oh, so you just welded this coupling over the cylinder?? I would never thought of that! My problem is I do not have any metal lathe and if I am about to go to a machine shop it will cost me the same as buying an more expensive trunnion cylinder in the first place. Anyway I will keep that option in my mind.
Homemade Backhoe for LS Tractor (XG3140)
- Thread starter polemidis
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TMGT
Elite Member
I dont have a picture on my phone but I was able to make a trunion without a lathe so it's still doable. Not as nice as BFreaky's but it works.
TMGT
Elite Member
I lied, found a couple pics. The 1/4" flat stock was heated and formed more to the cylinder after it was bent, the pin is a piece of 1144 pressed and welded on the backside into a piece of DOM tube.
Ok good. For some reason I had never thought that I could weld on the cylinder.
So, I am doing the geometry circles and stuff. I really do not see any huge difference with the trunnion, on the force or on the angle spread. In my mind yes, it should work better, but in paper it does not. I can post the diagrams to support what I am saying if you want. One thing i see different is the swing angle that has the max force. With the trunnion is closer to the ends of the swing arc, with the regular cylinder mount is towards the center.
If the industry uses trunnion is should be for a reason, but I have not figured out it yet
Maybe because the mounts are more convenient located?
So, I am doing the geometry circles and stuff. I really do not see any huge difference with the trunnion, on the force or on the angle spread. In my mind yes, it should work better, but in paper it does not. I can post the diagrams to support what I am saying if you want. One thing i see different is the swing angle that has the max force. With the trunnion is closer to the ends of the swing arc, with the regular cylinder mount is towards the center.
If the industry uses trunnion is should be for a reason, but I have not figured out it yet
Maybe because the mounts are more convenient located?
ptsg
Super Member
Trunnion mounts usually takes less space and by moving the pivot point forward, it will allow the backhoe to rotate a full 180 degree from one side to another without the cylinder overpass the main pivot point which would cause problems.
TMGT
Elite Member
How many degrees of swing are you going for? If you're going for a bit less then 180* then yes you can get by without trunion mounts. Otherwise you will run into overcenter issues or stall problems because the cylinders start fighting each other.
One thing I can say from experience, you'll want as much swing as possible, a lot of times I wish I had more then 180!
One thing I can say from experience, you'll want as much swing as possible, a lot of times I wish I had more then 180!
texasranger556
Platinum Member
SC has several options in the sub $100 range
Surplus Center
Another option is a dual ended cylinder and chain like Woods used to use.
https://www.tractorbynet.com/forums...6500-backhoe-dolly-kubota-20130421_175138-jpg
And a general note, most backhoes I've seen run the swing cylinders between the upper and lower pivots. It balances the forces better and leaves more room for your feet.
Surplus Center
Another option is a dual ended cylinder and chain like Woods used to use.
https://www.tractorbynet.com/forums...6500-backhoe-dolly-kubota-20130421_175138-jpg
And a general note, most backhoes I've seen run the swing cylinders between the upper and lower pivots. It balances the forces better and leaves more room for your feet.
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Sorry guys, somehow my reply didnt get through.
Texasranger, the cylinders have to go above the upper pivot, as Bfreaky's one. The reason is that the hydraulic tank is in the way. I understand it should go somewhere between the upper and lower, but really, there is no other place. I dont worry much though because the swing cylinders are only moving the backhoe, they are not applying lots of force. I actually think to add an extra relief valve (a crossover valve actually )on their circuit in order to limit the pressure so to avoid possible damage on BH in case of some collision.
Bfreaky! what is that monster?? hahaha! I would actually want 360, and build an excavator but thats another project for another day I keep finding cheap 150hp diesel engines and i get temped but no money-no honey
TMGT, I will go with just below 180. I could not find how the trunnion will help. This is my sketch for regular cheap cylinders. The blue line is 180 line for the left (upper in the sketch) swing cylinder rod pivot. Bfreaky explained it to me, I may hadn't thought it on my own, that the trick that make 180 possible is that the cylinder rod can go over the central pivot point, because the cylinders are on top of the assembly (and not between the upper and lower pivots)
The blue mount in theory can move up to <180ｰ , you can see in one picture that the cylinder rod (purple) has almost 0.5" more to retract.
So I will just put my bumper end stops 1ｰ below 180 and I will just adjust them to make sure it will never go above 180 in the actual practice.
In the diagram, the big arcs are the cylinder limits. I regular 3"x8" cylinder with 20.25" retractred length, and 28.25 extended length. (I should use 3x6" but surplus didnt had them cheap, but it does not really matter)
Texasranger, the cylinders have to go above the upper pivot, as Bfreaky's one. The reason is that the hydraulic tank is in the way. I understand it should go somewhere between the upper and lower, but really, there is no other place. I dont worry much though because the swing cylinders are only moving the backhoe, they are not applying lots of force. I actually think to add an extra relief valve (a crossover valve actually )on their circuit in order to limit the pressure so to avoid possible damage on BH in case of some collision.
