On Dec. 31, I posted comments about a cracked brake drum on my 25 touring. Thanks to all for the suggestions for the cause. I got it apart and found a few items of interest.
Not only was the face of the brake drum cracked, but so was the reverse drum. Reverse was cracked in the web, only to be determined with magnaflux.
A response to my request for ideas from Rich Peterson, lead me to the pedals and worn supports on both the brake and reverse. Rich had suggested that my adjustment of the bands had been to tight and that worn supports attributed to loss of motion of the pedal as it engaged the band. Checking the movement of the pedal showed more than 1 inch of travel before any activation of the band. I had never checked this travel before, but wound up replacing both supports and the slow speed notch. Now the travel is about 3/8". Thanks to Rich for this suggestion.
I have everything back together and will get the assembly installed in the car this week end.
I always thought I did a pretty good job of checking out items and doing my maintenance. But a thorough as inspection as possible will be done on these parts of the transmission in the future. It makes me wonder how many T's are being driven regularly with cracked drums, unknown to the driver. Had the cracked face on the drum not been eating up my Kevlar bands, I would have never known. The resulting failure could have been bad.
Thanks again to all who responded and to Rich especially.
It makes me wonder how many T's are being driven regularly with cracked drums, unknown to the driver.
I'll bet a lot more than many of us would like to know.
I am in the middle of redoing a tranny right now.I always media blast the drums to clean them up.If you let them set for an hour or so,a crack will show as a black line due to oil seeping out from deep inside. This transmission's reverse drum was like a hand grenade,ready to go off. It has about six cracks. I was glad I tore into it.
Here's one I pulled a few years back, wonder how long it ran? Thinking about using it in one of my projects! KGB
There is a crack going to that rivet also. Make a good wall hanger .
Jack, every now and then a crack shows up around the rivets. If it doesn't extend into the web, I do not worry about them. They most likely happened when the rivets were set.
Without the cracks would be better.
Allan from down under
I pulled reverse drums from three transmissions before I found one that wasn't cracked. It seems reverse is the one most likely to go.
A crack at the rivet could be a dead end, but Not On the other end, that's is what you should be concerned about.
In fact the crack goes the other way clear to the Brass weld!
Do you think your crack checking method is as good as manga flux. Sure would be cheaper if so.
Steve. I had accumulated 8 reverse drums and 6 were cracked. According to Bruce McCaulley, the reverse drum is the most commonly cracked drum of them all. He states they were a lighter casting than the others! Or at lest that is the way I read it to mean.
Of course, you can buy a new one for only $525.
Tom,I feel my way is cheaper,and it also has the advantage of cleaning the drum up. I always coat a good drum with electrical varnish so it sheds oil better and stays clean. I have some that were done 20 or so years ago that are just as nice now as when I finished them. I coat pans,transmission covers too.
Tom its not that the drum is lighter that makes them crack its guys using the reverse as a brake drum. The drum is turning one way and then is suddenly jerked in the opposite direction. REVERSE DRUMS SHOULD NEVER BE USED AS A BRAKE.
Every once in awhile I see guys on here recommending that the reverse drum be used as a brake, good luck if you do its not will the reverse drum crack but WHEN WILL It CRACK.
Thanks guys. I do know some use reverse for the brake but years ago I was taught not to do that and never have. I guess if I had a real emergency, I would.
And if I replace drums, I would use the much cheaper Dave Nolting drums and put my own gear back on. Somewhere around $250 I believe is the price. He will also install the your gear on his new drum for $25.
I have always held the belief that many of the reverse drums were cracked when they were made. Those are very thin castings in the web area and getting even cooling after they were cast was likely not happening. Just my opinion.
The word to remember on anything Model T is magnaflux.!
Did this fail in the car or did you break it once you removed it?
Either way, it is ugly!
This was in an engine we disassembled.There was a dent in oil pan where it went Ka-Boom.
I am seeing several photos of brazed webs and band serfaces. Does this HOLD? when is it acceptable to do this? On only ONE crack or???
Joseph, the picture I posted is a drum I removed from a car I worked on for another guy, I would not recommend using it but would be interesting to know how long it had been in service that way. I do know the car was restored in the early sixties but not if the repair was done at that time or earlier in it's life. KGB
The drums were cast iron for durability, am I correct?
