Case/Davis trencher backhoe

[Eugen]

Tested the backhoe some more. All of a sudden the engine sounds like there's a hole in the muffler. I take a look and see one of the bolts fastening the muffler too the engine has sheared.

How or why is beyond me. This was a new engine.

The good news is that there's enough room to drill a hole.

And then use the extractor.

Came out easy.

Then I drilled the hole with a 5/16 bit and threaded with the 3/8-16 tap. New bolt and back to digging.

A few more impressions about the backhoe. I don't really understand why this engine, rated at 15hp, slows down and even dies when the digging gets very hard. As far as I know the there are 644 lbh tractors equipped with the D100 backhoe, so if the Kohler 14hp was enough for good operation of the backhoe, why this 15hp isn't?

@Harry , I'm curious, how does your 644 lbh behave when digging?

[Timj]

Do you know the size of the pump section that drives the backhoe? Maybe it's more than 15hp can handle.

[Eugen]

Do you know the size of the pump section that drives the backhoe? Maybe it's more than 15hp can handle.

Oh Tim, you hit the nail on the head. Pretty dumb of me, I forgot about the pump.I don't have measurements but it's quite big in comparison to the 644 pump.

[Timj]

Do you know the size of the pump section that drives the backhoe? Maybe it's more than 15hp can handle.

Oh Tim, you hit the nail on the head. Pretty dumb of me, I forgot about the pump.I don't have measurements but it's quite big in comparison to the 644 pump.

Be curious to know the displacement of that pump to compare to a 644. But by the looks of it all the markings are on the bottom.

[Harry]

Tested the backhoe some more. All of a sudden the engine sounds like there's a hole in the muffler. I take a look and see one of the bolts fastening the muffler too the engine has sheared.

385BF98B-46C1-4E80-8F54-76A7C49CDE0B.jpeg

How or why is beyond me. This was a new engine.

The good news is that there's enough room to drill a hole.

E8D58780-2B46-442E-B45A-F2B608A7F1D0.jpeg


And then use the extractor.

873C27B0-62A6-454B-A5A0-EE08CA2895A0.jpeg


Came out easy.


1A187244-43A7-4B98-95C4-FD64E43957C7.jpeg


Then I drilled the hole with a 5/16 bit and threaded with the 3/8-16 tap. New bolt and back to digging.

A few more impressions about the backhoe. I don't really understand why this engine , rated at 15hp, slows down and even dies when the digging gets very hard. As far as I know the there are 644 lbh tractors equipped with the D100 backhoe, so if the Kohler 14hp was enough for good operation of the backhoe, why this 15hp isn't?

@Harry , I'm curious, how does your 644 lbh behave when digging?

I was just using it the other day Eugen. I don’t use it with much throttle but not sure at what rpm. It’s always seems to be effortless for the backhoe to dig. Once I was trying to dig around a stump and it would catch on the roots and pull the whole tractor closer to the stump. No pressure relief squeal or governor kicking in either. The hoe is phenomenal for digging. The loader is another story with the pressure relief kicking in under a heavy loader. If it wasn’t such a PITA to turn up the pressure relief, it would have already been done. Harry

[Toolslinger]

I concur... The hoe shouldn't be the issue unless there's something seriously restricting the flow... Probably just a big displacement pump to handle the high flow for the trencher motor drive. I'd suspect that wouldn't take a ton of pressure, but lots of flow. I don't think I've ever run the hoe over 1/2 throttle, and most of the time I'm barely over idle.

[Eugen]

Thanks guys, this makes a lot more sense now, and it's logical. The original J60 or JB Onan on this device has 60 cubic inches displacement and a compression ratio of 6.5:1. It was a popular engine used on the 7.5B Onan generator, capable of 7500W at 1800RPM. I could not find a definite horse power spec for this engine, but it must've been capable of about 12 HP at 1800RPM, and maybe up to 17 HP at around 2600RPM.

The engine currently in the trencher's spec'ed at 15 HP, but it's about half the displacement of the J60/JB engine. I think clearly this engine is underpowered. More reason to kick myself for not getting that Hatz 26HP diesel a few months ago

[Eugen]

H
Wonder if anyone could recognize these markings on the hydraulic pump

[Eugen]

I just thought I had my ramble for today but now I feel another one building up.

You all thought perhaps that the trencher saga will slowly dwindle to and end, and having the crawler and backhoe somewhat functional marks the beginning of that end. Well, what can I tell you, this might not happen yet. Here's a preview of the next season.

Remember how I said the engine struggles? I've been keeping an eye on the market for many months for a diesel engine of about 20 to 26 hp. There were none until two days ago when one came up for sale at one of those too good to be true prices. Against all common sense telling me that too good to be true really means too good to be true, I tell the seller I want to get that engine. The description said 'runs like a top' so I'm thinking even if 75% of that rings true, it's still a good deal. Pictures didn't look too bad, and the distance to it manageable. From what I've see on the market so far, running diesel engines of this size and at a decent price don't last long at all, so you don't have much time to ask questions or sit on it, if you want it, you shoot first and ask questions later. But I value my life so I did say to about it, and she didn't object so I went for it, thinking that I can deal with details later.

After reaching a deal with the seller, wise little me starts looking for the specs on the Kubota D1703 engine.

It was a pretty engine when it was new. Of course the one I get will look a lot worse, but hopefully it runs and I can use it.

Hm.. somehow it didn't cross my mind that it could possibly not fit in the crawler, seeing as to the large empty space it has in the middle, where the original Onan J60 was. Plus this crawler was equipped either with the Onan, or a Deutz engine. Still, I went and measured the cavity in the crawler and compared with the specified dimensions of the D1703 engine. It might barely fit.

The plan is to pick the engine up tomorrow.

To make matters more fun, it's missing the fan, radiator, exhaust, and more importantly, a bell housing adapter to the hydraulic pump.

[thebuildist]

You just HAD to go and make us all jealous! I hope she's a runner!

Bob