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Alternator output on '82 R100RS
I'm thinking of getting a heated vest for winter touring but have doubts as to their power consumption. The output on my bike is barely adequate as it is- at night when I have my 65Watt headlight plus two spotlamps, (50 Watts each), I have to keep to over 4,000rpm or else the alternator is unable to keep up and the battery starts to run down, so what I need to know is whether there is a worthwhile modification available? Also, can anybody confirm that heated vests are any good?
Cheers John ------------------ Johnefyn |
One of Horizons sponcers is -
http://www.motoelekt.com/ They have the Omega 400 watt kit. I have had one for 3 years and they work great. They have them in the UK but I am not sure who has them. |
Motorrad Elektrik (check the links page) makes a 400 watt "Omega" alternator/ rotor/ voltage regulator/ diode conversion that I have heard good reports of. I think it runs about $500-600 USD. The only other option I know of is to buy a newer bike with a 600+watt alternator! I guess 280 watts seemed like a lot back in the 70's.... BTW, it is not a bad idea to run above 4000rpm anyway, the airhead perfers a bit of RPM.
Good luck! [This message has been edited by Timo (edited 08 January 2005).] |
Boy, You have to love the speed and efficiency of this site: 2 replies at the same time in less then 5 minutes! Where else do you get that kind of service and attention these days?!
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Thank you both for the lightning responses! I've just checked the handbook for the output and it's 280Watts, so obviously an increase to 400Watts is definitely worthwhile.
Mind, $575 is seious money to spend on an old banger that still needs a complete exhaust system, brake lines, two cast iron front discs, timing chain plus what else-I-dread-to-think. Any technical bods out there that can tell me how to rewire / rewind my present alternator to increase its output? I did a degree in electrical engineering when I were a lad, I'd just love to give it a try. Thanks John PS I was browsing through some coffe-table books the other day in the book shop and in the section about the R100RS one said it was possibly still one of the world's best sports tourers. Must have been talking bollocks.... wasn't he....? ------------------ Johnefyn |
No, He should have just qualified the remark: in the daylight, in a warm climate! Honestly, I 've never had the pleasure of riding an RS, but the legend is large indeed. The same people will tell you that the G/S is the best overlander ever made (which of course it is if you own one...). Love the one your with.
Boy, I'm glad you mentioned the bon-i-fide engineer bit, I might have gone and stuck my foot well down my throat. give Mottorad Elektrik a ring, maybe they can walk you through the procedure? Keep in mind the up-grade kit is more then just an alternator; the rotor (a weak point) and everything else in the charging system is improved as well. |
Timo, could you expand on what you said about keeping an airhead spinning at over 4000, please? Throttle response? Increased engine life??
Going back to your suggestion re getting another bike, well, the truth is I DO love the one I'm with, as you suggest! Decent fairing, ankle warmers (cylinders), quick enough (for me), panniers, luggage rack, and most times, roadside-fixable and roadside-puncture repairable (tubes). Decent lights with extra driving lamps. And by now we're used to each other. Oh, as for electrically heated vests, are they really as good as they say they are; I'm planning on UK-Prague-Istanbul, possibly before April, failing that, some time after September; none too warm. Many thanks John ------------------ Johnefyn |
The Omega kit has a larger stator and rotor.
The stator is a larger gauge wire. I don't think that there is a way to increase the output without increasing the wire size. If you get one you can find a stator cover cheap, wire that to the new stator. That way you can have a compleat stock alternator to put on your bike when you sell it. There are voltage regulators that will increase the charging voltage for the battery for short distance riding but they don't increase the output, and they may cook a battery if used for a long time. |
What I have heard is that Airheads do not like to be lugged at low RPM in top gear. Most of the Airheads engines are tuned to run best at 3500 RPM and up, and are not as smooth at <3000. Apparently, BMW had a number of engine failures when they first started importing the twins to North America, which was traced to engines being run at low RPM's consistently in top gear (I guess the Americans were used to lower reving engines). On the electrical side, the Alternator is direct drive off the end of the crank shaft where as the newer oilheads have a the alternator turning at twice the speed of the engine, which helps to produce good current at lower RPM's.
