1986 TMC 102A3 - broken frame members

jraynor · June 30, 2018, 05:45:00 PM

Hello all,

During my floor removal and replacement, I found a few members that are broken. There are 4 total, 2 on each side. 3 I can weld in place but the other I will have to jack the frame up to line it back up before welding.

My question is, has anyone else seen this before? Should I just weld them back and forget it or look for an underlying issue?

I will attach 5 photos. A zoomed out image and the 4 breaks .

All information is appreciated

jraynor · June 30, 2018, 05:45:55 PM

Here is the other 2 images. One of which is the worst to weld

Astro · June 30, 2018, 06:11:47 PM

Although I havent any direct knowledge of your model bus and i can't tell if its a welded box beam configuration, without understanding the root cause of the breaks, I would doubt welding would fix it for long. I would consider doublers attached over a wider area where possible.

Pattern appears to be weak structure points and/ or too much torque applied to the frame. It looks like what i would imagine to be the bus driven a bit with deflated air bags or some other version of improper suspension or motor dampening... Just thinking out loud....

brmax · June 30, 2018, 06:33:37 PM

On a side break as there you could in my opinion fabricate an addition plate to weld on and bolster the break. A similar design like a widened octagon. Or a elongated diamond shape is quite common.

Good day

Floyd

buswarrior · June 30, 2018, 07:51:09 PM

MCI have been cracking since the beginning of time.

Keep your perspective, howmany miles to get like that, vs how many miles you are going to put on...

Weld 'em up and add a bit of strengthening where you don't like your welding.

Pay attention to the body panels outside,they tell a story in their ripples, bends and tears.

Happy coaching!
Buswarrior

luvrbus · June 30, 2018, 08:59:20 PM

With the design on buses using stainless and steel since stainless has no flexibility it finds the weakest point to crack from flexing, most of the time it is the stainless steel that cracks on MCI's and Prevost , gusset and welded it all you can do

buswarrior · July 01, 2018, 06:08:03 AM

Yes, stainless steel has been a blessing and a curse to the bus industry.

The horrible rust issues have been replaced with massive frame cracking, with the stainless being much stiffer, it cracks instead of bending, and stainless welding repairs are not as simple as old steel.

Theindustry is trying out an "in the middle" steel that is rust resitant, but more flexible, I have not heard how this latest fad is working out...

The busnut will be entering the stainless era now, and having to add stainless welding to the skill set.

Happy coching!
Buswarrior

jraynor · July 01, 2018, 06:46:02 AM

So this isn't regular steel in these areas but stainless steel?

luvrbus · July 01, 2018, 06:57:02 AM

It can be both just use a magnet if it sticks it is metal if not it is stainless that is the way I tell on the painted metals,on later models I know that area is stainless never been there on a 102A

bevans6 · July 01, 2018, 08:16:35 AM

Where in the chassis that that section? front, middle, rear, part of the bulkhead that the engine hangs from? If it's stainless you should try to TIG weld it with a flux or gas shield inside the tube, or you get oxides forming inside the weld that lead to cracks (again). Try to reverse-engineer why the cracks happened, so you can get your plan to fix it right.

buswarrior · July 01, 2018, 08:56:43 AM

I doubt any stainless in frame for a 1986.

Too soon.

The hapless Flyers, 1990 vintage, werethe buses thattaught the political administrators about the word "rust", then the marketers taught them the word "stainless" with no other important info... and into the spec it went, and manufacturers either built with it, or lost the contracts...

Happy coaching!
Buswarrior

jraynor · July 01, 2018, 09:23:10 AM

These cracks are in the rear where the return vent starts right over the rear wheels. It's the frame that crosses over the middle of the 2 tires from side to side. It's pretty severe and probably irreversible at this point. I placed a jack underneath between the tires as far as I can get and no results as far as moving it. Right now I plan to weld everything together as is and add some strengthening plates to hopefully prevent any more breakage. I can't tell what the culprit is

Jim Eh. · July 01, 2018, 09:27:21 AM

Dill a 1/8" hole at the end of any crack that you can before any repair. This will help in preventing the crack from migrating further. Drill, weld, plate, prime, stir, enjoy!

luvrbus · July 01, 2018, 09:52:30 AM

When repairing make gussets in a diamond shape with rounded corners or if you use a L shape round the welding surface on each end, never do a plate or gusset with straight welds it will just crack again and use T1 steel to make your gussets then it will last.
Sam Caylor the MCI guru won't repair those cracks I have saw him scrap some nice buses just for cracks

jraynor · July 01, 2018, 11:44:51 AM

Post weld update.

Well I can say it's hard to do a good job at welding when you haven't done it since sophomore year in high school ~11 years, but trail and error leads the way. Here are my after pictures. I placed a single diamond gusset over the 2 minor cracks. For the other cracks I welded the cracks and welded a set of corner gussets turned different ways in each weld. I didn't bother with the lower portion of the member as I believe the extent of the break is at it's max. The weld will look better once I either fix or replace my angle grinder. As for now, ites grind and prime then forward towards the front with frame prep for new plywood.