What is this "dual band" brake system ?

[Steve Swan]

I'd appreciate who can tell me about this brake system. What are "dual bands" ? https://www.ebay.com/itm/Harley-Davi...1Z6wY5&vxp=mtr

[TechNoir]

Hi Steve, this is a topic that was touched on in my 20F build thread but it is worth going into a bit more detail here.

I can only speak of the up to 1920 set up after which it changed. Those parts differ slightly from mine so I am guessing that they are from a bike post 1920.

Up to 1920 Harley Davidson F & J models had an internal expanding drum brake as standard in the USA. This brake used a single piece of flexible steel as the internal shoe that expanded to operate on the inside of the drum.

However in several export markets, including the UK, a bike had to have 2 separate and independently operated brakes to meet legal requirements. H-D complied with tis requirement by fitting an external band brake that fitted over the same brake drum as the internal brake but operated by contracting against the outside of the drum.

The internal brake was operated by a foot pedal on the right via a brake rod. The the external brake was operated by a hand lever on the right bar via a cable. This set up was standard on the export models but in the USA it was an optional extra.

The rear brake plate is different for the dual brake set up to the standard USA model set up.

Here are some pictures from the UK brochure (I posted some of these on your J&JD spec thread but here are better quality ones.)













Also here is an extract from the 1921 parts book showing the different brake parts. Note the various options for the brake plate or as H-D call it the "brake side cover".















Here is my brake setup and also a picture of the internal band (note I took this when I snapped the locating pin which is rivited on, I made a new one after this)










Also, if you look at post #54 on my CAIMAG thread, axeric has posted pictures of his brake set up on his 1916 bike which you will see is the same as my 1920.


Its worth mentioning that the external band was pretty poor. It is however good enough (only just) to stop the bike rolling when at a standstill. Therefore its a much better set up for hill starts (because it works of a hand lever just like a modern bike) than the USA standard single brake set up or the later heel/toe set up.


However.

After 1920 H-D changed it. I am not familiar with the arrangement but I believe that the brake pedal was changed to a dual acting set up with both heel and toe rocker operation. This set up operated one brake with the toe and the other with the heel so that only one brake could be operated at one time. I am not sure if this set up was only for the USA or was the same for the export markets. Someone with a 1921 or later bike will hopefully chip in to explain the later set up as I am interested in that also.

John

[MMasa]

Steve
That is the 1923 and 1924 version of the dual brake setup as explained above.
The backing plate of the 1925-1929 version is a slightly different shape, presumably because of the new 25 frame.
I've never tried to install a 25-29 on a loop frame or vice versa.
Mark Masa

[Steve Swan]

John and Mark, thank you for your great answers. Not having seen one of these setups before and the one on ebay being so rusted, it was difficult to imagine the different parts and how they worked.

[Chris Haynes]

[Jerry Wieland]

I run a dual brake setup on my Cannonball JD in 2014 and I think the expanding brake worked better than the collapsing band brake. Tommo from this website sold it to me and it was the first I had ever heard of it.

Jerry

[Steve Swan]

I run a dual brake setup on my Cannonball JD in 2014 and I think the expanding brake worked better than the collapsing band brake. Tommo from this website sold it to me and it was the first I had ever heard of it.

Jerry

unless i am missing something, i can see where the internal band would work better than the external band. the external band is actuated by a handlebar lever running a cable to the rear brake and the internal band is foot actuated.

i was thinking of looking for one of theses setups, but i'm not sure it would be much better than single brake US version, i.e., rear brake foot pedal with connecting rod to externally contracting band. Tommo said he and a group of buddies rode the USA on contracting band only brakes with no problem. i've built more confidence with my '27, i've stepping on the brake pedal is alt different experience than stepping on the pedal on a 70's drum brake. the '27 just takes more pressure on the foot pedal and paying attention to the clown cars.

[Steve Swan]

Chris, that's a really great blueprint you have there. And also John with your factory sketches. GOOD STUFF !

[Chris Haynes]

Chris, that's a really great blueprint you have there. And also John with your factory sketches. GOOD STUFF !

I don't know where all this stuff comes from. It just keeps winding up in my shop. :-)

[Tommo]

These 3 pictures should help with identification of this era of HD rear brakes.
The first photo shows the Late 1922/23/24 rear wheel on the left and the one on the right is the 1925 to 29 rear wheel
The 1925 exhaust needed clearance so the internal brake operating arm was shifted from the bottom centre of the brake plate to the rear of the brake plate as illustrated in the next two photos.
In NZ, after 1922, all these brakes were operated by foot pedals, a heel pedal for the internal band and the front foot pedal for the external band.
Even when the front brake arrived in 1928 the two band system was continued and the front brake was controlled by the handlebar lever.
Most bikes were hauling sidecars or sideboxes so the demand was to retain the two band system.

[Steve Swan]

Tommo, i note the rims on both wheels are drop center, would rims have originally been clincher for pre-29 models with dual band setup?

And were heavy duty hubs used for this type of brake for sidecar use pre-28?

[Tommo]

Both those wheels have been rebuilt onto Dunlop rims at some stage in their life and one has heavy gauge spokes which suggests sidecar use.
Both would have originally had clincher rims on them.
I'm not sure as to what you mean by heavy duty hubs.
Early hubs were cup and cone with balls.
Later ones were roller bearing hubs.
I do have some nos hubs that have thicker than normal spoke flanges.

[Steve Swan]

the 27-31 parts book shows 3960-23 "rear hub shell (for light spokes) 23 to first 28 twins" and shows 3960-28 "rear hub shell (for heavy spokes) later 28 & 29 - 61" & 74" twins."

the book also shows 18" and 20" clincher rims for light and heavy spokes. pn's are 3940-27 for light spoke 18" rims, 3940-28 for heavy spoke 20" rims and 3940-29 for heavy spoke 18" rims.

the book also gives pn's for light and heavy spokes and nipples.

these pn's and descriptions are on pages 65 & 66 of the 27-31 parts book.