Bfreaky! what is that monster?? hahaha! I would actually want 360, and build an excavator but thats another project for another day
I keep finding cheap 150hp diesel engines and i get temped but no money-no honey TMGT, I will go with just below 180. I could not find how the trunnion will help. This is my sketch for regular cheap cylinders. The blue line is 180 line for the left (upper in the sketch) swing cylinder rod pivot. Bfreaky explained it to me, I may hadn't thought it on my own, that the trick that make 180 possible is that the cylinder rod can go over the central pivot point, because the cylinders are on top of the assembly (and not between the upper and lower pivots)
The blue mount in theory can move up to <180ｰ , you can see in one picture that the cylinder rod (purple) has almost 0.5" more to retract.
So I will just put my bumper end stops 1ｰ below 180 and I will just adjust them to make sure it will never go above 180 in the actual practice.
In the diagram, the big arcs are the cylinder limits. I regular 3"x8" cylinder with 20.25" retractred length, and 28.25 extended length. (I should use 3x6" but surplus didnt had them cheap, but it does not really matter)
texasranger556
Platinum Member
I wouldn't want to give up swing power, you will use it more than you think backfilling dirt, moving the pile over, or to reposition the rear of your tractor while digging or stuck.
Shoot for full 180 swing, you will appreciate the space savings in your shed or fitting on a trailer. Your proposed swing geometry looks like it will be very non-linear near the extremes and may even lock. I can measure the pivots on mine if you don't have access to a good example locally. It uses trunnion cylinders.
How much hydraulic flow does your tractor have? I would use the tractor hydraulics and avoid the extra pump, tank, filter, relief, etc. My tractor is rated at 8.3 GPM and runs the 8' hoe fairly well between half and two thirds throttle.
Shoot for full 180 swing, you will appreciate the space savings in your shed or fitting on a trailer. Your proposed swing geometry looks like it will be very non-linear near the extremes and may even lock. I can measure the pivots on mine if you don't have access to a good example locally. It uses trunnion cylinders.
How much hydraulic flow does your tractor have? I would use the tractor hydraulics and avoid the extra pump, tank, filter, relief, etc. My tractor is rated at 8.3 GPM and runs the 8' hoe fairly well between half and two thirds throttle.
No worries, I think the crossover relief valve is a good safety measure anyway. And Its easy to adjust. And it really does not add much to the cost.
About the tractor hydraulics. I was considering that. My LS is rated at 8.2gpm. The remote hydraulics would simplify everything. A lot. I mean I could have it 100% done ready for the plasma cutting in a week. But, I decided to go with the pto pump, for a few reasons:
a) Right now I do not have remotes. I have a 3rd function in front but its not rated for continuous operation. So I would have to pay $700 for the rear remotes. I have no doubt they would become handy at other projects though.
b) The pto pump will boost the flow to 14gpm at least. That extra flow will allow me to use wider cylinders, without sacrificing operating speed.
c) I have never welded with more than 180Amps. Nothing thicker than 1/4", not with proper penetration at least. I want a project to get experience with thicker still
Stupid reason I know, but I have to start from somewhere! I just got a Lincoln IdealArc sp-250 (for $300 only!!!!!!!) and I want to use it in a proper project!!!Rational thinking I should go with the remotes as you say. But I want a challenge
texasranger556
Platinum Member
For a backhoe or anything with it's own valve you can just cut the line that connects the loader valve power beyond port and the three point input. Run the power beyond to your backhoe inlet, and the backhoe return to the tractor's sump. The three point gets no supply when the backhoe is installed...in my case I have to remove the 3 point arms anyway while the BH is installed.
Depending how your system is configured it could be as simple as making a couple hoses and adding some quick disconnects. For ultra cheap, if the line is steel you can cut it and braze JIC fittings straight to the steel lines. We have done that on several backhoe installs where I used to work, usually when the tractor used metric or ORFS fittings (pretty much anything beyond SAE/ORB, JIC, or pipe) that we couldn't find locally and customer was in a rush.
Depending how your system is configured it could be as simple as making a couple hoses and adding some quick disconnects. For ultra cheap, if the line is steel you can cut it and braze JIC fittings straight to the steel lines. We have done that on several backhoe installs where I used to work, usually when the tractor used metric or ORFS fittings (pretty much anything beyond SAE/ORB, JIC, or pipe) that we couldn't find locally and customer was in a rush.
