The 2 the Max Project

[hodakamax]

Hey Ed and all. Here's a really quick and dirty mock-up of the pivot point I envision. I probably could have incorporated the original tube shaft if the DPO hadn't cut off the bracket. Pretty clunky looking now but could be precision made.

I'm still trying to envision the cable hook up which is still a possibility but the vision has not come to me yet.

Maxie

[Bullfrog]

It may be photo perspective . . . but is there any reason to be concerned about the toe end of the lever swinging down and contacting the actuating rod?

Yeah, while a cable seems easy on first thought, creating the "anchor" spots for the cable housing ends won't be easy. And there is the worry about rear brake cables which aren't nearly stout enough to do the job without housing "compression"/deformation.

Ed

[hodakamax]

All clear here Ed. Now that I take a closer look, the Heim joint probably could be on the inside of the brake arm giving even more clearance.

Maxie

[Bullfrog]

Kewell!

. . . and it occurs to me that my concern about a truly stout rear brake cable housings is coming mostly from a dirt biker perspective . . . prolly not a big deal for speed record type of bike.

Ed

[hodakamax]

To really be serious on the record attempt theme some other serious mods will have to be made. Don't forget the dual purpose road racer identity with its large heavy front brake and some corner turning tires which it will have first. The general design should lend itself to both purposes. Top speed can extensively tested in the road racer guise and should one want to try some record attempts other wheels could be fitted. Skinny aluminum rims and tires would be needed for less weight and rolling resistance along with less frontal area. Real gains would be noticed along with a reduction in billfold thickness. Just putting things in perspective as the project moves slowly along. Meanwhile one of the main objectives of entertaining me is being met as this is a really fun project without deadlines. Having it in the shop also gives me a feeling of well being at least in the motorcycle department. Just philosophizing here.

Maxie

[Bill2001]

"A reduction in billfold thickness"

He he.

[hodakamax]

I see that I'm getting ready to be put on page two which means I haven't been reporting lately. Things are still slowly happening and distractions are still present. It appears that the best solution to the rear brake hook up will be with a one pivot linkage rather than a cable. This was all mocked up using a damaged front wheel brake plate with a cable end hold. It fits fine with the bearing collar cut down. A sealed bearing will be used as there is not room for the stock seal. I'm out of rear brake plates and have a useable front by cutting down the collar once again. This will also leave the option of a cable later.

Check out the brake cam lever after removal. I've never had one be so tough. It appears that it was pressed on at the factory in the right position and was to be a permanent fixture. I didn't have any pullers that small but did get a chain breaker in there which only bent the lever. Hmmm, I have more levers, let's get this thing off by sawing through the slots around the shaft where the bolt goes through. A fight to the end.

Also the tires have finally arrived for the road race version. I'm still cleaning and shining the rims which is no small matter. I'm quite mobile after the knee operation but not quite ready for wrestling tires on the garage floor. My cruel motorcycle friends call me the one-legged arse kicker. Maybe I'll make them help.

Well, that's the story for now, just checking in!

Maxie

[hodakamax]

I was searching the Hodaka shed a few minutes ago for miscellaneous project parts and run across most of a kick starter assembly. Just for fun and my own curiosity I threw them on the scales. Hmm, more than I thought at 2 1/2 pounds. That along with the gear running in oil all adds up to additional mass and negative forces in our equation F=ma. Probably worth the effort except for an easy start.

Maxie

[hodakamax]

Well you're probably tired of Max's engineering on the linkage path to the rear brake. Many paths have been explored each with their problems or at least challenges. Hey, solving problems along with entertainment is one of the main themes of this project and with no deadlines I can mess with it all I want.

On the non-cable approach a shaft is needed for the pivot arms. One quick way would be to install a 3/8" diameter bolt into the existing brake shaft hole in the frame (or drill a new one). 1/2" tubing fits nicely over the and the two arms could be welded directly to the tube as shown in the mock-up. Not hi-tech but probably sufficient to fulfill the mission to pull the rear brake.

