When I rebuild my engine over last winter (2 piece crank club) I replaced both the brake drum in the transmission, and the low drum. Both were good used drums. They had to be good drums for the machinist who assembled my engine to accept them. I also installed new Kevlar band linings. I had the engine back in the car, and the car running the first of March. I probably put 50 to 75 miles on the car a week. From the very beginning I have gotten a lot of band fuzz in the oil screen, and the low band has needed adjustment about every 3 to 4 weeks all summer. I have been aware I have a problem, and figured the band was already boogered, so why not drive and enjoy the car until fall and fix it.
Sunday, the time between the last adjustment and it requiring adjustment again was shorter than the previous times, and it began slipping a little. Of course I was still 10 miles from home, and every light I hit turned red for me. Time has come to find the problem.
I assumed I had a cracked drum, but for the life of me I could not think of a situation where I had slipped it enough to crack it. I opened it up tonight, and removed the adjustment screw, and spring. I had a friend crank it over, while I watched, and I cranked it over while he watched, and there are no cracks in the drum. Has anybody ever heard if faulty Kevlar bands? It was too humid to mess with tonight much longer, and the next couple of days are supposed to be worse, but I'll get the bands out in the next week or so and see what else I can find
It is a 1927 engine, my car is a 21 Touring. Any thoughts or input?
What is the surface finish on the low drum and does it differ from the other two?
that would be my first question, too. Second would be "was it ground, turned, or otherwise machined?"
The drum looks like the other drums. There is some minor pitting, but otherwise smooth. It was not machined, just had new bushings installed
Do you have a transmission screen? In that case, is it full of kevlar fuzz?
Doug - Here a my current adventure if you want to follow along. I didn't see a crack either until I pulled the hosghead.
I've been gathering the necessary repair parts and am currently preparing to remove engine. It will be reinstalled with new good used drums and wood bands.
That minor pitting may seem minor, but it isn't. I had drums like that and when I replaced with new drums, no more fuzz from Kevlar bands. I do run a screen and it did collect a bunch of fuzz, but not since the new drums.
Did the machinist magnaflux the replacement drums or just visually inspect them?
My Fordor required two seasons of adjusting the bands before they (Kevlar) finally settled in. I haven't had to adjust them in four years now. Its a 27 Fordor and I assumed because of the weight of the car, it took a longer break-in period.
Yes I have a screen, and yes it is full of fuzz.
yes the drums were magnafluxed before they were used
I had put new Kevlar bands in the previous engine, and they hardly fuzzed at all
The instructions that Dan posted in my thread from Rocky Mountain Machine Co describe the several possible causes of lining failure.
Doug, you have to keep in mind that drums were designed to have cotton applied to them. The cotton bands take the wear- not the drums. Kevlar is way too tough for 100 year old drums as the drum takes the wear not the kevlar.
"Currently, Kevlar has many applications, ranging from bicycle tires and racing sails to body armor, because of its high tensile strength-to-weight ratio; by this measure it is 5 TIMES STRONGER THAN STEEL. It is also used to make modern drumheads that withstand high impact."
Will a cotton band fair better with a pitted drum?
All the bands seem to be yellow now.
I do believe that some bands represented and sold as Kevlar are in fact cotton.
Kevlar bands should be purchased from a reliable distributor.
My same Kevlar bands have been in use for 15 years now.
They will need several adjustments when first installed, but usually only a half a turn or a little more, until they collapse .
Then they will only need about a half a turn a year and last many years.
Of course the real secret of driving a Model T is to keep your feet off those pedals as much as possible.
"Kevlar is way too tough for the drums"
(so don't dare use it, I assume)
and by that token, disc brakes are too tough for wood spokes; high compression heads are too tough for rods; high lift cams make the engine turn too many RPM's and that's too tough for the crank; 3-1 rear end gearing is too tough for the drive shaft pinion.
Tens of thousands of sets of kevlar installed, resulting in tens of thousands of ruined transmissions (not). I am completely mystified by the broken drum I found in a cotton equipped transmission. How on earth could that have possibly happened? Perhaps because anything that has received 100 years of abuse may occasionally fail? Of course Kevlar is tougher than cotton; that's never been disputed...it can however be used successfully by thousands of people driving many many thousands of miles with no ill effects. And I can most certainly attest to the fact that with proper use, they will not even make a mark, much less wear out or break a drum.
