The 2 the Max Project

[viclioce]

“Hodaka alternators aren't really all that weak, even if their watt ratings are not impressive, somspark isn't usually an issue.”

True dat! I’ve felt the bite of a Hodaka alternator, forgetting to hold the plug with something insulating my hand!
Victor

[taber hodaka]

Are you talking about spark at the plug Victor? That is not the alternator at work. ---------------Clarence

[Hydraulic Jack]

Are you talking about spark at the plug Victor? That is not the alternator at work. ---------------Clarence

No it isn't. But you have to have a useable range of both voltage and amperage at the primary to get the secondary to do its full job. Hodaka alternators do a fair job of this but I have never tried to bench test ratings to know what they will do, or to find out what the secondary coil needs in the way of excitement to give a good spark. I know a standard bike battery will provide but don't know what minimum requirements are for supplied current through the points.

[hodakamax]

More observations but not in the line of definitive answers. I claim lack of knowledge on the subject. Many new cars have teeny coils for each cylinder that obviously put out a killer spark. I visualize a hot spark and light weight for the project with weight savings in pounds, not ounces. Flywheel, battery and coil could be 1 to 4% of the total weight of a small vehicle depending on the configuration we use. No small thing in the equation with m as mass to slow you down. Isn't this fun?

Maxie

[Bill2001]

That is the idea, Max. See what your current draw is and size the battery accordingly. My Exh Gas Temp gauge is powered by a 750 mAh NiMh pack (next generation "nicad") with a calculated service life of 10hrs betw chargings; with intermittent use, the life is somewhat longer.
The GPS is powered by one if those cell.phone external battery packs. 5v @ 4000mAh will run the GPS for a "couple of outings". That is a full mapping GPS, your GPS Speedo should run longer.

[Bill2001]

"The HF batteries are nicad"

No shorty, they are Lithium.Ion, likely a variant of the A123 LiFePO4 cylindrical cell technology. 1300mAh @ 12v is not a barnburner, but it has proven enough to keep a light electric impact or a small drill running with intermittent shop use all summer and fall.

[hodakamax]

The project and I have fallen behind a bit due to a new unobtainum knee being installed on the builder three weeks ago. All is well and I'm on the move again. Today I could actually drive a car and go and retrieve the rearset plates from the metal fab shop. I could have cut the plates with hand tools but I thought it would be easier to have them cut out on a local robot plasma cutter. The holes are not as smooth as I had hoped but it all looks as though this will work. I had already built the spacers but had some new ones cut out on the run to better match the plates. They now can be clamped together and the edges smoothed in the same operation. Here's a shot of the progress and concept so far.

Max

[Bill2001]

Looks good !!

Remember, with any digital project, a circle is not a circle, but a many-sided polygon. The number of sides depends on the digital resolution of the CAD cutting table and the width of the plasma beam (the "kerf").

[Bullfrog]

Having the rear-set brackets cut out by high tech means certainly eases the time spent with a file compared to mfging by hacksaw and vice! Looking pretty nifty?

Have you contracted for a custom flame job painted on the rocket-ship walker yet? Sounds like your speeds are picking up, so it would be appropriate.

Note that Lithium ion batteries have an energy density some 3-5 times as high as lead acid batteries, and high amp juice delivery is certainly in their bailiwick (witness electric cars and cordless power tools). While the "bang-for-the- buck" decision must consider a host of factors, it seems sure that modern lithium batteries can easily provide the electric power you'll need in a smaller and lighter package than can be provided by lead/acid technology. The power requirements of your GPS are probably listed in the spec sheet. The real unknown we have going on here is the power "draw" of the battery powered point type ignition system. I suspect that you will not be able to use the new-fangled "on plug" automotive coils since they are probably provided with a relatively high voltage, custom "shaped" pulse from an electronic system to "fire" the coil/plug. The planned point timing system will still be interrupting an energy flow through the primary winding of the high tension coil - and it is the rapid collapse of the energy flow through the primary windings which induces the spark voltage in the secondary windings. So, here's a question. Did the old tuning sheets specify a particular coil for use with the "total loss" battery powered point-type ignition system? I would expect that there was such a recommendation - but I don't have the time right now to go into the basement Hodaka mine to dig out pertinent info.

Ed

[Hydraulic Jack]

Max,

Didn't you run a battery powered total loss system "back in the day" when racing circle track? If so, do you recall whether the battery you used was a standard Hodaka style 6V lead acid battery, and if so, do you recall how long your bike would run before ignition started to fail? Perhaps we can back into the electrical needs of the windings and capacitor if we you can recall how long a battery at that time would last.

