Stripped some bolts - how to easily fix?

[captinjack]

have a chinese Kama 554 tractor that I recently noticed that a couple of bolts were loose. I tightened them and found out that they were loose again in a short time. After the third time, I removed the bolts and it appears that they are stripped of the threads and I'm also concerned that the female threads are stripped as well.

This is a picture of where they come from.



It's the bolts holding down the 3 pt. hitch tank. Only the two bolts closest to the top link are stripped. I'm guessing that upward forces from the back hoe and ground engagement implements has caused this problem.

Here is a picture of the two removed bolts.



And a closer up look at the worst threads.



I appears that some of the female threads came out with the bolts.

My question is.............How can I easily fix this? I know the tank would have to be removed to do it right, but I want to try some other easier fix first and do the good repair later when I MUST remove the tank for other reasons.

I'm thinking JB weld or red lock-tight or something like that. A heli-coil insert is what would be best, but I know there is someone out there that has been there before and would have some real life experience to help me out.

I don't know whether the female threads are closed off at the bottom or whether the theads are open and a longer bolt could "go thru" making bolt length less important.

I'm planning on buying new harder bolts and giving it a try the next time I get to visit my property.

Thanks in advance for any tips. I'm thick skinned so if I'm "peeing down my leg" thinking I'm getting warmer, don't hesitate to say that I'm SOL and will have to fix it right.

[bradblazer]

Ouch. I'm at work and can't see your pics. but the description is good. Seeing the problems Rob had with his 3ph box sliding around was a big part of my incentive for making the backhoe subframe mount.

As I remember there are some horizontal threaded holes on the back of your 3ph box and differential. The ones on the hitch box may be the top link bracket mounts. I have thought about making some stout brackets that would tie the 3ph box with the differential case below it using those holes. Maybe also tying in the frame that supports the lower links and drawbar.

That may be a solution for your temporary fix. When you do the permanent fix see if there are some places where you can add dowel pins between the differential and hitch box castings. The lack of such dowel pins is a significant design flaw in this model. I wouldn't be surprised if they were in the original design but omitted in manufacturing.

It is okay to apply a shear load to a bolted connection where the plates are in metal to metal contact and the bolts can be torqued to a high preload value. Unfortunately, the hitch box requires a gasket.

For a gasketed connection you need close tolerance dowel pins or similar mechanical interlocking features to take the shear load. Bolt holes always require clearance so a bolt just can't properly constrain a gasketed assembly in shear.

Brad

[GuglioLS]

Hi Captinjack,

Long time no here. If it were mine, I'd get hardened replacement bolts, with blue locktite. And forgo the JB weld or red locktite simply because it will make it all that harder to remove and repair once you have the time to do it right. With any luck the threads in the casting are sill enough to hold a new bolt with good threads.

Another idea that just came to mind is to use a stud or threaded rod with a nut on top instead of a bolt head, that way you could use JB weld and anchor the rod semi permanently into the casting.

Whatever you wind up doing I wish you an easy repair. Good luck.

Larry

[captinjack]

I haven't been away from the site. Just didn't have much to contribute as you guys way out class me with your abilities. I am in awe.

Thanks for the reply fella's. I can't figure out what the bolts are yet. I didn't have precision measuring tools handy, but will tonight and I'll post the dimensions tomorrow. The damn parts manual is worthless as it lists the bolts as being 120 mm long and these are about 105 mm long. Go figure. The threads are larger in diameter than the shank. HUH?

I am not done investigating what I'm going to try first, but I'll probably talk to Chip to see how much work and complicated it is to remove the lift box to fix it right. I did take the cover off the lift box once and there sure is a lot of stuff in there. Maybe the valves and cylinder can stay if the box is open at the bottom. Now that would be too easy. I also was thinking about reinforcing the box connection with a gizmo that would fit under the bolt head and connect down to where the PTO shield connects.

Brad
I think you are correct about the shear forces on the box as being the cause of my problem. I will install locating dowels around the perimeter when I do take it off. That's a great idea plus I'm going to look up Rob's backhoe brace mod to once again see how he braced his to I believe the ROPS. That should reduce the shear force as well.

[bradblazer]

Jack,
Sounds like you have a plan. I saw your pics. Do you have a picture of your backhoe connection to the tractor? If it relies on a rigid toplink for all downforce I can also envision a tensile failure of those bolts. A bracket connecting the backhoe to the drawbar frame may be the ticket for providing the downforce. I think Rob's subframe links provide that function for him.

I'm sure you saw my subframe pics. If you want to try anything like that and have any questions let me know.

[3RRL]

Hi Jack,
Just saw this thread.
Man, I hope the female threads are still OK so getting new (and I would try at least one longer) bolts might do the trick. You know from what Brad said I had a similar problem, except my bolts were not stripped. I fixed it by using ample amounts of lock tight. Plus, once I got my backhoe subframe, those bolts have not come loose except once. I do check them from time to time and "snug" them up best I can. Problem is that they are very hard to get to ... just to tighten them up. Adding dowels like Brad suggested is a great improvement, but appears pretty hard to do from what I remember.

My backhoe subframe is not as good as Brads.
Mine still has some play in it, but not enough to put as much pressure on the top link as there used to be. The top link connection moves in and out slightly like for draft control, but that's all. If you're going to make a subframe, I'd make it more like Brads.

I do have many photos of when I did the hydraulic box repair.
I see I never posted that thread on this forum so I'll work on moving it over. I was going to give you the link to Joe's forum, but it appears the thread no longer exist there, so I'll try to re-create it from my back up files. I'll make it a new thread here so as not to disturb yours.
Look for it under the Kama heading. I'll call it "Hydraulic Box Repair, Kama 554".
Rob-