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Discussion Starter #61
I think you must have only looked at his mock up and not his actual design. He has the up rights in the same place as a JD 40, beside the foot pads. It looks overbuilt to me but that is better than under built. I believe it will work well and give you many years of fun and back saving work! One thing I have always wondered about is designing two frame mounted stops so that the bucket in the completely down position to be used in a dozier mode would be possible to absorb much of the impact of the ramming by the bucket. I have read in the manuals that the bucket should not be used as a ram. Have any of you ever thought about this feature?
I think there was some confusion when JCarfield hopped on my thread and posted some of his mock up pics (using the Kubota bucket). Since we both have 425's I didn't see an issue with expanding the discussion. My design is based on Paul at P.F. Engineering's plans, which I think are well worth the fee. I made some modifications to suit my specific build.

As for the stops, I have been curious about that myself. I have seen them on a number of OEM FEL's. I welded one back onto a small Kubota for a friend years ago when he broke it off. I'd bet a 6 pack that Tudor has some insight on the topic, and I would enjoy to hear from anyone else that has either used them on OEM FEL's or added them to their homebuilts.
 

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Red Plaid is Timeless
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I call them "saddles" for lack of a better word and incorporated them on my homemade loader. The bucket, blade, and thrower are all built to be about operating level with the loader arms floating in the saddle. The bucket heel, at rest, sits about 1-1/2" off level ground at rest. To dig, the bucket needs to tip down just a bit. Almost all my operations start by having the implement resting in the saddles. I just rock the blade or blower back slightly and float the arms into the saddles and then drop the blade or blower to the ground.
 

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Yep, wrong tractor. Sorry, but the mock-up has the the pivots close together too.

I always thought the arms should go hard against stops. Lots of older loaders do. But I’ve seen so many working fine without them I don’t think it’s as important as I did. It’s hard to tell in the picture attached but I have seen them at Home Depot and they don’t have stops (it also has really skinny cylinders). A Bobcat I had would hit the hard stops without lifting the front wheels. Tilting the bucket would lift the wheels. It could dig no problem.
 

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As for the stops, I have been curious about that myself. I have seen them on a number of OEM FEL's. I welded one back onto a small Kubota for a friend years ago when he broke it off. I'd bet a 6 pack that Tudor has some insight on the topic, and I would enjoy to hear from anyone else that has either used them on OEM FEL's or added them to their homebuilts.
Personally, I don't like them. They induce a shock load on the hydraulic system that doesn't need to be there if the design is correct. Hydraulic cylinders have a cushion built in at the ends of the stroke to limit or prevent end-of-travel shock loads.

I can understand why stops are used when a cylinder has been replaced. All cylinders are not created equal, even if the stroke is. But for new construction, use the end of cylinder stroke as the stop.

There is no difference between mechanical stops and end of cylinder stroke in the forces applied to the rest of the loader assembly, or tractor, while working. Impact is impact, and I'd rather have a bit of fluid to absorb the worst cases. The fluid at least can expand the hoses slightly (cushion) when a pressure spike occurs should an immovable object be encountered.
 

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I am afraid I have to disagree with Mr. T. On several of the loaders that I have had the lift ram is fully closed or less than an inch of travel in the ramming position and thus there is no shock absorber effect. The second thing is the force applied with the bucket fully down and ramming into anything stubborn is being applied through the front mounted side braces and a rotational force through the vertical posts onto the sub frame. Would you rather have the entire tractor frame take the initial force or the rear axle like on a JD 40? I realize that for most uses this will not be an issue but many of the older JD's and even some of the newer ones have problems where the rear axles are bolted to the frames. On the JD 40 the sub frame is directly attached to the axle housing and thus it will take much of any unusual force and the subsequent effect of trying to separate the axle from the frame. The entire force on a JD 40 is basically taken up by four bolts at the rear axle/frame junction and two bolts at the front. By having a fixed stop to the rear of the bucket all of the force in a ramming would go into the stops and thus into the entire frame, not just the axle housing or bolts. Of course, mounting very hard rubber blocks on the frame studs could be used to help some with impact forces. This is a mental exercise for me because I can never let well enough alone. I just have felt that ramming into something is hard on the loader frame and attaching points and there might be something that could help. I did not know that anyone had ever actually made them. BTW, in the operator's manual that I got with my latest JD 40, it states as a warning to not use the bucket as a ram. There has to be a reason for that warning.
 

