MTFCA Forum

Hi,

Take a look at this short video: https://www.youtube.com/watch?v=aFvdphz9utc (Im speaking danish, but I say it's bad that the rivets are loose)

Can I save this by trying to heat the rivets individually (somehow) and hammer them so when they cool it will be tight again? Or what does one do?
(Apart from finding another)

I have seen the brake drum rivets staked to get tight, that is a very short term fix as is what you are suggesting. There is a lot of stress on that drum between using it for brakes and clutch. My suggestion is new over sized rivets if needed and re do, but depends on how wallowed out the holes are, what size would be needed. Be aware these are not off the shelf rivets, the head angle is not standard and the drum would need to be faced after riveting. Depending on how worn things are, even oversize rivets might not fix it.
Standard size;
https://www.modeltford.com/item/3311RIV.aspx
Over sized;
https://www.modeltford.com/item/3311RIVO.aspx
Would this be a 26/27 drum?

When I was a young boy in school learning to become a ships engineer I was told that hot or cold riveting depends on what the use of the parts would be;

If the purpose was to have a tight seam, like in a boiler or a ships hull hot riveting was the way to go.

If the purpose was to transfer a mechanical load, cold riveting was preferred.

The reasoning behind it was that by hot riveting the rivet shrinks when cooling resulting in a force pulling both plates tighter together, but the shrinkage also meant that the shank of the rivet got just a tiny bit smaller in diameter, which you don't want if you have to transfer a radial load say on a brake drum or a sprocket on a axle, then you want to fill the holes in the flange and the drum as tightly as possible, so you rivet it cold so the shank of the rivet does not shrink and fills the hole entirely around its circumference to resist shearing forces better.

Dave Nolting, manufacturer of the wonderful new T transmission drums, rivets them to their hubs cold (using a press).

Cold riveting is the way to go on transmission drums and it really should be carefully done in a press. The rivets then need to be faced in a lathe.

Round trip shipping might be too pricey to be worthwhile for you, but I re-rivet transmission drums for $40.

Can I save this by trying to heat the rivets individually (somehow) and hammer them so when they cool it will be tight again? Or what does one do?
(Apart from finding another)

It is better to remove them and purchase replacements and then start over. The rivets along with the holes will be worn and if you reset them they will loosen up shortly. You would need to cold rivet them.
Once you install the rivets you will need to remachine the surface as shown in pictures so the heads don't interfere with the thrust washers.
We also make the tranmsission drums and gears see above.

One more thing, Since no one else has mentioned this.
Since the brake drum is loose on the hub It would be wise to get the Brake drum crack inspected.
Most often we see engines with good drums only to fail the crack inspection as the rivet holes are cracked around the rivets.
Makes no sense to rerivet the drum only for it to loosen again and fail.
Above picture is a crack in the rivet hole on a reverse drum but same thing occurs to all the drums even drive plate.
It's worth it to have them checked.

I don't know if it has been mentioned or not, but not only when rivets work loose, the holes become elongated and the edges of the holes create ridges that won't let the flat surfaces clamp down even if the rivets are just peined again. As said, it's by far better to remove the parts and repair/replace/revivet everything. JMHO Dave

All,
thanks for all the good advice. I have a buddy who are familiar with rivetting - hot and cold and we will obviously go with cold. Oversize rivets are ordered and picked up tomorrow together with new bushings for various shafts.
J & M - I do not have access to Magnaflux, but will clean up the drum thoroughly and see if I can see cracks by naked eye with magnifying glass.

I would replace the rivets one at a time. Drill one out, fit one in.That will keep the hub and drum in line when fitting them together. I note the cracks in the JM photo. I have found a number of such cracks over the years. If the rest of the drum is sound, I have re-used them. There is every chance that such cracks occurred when the two were initially riveted together. Better without the cracks, but not a real problem.

I could be wrong.
Allan from down under.