LT40 Alternator Mount Issue

Ga Mtn Man · February 23, 2014, 07:31:11 PM

I was checking the alternator belt tension on my LT40HD when I noticed the alternator had quite a bit of fore and aft movement. Further investigation revealed that one of the two bolts that hold the alternator mounting bracket to the engine tilt plate weldment was missing. To get better access to the bolts I removed the alternator and the mounting bracket and found this:

The bottom bolt is sheared off in the hole and if you look closely at the top hole you can see the shiny ring at the bottom of the hole caused by the bolt bottoming out. I put the bracket back on with just the top bolt and confirmed my suspicion that the bolt bottomed out before tightening properly against the bracket. Also you can see the pattern left behind by star washers that were placed between the bracket and weldment, I assume to help keep the bracket from moving. Having the star washers in that location effectively creates a pivot point with the weight of the alternator and the vibrating pull of the belt levering on that point. This doesn't seem like a good idea to me and I suspect it is responsible for the bolt shearing off. I extracted the broken bolt, used a shorter bolt for the top hole and left off the star washers and all is well again (assuming the bracket doesn't move).

Anyone else had a similar problem?

Sixacresand · February 23, 2014, 08:45:04 PM

GMM, You found the problem during an inspection and got it fixed before it broke down the job. That's what you call preventative maintenance. Good job. I will watch out for that on my mill.

Chuck White · February 23, 2014, 09:17:54 PM

Good catch, GMM!

MartyParsons · February 23, 2014, 09:37:00 PM

Hello the star washer would be to help with grounding the alternator. I have never see this issue. I would think the hole should of been drilled through?
Marty

Brucer · February 23, 2014, 10:40:14 PM

I had a similar problem with the box housing the EFI computer on my mill. There were two very long bolts running to the base of the engine, with star washers to cut through the paint and ground the unit. One of the bolts fatigue failed and it certainly looked as though the whole unit could rock on the star washers, causing excess vibration.

As it happens, my unit already had a separate ground wire so I got rid of the star washers. In your situation you could sand off the paint and apply a conductive grease to prevent the bare metal from corroding (IF grounding becomes an issue).

backwoods sawyer · February 24, 2014, 01:23:30 AM

I have a different mount then yours but have had alternator bolts shear off and guards crack from vibration as well as holes waller out in the mounts. The Kubota is mounted solid to the head and the alternator gets a lot of vibration, I Keep the bolts tight and check regularly.

Ga Mtn Man · February 24, 2014, 08:24:48 AM

Quote from: Brucer on February 23, 2014, 10:40:14 PM
I had a similar problem with the box housing the EFI computer on my mill. There were two very long bolts running to the base of the engine, with star washers to cut through the paint and ground the unit. One of the bolts fatigue failed and it certainly looked as though the whole unit could rock on the star washers, causing excess vibration.

As it happens, my unit already had a separate ground wire so I got rid of the star washers. In your situation you could sand off the paint and apply a conductive grease to prevent the bare metal from corroding (IF grounding becomes an issue).

The alternator does have a chassis grounding wire but think I will take your suggestion. Can I find conductive grease at an auto parts store?

Nomad · February 24, 2014, 06:00:51 PM

Quote from: Ga Mtn Man on February 24, 2014, 08:24:48 AM
Quote from: Brucer on February 23, 2014, 10:40:14 PM
I had a similar problem with the box housing the EFI computer on my mill. There were two very long bolts running to the base of the engine, with star washers to cut through the paint and ground the unit. One of the bolts fatigue failed and it certainly looked as though the whole unit could rock on the star washers, causing excess vibration.

As it happens, my unit already had a separate ground wire so I got rid of the star washers. In your situation you could sand off the paint and apply a conductive grease to prevent the bare metal from corroding (IF grounding becomes an issue).

The alternator does have a chassis grounding wire but think I will take your suggestion. Can I find conductive grease at an auto parts store?

Yes, any Napa should have it. Otherwise, try a boat shop or marina.

Jim H · February 24, 2014, 07:26:15 PM

I had the same thing happen a couple of years ago. I used a grade 5 bolt to replace the one that broke.

sawman · August 06, 2015, 08:16:30 PM

Dad said this happened on ours today. Both bolts broke on him.

Sixacresand · August 11, 2015, 09:11:42 AM

Georgia Mountain Man. Your ears should have been burning this morning. Found this going on this morning before starting up. Easy fix, gotta bring out the Metric tools.

Ga Mtn Man · August 11, 2015, 09:48:09 AM

Did it fall off while you were running?

This is an assembly/design defect that WM needs to correct. Anyone from Wood-Mizer reading this?

beenthere · August 11, 2015, 11:37:10 AM

Hard to draw any firm conclusions from the few facts that we know.

Sixacresand · August 11, 2015, 11:51:18 AM

Quote from: Ga Mtn Man on August 11, 2015, 09:48:09 AM
Did it fall off while you were running?

I really don't know how long the bolts have been broken. Tbe tension bracket was keeping the alternator from falling off. I noticed with the replacement bolt the top bolt bottomed out before compressing the lock washer so I added two spacers. I saw this your in original post. I did not remove the star washers but do not see any need for them either. There is a ground cable attached. The next time they break I will take them out.
Since it is still under warranty, I notified WM of the problem. Hope it is a defect that WM can remedy easily. Meantime they are sending me two new replacement bolts.

pineywoods · August 11, 2015, 02:23:41 PM

I have seen the exact same problem on a friends super. Matter of fact, I welded up the broken parts for him and installed new bolts. BUT, that was on a 97 mill with 7500+ hours on it. Problem seems more prevalent on mills with diesel power, they do shake and vibrate a bit more.

POSTON WIDEHEAD · August 11, 2015, 04:18:09 PM

Would the cause of the breakage be from traveling and hitting pot holes, rough dirt roads, etc.

I'm probably wrong as usual, but I don't think that would happen on a stationary mill.

Sixacresand · August 11, 2015, 04:37:07 PM

Quote from: POSTONLT40HD on August 11, 2015, 04:18:09 PM
Would the cause of the breakage be from traveling and hitting pot holes, rough dirt roads, etc.

I'm probably wrong as usual, but I don't think that would happen on a stationary mill.

Could be. Mine is not stationary.

Jim_Rogers · August 11, 2015, 06:50:35 PM

Today, one of my errands was to take my spare alternator to the repair shop to have it rebuilt.
They tested it and it worked fine.
The mounting bracket on the front cover had an oblong hole in it and they are going to replace the front cover.
Hopefully for only $30.
I was expecting to pay over $100 for a rebuild.
I'll let you know how I make out.
Jim Rogers

Cutting Edge · August 12, 2015, 01:06:09 PM

I've observed the same issue on an LT40 Super with a 38hp Kohler .

Bottom bolt broken off below flush, identical to the picture Ga Mtn Man posted.

Jim_Rogers · August 12, 2015, 09:50:18 PM

I picked up my alternator today, $40 for a new end including installing it.

Jim Rogers

mometal77 · August 13, 2015, 06:16:24 AM

I found it harder and harder to find (rebuilt kits) for anything. I did find a rebuilt kit for my cummins starter which was 70 bucks on craigslist a guy in utah sells them cheap. Vs from the dealer a lot more money i was quoted almost 600. You take the serial and input it into e bay.