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The reason for that warning is that impacts have the potential to create a massive spike in hydraulic pressure. The one blown hose I've had on my machine happened in the winter, when I was going through the yard "bulldozing" foot deep snow to get to the driveway. On the way I started to lift the blade to clear a very large root I knew was there but couldn't see. I misjudged and raised too late while still moving forward and caught the root, while moving at a decent clip - maybe 3-4 mph - and while simultaneously raising the boom. When I hit, the tractor stopped cold and the line blew. That kind of pressure/impact is why they don't want people bulldozing and ramming into things. Having a solid stop would avoid that pressure spike but has the potential to break or bend something.

In a nutshell, if the tractor can't push whatever you want to move under it's own power, you shouldn't be trying to ram it to move it, so there should be no need to be up against a solid stop anyway. I'm with Tudor, I'd rather replace a hydraulic line than bend or break the loader or tractor frame. The rubber hoses can give at least some form of cushion or if necessary, relief when they burst.
 

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You are doing what Tudor did and assuming that the bucket is out with some of the ram still uncompressed in the cylinder. I am talking about when you want to break something lose by hitting it pretty hard but with the bucket down and the lift rams all the way in. There will be no hydraulic shock under those circumstances. As for the affect on the tractor, I would rather have the impact forces focused onto the front of the frame longitudinally instead of a twisting force at the up rights and the rear axle bolts. Or even worse, an off center hit with the bucket. As Jay calls them, the saddles would take the blow and there would be no twisting force applied to the lift arms. I agree that a loader should not be used a ram but we have all done it at one time or another either intentionally or by accident. I do not have any experience with these but I enjoy talking about the pros and cons of them and it makes me feel good to know that some before me have already invented them and used them.
 

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Discussion Starter #68
Rudy, would you be willing to take a few pics of the stops on the 40 loader? It would be helpful to see them as engineered by Deere.

I made some good progress plumbing today but hit a few snags. The biggest one is that I didn't realize that I need ferrules between the tube nuts and the 37 deg flare on the end of the tubing. The nuts would not tighten down on some of the unions I got. When I called the supplier to ask why they were not compatible they explained that I need a ferrule to take up the space. Ugh, now I need to cut off one flare from each tube and add the ferrules and re-flare one end. I'm two tubes from done with the hard lines so I have to take everything apart again. Good news, the supplier apologized for not noticing they were missing from my order and is sending them for free. The folks at hoseandfittings.com have been really nice. They answered a bunch of newb questions before I placed the order that were very helpful. I ordered all the fittings and tubing from them, but I ordered the hoses from surplus center because their pre-made hoses were half the price.
 

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As for the affect on the tractor, I would rather have the impact forces focused onto the front of the frame longitudinally instead of a twisting force at the up rights and the rear axle bolts. Or even worse, an off center hit with the bucket. As Jay calls them, the saddles would take the blow and there would be no twisting force applied to the lift arms. I agree that a loader should not be used a ram but we have all done it at one time or another either intentionally or by accident. I do not have any experience with these but I enjoy talking about the pros and cons of them and it makes me feel good to know that some before me have already invented them and used them.
And virtually every skidloader is designed with this feature. It is not hard to make "stops" coincide with the full retraction of the cylinders.
 

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You are doing what Tudor did and assuming that the bucket is out with some of the ram still uncompressed in the cylinder. I am talking about when you want to break something lose by hitting it pretty hard but with the bucket down and the lift rams all the way in. There will be no hydraulic shock under those circumstances. As for the affect on the tractor, I would rather have the impact forces focused onto the front of the frame longitudinally instead of a twisting force at the up rights and the rear axle bolts. Or even worse, an off center hit with the bucket. As Jay calls them, the saddles would take the blow and there would be no twisting force applied to the lift arms. I agree that a loader should not be used a ram but we have all done it at one time or another either intentionally or by accident. I do not have any experience with these but I enjoy talking about the pros and cons of them and it makes me feel good to know that some before me have already invented them and used them.
Gotta love the Laws of Physics! No cops needed to enforce them.

