As far as I can tell pretty much nothing changed on the Transmission Slow Speed Drum Assembly other than the rivets...they went from 7/32 x 11/16 (T708) to 1/4 x 13/16 (T711) and were used at the same time as the previous mentioned rivets until May of 1915. But retained the same part number (T711) through the end of production.





Cross Section...and of course I colored it.

As always, if you see something I've missed, or have a correction, please let me know, at best I'm guessing from drawings I have collected and trying very hard to make drawings as accurate as I can from them.

Very nice...and informative.

Martin, when are you going to do the Rocky Mountain brakes? A lot of people are confused as to what the originals look like!

Good work Martin.

The hub is counter bored for the bushing?? That is not shown in the isometric view. I thought all drum hubs were a uniform straight-thru bore.

Not the low drum & Stevens made a nifty expansion tool to grab & remove that particular bushing !

James the counter bore is shown very slightly and you can only see a little of it at the back of the bore hole.

Steve, cross section drawing is drawn from the Ford factory drawing. Now it may be that they didn't both C-boring this part because the bushing sets flush with the back of the gear hub, which would figure (as it is one less step and as such would save money and we all know Henry was all about saving money).

Royce Peterson has informed me that the rivets go in through the rear so as to make machining the peen off easier (which is also contrary to the Ford drawing, but it makes more sense than what the Ford assembly drawing shows anyway).

Ah, Larry...the unfortunate part is that all of those drawings and photos were on the drive that got destroyed in the fire...so I'm going to have to come over again and take pictures of your brake system (again) and this time I'll back them up to the "cloud" with my other stuff, so as not to go through a mess like that ever again. Yours wasn't the only assembly I lost that day either...I lost all my Ruckstell's, the TT and the Fordson rear axles (basically the same axle, with the exception of where the drive shaft comes off the drive gear at) and Peter Kable's Kamp Kar (which was a really big loss, they were the plans for building a Kamp Kar) too.

Correction...Royce Peterson pointed out to me that the rivets go in from the reverse side than where I had them in my previous drawing. He said it was done that way so as to make machining the peen excess easier, seemed reasonable, so I moved things around a bit and re-drew the rivets to reflect the new direction.

The cross section doesn't change, at least I don't think it needs to, but let me know if you guys think it should.

Martin, excellent work as usual. The only thing I can see is the end of the rivet where it is peened over in the cross section has no line when installed like there is under the countersunk head. It just fills the void.

Allan from down under.

Martin, these are great drawings. Your axle drawings really helped when I rebuilt the rear end on my tourer.

Just out of curiosity, I noticed that the hob radius looks different between the isometric and the cross section. Do you create these from a solid model or are they drawn by hand?

Good info on all the drums at http://modelt-tips.com/Transmission/01.html. Mike shows how to remove the old rivets and install them using new or better parts.

Stick by the FORD drawing on the direction of the rivets. This is very important. The machined tapered head of the rivet should be placed in the machined hole in the cast iron drum. The rivet should be backed on the drum side and peened into the flange of the gear. The reason: peening on the drum side of this assembly is much more likely to crack the drum flange due to the initial uneven expansion of the rivets.

Also worthy of note is that low speed drum gears and bushings were drilled into the oil grooves of the bushing for oil lubrication prior to about 1914 (not sure of exact year). ALSO, all drum rivets were originally made of malleable iron and these slightly stronger rivets haven’t been available for decades.

In my post above I meant to say “WROUGHT IRON” not “malleable iron”. Drum rivets were originally made of wrought iron.

Adam, I have the drawings for the rivets too and I read the notes and they do mention that also...but I guess, since the new drums are not cast iron, but steel, they're a bit tougher than the original cast iron drum. I originally drew them in the other position. Your suggestion presents a problem, that I'm not sure how to show and yet placate everybody...maybe I should show them in the "Ford Correct" position (drum side to rear of shaft) and just make a notation on the drawing that newer drums are mounted with the rivets from the back to the drum side...I'll have to cogitate on that some...I think. ;)

I've always mounted new drums the other way from your drawing. I then machine the rivets smooth from both sides. I don't see how or why you'd do it any other way from this.

Tom, Do you mean to say you mount your drums as shown in his first drawing, or as shown in his second drawing?

First.

Yep, I knew that first drawing was correct...you'd never buck a rivet from the cast iron side, you always want to set the rivet from the steel side.

Good thing I never delete anything, isn't it?