What causes low band chattering? Is it an adjustment issue or a lining issue? Or both? It seems that lately just about every start is not as "smooth" as it used to be. I have cotton bands on this T just so everyone knows. Thanks.
I'm no expert, but I would say it is an adjustment issue as in the clutch band is not tight enough to fully stop the clutch drum, which is what is necessary to fully engage the low speed. Perhaps others can correct me if I am wrong but, if it chatters when the clutch pedal is pressed down, to engage your low speed, it is an indication that the drum is still spinning under the band and that the band is not tight enough to fully stop the drum from spinning. If the band were tight enough to stop the clutch band and fully engage your low speed, then I doubt that there would be any chatter. Jim Patrick
Chattering in low with cotton band linings is a new one on me. I've only experienced it coming to a stop on a downhill slope and rarely with cotton. Perhaps some of your lining has torn loose. Open the inspection door and peer inside. If a patch has torn loose it will be at one of the ends. It could also be the lining is simiply worn down and needs replacing. Usually they wear on one side more than another and that kind of wear can only be detected with the band out of the car. With a pre 26 car, the brake band lining is the first to go, however.
Some folks try adding a quart of ATF to the crankcase. Personally, I've never had success with that.
I agree the first step would be to adjust band.
If all else fails, my bet is that the lining is worn and needs to be replaced.
Band chatter in Model Ts dates back to 1909, and is due to stick/slip between two moving parts. Chatter in any mechanical device will always be traced back to unwanted resiliance/flexibiliby in some part of the mechanism. Brakes and reverse are self energizing bands and chatter there may or may not be due to the same thing which will cause low, which is not self energizing, to chatter. Plenty of patent fluids and methods have been employed over the years to combat this, with mixed results.
I'd test the front drive shaft bushing, U-Joint, and drive shaft fore/aft for wear. You can do this through the u-joint rivet access plug.
Then I'd relax the low band adjustment (right side hog's head) and give the low pedal a good working over and see how wobbly it is in it's bushing. Excessive movement here may be a clue as to why the band and drum are experiencing stick/slip. Old style bands with the low shaft supported on both ends was a far superior design, though, of course, kept one from using removable ear bands.
Wear in any one component may be the final straw that causes the root cause of chatter to become apparent. Example: cotton band wears down, and becomes harder - result is that it is now more aggressive in it's take up and causes the low pedal shaft to flex enough to cause chatter. The worn cotton band is a contributing factor, but the worn shaft is the root cause. This is why (for instance) changing bands makes a problem go away for awhile, and then come back (root cause was not rectified).
Not saying this is what you have, but to explain that there are other possibilities other than simply worn bands.
That makes tons of sense Scott. Thanks for your contributions.
I believe LOW is self energizing as well.
If so, then none of them are on a RHD car, correct?
Only when you are in the southern hemisphere Seth.
I can't say, I've never studied a RHD car. But, on a LHD car, the BRAKE and REVERSE band tighten by pulling the right hand side of the band toward the left hand side of the car (CCW as viewed from the driver seat). The LOW band tightens by pushing the left hand side of the band toward the right hand side of the car (CW as viewed from the driver seat).
When the car is moving forward, the BRAKE drum is rotating CCW, the BRAKE band tightens CCW, therefore self energizing.
With the car at rest, in neutral, the REVERSE drum is turning CCW, the REVERSE band tightens CCW, therfore self energizing.
With the car at rest, in neutral, the LOW drum is turning CW, the LOW band tightens CW, therfore self energizing.
Could someone post pics or at least descriptions of how the RHD hog's head tightens it's bands?
Kudos to Hal. I sat down with a sketch and realize that he's right in that low is also self-energizing. However, I don't think that my error here negates the premise that unwanted flexing or deflecting of parts frequently contributes to band chatter.
One last thought. Unless you're on a hill, most T's can be started from a stop with the spark slightly retarded and the engine at idle speed. Many if not most folks that I've seen will rev the engine like a modern car and slip the clutch. These cars weren't designed to be driven like this, and a few cars (but not all) that I've driven which had a tendancy to chatter in low, settled right down if eased into low with a very low reving engine. This really didn't solve the underlying problem, but illustrates the effect of driving technique vs inherent wear in the system.