An improvement could be made by replacing the grease filled bushing with ball bearings. Check out these cool little 1/4" shaft bearings that arrived yesterday to solve the problem. The arms can then can be welded or bolted to the nearly friction free shaft.

OK, that's the plan for now---Reporting,

Maxie

[hodakamax]

Ah, I think this is going to work. The levers are just mock-ups. It looks like welding the levers on will work. Once the levers are welded in place and the shaft cut to length it will just be a matter of sliding the shaft through the two bearings and securing the Allen screws in the bearings. Since all forces are pulls, I ordered 1/4" Aluminum rods for linkage and new rear brake rod. I never pass up the chance to save a few grams. And yes, that foot peg plate has to go. More than a few ounces there!

Max

[hodakamax]

Hmm, the more I look at this I think the inner lever should be adjustable on the shaft while the outer one can be permanently welded. I've already done quite a search for a bolt on to no avail. I'm off to Ace Hardware and/or the local farm store as we speak to find a collar to build my lever around this example.

I'm sure you have probably noticed by now that I prototype a lot to say the least. I'm always amazed by people who can look at an engineering problem and come up with a total solution in their head and proceed to build a solution. Not me. I've got to see and proceed which also works but can be time consuming. More than one way to skin a cat but you wouldn't want me to be designing a product for you and being paid by the hour, LOL. So much for my spacial relationship deficiency but this project is really good for my problem. I highly recommend it! Slow but sure but really fun! I must also say that everyone's input is appreciated!

Maxie

[racerclam]

very cool high tech brake pedal and linkage

Rich

[Bullfrog]

Maxie,

I REALLY like watching your prototyping efforts! I too have found that many "errors" can be avoided by prototyping in cardboard and wood dowel (etc) before putting major time into metal working.

It is probably my inability to relate well to bikes meant for hard surfaces . . . but will a 1/4" brake pivot rod be a bit of a "flexi-flyer" torsion rod actuating system?

Ed

[Hydraulic Jack]

It is probably my inability to relate well to bikes meant for hard surfaces . . . but will a 1/4" brake pivot rod be a bit of a "flexi-flyer" torsion rod actuating system?

Ed

Yes and no. Quarter inch is pretty light for a torsional load. On the other hand, the reach between levers is short, which will mitigate the issue. A full panic stomp will probably twist the rod permanently. I would also have an issue with the idea that one of the levers will be intentionally adjustable. During prototyping, that's fine. Once locations become certain, I would fully weld both levers AND I would seriously consider slipping a tight fitting stiffening tube over the rod, and welding that, just between the two levers, to help transmit torsional loads. The free length that goes through the bearings is okay for now unless it becomes clear that the rod will also bend too easily at the first bearing. If the rod bears on the frame tube midpoint between the two levers as it appears to do, it will probably be okay, but is something to watch for. Otherwise, either heavier construction or a pillow block at the frame to make the brakes dependable during less than optimal situations.

[hodakamax]

Hey thanks all! The 1/4" shaft is under scrutiny but really seems really solid. The rod only protrudes past the bearing less than two inches and appears to be adequate. Jack, I like and agree your idea of a stiffening tube to strengthen things up things up between the levers. After looking at the idea of that little allen screw actually holding the lever on the shaft seems somewhat iffy. Probably welding is the way to go as you say. All to be tested for sure. My mind changes every few minutes and everyone's input is appreciated. I do have an open mind. Your voices have been heard and will certainly be considered come dawn.

Meanwhile I built an aluminum rear brake rod from 1/4" stock which is slightly larger diameter than the stock steel one. The brake adjusting nut was drilled and re-tapped as was the rod was threaded to 1/4-20. The die did fight me a bit (quite a bit actually) and kept clogging on the aluminum. The heim fitting for the other end requires a 1/4-28 and I hope it goes a little smoother than the other end. The steel 1/4' rod threads really nice but the weight difference of 3-4 feet is noticeable. We'll see.