Most loader buckets are below grade when fully down and flat. If they are at grade when flat, there is either fluid on both sides of the pistons, or the front wheels are in the air.

Assume for discussion purposes that the bucket is flat on grade and yet fully down with fluid on only one side of the piston. When impacting an immovable object, the cutting edge becomes the center of rotation as the tractor, with its CofG some distance above grade, soaks up most of the forward momentum by rotating around that center. With the bucket on the ground and the rear wheels rising, the tendency is for the lift cylinders to extend forcing the fluid to exit the head ends of the cylinders as much as possible resulting in a spike of hydraulic pressure well above normal to be absorbed by the hoses. There will be a corresponding vacuum at the base ends of the cylinders which will also contribute to the cushioning effect.

The same effects can be seen for the operator. Upon impact, the feet are scrambling trying to find traction (no immovable object), the butt leaves the seat, the face heads towards the hood, and the arms are trying to bend the steering wheel to keep the face safe.

The purpose of a loader subframe is to direct the forces acting against the cutting edge to the part of the tractor moving it forward, the rear tires and, by association, the rear axle tubes, without applying more stress than necessary to the tractor's frame.

Ramming with a loader, or a blade for that matter, is not recommended due to the possibility of operator injury. A decently designed subframe will protect the tractor.
 

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For some reason I cannot picture a piston bottomed out inside the cylinder doing anything in an impact except sitting there. If like Jay says the ram is completely bottomed out then the lift arms are not going to do anything on impact if there are physical stops behind the bucket. Since the lift rams are bottomed out the downward force caused by the bucket edge would tend to drive the lift rams even further down not up. If there are two stops mated with the rear of the bucket a twisting force will have much less inertia once it makes contact with the stops. At that point the force will be transmitted throughout the frame and wheels. With the bucket fully down and the curl up to not scalp, the bucket is in effect a push blade with mechanical stops behind it. At that point there are no hydraulic forces at work. I can see the rear of the tractor rising due to the rotational forces at play but there would be no hydraulic action that I can see. Since these stops are in fact real and being used there must be a reason for them.
 

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Discussion Starter #74


This looks like a stop to limit full curl on a 40 loader. It might be to protect the curl cylinders from bottoming on full extension. I would think bottoming on full extension would be more damaging to a cylinder than on compression due to the reduced surface area.


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For some reason I cannot picture a piston bottomed out inside the cylinder doing anything in an impact except sitting there. If like Jay says the ram is completely bottomed out then the lift arms are not going to do anything on impact if there are physical stops behind the bucket. Since the lift rams are bottomed out the downward force caused by the bucket edge would tend to drive the lift rams even further down not up. If there are two stops mated with the rear of the bucket a twisting force will have much less inertia once it makes contact with the stops. At that point the force will be transmitted throughout the frame and wheels. With the bucket fully down and the curl up to not scalp, the bucket is in effect a push blade with mechanical stops behind it. At that point there are no hydraulic forces at work. I can see the rear of the tractor rising due to the rotational forces at play but there would be no hydraulic action that I can see. Since these stops are in fact real and being used there must be a reason for them.
There are two sources for hydraulic pressure, the action of the pump, and the action of the business end of the equipment, i.e. the bucket on a loader. If the bucket is on the ground and the rear of the tractor rises due to impact, the cylinder will extend, not retract. It won't matter if there are stops to prevent retraction, or if the cylinder has bottomed out retracting, there is nothing mechanical to prevent extension except hydraulic pressure.

Install a gauge in the line for the head (rod) end of a lift cylinder and jack up the rear of a tractor with the loader bucket on the ground. The pressure will rise as the rod tries to extend.

We are accustomed to thinking in terms of the pump as being the source for moving fluid. In this case, the cylinder piston is moving the fluid and you have to think in reverse to understand the concept. Action vs reaction.

