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31st Dec 2020, 11:33 PM #16Golden Member
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That's very generous Grunto. Thank you. I'm tossing around some different design options in my head at present, there are several different design features on the commercial grapples that I think I can amalgamate and improve upon in a couple of ways. I'm going to try and come up with some ideas and dimensions on paper but I'm juggling family commitments over the next week and might not be able to get a run at it. I'll probably post a design sketch or two on here and ask for feedback about a couple of things.
Currently I'm considering something along the lines of this model, but with a split top section
https://www.everythingattachments.co...ta-cmp-rrg.htm
I also have another couple of questions for the brains trust, as this is a new level of fabrication for me...
The round tube that is used as a cross member in the upper and lower assemblies of the unit above, and in the top section of the green one in my original picture; what would be a suitable high-tensile tube for that purpose? I plan on using Bisalloy 400 plate or similar for the tines so would want to use a HT material for the round as well. Aus Tube Mills' C450 appears suitable..? Would this be difficult to source in smallish quantities?
Most of my fabrication projects to date involve RHS and SHS but it makes sense to use round tube where it has to pass through other components, i.e. easier to make a line of round holes than square ones, and keeping weight under control will be important rather than my usual thing of mild steel RHS and go big with the wall thickness.
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1st Jan 2021, 09:09 AM #17Most Valued Member
- Join Date
- Apr 2012
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- Healesville
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- 2,129
Pete i used duraflex when i made the rippers for a yeomans plow that i built, my thinking at the time was that if the leading edge's suffered from abrsision then they could be repaired with hard facing rods, they hardly wore at all.
Bisalloy is costly and usualy only used on the cutting edges. I used yeomans wombat points.
Then you may also have problems with welds cracking as it is hard and wont have the flex that is needed in this application.
To weld it properly it also needs preheating and low hydrogen.
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1st Jan 2021, 12:00 PM #18Most Valued Member
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- Nov 2017
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- Geelong, Australia
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- 57
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Pete, just some random thoughts without any personal experience in building one.
I’d be inclined to stick with standard steels, use a stiff core for the bits that will be a PITA if they bend etc and go lighter on the rest with thought around stress points and later repair IF required.
My logic being that you won’t be abusing it like a unit being used commercially, you will be keeping an eye on it for any signs of issues, and it’s not something that is likely to have a catastrophic failure.
I’m typically one to just overbuild things, but slowly coming to realize that it’s unnecessary for most of the stuff I do, and just makes the project harder and more expensive.
Just my 2c
Steve
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1st Jan 2021, 05:53 PM #19Diamond Member
- Join Date
- Mar 2014
- Location
- South of Adelaide
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- 1,225
HT tube is over kill for what you are making, medium wall MS pipe or heavier will be fine, all the pipe is doing is keeping the tines spaced apart. the failures i have seen are normally broken tines or hitches, and i think the operators try really hard to find new ways to brake them, assume you wont as you will have to fix it.
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1st Jan 2021, 09:14 PM #20Most Valued Member
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- May 2011
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- Murray Bridge S Aust.
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- 71
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2nd Jan 2021, 10:22 AM #21Golden Member
- Join Date
- Apr 2018
- Location
- Drouin Vic
- Posts
- 633
My thinking with HT tube is to keep the weight down a bit- my usual fab method ends up with something twice as heavy as it needs to be- usually not an issue but I don't want this thing to take up 50% of the lifting capacity of the tractor (unknown) before I pick something up with it. Makes a difference with things like being able to pick up stumps etc to put on the burn pile without having to run the chainsaw through them just to be able to move them.
I guess an extra few kg in the form of 1.6 meters of 5mm wall 75x75 shs would not be the end of the world, certainly easier for me to find than fancy stuff, but I find it's easy for weight to get out of control.
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2nd Jan 2021, 06:44 PM #22
Hi Pete,
As far as plate is concerned the laser cutters will be able to tell you exactly what the component weight is, since, at least the one I talk to, buys based on sheet weight.Best Regards:
Baron J.
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2nd Jan 2021, 06:51 PM #23Golden Member
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- May 2020
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- Willowbank QLD
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- 520
If you are going laser cut most of the price is in setup. Therefore would it be practical to have a piece cut out of the center of some of the larger tines. most of the strength of a tine is in the perimeter. You may be able to save enough weight to offset the need for special metals.
Steve
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2nd Jan 2021, 10:36 PM #24Golden Member
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- Apr 2018
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- Drouin Vic
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- 633
Yes a bunch of holes like an aircraft frame member has occurred to me. I have seen some U.S. commercial ones with lightening holes. Definitely a worthwhile consideration.
I think one of the big advantages of CAD that I've seen is the ability to calculate weight from the drawings. I must learn to use it one of these days, have never been able to dedicate the time to it yet.
I've started some sketches and hope to come up with some decent drawings over the next few days.
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3rd Jan 2021, 12:29 AM #25
Hi Pete, Guys,
Download a copy of "Qcad" from Ribbonsoft
https://www.ribbonsoft.com/en/
The free download and community edition is very worthwhile, I'm sure that you have seen the drawings that I have posted, all done with Qcad.
The time spent doing paper drawings could easily be put to use learning how to drive a 2D CAD program.Best Regards:
Baron J.
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3rd Jan 2021, 12:39 PM #26Diamond Member
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- Mar 2014
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- South of Adelaide
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- 1,225
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3rd Jan 2021, 12:41 PM #27Diamond Member
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- Mar 2014
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- South of Adelaide
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- 1,225
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9th Jan 2021, 03:21 PM #28Golden Member
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- Apr 2018
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- Drouin Vic
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- 633
Fellas thanks for all the input on this; I have just been away on a high-country camping trip for the past week and did not want to publish that fact in advance on the internet. I've made some preliminary sketches by the campfire (or under a tarp!) and hope to get a bit more drawn up over the next few days.
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18th Jan 2021, 01:52 PM #29Golden Member
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- Apr 2018
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- Drouin Vic
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- 633
An update- I managed to get my pencil drawings done and Steve is now very kindly converting them to CAD for me and I will then be able to get some quotes on the components. I've decided to go for a single-lid clamshell design very similar to a US made commercial unit that is unfortunately unavailable here. 10mm duraflex for all the tines and 75x75x5 SHS main frame. Mr Singh in Dandenong will be my first port of call for the laser cutting as I can drop in there whilst on shift. I'll most likely start a 'project' thread once there is actual steel. One of my design sketches below.
IMAG3251[1].jpg
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19th Jan 2021, 09:24 PM #30Senior Member
- Join Date
- Sep 2009
- Location
- Newcastle
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- 341
I'm keen to hear what it costs
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