Yeah, great input. I am completely comfortable with the hydraulics. (I have spent about $10,000 on surpluscenter already.... :confused3
I do not know man, I had 2nd thoughts... Making a simple backhoe has a lot advantages. Anyway, I have finished the tank, i will keep doing the external hydraulic system just for getting experience.
I made some more progress yesterday, I moved the swing cylinders towards the center and replaced them with smaller stroke ones.
Guys my progress is on the gitlab server. Usually I make progress twice per week, and I dont post all the details here to avoid overload you with too many useless details. I am mention it again, feel free to download the CAD files. If you are not familiar with Freecad, everything can be exported to .STEP files (kind of universal format)
It starts to take shape. I would like to review a few things (yes, the trunnion mount is one of them!! )though. My main concern is that I have no much experience with heavy equipment and I do not know what is the industry standards.
Can you plz give your input on these things plz?
a) Pin size. Some basic calculations show that 1.25" diameter pins of mild steel are adequate. But I am not engineer so thats maybe completely off. does it sound good to you guys? What size pins do mini excavators have? If that size is at about the limits, maybe I will just buy harder steel, even though I would prefer to replace the pins and not the welded bushings. Mostl likely I will use 3" diameter cylinders on 2200-2500 psi
b) for bushings I am planning to buy 2" OD DOM tube, with 0.375" wall, and weld them, does that sounds good approach to you?
c) Unfortunately I cannot run the Finite Element Analysis. Maybe I have to simplify the model a lot and retry. But from your experience, what thickness should I go for the plates? 1/4" for the main shell, and 1/2" for the laminated ends (where the stresses are higher)?
Thank you guys!
p.s. I am mentioning it again, the model is on the link I gave you before, available to download. All my progress is there.
)though. My main concern is that I have no much experience with heavy equipment and I do not know what is the industry standards.Can you plz give your input on these things plz?
a) Pin size. Some basic calculations show that 1.25" diameter pins of mild steel are adequate. But I am not engineer so thats maybe completely off. does it sound good to you guys? What size pins do mini excavators have? If that size is at about the limits, maybe I will just buy harder steel, even though I would prefer to replace the pins and not the welded bushings. Mostl likely I will use 3" diameter cylinders on 2200-2500 psi
b) for bushings I am planning to buy 2" OD DOM tube, with 0.375" wall, and weld them, does that sounds good approach to you?
c) Unfortunately I cannot run the Finite Element Analysis. Maybe I have to simplify the model a lot and retry. But from your experience, what thickness should I go for the plates? 1/4" for the main shell, and 1/2" for the laminated ends (where the stresses are higher)?
Thank you guys!
p.s. I am mentioning it again, the model is on the link I gave you before, available to download. All my progress is there.
TMGT
Elite Member
1.25 pins should be good for most of the pivots, I would step up to 1.5 for the main swing pivots and where the main boom and crowd arm mounts. Would recommend 1144 stressproof or at least 1045. For mine I used DOM with replaceable spring steel bushing or bronze bushing for the major pivots.
As for plating, mine has 1/4-1/2 depending on location.
As for plating, mine has 1/4-1/2 depending on location.
Thanks for the info!. Yeah for the king pin I have designed bigger pin, 2" i think.
But How these "replacing spring bushings" work? If the DOM will be 2"OD 1.25" ID, and the pin 1.25", how they fit? I like that idea to go with harder pins and put replaceable sleeve bushings, but I do not know how.
But How these "replacing spring bushings" work? If the DOM will be 2"OD 1.25" ID, and the pin 1.25", how they fit? I like that idea to go with harder pins and put replaceable sleeve bushings, but I do not know how.
TMGT
Elite Member
Bushings are 1/8" wall so just make the ID of the DOM .250" larger to compensate. Most of my sleeves are .250" wall DOM, .375 is a good wall thickness.
Do you have a lathe? You're going to need one to get good pin fitment either way using DOM.
Do you have a lathe? You're going to need one to get good pin fitment either way using DOM.
Plz let me know if I got it wrong:
Pin: 1144 steel 1.25" dia
Bushing: 1.25" ID 1.5" OD Something like this?
Housing: DOM Tubing 1.5" ID , with wall either 0.25" or .375"
And the DOM will be welded to the holes of the plates, which will be a little bigger as the plasma does not cut exactly precise.
If thats the case then grease has to come through the pin? Make 2 crossed holes?
Pin: 1144 steel 1.25" dia
Bushing: 1.25" ID 1.5" OD Something like this?
Housing: DOM Tubing 1.5" ID , with wall either 0.25" or .375"
And the DOM will be welded to the holes of the plates, which will be a little bigger as the plasma does not cut exactly precise.
If thats the case then grease has to come through the pin? Make 2 crossed holes?
