Replacing gears on transmission drums - help needed

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Model T Ford Forum: Forum 2012: Replacing gears on transmission drums - help needed
Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Thursday, May 03, 2012 - 04:16 pm:

Any advice on how to replace the gear on a reverse drum would be greatly appreciated.

I have a very good gear I wish to use, but alas, the drum is cracked...badly. I have a good drum with a bad gear so, my challenge is to make the change.

I understand I must drill out the old rivets and remove the gear then re-rivet the gear to the good drum (Sounds easy) but I'm sure there's a right way to do this. -HELP!

-John


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Thursday, May 03, 2012 - 08:49 pm:

A Ha! I set up my drill press to drill the buggers out, next buy new rivets from Chaffins.

Heat em up, smack em down, turn the surface with my lathe. OK so far?

Will provide pictures as I go. Hope this works!


Top of pagePrevious messageNext messageBottom of page Link to this message  By Thomas Mullin on Thursday, May 03, 2012 - 09:02 pm:

John,

Are pressing in a new bushing also? That would be a good place to make sure everything is concentric.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Michael Deichmann, Blistrup, Denmark on Friday, May 04, 2012 - 01:28 am:

Yeah - lets get reports and pictures of your progress as I am in the exact same situation. At least the reverse and low drums from the gearbox I smashed (see http://www.mtfca.com/discus/messages/257047/285459.html?1336075712 ) is in perfect shape, but the gears are bad. I have another set of cracked drums and good gears.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson, Indianapolis on Friday, May 04, 2012 - 06:48 am:

John, You need to be careful when you "smack em down". The drums are very fragile and the rivet holes will split out. I use a press to smash them down. Heating is unnecessary and the rivets have too small of a mass and too much heat transfer to keep them red for over a couple seconds. Order a few extra rivets and practice on your old parts first.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Allan Richard Bennett on Friday, May 04, 2012 - 06:58 am:

John, I have just finished re-riveting a clutch driven plate to its shaft, as the original rivets were loose. I always hot rivet them. This one I could do on my own, heating the rivets to cherry red, placing them on a buck in the vice, lowering the assembled parts over the rivet and "smacking' them down. I would suggest bolting the gear into the drum with 4 bolts to hold it together, and then riveting the 4 intermediate holes first.

It is easier if someone else heats the rivets, leaving you free to manipulate the parts and the "smacker".

Hope this helps.

Allan from down under.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Friday, May 04, 2012 - 07:27 am:

The rivets should not be heated. They can be driven easily cold. Heating them is going to destroy the temper and cause the rivets to loosen soon and then fail.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Anthony Bennett on Friday, May 04, 2012 - 09:47 am:

Royce,

How can a rivet loose it's temper? I was always under the illusion that a rivet, by definition, was soft thus it can be formed or driven into many different retaining situations.

Hot riveting is a favorite hobby of mine, and in this situation the rivets are indeed still hot when they're driven with a punch.

Just curious.

Thanks

Anthony


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kohnke Rebabbitting on Friday, May 04, 2012 - 11:37 am:

Must be a lot of buildings, and bridges ready to fall down with all those temperless Rivets!


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Friday, May 04, 2012 - 11:57 am:

Thank you all for your advice.

I think I will try cold pressing the rivets after bolting alternate holes per Kenny and Allan's recommendation.

Royce, your picture shows you centering the tail shaft on your brake drum. Would that be necessary with the reverse drum? I was planning to chuck the drum with my three jaw chuck with no center, to face off the rivet heads.

Alternatively I could spot face the rivets on my neighbors Bridgeport. Any thoughts?

-John


Top of pagePrevious messageNext messageBottom of page Link to this message  By Scott Conger on Friday, May 04, 2012 - 12:10 pm:

Royce's setup looks good and safe, though I'd personally keep the tool closer to the lantern post. Could be set up just for photo.

I don't know how you'd hold the brake with a 3 jaw, as that's a rough casting inside and would never center it...use a 4 jaw inside (unless you have a big chuck and can hold the OD)and get it running dead on...putting a center on the end is just a good safety and keeps one from having a once-every-10-year-crash on the lathe.