I know and understand it's virtues and drawbacks, and have my care tuned to where I can get the car rolling in low at an idle without touching the gas. On the other hand if owners who can't start up or back up without racing the engine and slipping bands, then kevlar might not be for them.
I'm going to celebrate my kevlar bands right now by taking a drive. If the experts are right, I'll probably be taking a taxi home...so I'll let you know. While I'm out, feel free to explain how wrong and ignorant I and many thousands of kevlar users are.
Thanks Scott I feel the same. I had Kevlar bands in my previous engine before the crankshaft broke. It probably only had a couple of thousand miles on the bands and they worked as advertised. Once seated and compressed after a short period of time, they were fine. That drum had some pits in it too. As one person told me the pits hold more oil for the bands. True or not I don't know. The cracked drum in the case of my previous engine, I know how and when I did it, and it was not exclusively due to Kevlar bands, but that's another story
"Tens of thousands of sets of kevlar installed"
"used successfully by thousands of people driving many many thousands of miles"
Scott, please reference where you obtained this information as I wish to know how this information was complied and by who. Or perhaps you just made it up?
"and by that token, disc brakes are too tough for wood spokes; high compression heads are too tough for rods; high lift cams make the engine turn too many RPM's and that's too tough for the crank; 3-1 rear end gearing is too tough for the drive shaft pinion."
That's quite a leap!
We have an obligation to stop disinformation...
I was always told, do not slip the bands. With a proper running engine, retard the spark about half way, throttle all the way up, gently push the peddle down while moving the throttle a few notches down at the same time. The timing also is moved down a little, in this process. The peddle movement should be in a steady motion to it's limit and the car will gracefully move. Once the automobile is in motion then is the time for higher engine rpm's.
I am with you Scott.
Never any trouble since they came out.
We have used nothing else.
If you have problems, it isn't the bands, if they are the right make.
I installed Kevlar linings in my '27.
I bought the linings from Rocky Mountain Machine and installed them "The Kohnke Way".
That was at least 3 years ago at which time I had to adjust the bands once.
I need to take them up a bit again but they've been perfect with very lint getting trapped in the screen since I installed them.
"Kevlar is way too tough for the drums"
if ever there was disinformation, THAT is it.
BTW, just had a very nice drive on them bad ol' bands
Ditto, but on cotton bands- never an issue (unlike Kevlar)...
Herm, what process are you using to bore the holes in the cover? Beautiful work as always.
what factual evidence can you point to that there is never an issue with cotton? Dave Huson has torn down many dozens of old transmissions with cotton bands and has reported to this forum that he has seen dozens of broken drums. I have witnessed the same, though on a lesser count of transmissions.
Sorry about that, but what's good for the goose is good for the gander. BTW, lovely picture. Surprised I didn't see you on the road!
A picture of a flat road is not what I would have posted to promote kevlar! Sorry, but that's too funny.
Hopefully we can get back to figuring out the causes of kevlar lint production.
Tim R., have you seen or can you post some pictures of drums that have been worn out by Kevlar? Kevlar IS tough, but it doesn't grind down the drums. That is just silly. If it did, there would be a LOT of drums worn out by now. I have been running them for several years and the drums look just like they did when I put them in. I have plowed through mud leaving six inch deep ruts going up a slight hill, and the drums survived. That was equal to many thousands of miles of normal driving. JMHO Dave
If one drives properly and the band's don't drag otherwise due to out of roundness, then I'm sure Kevlar band's are fine. My theory is that if you drive properly and your band's don't drag otherwise due to out of roundness, then why do I need Kevlar? Kind of a catch 22.
As for Kevlar wearing drums, no I can't see it. It's not that Kevlar is harder than steel and tends to wear it or cut it somehow. It's that if one slips band's, the heat that is generated can crack the drum before any noticeable wear to the Kevlar. With cotton or wood, a high degree of slippage will still generate heat, but it will wear the band and the driver will realize the error of his ways. With Kevlar, a poor driver might assume he doesn't need to worry about slipping the band's because he thinks they're bullet proof (see what I did there?). And he's right, but his drums are not.
Spot on Hal. Everyone agrees that you must operate the transmission properly. Cotton bands will give great service without the problems of kevlar if everything is in order.