[Bullfrog]

That is a very good question. Do you remember having to change (or charge) the battery during a day at the flat track?
Ed

[Bullfrog]

Geez, I may HAVE to go to the basement Hodaka data mine! . . . and did you use a 6 volt or a 12 Volt battery back in the day?

Ed

[Hydraulic Jack]

I have nothing against lithium batteries. I use them in lots of different applications from cell phones to flashlights to RC helicopters. My problem going in is that without knowing at least generally what the draw demands are of the ignition system, required battery capacity is a crap shoot, and lithium batteries are not cheap if they are any good at all.

The mentioned A123 cells for example are in the 1.1 amp range but have only around 3.2 or 3.3 volts, so you would need multiples to create either 6 or 12 volts, assuming you really need voltage in that range. My recollection is that the voltage requirement is driven by the coil system.

So if you needed 12V just as a starting point in an example, using lithium cells would require 4 cells to create a nominal 12V system (roughly 12.8 would emulate a standard bike battery.) But the amps available from four cells in series would still be 1.1 amps. Maybe not enough. Doubling the quad cell arrangement would give you 12.8 volts and 2.2 amps. Getting closer. But 8 A123 cells is going to weigh 3/4 pound (39 grams each), which is not so very far from an SLA battery of triple the capacity, and which would not require construction, nor is it even close to the cost of 8 lithium cells. One nanophosphate lithium A123 can cost close to $10 each if you buy good ones. A simple 12V SLA battery can cost around $12 at the hardware store, and is ready to go.

Then, you need to charge your batteries. Lithium cells require a special, dedicated charger to avoid explosions or fire. An SLA battery can be charged with any bike charger.

Another consideration is that lithium batteries have a very steep drop off when they approach discharge. You may not notice any ignition drop off until it is seconds from quiting, leaving you somewhere away from the pits. A lead battery reacts the way we have come to know. They fade gradually, and with a total loss system, you really don't want to run the system until ignition fails.

Electric cars are not an apples/apples comparison. The battery system in the back of the hybrid Camry I used to have weighed a ton. Lithium batteries weigh less than lead batteries, but when capacity is matched, they are not so light anymore.

Once we have a rough idea of how much electrical capacity is actually needed to run your system for the length of time you need it to survive, picking a power source will be much easier. Certainly you can try lithium batteries if you want to, and you can find lithium cells that will provide lots of current, but under high current demand, they don't last very long. Even my mid sized electric helicopter flies for only 8 or 9 minutes before it has to land, and I usually get about a 10 second warning of pending battery failure. Not much of a buffer.

[Bullfrog]

. . . and what would the weight be for a lead/acid battery pack for your RC Helicopter with equivalent Watt-Hour capacity? Just curious.

Ed

[Bullfrog]

It seems like the flight pack for an RC aircraft or quadricopter drone with matching charger might be good for consideration. The charging system and battery are "off-shelf" engineered solutions for a use regime requiring light weight and very high power output. Certainly more spendy than an a lead/acid power pack for the bike . . . but it seems certain that a weight penalty on the bike would have to be paid by that choice.

Again, there is no contest on cost . . . but we are doing thought experiments here. Is there a reasonably inexpensive way to use high-tech, modern, high-energy density batteries and chargers for the project? I'm thinking there just might be.

While we are at it . . . how about a total loss water cooling system? Mayhaps a 1 liter pop bottle pressurized to deliver 1/2 liter of water spray directly to exterior of the head, metered to spray for "x" minutes? Goofy? Yes. But fun to consider for speed runs - and probably totally wrong. Would probably be shifted to "water cooled" class going up against machines with REAL water cooling systems. (Hmmm, purposefully increasing humidity in proximity to the air cleaner inlet? Hmmm . . .)
Ed

[hodakamax]

A couple of answers for the questions. When we did run the battery ignition for a while in the old days the standard Hodaka 6V battery was used and it seemed to last a day of racing. Harry Taylor's Bulletins on Flat track and Road Racing both showed the standard 6V battery and a 6V coil with a Hodaka number of 913009R. Harry's road races were probably quite a bit longer than the flat track agenda.

Max

[Bullfrog]

Thanks for that info Maxie. And it prompts the question, did Harry's Road Racer run total loss ignition?
Ed

[Bullfrog]

DOH. Of course Harry's road racer ran total loss ignition. His road racers (there were several) were the models/development machines which provided the specs for the road race tuning sheet!

