Reversing brake on Big Twin

[Lonnie]

I don't know quite where this thread belongs but this as good a place as any.

I'm trying to separate the rigid brake assembly (stock mechanical) from the rear drive sprocket on a '47 knuckle. I was led to believe that this was a racers trick in the late 30's - early 50's for the Big Twins and saw an example in a magazine about 10 years ago or so. It allows for quick gearing changes by allowing the changeout from the 51-tooth sprocket to any number of other sprocket sizes. So the brake is then on the right side with the sprocket by itself on the left.

Note to purists - I am attempting to duplicate what I would believe a racer of that era would run, including a raised transmission, shortened oil tank, XA front end, etc., starting with a set of swap meet cases. A TT bike, I reckon, but street ridden.

I'm pretty well along with the brake scenario which involves merely separating the brake backing plate components, then reversing the internal reinforcement plate and the external tab, etc. This was the easy part. And I know I can use a later stock style rear disc sprocket for that part of the project.

What's driving me nuts is how to incorporate the sprocket attachment to the star side of the hub. I can see several alternatives, all of which seem to involve some really professional machine work of which I am not capable. And I can see that it would be easier with a '67 - '72 style hub but that would not really be correct for that era.

My question is, has anyone else seen this done and/or have any suggestions on how to proceed? Any ideas would be greatly appreciated and when I make the big-time, credit would be given.

Thanks for any help.

Lonnie C from SC

[Lonnie]

I believe the bike I was referring to was built by a fellow named Ed Reddish, I don't know his location. Bike was also a shovelhead top end on a UL bottom end. Ring any bells, anyone?

Thanks,
Lonnie

[Chopperdave]

yes

im workin on it

PM made an adapter to do just that, gimme a few days

and thats something i never thought about to do with my knuckle, i fully would do it!

[Lonnie]

While you're at it, make two!!

There is one thing to consider with flipping the wheel over that I had not thought about if the use of the '36 - '66 star hub is attempted. I had not considered this aspect, which my buddy Larry Gee brought up, and that is that the larger bearing in those hubs is on the drive side, apparently to take the additional stress. He pointed out that the bearing in the "open" side of the hub is the weaker of the the two and even with the addition of the grease fitting in the later versions, is still the weak spot, bearing-wise. He has rebuilt many star hubs and is a stickler for the detail required to do a successful rebuild so I take this point seriously.

I am using Star Hub Pro rebuilt hubs that use timken bearings on my '41 EL that Larry is finishing and that may be a better option. The best choice, however, could very well be the '67 - '72 "mid-star" hub since it uses the same timkens on both sides.

My initial goal to make this more user-friendly was to have an adapter to allow for the use of a basically stock hub. In other words, have the adapter made to fit the hub with no modifications to the hub.

Or, if you are going to shoot for something, shoot for the moon!

Lonnie C from SC

[Jerry Wieland]

Lonnie I cannot imagine that a brake is going to overload that smalller rightside bearing. A drum brake is a "balanced load" meaning that it does not pull or thrust overly hard in any direction. That bigger leftside bearing was put there to control the pulling of the chain and not the brake.

I've rebuilt a lot of starhubs and while I agree that the star side is a problem I do not think it is from overloading. The star side is always exposed (leftside is hidden inside brake drum) and on the uphill side. Usually the starside has damage associated with water.

Jerry

[Lonnie]

Jerry, you're correct especially in regard to the bigger bearing being there due to the chain/torque load. However, my thought was that in flipping the brake to the right side, the hub reverses also since the lug bolt side remains attached to the brake drum. In my assumption, the sprocket would then attach to the star hub, i.e. weaker, side of the hub.

And you are definitely correct in that much of the damage to star hubs is due to water penetrating into the bearing area and just a plain lack of grease. I've been told that after the hare and hound type events of the first half of the last century, where streams and mudholes were traversed, that it was necessary to disassemble, clean out and regrease the hubs. I would imagine that everyone did not always do so. And I know that even now there are folks running star hubs who have never been inside them to see just what their condition is, assuming that if it ain't locked up, it must be okay!

In any case, keep the ideas coming!

Thanks,
Lonnie C from SC

[Chopperdave]

it would be pretty easy to make an adapter that would replace the top star cover, but it would need to have different hardware used as the 1/4 bolts wouldnt be enough for a sprocket. im not at my shop and i cant say for sure if you could get a nut behind there... but then again that means youd be modifying the hub, id rather make something that would not damage the hub...

[Lonnie]

My concept requires strong visualization techniques, so bear with me. This is based on using a star hub which I now think may not be up to the task on the smaller bearing side as was pointed out to me earlier.....

