Hi All, As I've dug deeper into this IH3400A backhoe, I've discovered that both the MCV and primary hydraulic pumps are toast. Based on the damage in the pumps it appears likely that the previous owner ran it out of oil while using the backhoe. Anyhow, the MCV pump is relatively cheap (about $350) but the Primary pump is about 900 bucks (I also have to replace the gear that mounts to the pump, but that's a whole separate issue). The factory style pump is an 18-20gpm Cessna SAE B 2 bolt with a tapered input shaft. Whats frustrating is that I can buy almost exactly the same pump with a straight keyed shaft (3/4 or 7/8) for around 400 bucks all day long, and the appropriate gear to fit on the shaft for about 50-100. The problem is that these pumps seem to be made for "coupler" connections to a power source, not to hold a gear. I was wondering if anyone has drilled and tapped the end of these input shafts to accept a bolt? If I had a bolt on the end I could use shims between the gear and the shaft shoulder to get the proper gear alignment. I assume the shaft is probably hardened in some form or another, but I'm hoping the interior is soft enough for a good quality tap to cut. I'd appreciate your input. Thanks.
Think I know what you are aiming at picture would help, but I. The mean time, what about a taper lock gear or sprocket on the parallel keyed shaft?
The existing pump looks similar to this, but with a larger displacement. http://www.surpluscenter.com/Hydraulics/Hydraulic-Pumps/Gear-Pumps/1-02-cu-in-CESSNA-GEAR-PUMP-26006-LAS-TAPERED-9-6371.axd This is the pump I would like to use, if it had a way to retain the gear on the shaft. http://www.northerntool.com/shop/tools/product_200329730_200329730 I was thinking I could drill and tap the input shaft where the current dimple looking thing is, and use a bolt and red thread lock to secure the gear. I've considered a locking collar, but once the gear is on, I'm not sure there will be enough shaft real estate for the collar to clamp on. Plus I've never used locking collars on internal gears so I'm not sure how confident I am in their holding power, although that is just a gut feeling, I've been wrong before.
What gear or sprocket do you want on the ouput? I guess your idea would work, but the gear would still have lateral travel? For me, I'd employ a taper lock over red loctite, but that's just me! Drilling and tapping or using off the shelf components to achieve the same end result
Are you sure you can find a gear that has the same teeth as the original one? I'm thinking that would be the hardest thing to source.
Yair . . . farmerengineer . I would have thought any good machine shop could organise a shrink fit, a grub screw into the key, a scotch key into the end of the shaft, a tapered pin reamed into the shaft, or as you say dismantle the pump, chuck it up in a lathe and bore and tap the centre hole. It depends a bit on the gear boss and how the teeth are positioned in relation to the drive gear but I wouldn't think it was a major problem . . . I know a bloke who could fill that keyway and machine/grind a taper if that's what you wanted, anything is possible it all comes back to cost. Cheers.
Thanks for the input everyone. I've talked with the manager of a local gear machine shop a couple of times and he was very helpful in figuring out what gear I need to match the internal drive gear. Turns out it's a 25 tooth, 10dp gear with a 20 degree pressure angle that is available off the shelf fairly readily. The only concern I have is that the internal drive gear is hardened, which makes me think that the driven gear is probably supposed to be hardened as well. However I know that with distributor gears you often choose one that is softer than the cam gear to prevent undue wear. Would running a high carbon driven gear with a hardened drive gear be a worry? The reason I have to replace the gear in the first place is because the one that was on the machine isn't the correct one. It seems to mesh with the driven gear, but when you roll them together it just doesn't feel right. The Gear Machine shop verified that they were indeed different pitches, the driven was a metric 2.5mod and the drive gear is a 10DP. The existing driven gear has obvious grinder marks where the previous owner must have shortened or removed a hub from a gear they had laying about.
Yair . . . farmerengineer . It sounds like you are getting on top of it . . . just as well you were suspicious about the meshing of the gears. As with all these threads I (and I think most folks folks on here) would be real interested to see what you come up with . . . some pictures in due course if you have the time to post? Cheers.
I would think the difference if any between the hardness of the gears wouldn't be important, what is important is the loading on the driven gear. If the load induced by the pump is within the rating of the driven gear, it should give satisfactory service. Usually the gear manufacturer will provide a chart, or an online wizard that will calculate the power rating. YMMV