MTFCA Forum

How do I know if my bendix spring is good. I have the speedster project engine back together and now my starter is making a strange sound when cranking. I noticed my spring "eyes" were not lined up or straight across from each other. Is my spring weak and not letting the bendix act right ?? I am using a 12 volt battery and about 8 foot of small 12 volt cable to help reduce the shock to the bendix. I have always did the long cable solution to 12 volts with no problems before. I have a rebuilt starter and I rebuilt the bendix last time I had it off. Im pretty sure the spring eyes were lined up then. The only thing I noticed this time was the mismatched spring eyes. So could that be my issue... Im unsure what a weak spring would cause ... Thanks .....

Spring eye bolt holes should be directly across from each other.

I sold my Model T in 1996 and after the buyer passed away in 2001, his widow contacted me and I bought it back for what I sold it to him for. In the time he had it, he converted it to a 12V system. In changing it back to a 6V system, I discovered the bendix spring had been destroyed by the starter by slamming the bendix gear into the ring gear. The first two photos show the spring from different angles. Note how the spring is distorted and the screw holes are on opposite sides. The forces necessary to distort a hardened bendix spring cannot be good for the starter, the bendix, the ring gear, or the engine in general. The third photo shows the new spring I bought to replace the mangled spring. Notice how the screw holes are in line with eachother. I would recommend you replace the spring and go back to a 6V system. With a 12V system providing power for a 6V starter, it will only get worse with continued use until something breaks. Jim Patrick.

The small cable will not keep the starter from slamming into the flywheel. It is especially bad if you should forget to put the car in neutral before you hit the starter. Unfortunately, the smaller cable will only drop the voltage after the gear starts to turn the flywheel. Before it hits the flywheel you have the full voltage on the starter. since you converted back to 6 volts, all you need to do is replace the spring, however if you want to keep 12 volts you need to rewire the starter. You can purchase one made for 12 volts. There is a way to convert a 6 volt starter to 12 volts, but I will let someone else describe how to do it. It has been on previous posts.
Norm

quick question,

How are the repro bendix springs these days vs the NOS ones? I run 12v.

Thanks,
Tim

Thanks for the reply. I have always used 12 volt with long cables on my cars and this is the first spring I have hurt. I may have just been lucky ?? Since this is on the speedster project I do not really need the 12 volt. I may just get a 6 volt battery for it. Ill have to change my cables and also get a 6 volt coil for the Bosch distributor.

Good question Tim. I would also like to know how the repro springs are. I'm out of NOS . I used what I thought was a good used one last time but it appears it was not good even though its eyes were straight across at that time. I have not started the engine many times since I put the starter on last time.

Thanks for the input ....

Repro springs work fine as long as they are used on 6V systems. My pictures show what happens with a stronger original spring when used with a 12V system (it is only my opinion that original bendix springs are stronger. Of course I could be wrong) so, I shudder to think how much worse it would have been had my spring been a repro. If the bendix spring had shattered as the engine started, the hardened pieces could have caused massive damage to the engine. Jim Patrick

Basically, the purpose of the bendix spring is as a shock absorber that absorbs the shock of the bendix gear as it meshes with the flywheel ring gear and starts turning the heavy flywheel from a dead stop. The 6 volt starter provides the proper amount of torque to start turning the flywheel and then disengages and returns the bendix gear back to its’ proper position out of the way of the ring gear, once the engine starts and the flywheel gains enough momentum to disengage the bendix gear from the flywheel gear without stressing and unwinding the bendix spring.

Needless to say, the 12V system provides double the necessary power and thus, double the torque needed to start the engine. The bendix spring was not designed for this kind of torque so that when the gear slams into the flywheel ring gear, the bendix gear goes beyond the shock absorption potential of the bendix spring and unwinds the spring, distorting it and destroying the shock absorption and gear return capabilities it was designed for. Over time, the spring will almost certainly break as it looses its’ flexibility by being unwound and distorted on the shaft, eventually making the spring so loose as to be unable of disengaging the bendix gear from the ring gear and returning it to its proper position out of the way of the spinning flywheel. Eventually, without the shock absorbing qualities of the unwound bendix spring, if the spring does not shatter, the bendix gear will break the softer teeth of the ring gear, the replacement of which, requires removal of the engine from the car and separation of the transmission from the oil pan. A major job if you want to be able to start the car with a starter.

To all who are reading this... if my interpretation of the function and purpose of the bendix spring is incorrect, please feel free to correct me. Jim Patrick

I have a Becker 12 volt starter. It was still deforming bendix springs. I started using a Model A bendix spring and have had no trouble. You have to be careful with the two spring bolts. Somtimes the heads are too thick, combined with the thicker spring it will rub the bendix cover. I have had to file down the bolt heads for better clearance. The bolts have to be tight and the lock washers very tight.

Model A springs are thicker. I found they dont fit inside the cover. The new covers are smaller than stock.(Be aware) & have to be carefully centered.
Good to know its "possible" to fit an A spring. Normal A springs(late, non AR) have eyes for 3/8" bolts.
Are you using early springs, closing the eyes, or using 3/8 eyed springs as is?
What is a Becker starter?

The repop springs I used to get from Bobs were spot on. I presume he bought them from one of the other major parts suppliers.

There are/were repops made where the spring edges looked sharper than stock. They were a bit weak.

I have found period replacement springs that were an in between thickness to a T or A. With the correct 5/16 eyes of course.
I steered them toward Howard Genrich when he bought a rebuilt bendix every other year.

I have also found NOS replacement labeled springs with the eyes 90 degrees apart.

So, you can see there is a whole range when it comes to usable T bendix springs.

What Norm said about using a 12V cable is correct. It doesnt reduce the BANG, it slows the starter motor down a bit after engagement.
Opposite of what is desired.
Neither does the use of a bendix spring as a resistor between the starter post & the cable.

Jim B. The bendix spring makes a softer connection between the drive head & the body. It doesnt have any effect on the drive gear's return.
The little pin & spring inside the counterweight's edge rides on the top of one of the flat threads. Once the motor is started, The gear is kicked back. The pin holds/retains the gear in a rear neutral position in the slightly recessed area behind the thread until flung forward into engagement with the next start.

replacing the T bendix spring with an "A" spring to avoid damage to the spring simply moves the damage further into the system.

I would personally prefer to replace the bendix spring rather than the ring gear, which is now taking the full brunt of the 12V bang.

Fortunately, I don't need to replace either part, for reasons which are apparently not obvious to a lot of people.

Donnie, I think you've just been lucky...and you know the fix...

Besides cushioning the initial engagement, I believe the correct Bendix spring in good condition helps kick the starter pinion out of mesh as soon as the starter motor is disconnected from the battery, and before the ring gear is moving very fast. Starters that disengage with a screech may have a weak or damaged spring, or a gummy thread.

"What is a Becker starter?"

Several years ago Larry (LD) Becker was converting 12 volt Delco starters with a new shaft and mounting to bolt up to a model T. They were excellent starters, less bang into the ring gear. Larry passed away, there was a Family Feud over the business between his two sons. Quality went down and eventually they quit making them.

jsaylor wrote: ↑

Sat Mar 04, 2023 6:53 pm

"What is a Becker starter?"

Several years ago Larry (LD) Becker was converting 12 volt Delco starters with a new shaft and mounting to bolt up to a model T. They were excellent starters, less bang into the ring gear. Larry passed away, there was a Family Feud over the business between his two sons. Quality went down and eventually they quit making them.

Was that starter built with a new aluminum cast model T looking end?
If so, have seen them. thank you.