As background I used one of those 1972 Big Twin front disc brake adapters just to give me something to look at. For these purposes, the adapter would have to meet several criteria:

1> In order to be something transferrable from hub to hub I believe a split plate could be manufactured that would completely cover the inside area of the hub, with raised portions that would be an interference fit into the five holes that the lug wrench would normally go through. This plate would be split so that one portion would cover three of the holes and the other part would cover the other two. Each part would be drilled to accept the 1/4 x 20 screws that would secure it to the hub. When this would be installed, the hub would present a flush appearance on the star side EXCEPT that the five screws would need to extend beyond the hub for the reason noted in #3 below.

2> In the plate, in the raised "rings" now filling the five lug wrench holes, each of the rings would have a hole drilled to secure the outer hub-to-sprocket adapter to the hub. I'm thinking at least 3/8", maybe 7/16 bolts, probably NF if the hub is made of steel (which it probably should be). The outside of the hub would of course be machined to accept standard '73 style sprockets.

3> The sprocket adapter would need to be hollow since the wheel spacer that locks the inner portion of the bearing would need to slip inside with enough clearance to allow a factory spacer to clear with no danger of interference. Additionally, there would have to be enough clearance machined into the base(where it bolts to the hub) to allow the placement of the star hub gasket and inner plate (that piece that has the grease fitting on the later hubs). (Also note that an earlier version without the fitting would be required as there would be no room for the fitting). This machined-in clearance would need to be of close enough tolerance to secure these parts securely but without causing any bind. The exposed screw ends noted in #1 above would serveto locate them in position. These screw ends could fit into small holes also made into the adapter.

Is this deviant or what? How about complicated??

Anywho, this same theory would apply to the mid-star hub as well except there would not be the additional complication of the star clearance.

Lonnie C from SC

[Chopperdave]

supposedly Performance machine made something like that.

i talked to a guy at PM yesterday about it and he said that the one they made (back in the day) replaced the drum side.
but
the other guy I know (who is an insane purveyer of info) swears its for the star side...

still lookin

your idea would work, nice and complicated too!

damn i need to look at a hub.

i just wish that the 1/4 bolts would be strong enough...

[Lonnie]

It's all within reason and do-able. The worst part is the machining out of the adapter to accommodate the star hub components which would require some precise mill work and with a small mill at that to get into the areas that would accomodate the five points of the star.

The bright side is there are only five points, not six.

Hmmm.......

I've got about 10 or so unused star hubs (only a few internal pieces however) but none of the '67-style mid-star hubs. I'm going to try and round up one of those this weekend and ponder on it for awhile.

I'd even though about cutting in half of a mid-star hub and a later disc brake hub and welding the appropriate sides together but that would be cruel and unusual.

Lonnie C. from SC

[Chopperdave]

i have a couple weird ideas for it as well, but i am going to look at a hub tomorrow and see, i might have a half a hub! i have a brake side that i cut up once to use as an arbor to cut drums, but that leaves the star side...
never mind...

[23JDCA 808]

Originally posted by Lonnie
It's all within reason and do-able. The worst part is the machining out of the adapter to accommodate the star hub components which would require some precise mill work and with a small mill at that to get into the areas that would accomodate the five points of the star.

There are programmable CAD-CAM setups that could do this. The programming allows you to get everything symmetrical and true before you start on the real part(s). You would use plastic or something easy to prototype with. They even make milling machines now that hook up to a micro-computer. There are probably members here who'd welcome a winter project. ...bill

[Chopperdave]

ok!

i found the PM adapter!

but, i believe its for a 67 to 72 hub...

here are pix

as you can see, it adds a much needed extra bearing...

[Lonnie]

Man, it took some doing to get back on this forum - thanks, Michael.

This PM adapter looks very similar to the factory Harley '72-only adapter that allowed the mid-star ('67-'72) hub to be used with the '72-up front banana caliper. The adapter in your photos is similar except it looks like it is mounting a custom disc rotor. In both cases, the adapter bolts to the drum side in lieu of the brake drum.

It would seem like I am back to the point of designing an adapter like I described somewhere in this thread and take a chance on the strength of the small star-side bearing in the star hub. I have looked at trying to adapt the mid-star to the early mechanical brake drum which seems would require a bushing since the part of the hub that slips into the drum is smaller on the '67-'72 drum than the hole in the '36-'57 drum. Granted, the hub in any case registers off the 5 pins on the drum but having a slip fit on the center hole would keep water out. However, as you note the adapter could encompass a bearing for the support to make up for the smaller and perhaps weaker small side of the star hub.

I still think this is doable; however some of my ideas seem to come out of a Little Shop of Horrors.

Lonnie

[Chopperdave]

that adapter isnt on the brake side its on the star side!

and hell yes its doable!

i just need to find a good way to stabilize the drum from turning that doesnt involve me re-powdercoating my knuck frame...