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stroud on Friday, May 04, 2012 - 04:57 pm:

Royce, where did you hear that rivets were tempered? Just curious. Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Friday, May 04, 2012 - 08:45 pm:

Thanks Scott, I'll use my 4 jaw with a center.. Unless I decide to spot face with a mill.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Friday, May 04, 2012 - 08:47 pm:

Michael, I will take photos of my progress and post them. Today was clean up and crack repair.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Wayne Sheldon, Grass Valley, CA on Saturday, May 05, 2012 - 03:00 am:

Many (many) years ago, I took a short course in what amounted to mechanical engineering. There was quite a discussion on the pros and cons of heating rivets. Everyone agreed from the start, that as a heated rivet cooled, it shrank (shrunk?) in size lengthwise resulting in a tighter hold. However, what was a little more difficult to grasp, was that as a heated rivet cooled, it also shrank in size in diameter. This resulted in a weaker hold. The best that could be said from almost an hour of discussion by so-called experts, was that no one won their argument completely. They were both right. And what is the best way to work a rivet depends upon the stresses demanded of it in its application. Because the primary stress on the drums is rotational, the more critical stress is against the diameter of the rivet, not the length of the rivet. So I would do them cold. This way, the hammered cold rivet swells in size (diameter) to fill the holes. It does not shrink in diameter as it cools because it begins and ends cold. It will be stronger in the rotational direction.
Drive carefully, and enjoy, W2


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stroud on Saturday, May 05, 2012 - 04:18 am:

Wayne, just my two cents worth. Rivets hold much the same way as bolts do, their strength is in the friction that is created when they are tight, not whether the hole is full. Granted, if the hole is full, it can't hurt, but if that is where the strength of the connection needs to be, then the head of the bolt and the nut should be tapered, as should a rivet and the hole that it is filling. A hot rivet will fill a hole better than a bolt if it is installed correctly, even after it cools and will be much stronger than a cold one. I think a hot rivet will swell into the hole better than a cold one, and the diameter will shrink much less than the length does when it cools. IMHO. This does not take into consideration alloy bolts, that is a whole 'nuther subject. This is just based on forty five years of observations and absolutely no scientific proof<g>. Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stroud on Saturday, May 05, 2012 - 04:20 am:

By the way, that doesn't include tempered rivets<g>. Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By David Stroud on Sunday, May 06, 2012 - 05:09 am:

Royce, are you there? Dave


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Sunday, May 06, 2012 - 07:44 am:

Metal properties are affected by many factors. The mild steel rivets we use to attach drums have properties endowed upon them through their metallurgical make up and also by their state of temper.

When we drive the rivets cold the rivets are work hardened. This makes them harder than they were before driving.

If the rivets are heated the drawback David mentions is valid, but one also needs to consider that the rivets are now annealed and are in a soft state. They are not work hardened and they are not swelled as tightly in the holes as they would be if they were driven cold. Bottom line the rivets are going to be far stronger if they are not heated.

You can also drive the rivets with a pneumatic rivet squeezer or with a hydraulic press for the same results. I use a hammer simply because it is easy. As mentioned above I bolt the drum to the hub and then install the rivets one at a time, removing bolts as I go.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Kenny Edmondson, Indianapolis on Sunday, May 06, 2012 - 08:24 am:

Royce, I agree and was just getting ready to respond to some of this. The rivets are work hardened when put in cold. My other thought has always been that if the rivets are heated, the red part will compress before the other areas of the rivet and may not fill the hole correctly. The cold press method (and probably the hammer method) expands the rivet in the hole as well as compressing it and expanding the top.

We don't use 3/8" bolts in 7/16" holes and rivets should be treated the same way. Any movement possibilities will cause looseness eventually.

John, if you have any questions, contact me off line with your phone # and we can discuss.


Top of pagePrevious messageNext messageBottom of page Link to this message  By John Semprez-Templeton, CA on Sunday, May 06, 2012 - 12:19 pm:

Thank you Royce and Kenny. Pressing the rivet in it's SO state makes perfect sense. I will use this method.

I assume that you use a shaped mandrel of some sort behind the rivet head, so that the force is applied to the rivet only (not the casting). Suggestions here would be appreciated.
-John


Top of pagePrevious messageNext messageBottom of page Link to this message  By Bill in Adelaida Calif on Sunday, May 06, 2012 - 01:42 pm:

John
What car is this drum for? Sounds like you have a great project there.

wobbly wheeled Bill


Top of pagePrevious messageNext messageBottom of page Link to this message  By Erich Bruckner, Vancouver, WA on Sunday, May 06, 2012 - 01:50 pm:

Does the rivet get more work hardened from setting via hammer than from a one stroke press?


Top of pagePrevious messageNext messageBottom of page Link to this message  By Royce in Dallas TX on Sunday, May 06, 2012 - 08:33 pm:

Erich,

Probably. Ford used a hydraulic press. If you have the time and the equipment that is the best way.

John,
I don't use any special mandrel. Just a flat steel bucking bar and a 2 pound hammer.


Top of pagePrevious messageNext messageBottom of page Link to this message  By Joseph Magedanz on Sunday, May 06, 2012 - 10:41 pm:

If you were going to use a press, how large (how many tons) would you need?
My 12 ton probably wouldn't manage, would it?


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