This looks like a stop to limit full curl on a 40 loader. It might be to protect the curl cylinders from bottoming on full extension. I would think bottoming on full extension would be more damaging to a cylinder than on compression due to the reduced surface area.
Geometry. Only a percentage of the force applied by the cylinder can be applied to moving a load, such as curling the bucket. The angle between the centerline of the cylinder and the line connecting the two pins of the bucket dictates that percentage. The calculation of that percentage is quite simple, measure the angle and find the sine of that angle. It is the percentage expressed as a decimal.

Of more concern is the fact that as the angle is reduced towards the extreme end of extending the cylinder, there is a risk of making contact with the bucket or arm and bending the rod. The two ways of preventing this situation are to mechanically stop the cylinder from extending, or the bucket from rotating, too far, or to design the mounts so that the full stroke can be utilized without the risk of cylinder or rod contact.

To me, the use of stops is due to poor initial design, or to compensate for using a replacement cylinder that does not meet the criteria of the original design. That doesn't mean that I totally disagree with their use, I just prefer to have the full stroke of the cylinder that I paid for available for my use.
 

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I don't disagree with what you are saying in theory but I think you are animating the event. If the bucket is on the ground with the rams bottomed out and the bucket is against physical stops when an unexpected object is hit, say an old stump, The bucket will impact the stops first, the bucket will try to go under the tractor, then there will be a small rise at the rear for just a small moment in time. The rotational force will be around the edge of the bucket and the inertia of the tractor, say 1,000 pounds, propel it slightly upward/forward in the rear but downward and forward in the front. If you look at the plane view of the tractor/loader as a unit there will be no rise in the lift arms because the rise in the rear is measured in CM's and the time interval is in milliseconds and the bucket and tractor act as a rigid unit. Remember the axis of rotation is the bottom edge of the bucket, not the front tires. Most likely we are talking about 3 to 4 mph at impact, not 30 or 40 mph. If this event is looked at in that frame of reference then all of this talk about big spikes in hydraulic pressure is hyperbole IMO. I would like for someone on this forum who is familiar with the use of stops on a production unit to post a picture so we can evaluate how it works. It's interesting to dive into this stuff and try to imagine what is going on in an instant in time.
 

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You are correct in that theory is involved and that the timeframe is milliseconds. So it is with air bags in cars that cushion the passengers in a crash.

We are discussing whether or not there is a cushion effect through the hydraulics. Nothing has been suggested about the quantity of that effect, only that it is present to somewhat lessen the effects of the impact.

I've tried to keep the math out of this discussion, but here is a small portion . While a rise of 7/8" in the rear axle will have the same effect as raising the bucket cutting edge 1", it will only cause the cylinder to extend about 1/3". For a 2" cylinder this is about 1 cu-in of fluid and there are two of them on a loader. There are 40-60 inches of 1/4" hose involved on a typical GT using hard lines on the loader arms and each 20" segment contains 1 cu-in of fluid. While the hoses will swell when subjected to high pressure, they will not swell enough to absorb two additional cu-in of fluid without bursting, so the actual movement is considerably less, but the cushion effect is still there. If the hose volume increases 3% in 5 milliseconds, it will absorb the energy equivalent of about 0.1 hp if the pressure spike is 1500 psi. The pressure spike will be greater than 1500 psi.

Note that the rear axle of my GT will rise 1.25" when air is pumped in to raise the pressure from 9 psi to 14 psi. I'm trying to be realistic with my numbers while remaining conservative with the effect. It would take some serious lab equipment to get the accurate results.
 

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The problem with that (bucket on the ground against the stops) is that the stops won't normally be in effect with the bucket touching level ground. The stops on most OEM machines are usually set so that the bucket is 4" or so below level grade.
 

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Mmm. Not really an issue. I have had the arms down all the way to lift the front of the tractor off the ground for more weight on the cutting edge when scrapping hard packed snow off of the driveway.

It sorta gets your attention to be stopped dead by a frost heaved concrete patio slab that wasn't in evidence the last time the driveway was cleared when you're boogying down the driveway flat out at 2/3 throttle in LO. That's about 3.5 mph.

Since that particular episode, I've learned to tip the bucket forward to keep the tires in light contact instead of lifting the front end that high. It's called 'learning by experience'. Every newbie learns the hard way. It doesn't help with the impact, but it gives you a chance to steer the tractor straight down the driveway instead of drifting off the edge toward the walkway.
 

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