Wombat Front Brakes

[Bill2001]

The front brakes "look good"-- new SH shoes, new brake cable, brake cam lubed, new brake springs all around and the brake drums/hubs cleaned up nice. Brake lever arm adjusted "correctly". The brakes seem to work well enough, but once the brake shoes make full contact, the hand lever never seems to "firm up"-- it stays "mushy" and springy, like a frayed cable. I'll double check the cable tomorrow. I didn;t see any cracks in the drum, and the brakes operate smoothly (no pulsating, at least from my low speed testing stops). No idea of the diameter of the drum, I'll measure that. No idea what the "angle"of the brake cam is at full contact, I'll check that tomorrow. Ideas for other things to check whilst I'm looking?

--Bill

[Dale]

Bill,
Here is a link to a discussion about front brakes. Look for the reference to an article in the Resonator. I think that information will be useful.
Dale
viewtopic.php?f=1&t=438&p=1351&hilit=Axle#p1327

[Bill2001]

The link looks good-- I'll try it later. My BMW has a similar tapdance on tightening the front axle. And with double leading shoes, a perverse procedure for adjusting the two cam levers. The only other "new machine headache" is a funky carb, which will be cured in a couple of days with a package from SH...

Thanks!!

--Bill

[Bullfrog]

Quick summary: 1) proper axle tightening procedures to allow for true centering of the brake backing plate/shoes and non-binding forks, 2) brake shoe friction material making full contact with the drum, 3) "modern" production (heavy housing) brake cable (OEM Hodaka cables are too light and the housing "squishes" under full brake pressure and feels spongy).

Ed

[racerclam]

ED

Does Paul have the improved cables? I'm currently building a 1978 Yamaha 175 endure with a Hodaka front end That I bought from Harry Guess I should have good brakes.

Rich

[hodakamax]

The last two sets I got from Paul were Motion-pro. They seem to work great.

Max

[Bullfrog]

Yes, those Motion-Pro cables from Paul are heavier duty than the OEM cables . . . and they don't feel spongy.
Ed

[racerclam]

thanks ED

[Bill2001]

Recentered the back plate today (helps a lot), moved the brake cam arm one spline clockwise (helped a little), put a spacer in and checked the brake cable for springiness (it's rock solid). Still have some mushiness in the handlever. Went riding this afternoon, replacing the carb tomorrow, so this weekend I'll pull the wheel and check the internals.

Need to download all those Resonator articles.

--Bill

[---]

Over the years I have learned to accept a degree of mushiness in Hodaka brakes. Aside from the cables, which are a big part of the feel, the original linings were not outstanding, and the arch of the brake shoe never really matched the drum. They are narrow, small diameter, and less than modern. If they get wet, all bets are off. The cam is too short, is flat, and doesn't have a lot of leverage against the shoe so it takes more effort to get brake force going.

I have tried shaping the friction surface to more nearly match the drum arch, in an effort to get more contact. This help some, but not enough. I have tried shimming the standing end of the shoe as well as the cam face to change the angle of the shoe on contact, and this helps a bit. I have not tried the new after market style shoes, but looked at them last year at Hodaka Days. Can't remember the brand at the moment, but I have seen them either here or at the Hodaka Parts site. They look better made with better friction material, and may have been re-arched to fit better. Maybe someone here is using them and can report.

[Bill2001]

Update: still has the mushy feel, and finally got the chance to pull the wheel and inspect. The angle of that brake cam is way too much counterclockwise-- it should be about "flat" between the shoes. It _seems_ that the flat area on the end of the shoes is too thin, by only 2.5 mm or 0.10 inch. Shoes are EBC from Hodaka-Parts.com, part# 909219R.

What should that cam/shoe end look like? Are these shoes right? I can weld a "pad" on the shoe ends and mill it, but if the part is wrong I'll replace it.

Brake drum dia is 110mm and installed shoe dim is 109.9mm. A photo link is given below.


https://photos.smugmug.com/Sample-Galle ... 4330-L.jpg

[MWL]

Brake cam looks correct. Is there any wear in the brake cam shaft/backing plate bore? With the angle of the cam, I would be concerned that it could rotate too far and not return.

[Bullfrog]

If you want to do a development project on the Wombat front brake (and who doesn't?) here are some thoughts for your consideration before you break out the welder - though you'll need it anyway.

1. Do the welding (brazing?) on the cam to change its thickness. Do that one part - as opposed to modifying the two shoes without comprising the adhesive for the friction material.
2. Modify the brake lever at the hub (longer). (more welding)
3. Create a new brake stay with cable end fitting to achieve a proper "line" for the cable to pull on the new long lever. (more welding)

My trials bike will almost do "stoppies" with those sorts of modifications. It might actually be able to do stoppies, but I don't like the taste of dirt so I've never really tried to do one.

Note: I'm not getting into friction material thickness or material type or arcing the material differently cuz I think that is more difficult for the average guy to develop than the welding needed to improve the actuation geometry at the hub.

Ed

[Bill2001]

If the brake cam looks correct, then I'll not worry that it is incorrect. On the Beemer, the cam is at much lower angle.

Good idea to not weld on the brake shoe plate. I'll try a little R&D on the brke cam to optimize it's contact with the shoes, and then try Captn Eddie's geometric mods (from his Resonator articles). I've enjoyed effective and troublefree drum brakes on the Beemer for years and I'm spoiled.