Maxie

[Hydraulic Jack]

Oil the die and rod.

[Bill2001]

Enjoying your "TLAR" engineering sessions, continue on.
I think the torsional strength will not be a problem. This is a rear brake and you'll reach the limit where the wheel locks. It might even help the "feel" of the brake to have a bit of torsional springiness.

[Hydraulic Jack]

Bill,

Here is where I will disagree completely. Torsional springiness is the verbal equivalent of spongy brakes. This is a safety issue as well as a functionality issue. Brakes should have a nearly linear response to pressure, otherwise, you will never know what your brakes will do until you wait for a reaction from the bike. At 80mph this is not acceptable. It gets worse as speed builds. You can't hit the rear brake and wait for the rear tire to break free to know how much force you are applying, and frankly, my attention at speed will be focused somewhere else than filtering feedback from a spongy brake rod.

Brakes and steering are critical components of a safe motorcycle. Compromise for the sake of weight isn't a wise approach. For an example, look no farther than the front brake hub assembly to be used here. If that's lighter than an Ace 90 front hub I'm the Pope. So the real question is whether the brake assembly is reliable. It is possible that a quarter inch rod will be enough, but if it has any wrap to it under pressure, all that will create is a lack of feel and a tendency to shudder. Having the back end bunny hopping because of a springy brake rod would be entertaining, but not really something to aim for.

Look at the brake assemblies used by Hodaka on its various models. You won't find a torsionally resilient rod anywhere in any of these parts. Using a quarter inch pivot rod through the bearings may well work if the foot end of the assembly is well supported because the bearing end of the assembly doesn't carry a load and isn't being twisted. But for the parts that matter, it would be better if the two levers stood off on a half inch welded tube rather than a quarter inch rod. These parts may feel stiff now, but I ask if that feeling arises from the hands or the feet. The Ace series used a hefty welded tube between levers, and generally, the foot lever would bend well before any other part of the system failed. The footpeg setback here should also be strong enough that it is not the functional link between levers that fails first.

[taber hodaka]

When Max is in the finished up mode and into his test cycle, if it feels really really good and functions really well only functional parts will satisfy. Anything less will be modified. Hodaka was created by the folks thinking outside the box. If it does not function to desired standard, seek the wisdom of Jack the researcher, talent minded with comprehension. -----------Clarence

[taber hodaka]

Because we are sharing thoughts here and I would normally be accused of overbuilding. The 1/4 shaft seems light too me.. Also the bearing on the other side of the frame is adding little support. A bearing fastened to the frame would help support the shaft and balance the thrust. ------------Clarence

[Bullfrog]

I went to the garage to run a quick prototyping test. I clamped a 1/4 diameter steel rod in my bench vise with 2" of rod sticking up above the vise jaws. Then I clamped a ViseGrip to the upper end of the rod - leaving slightly less than 1.75" of "free length" between ViseGrip and vise. I then hooked the end joint of my pinky finger on my left hand onto the ViseGrip and easily pulled approximately 3/8" torsional rotation into the rod. So we have 1-pinky finger of force on about a 9" lever arm with 3/8" of torsional "wind up" in the rod (measured at the end of the ViseGrip). If my fishing scale hadn't expired, I could give you a real force measurement. Ennnneywayeeeee, I still think the 1/4" rod is wayeeee undersized. Your mileage may vary.

Ed

[hodakamax]

Ah, a fun and satisfying day in the Hodaka shop. A leisurely pace of design and manufacturing eventually ate up the whole day. First the building of the pivot levers which you must remember was done with a drill press, hack saw, bench grinder and associated files etc. Big fun. A test assembly to check clearances which I somewhat got through. My, some of this is really close . It all fits and I still have some options with jam nuts and shortening some bolts. The 1/4 inch shaft is looking a bit wimpy and I'll probably go with Jack's idea of a tube between the two levers. We can get a few more welds with that set-up for strength and it will be an accurate spacer for a some what critical measurement between the levers. Luckily the angle between the two levers turned out to be 180 degrees which simplifies things.