It is misleading to believe that kevlar is the solution to worn out cotton bands because if they wear prematurely there is something else wrong.
(Message edited by Antique_iron on September 14, 2017)
There are a few things that will fuzz a lining. Rust pits, big time, Sharp edges on the drum, and lining not installed right, and ends of the lining not coated good enough.
Drums need to be turned, and do not have to be ground. If you don't have a true surface, you can get chatter, and a forward, and rearward action, just like new disk brake pads, and old wore out, or warped rotors.
You don't get grooves in a drum, unless you don't know how to sharpen a lath cutter.
We have rebuilt, lots and lots of Model T transmissions, and have always trued the drums. All have worked good, and NO broken drums.
If .025 to .040 thousandths makes the difference of a drum braking, then none should used.
Since we're off into the eternal Which lining debate, I'll throw in a couple of photos and tell what I think they mean.
I pulled this brake band out of my 1923 touring. As you can see, the lining was being held to it by just one rivet. As far as I can tell, the guys who "restored" this car's body didn't touch the chassis. There's no telling how many decades these cotton linings were in the car.
I suspect that cotton band linings are like cotton clothes, in that they will deteriorate and rot with age. I don't know how long it took the linings in this car to rot, but I replaced them with Kevlar to get around that problem.
I don't have enough Model T driving experience to pontificate on the long term use of Kevlar, but I suspect Hal is right in the short term. I'm guessing that either type, if used correctly, is OK. But in the long term, I expect Kevlar will prove more durable. I have no statistics to back up any of my suppositions, so time will tell.
There is no doubt about Kevlar bands lasting long. I have never replaced a Kevlar lining in any of my cars and some of them are going well over 15 years now. I do like the feel of cotton bands better but I don't think the difference is worth the hassle of more frequent band replacement especially without quick change bands. So far I guess I have been lucky as kevlar bands have not cracked any drums or caused excessive Kevlar fuzz.
If you don't have a lathe, what is the best way to put a smooth surface on a drum?
I have been able to get a decent finish using emory cloth and oil. Best if you can find a way to keep the drum rotating while you wrap the emory cloth part way around it to get a polishing effect. Kind of like polishing shoes. The drums on my cars are by no means perfect but I have not had any real issues with Kevlar fuzzing. I think pits are more of an issue than grooves as they are harder to smooth out. I am reluctant to cut the drums as they are thin enough as is so I use the emory cloth even though I have a lathe. I can usually get a decent surface just by spinning the drums in the lathe and using the emory cloth and oil.
That's how I polish them too, Val. My machinist buddy will also do them for me on his crank polisher, if it's knarly !
I don't know if the Kevlar did this to my transmission.
I was driving along about 30 mph. A strong smell arose,I just thought it was something outside. Then a few minutes later I heard a click click BANG from the transmission. I pulled over removed the inspection cover and this is what I found!
Nothing was dragging before this happened,and I had a pretty good neutral.
Could Kevlar caused my reverse and low drums to shatter into pieces ?
Well John if you are to believe what you read in this thread you would be crazy to think that kevlar harmed your transmission. Maybe some stray cotton fibers got in there and caused the failure?
It would be hard to deny that Kevlar contributed to it, if you were smelling something (which would all but certainly be heat) that's for sure. Free neutral, no feet on pedals, but enough heat to create a smell...I'd think there would have to be a corresponding loss of power, too. The question is what was the system failure that created a tight band with no feet on any pedals? Band material coming off the hoop would be one thing that would cause it, and if that were the case, Kevlar's tough nature would certainly kill a drum if it was wadded up thusly. I'm wondering where the demountable ear to low band is and how, if, or when it came off. Low band is certainly slammed hard "on". Whether the drum(s) destruction preceded the low band ear displacement or followed it certainly can't be determined from a picture or possibly ever.
What can be determined is that significant heat was generated with no operator input. A reasonable conclusion would be that Kevlar could be a factor, but only a contributing factor...the root cause would be the event that seemingly put either low or reverse "full on". Personally I only see that happening if the "low" ear came off or a Kevlar band came partly off due to faulty riveting.
This is interesting. I will be installing new linings this winter. I think from reading this and other threads that if I soak bands in MMO and run a water pump to keep the heat down then it wouldnt matter which linings I use.
Doug keep us posted on your findings when you get it opened up.