I've seen a lot of people drive like that myself. They probably all have Kevlar bands or intend to get them next time, not realizing their band wear problems stem from their driving technique.
I have wood bands in my TT and sometimes, not often, but occasionally, have a little chatter while braking, usually at the very end when I am almost stopped. When you brake, the band is slipping. Nothing you can do about that besides slow down as much as possible with the throttle before applying the brakes (Or some other pedal if desired). But LOW and REVERSE? No need to slip them hardly at all. I give it enough gas to not go dead, slip the band just enough to make the thing start moving, then stab the pedal to the floor while simultaneously giving it some more throttle. I bet the band doesn't slip more than a revolution or two before stopping the drum.
As for what causes chattering.....I think you may be right about wear in various parts of the system.
Well, I should have stuck to my guns...am too lazy to open up the transmission door to watch, so I'll include a link which will demonstrate what the drums (gears) do when the engine is running. See:
Run through the "gears" and you'll see that all of the drums will spin with the engine until held in place with the bands. Since both the reverse and low drums rotate in the direction of the engine, then the low band is not self energizing.
Don't try to run it through the gears with the engine running and the inspection cover off, or you will get a face full of oil! Have someone crank it with the rear wheel jacked up while you watch it.
Thanks Norm. I'm aware of that!
Pull your transmission door off. Have someone turn the crank for you. Look at the Low speed drum. It turns opposite the engine when the car is in neutral.
The animation does not appear to be correct. In neutral, it shows the triple gears skidding around the driven gear. They should be in mesh. In high gear, it shows relative motion between the flywheel and the triple gears. They would be locked together, ie, no rotation of the triple gears on on the triple gear pins. I don't know what software was used to do the animation. Perhaps it is done correctly, but due to 'stroboscopic' effect (My word, maybe not technically correct), it appears to be going the opposite direction kinda like wagon wheels in the movies when the spokes per second and frames per second don't geehaw.
At any rate, go look at a REAL T tranny, and you will see that the LOW drum turns opposite the engine when the car is in neutral.
Thanks Hal. So, apparently not everything on the web is true?
Unfortunately not. I like the way that animation is done. I just wish it were correct.
I will admit to having an advantage over some folks when it comes to T tranny's. I have a T tranny, from 3rd main to 4th main, set up on a display stand where you can rotate the flywheel and hold each drum still and see what happens. I painted each drum, and it's gear, a different color. I knew the paint on the gears wouldn't hold up real well, but you can still see what color each one is. I take it to car shows and display it in the back of my TT. It comes in real handy when someone says "So what do all those pedals do?" It makes explaining the T tranny much easier.
I had intentions of adding some sort of reduced width band to the thing, but never got around to doing it. It would somewhat obscure the drum, which I didn't want to do. Mostly, I haven't done it because it works fine like it is. You can hold the drums with your hand.
You actually can run the T with the trans door removed and not get deluged with oil. Do it only at idle speed. You may get a few drops at first but it will not come flooding out. I've done it myself. You will also see nothing but a torrent of oil washing over the top of the transmission drums. So, the whole experience is interesting but not of much value.
Do you have any pictures ( or maybe a video) of your display transmission to share? I was thinking of doing the same sort of thing.
Years ago at Pate SM the Dallas club had a T motor with a Plexglass trans door. I was amazed at how much oil is moved even at an idle. Without the door it would make a mess in a hurry. As for the band, I was always told not to slip the band anymore that you had to - push it to the floor.
I couldn't find any on the computer. I'll go out and take some tomorrow, hopefully.
Here's a few shots of my display tranny. I made a clutch spring out of some 1/8" dia. wire so I could compress it by hand. All the clutch discs are in there in their proper position. I thought about staggering them 2 and 2 or 3 and 3, but I tried it in the stock position and have a free neutral. I oiled them good before assembly. The block of wood is to hold the spring in the compressed position, ie, NEUTRAL. The front bearing (Rear main bearing) is oak. The rest of the base is just pine.
Maybe your band is bent and not making very good contact on the drum making it chatter. Your linings could also be loose.
Thanks, Hal. That looks like a great teaching set-up...maybe a good project for the winter.