But it seems its the cast iron that cracks and eventually fails.
Why not use a better material. Maybe a billet of something stronger that would wear just as well as cast iron.
Whats the reason?
The drums were cast iron because it was cheap. Sure you can make one from a CNC program from unobtanium. It might cost a bit more. How much can you afford to pay? How long is long enough for a drum to last?
Cast iron works fine for me.
Yes you are correct. I am sure the cast iron will outlast me...
Cheap also makes sense, thank you.
I'm having new ones made up and its been suggested to use cast steel. That's why I asked.
I had also heard that the cast iron produces "dust", and that when machining cast iron, the machines get very dirty from it.
By the way Royce, Do you know what the correct original OD of the transmission drum should be when new? I had asked the question a while back, but the thread did not produce an answer. Asking again.
Justin, the part drawing for T-709 Brake Drum shows the limits of the outside diameter of the drum to be 7.495" to 7.505" according to Trent Boggess. I think the other drums had the same specifications.
(from: http://www.mtfca.com/discus/messages/50893/61800.html?1217695385 )
Roger to the rescue again!
Thank you very very much!,
They measure 7 1/2 inches.
For well over most of the Model T years when Ford was selling all the Model T's they could build how close did Ford stick to the print?? I think what matters to most is the min size usable?? I can just imagine being on inspection and asking what do i do with these drum's at 7.490?? I'm sure Ford had Go and No Go gauges but what was the Salvage Limit?? I would have thought if a worker raised too many questions back then they were soon picking shit with the chickens in the street!! Bud in Wheeler.
Justin you can buy new drums. It may be a wash as far as cost and shipping compared to what you might be able to make them for.
I have a cracked reverse drum on the wear surface, and my brake drum has a crack around the rivets.
The OD of my drums vary from 7,4 to 7.46 inches, and my machinist suggested we make new from either cast iron or EN8
I've had him model up the entire transmission now, and in terms of costs, its a heck of a lot cheaper to re-make everything instead of buy and ship to SA. (my triple gears are well worn, the shafts not so much)
The machinist's main work is gears and splines so I feel like I'm in good hands getting it done all at once, and the transmission will be balanced etc already, so it sounds like a plan.
Anyway, thanks for all your help and advice, it is always much appreciated and I have much to learn..
We'll hopefully be back in the States in a year of so, and the T's are coming with. Then we can go for a ride and hear the comments.
I imagine a new drum at Ford .010" undersize would have been rejected and melted for scrap. Anything I've ever had the print for matched perfectly. Ford had very high quality standards and inspected parts very carefully considering how many were produced.
You might see how much it would cost to make ten of each. You may be able to sell them at a profit on your trip here.
Quote"I'm having new ones made up and its been suggested to use cast steel. That's why I asked.
Ours are made from ductile cast iron. Rather than crack as Ford's did. The ductile iron has a certain amount of give to it.
Sorry Royce,I don't buy it! Bud in Wheeler.
Justin -- It seems to me that you'd be money ahead to buy a new drum from J&M, since they are already making them.
I looked at just going ahead and buying drums and gears but because I had some used ones of unknown condition, I had the magna fluxed. It cost me $50 to get the two I needed, got the rivets and put my gear on the verified crack free drum. A couple hours work to re-rivet the old gear to the new drum and I was done. I like what the couple of machine shops are doing and they do good work. But for a little time and less than $60, I am back in business. In the future, because my stock of drums is getting low, the new ones will be an option. But for now, my cheapo (as my wife calls me) has got a good, reliable, and safe car for much less than new.
To J&M - those are beautiful! If was nearer to you I would go for it.
My transmission was so far out of whack, just about everything is questionable. That's why I had the transmission modeled and costed.
I'm keen to see what this machine shop can do. Everything will be new, CNC'd balanced and done by a gear and spline guy.. that's what he does. Besides, its economics. My Rands vs your Dollars..
I heard about Chickasha (sp) and its in March when I'm in the States. Hopefully I can make a turn for the weekend.
Cheers from Africa,