for Rock Rake with Grapple attachment.

Total Weight (steel or 304SS????) for assembly as shown is~ 464 pounds.

Please advise suggestions for horizontal tine length and vertical sections.

Tines and grapple are 1/4" thick and pipe is 1.5" schedule 40 pipe. Again this is very preliminary and mount for hyd. cyl. and PT plate still need to be added. Be nice we are just at the beginning- /forums/images/graemlins/wink.gif


Additional images and pdf drawing available at
www.auxprosys.com/RR/

It is easier to put them there than to upload all into a thread.

Best Regards,

Steve

 

[pequeajim]

Steve, it looks like you are moving along with the design. It looks really good! What is the width?

I do have a couple of comments strictly from a PT 425 user's perspective.

There may be too many tines. I don't know if you need that many. Less will save weight which is important with a limited lift capacity. Besides, the closer they are together, the more easily dirt will get trapped in there and prevent the sifting potential.

The longer the bottom tines are, the less breakout force the rake has. It looks like your length is just about right.

I like two seperate grapples with a cylinder each. This helps securely hold irregular objects like a funky shaped log or something like that.

For the 425, I would think a width of 48" would be about right.

Thanks for posting! I'm excited!

 

[rswyan]

I'm not a Power Trac owner but I have been planning on building my own Root Rake/Grapple.

I have looked at alot of designs and have always wondered what the motivation is from an engineering and economic perspective to build curved grapple arms, as opposed to using several pieces of bar stock cut at an angle (which achieves a curve, sorta) and welded together for each arm. Seems to me that one would waste alot less steel that way. I'd agree that you could get by with alot more space between the tines.

1/4" thick is probably on the light side of what most commercially available grapples are - but I plan on using it or 5/16" myself due to limited loader capacity (Kubota B2910) to keep it as light as possible.

 

[MuncyBob]

I think you are on the right track.....also agree with too many tines, with he 422 I would want to find a way to cut down on the weight but not so much that you lose functionality(is that a word? /forums/images/graemlins/crazy.gif)

 

[pequeajim]

Steve:

Something else that you may want to consider is the teeth that are cut into the middle of the bottom tines, (not the end), may turn out to be a fracture point for the rake? I'm not a mechanical engineer, but that seems like it could be a weak spot when people use the rake to pivot on the ground to break out roots and other growth?

Some of the other guys on here are more qualified to asses that than I /forums/images/graemlins/confused.gif

 

[Rip]

In addition to some of the other constructive comments, I would add that you should plan on the mounting plate to have a nominal 20 to 30 degree forward tilt in order to have roll back capability down near ground level.

You can achieve this by tilting the bottom of the plate out from the vertical back of the rake. The exact angle is not critical, but you need something in this range.

While a number of designs do have the grapple as two separate sections, I have not found any problem with the single grapple like you show or as my AnBo is made.

For a 422 size machine I would keep total weight as low as practical while maintaining strength and maximum "bite" so as to be able to carry as much as possible per trip.

You will also want to modify the lever for the aux hyd circuit so you can easily access it from on top of the dash. Several ways have been posted.

Looks like a nice project to work on during the winter.

 

[scarg]

Thank you for all of your inputs. I ran a quick finite element analysis on the new bottom tine design and when constraining the vertical section by the thru pipe supports / and applying a load on the very far end tooth each tine should fail at about 2,900 pounds of force. Does anyone know the actual breakout force of a 422?

I do have the vertical section angled on this design about 10 degrees. Is this the roll back allowance that people are referring to? The total weight of this design exactly as shown is about 266 pounds using 1/2" thick carbon steel. We still have a way to go / however because everyone is giving feedback I would rather piecemeal images until we nail it down. The rest of the design such as adding the cylinder etc... it not too difficult so I would rather just append that portion at the end in lieu of editing it with every change we make along the way.

My thoughts are that having four top grapple tines at the top would be best to have driven by one cylinder. But please advise your thoughts.

Steve

 

[pequeajim]

That's prety cool Steve. I like that better than the previous design as it will be lighter with less tines. Do you think the rear top and bottom supports should be square tube? Would this provide more support against twisting yet keep things light?

Also, your design really allows you to modify the grapple slightly by cutting out the center section and adding another cylinder if someone wants that sort of thing, nice!

Jol1269 did a little test of the 425 lifting capacity and it was over 900 lbs. Having a 400lb rake would be the ticket for the 425. You could lift a lot with that.

 

[cqaigy]

I'm thinking the round would provide more resistance to twisting then the square peueajim

 

[HomeBrew2]

Great to see the use of CAD and analytical software on this site !!! A much needed addition ! Will you be able to make a DXF file available when you complete your design?
Great job and thread so far!
Cheers!

 

[Charlie_Iliff]

<font color="red"> 2,900 pounds of force. Does anyone know the actual breakout force of a 422? </font>
Steve: I'm not sure that a theoretical breakout force gives quite enough information. Essentially, that could be derived from the various lever arms and hydraulic cylinder capability. If the grapple is used as a root rake, however, the procedure would be to wedge the tine(s) under a root, lift the front of the pt, and then lower and maybe bounce the machine while curling the rake. I've seen that process described using the fork attachment, resulting in some bent forks that had to be straightened. I have no suggestion how to put a factor in for the inertia/shock load that can be applied, but I'd be concerned that those of us adept at breaking things may be able to concentrate more than 2900# on a tine. That being said, it may be that occasional bending, or even fracture requiring repair, is preferable to an increase in weight of the assembly.
An aside: Are you using an integrated CAD/engineering package that allows you to do a finite element analysis based on your drawing?

 

[Rip]

The weight you show sounds good at this point... adding in the PT plate and cylinder & hoses, etc should still be in the 300 range. Ten degrees is better than vertical for the QA plate, but if you could space the bottom out a bit to get closer to 25 or 30 you'll like it better. Should be able to keep it plenty strong and no appreciable extra weight.

Be sure to work out all the motion details for mounting the hyd cyl.... measure 5 times and cut once!! Looking Good.

 

[scarg]

We ordered a grapple bucket from PT last week to have a live specimen for review at the factory. I have been on the road for the last week and plan to begin moving forward shortly after the bucket arrives.

Regarding breakout force for root extraction.

If only the outside tines are typically used for this we can make these out of thicker plate.

Steve

 

[Phils]

Can I have the old PT grapple bucket after you have finished looking at it?!?!? I'd gladly give you half of what you paid, less shipping to California! Easy way for you to recoup some of your expenses.

Phil