I mentioned earlier that I had some problems threading the aluminum shaft as the die kept cogging and wandering. I did use oil on the die and shaft and one would think that oil is oil and motor oil would do. Today I bought some Thread cutting oil (Ace Hardware of course) and things went much better. Quite the difference. All went well.

Here's a couple of shots of today's progress. A tube spacer and welding and all should work!

Maxie

Hey Ed, Good research going on there! I think the tube will help. I went with the 1/4" shaft because of availibily of hardware in that size. I tried to find 3/8 shaft bearings to no avail but I'm sure there's some metric next size stuff. First evaluate what we have and go from there. Live and learn!

[Bullfrog]

Welded-in tubing between the arms will remove the torsion bar "winding up and un-winding" . . . but you'll still have a pretty bad bending moment between the inner arm and the frame mounted bearing (as Hydraulic suggested). I'm putting my money on the brake pivot rod bending within the first three cautious and gingerly test rides.

Some easily turned aluminum pieces could be whipped up to house either larger ID ball bearings or bronze bushings to work with larger tube. I could turn some simple flanged cylindrical pieces to your specifications on my itsy-bitsy Taig lathe . . . and I have a small inventory of 6061 Aluminum round stock and some bearing bronze to work with. (Is this a sneaky way to attempt to get in on your scooter build or what? ) I have 1.75" dia aluminum (and smaller) on hand - and bronze stock to make bushings for 3/8 or 1/2" tube. (and if needed, I'd bring in some larger diameter stock . . . so I'd have some on the shelf for some as yet unidentified future project).

Wait just a second . . . I also have black delrin/acetal on hand. It might work for a semi-super light weight design where the bushing/bearing mount IS also the bushing. (Imagine your bearing assemblies out of single pieces of delrin with bores sized to the brake pivot tube.)

Food for thought.

Ed

Ed

[Bill2001]

I like delrin.

[hodakamax]

Here's a few more thoughts worth considering and discussing. When I pull a 6" aluminum front brake lever with my hand, I can stop the bike sufficiently. The rear brake lever is 5". Required braking forces on the rear are substantially less than the front due to weight transfer. The maximum force I can apply to the 5" lever is my entire weight which would be unlikely. In reality I'd probably putting hand like pressures no more than the front brake. This is not to say that my entire weight couldn't bend the shaft and should be designed for that scenario. Hmm, my entire weight could break most hand levers. All things to consider.

Some thoughts that come to mind are a stronger 1/4" shaft material to replace the soft iron. The length needed is 7". A search for a 1/4 x 7" hardened bolt has not yielded any results so far. A shorter bolt could be used by sandwiching the two bearings on the same side. A 1/4" drill bit is available which might break but not bend. All of these materials need to be welding compatible or a new mounting scheme figured out to mount the levers on the shaft. A larger shaft would certainly be better and maybe I can find bearings of the same outer size with larger inner size. Hey, just thinkin' here!

My thoughts are that it will probably work as is but as a prototype, now is the time to act if necessary.

Hey Ed! Thanks for your input and thinking outside the box, always appreciated and the same goes for the rest of the gang.

Fun stuff, engineering.

Maxie

PS---I did some somewhat crude testing with a 12" wrench and the shaft vs a standard bolt. The shaft material bent at about 15 foot pounds and the standard bolt at 25 foot pounds. I'm sure a tougher bolt would far exceed those numbers. I doubt we could generate those forces with the levers and linkage as designed now but doubting and testing are two different things.

OK, it's about an hour later and I'm still fiddling with measurements. A measurement at the front brake lever for a really hard pull is about 26 pounds but it's only about a 4" lever which means I'm only generating about 6 foot pounds into the system which gives a redundancy of 2-3X for bending the shaft at 15 foot pounds. Enough? We'll see.