I've looked up some part numbers and peered at some illustrated parts lists . . . and we may be on to something. First - the 913009R coil and the total loss system points cam 913007R were listed as ACE 90 racing parts. The parts illustration shows the coil to appear to be longer over all than the coils shown for the ACE 100 and the ACE 100-B, then the Model 93 Super Rat drawing shows what appears to be the same type of longer coil with a part number of 913008R (ditto for the Model 93A Rat). I wonder if anyone can provide the resistance specs for either of those coils? The specs might be in a suplement to the original Workshop Manual - but I don't have a full set of those supplements.

It sure appears that the stock chrome tank Super Rat coil may be very close in specifications to the earlier ACE 90 racing coil.

Ed

[taber hodaka]

The Ace 90 race items were used on the Super Rat including the crankshaft. All parts numbers starting with 91 were ace 90 parts including a head. -----------Clarence

[Hydraulic Jack]

. . . and what would the weight be for a lead/acid battery pack for your RC Helicopter with equivalent Watt-Hour capacity? Just curious.

Ed

Don't really know. I can't recall seeing an automotive class lead acid battery rated in watt hours, and RC models don't use lead acid batteries. I have seen RC battery packs that could easily provide the current needed, but the higher the current capacity of lithium cells, the more they cost and the hotter they get under load. I would also point out that lithium cells don't charge all that quickly, so it might become necessary to have more than one power pack at the track so you don't have to wait an hour to charge cells that run for ten minutes. A lead acid battery also charges slowly, but if it lasts all race day on one charge, recharge rates aren't really an issue.

As I said, I don't have a problem with using lithium cells. Once electrical capacity needs are worked out, it might be worth the cost to buy lithium cells and build a power pack or two. It just isn't where I would start due to cost. At about this point is where some actual research would come in handy.

[taber hodaka]

Only as I remember the small hodaka 6 volt battery did not run my total loss ignition very long, I was not impressed. I call Max's efforts research, he crawls out of the jello mold. ------------------------Clarence

[Bill2001]

He'll need to measure the current draw of his system. Best to use an old dial ammeter instead of a new digital ammeter. Since the points are opening and closing rapidly it might affect the fast digital readings. The dial meter would tend to average things out analogly.

I don't know how this "as working" value would compare with straight 12vdc going into the coil, but there is a lot of electrical stuff going on in that ignition circuit.

[Hydraulic Jack]

Looking at the tech specs for the 93 Super Rat as a starting point, I notice that the coil is specified at 5.35 ohms. That suggests to me that it is essentially a 12volt coil. Also, the 93 produced between 8 volts and 15 volts between 2,500 and 8,000 rpm. I think what you have there would pass for a 12volt system, which might explain why a 6volt battery didn't last as long as it should.

Since you intend to run high speeds anyway, start with the 15 volt output and the 5.35 ohm coil. Ohms law produces an amperage demand of 2.8 amps continuously. Round that to three amps at 15 volts, minimum.

Total loss systems used in drag cars commonly use 16 volt batteries instead of 12, probably for this reason, that demand is on the high end of he scale. Better to have 15 or 16 volts to stabilize a high rpm spark than to have a 12 volt spark that might blow out at high speeds.

So target a 12 volt battery system as a start point, with the capacity to give you not less than 3 amps for as long as you think is necessary for a target run session, with a reserve of anywhere from 50% to 100%. So if you want a half hour run time, you need to be able to produce no less than 3 amps continuously for one hour. You need a 3amp hour system, minimum. That is pretty close to what the old 12volt Hodaka battery was rated at, and a bit of surplus wouldn't hurt.

You can do that with lithium cells, but you are going to need more that a small handful of batteries to do it.

[taber hodaka]

Jack I did not know hodaka had a 12 volt,but then I was not around the newer bikes, good work detective!

[Hydraulic Jack]

I am not sure the secondary coil on the 93 series Super Rat is or was rated as 12 volts versus something else. rather, I assume that it technically is a 12 volt coil for two reasons. 1 is the operating voltage of the magneto, and 2 is the ohms rating of the coil. Coil resistance between 6 volt versus 12 volt applications isn't great, but usually, 6 volt coils have resistance in the 4 ohm range, and 12's have a rating in the 5+ range because of the difference in the number and gauge of windings.

At any rate, I think it is a place to start. I wouldn't begin with anything less than a 12 volt power source, and would want to see around a 5 amp hour capacity, just so there is a margin of error. If you undersize the power source, you might end up with a 20,000 volt spark, which could easily blow out under pressure.

Given the intended purpose of the machine, I wouldn't be trying to find the minimum acceptable ignition system. I would want a strong dependable ignition, even if it cost an extra half a pound in weight. Ignition is a critical component. Losing a half pound of body weight isn't that hard to do for the pilot. You could cut a pound of weight from the machine just in building a light weight saddle. For that matter, I suppose you could adapt a CDI ignition system and lose a half pound just in the flywheel.