MTFCA Forum

I put new bushings with shaft seal, brushes in my starter to resolve the oil leaking out of the starter peep hole. It spins fine and in the right direction. After I installed the bendix and cover, I pressed the starter pedal and I heard a clunk and then free-spinning of the starter. I took the cover off and found the outer spring bolt top in the cover. It sheared off flush with the outside of the #5019 nut. The key was still in the shaft and all looked right according to the diagram. It worked fine before I removed it. What can be the cause of the bolt shearing off? I ordered a new bolt set with lock tab washers.

Was it a new bolt, or reused bolt? Is it possible that the bolt was overtightened at assembly. Was it a "real" bendix bolt, or a turned down, modified, hardware store bolt?

Are you using the 6 volt battery? Some people try to use a 12 volt battery in the car with a 6 volt starter. This can lead to breaking the bendix, the spring, or the gears on the flywheel. If you must use a 12 volt battery, be sure to have the starter rewound for 12 volt use. If you are using the correct starter to match the battery, then you must have had a defective bolt. One other thing which could cause a problem would be to hit the starter with the parking brake forward in high gear. In that case the engine would not turn unless a rear wheel were jacked up.
Norm

The bolts from vendors appear to be grade nothing. Not a new story. Use originals or period replacements. New tabbed lock washers are OK.
Same failure just happened to a new member's first T.
No mystery. Bendix bolt failure has been common for the 40 years I have been in the hobby.

I reused the same bolt, origin unknown but looks rough. It could have had stress in that area and that was it's last dance. 6V, no mods.

That bolt appears to be an original. Originals do fail also. The bolt seats @ 2 points @ the same time. One being in the shaft recess & secondly on the spring loop. If the bolt, when tight doesnt lock the spring down, the bolt shaft gets a constant working.
Tightening the bolt a bit past its shear point fatigues the bolt at that very spot where it separated. That over torquing on the soft repop bolt shears in the same spot.

You should confirm you have the correct bendix spring.

That bolt has done its fair share for a long time. Not too shocking that it finally retired.

Correct bendix spring is essential. I seem to recall someone in the past posted a comparison picture of a Model T and a Model A bendix spring. For those like me who have both a T and an A, it is helpful to know the difference.

I can post a picture tonight of the spring but it appears to match the digram and the starter was working fine in spite of the worn bushings and brushes. The spring was not preloaded when I ran out the two bolts, does it get assembled in static state?

RecklessKelly wrote: ↑

Tue Dec 17, 2024 1:08 pm

The spring was not preloaded when I ran out the two bolts, does it get assembled in static state?

Yes. That's the only way it can be installed.

Be sure the two eye-ends of the spring are aligned with each other, as shown in the diagram. If not, it means that the spring has been distorted and should be replaced.

I mounted it as in the diagram. It looks straight. Not distorted.

Jones in Aiken SC wrote: ↑

Tue Dec 17, 2024 12:50 pm

Correct bendix spring is essential. I seem to recall someone in the past posted a comparison picture of a Model T and a Model A bendix spring. For those like me who have both a T and an A, it is helpful to know the difference.

The difference in A (L11-6X) and T (L10-6) Bendix springs is the A is larger in diameter and can strike the cover, and believe the loops on the A are thicker too, making the T bolt a bit short.

Mine is as in fig.1, a little stretched past 1.75, measures 1.85 on centers and the ID is 1.75.

That spring is way better than some I have seen that were still in service.
The bolt has broken just short of full engagement in the drive head. When fitted it is meant to jam the spring eye tight on the drive head. The lock washer is there to hold it in place, like Henry's split pins. The small end does not bottom out in the drive head. It is merely a locator, so the break is where the twisting is when too much torque is applied. Let the lock washer do its job, rather than loading up the bolt excessively.

Allan from down under

I really hate it when car parts a mere 100 years old fail.

That spring does show usage. For me, $15 for a new spring is good addition for starting pleasure. Fixing busted and bend spring from under the T is a pain

Photo from forum poster on his bent out of shape spring that needed replacing.

big2bird wrote: ↑

Tue Dec 17, 2024 7:30 pm

I really hate it when car parts a mere 100 years old fail.

Planned obsolesence, even in 1926!
I wont torque it too much.

DanTreace wrote: ↑

Wed Dec 18, 2024 8:03 am

That spring does show usage. For me, $15 for a new spring is good addition for starting pleasure. Fixing busted and bend spring from under the T is a pain

Photo from forum poster on his bent out of shape spring that needed replacing.
249116.jpg

I have more faith in the old one than a new one.

RecklessKelly wrote: ↑

Wed Dec 18, 2024 9:07 am

DanTreace wrote: ↑

Wed Dec 18, 2024 8:03 am

That spring does show usage. For me, $15 for a new spring is good addition for starting pleasure. Fixing busted and bend spring from under the T is a pain

Photo from forum poster on his bent out of shape spring that needed replacing.
249116.jpg

I have more faith in the old one than a new one.

That would be misplaced faith.

That is what is called Penny Wise and Pound Foolish in England!

J1MGOLDEN wrote: ↑

Wed Dec 18, 2024 10:27 am

That is what is called Penny Wise and Pound Foolish in England!

Change the pound to dollar and we use the same saying here.

John's faith may well be on target. How many new reproduction parts are superior to original parts? Just think of starter switches.

Allan from down under.

Yes Allan. Most of the time replacements arent good wuslity and need repair of tweaking before mounting. I think every moving part has the amount of wear present on that spring, and if all was replaced, it would be a Chinese car.

Allan wrote: ↑

Wed Dec 18, 2024 4:28 pm

John's faith may well be on target. How many new reproduction parts are superior to original parts? Just think of starter switches.

Allan from down under.

The starter springs are not known to be an issue. Are you aware of any particular problems with them?

RecklessKelly wrote: ↑

Wed Dec 18, 2024 6:23 pm

Yes Allan. Most of the time replacements arent good wuslity and need repair of tweaking before mounting. I think every moving part has the amount of wear present on that spring, and if all was replaced, it would be a Chinese car.

Best of luck to you.

We are missing an important feature of the bendix spring. That is the direction the spring is wound. All the photos of Model T springs are wound correct; however, the picture of the two springs with the chart of measurements have the Model T spring wound incorrectly. Looking at the end of the spring, the Model T spring must be wound counterclockwise. If not (and I have seen it) the spring expands and wedges in the cover. My inventory of new springs have many wound clockwise that are the same size as the Model T.

Interesting. Wind direction is probably the difference between R & L springs listed in the chart above. A guy at Hershey this year had a box of NOS bendix springs for cheap. They weren't all the same, difficult as it was I passed on them as I didn't know the correct diameter or numbr of turns. Never even considered clockwise vs counterclockwise.

Thanks

T Bendix springs are wound counter clockwise. Not a lot of the others are. I think it is because on a T the Bendix is pulled in to engage on the ring gear, whereas on other cars it is driven in.
In all the years I have played around with T's I have never broken a Bendix spring. i have replaced a few distorted ones. i have left non distorted ones with bolt eyes out of line in place. For me, they have been made of indestructium.
I once found a stash of 20 or so at a swap meet, for a dollar each! The same fellow had as many clockwise wound ones. I told another fellow about these, and he told me to go and get them for him. He said they were for a Chev.

Allan from down under