The only negative I have heard about using the Omega 400 watt kit for overland adventure is that you are installing a collection of non-stock parts, so parts will have to come from Motorrad Elektrik only. |
RE
1. RPM for airheads - remember that the airhead was designed originally for use in Germany, where they have autobahns, and ride fast everywhere. Keep it spinning, not lugging - as Timo says, 3500-4000 is the bottom you want to run at for best performance and longevity. Lower revs are hard on it. 2. Rick Jones, the guy that runs Motorrad Elektrik, is probably the worlds foremost airhead electrics expert. He tried for YEARS to get increased output from an airhead alternator. The culmination is the Omega. You may be able to do better or nearly as good for less, but Rick's no dummy. 3. The only reasonable? alternative is an Australian made system that costs even more - but mounts a car alternator at the top front of the engine, and puts out huge power. There's more info on the site - somewhere - including a link to the manufacturer. 4. As for heated vests - no-brainer must-have. I bought mine in 1981 - and I'm still using it- well at least the wires, which have never failed, and it's been around the world. The fabric wore out and Susan installed the wires into a nice down vest. We wouldn't travel without one. 5. Note that EARLY airheads - /5 - were only 240 watts, and considered good. The increase to 280 was awesome... at the time... 6. re reliability of the Omega - most of the components have been sold by Rick for years, and are preferred long distance travel upgrades to start with. The only new parts are the rotor and stator, and thus far the reliability record has been excellent. Note that Rick does say not to overload it. Trying to run 500 watts of goodies off it is not good. If the rotor stator fails, used ones are readily available almost anywhere BMW parts are available, so it's no worse than if the originals failed - and the original rotor is notorious for failing on a regular basis. One of Ricks standard replacement rotors is a popular long distance travel upgrade, so the Omega should be very reliable. hope that helps, ------------------ Grant Johnson Seek, and ye shall find. ------------------------ One world, Two wheels. www.HorizonsUnlimited.com [This message has been edited by Grant Johnson (edited 20 July 2005).] |
Thank you all for your, as always, well-informed replies.
Grant, I don't for a minute doubt that Rick Jones of Motorrad Elektrik has achieved the maximum output from the basic components and I'm quite sure that I couldn't improve on his results, it's just that I was wondering if by using a different gauge (thickness) of wire on the standard rotor and stator it would be possible to wring some more amps/watts out of it. Increasing the thickness would reduce the resistance allow the current to flow more easily, but would run hotter whereas reducing the thickness would make room for a greater number of turns in the space available but would result in a higher resistance, but again, might result in a higher number of ampere-turns, which is a good thing because the more amperes of current times the number of turns in a winding then the stronger the magnetic field it produces. The output depends on the strengths of the mag fields in both the stator and the rotor. All clear then? Funny, I don't remember writing all my notes at college in Greek and gibberish- sorry. Many thanks, too, for the recommendation of the electric vest, I got one and tried it today: bliss! If there's anybody still out there unsure of whether to get one or not-GO FOR IT! I also bought a new set of BMW heated grips at a bargain price (I repaired the old ones twice and they are by now beyond hope) and as the kit was for a different model of BMW I now need the little surround that fits around the panel-mounted off/half/full-power switch, Part No.03 8330 to allow me to mount it on the dash. ('82 R100RS) So can anyone tell me the part no of this bit, please? For possibly a greater audience I'm going to pose the question in a new thread- that ok by you, Grant? Thanks again J ------------------ Johnefyn |
Hi,
Re starting anew thread - of course! Always the best thing to do keep the Topic Subject on track, makes finding things easier for others later. (So we don't have to answer the same question #$%# times!) Glad you like the vest! Amazing how long we resist them isn't it? And when you get one, you wonder why you ever doubted it! Never met anyone yet who OWNS one who has ANY doubt! Re rewiring the rotot - good luck - but Rick and I discussed this years ago, long before the Omega, and he had tried - and tried everything, and the improvement wasn't enough to be worth doing. Complicated interactions between the rotor and stator, with the BIGGEST problem overall is the alternator turns at HALF speed 'cause it's on the cam, where everyone else mounts it on the crank, or on a belt system, off the crank usually, and speeded UP not down. Feel free to try and let us knw your results! There's a few thousand dead rotors out there to experiment on. ------------------ Grant Johnson Seek, and ye shall find. ------------------------ One world, Two wheels. www.HorizonsUnlimited.com |
Hello.
Re: electric vests, bought a used Gerbings from E-bay for $160...rode to Whistler and back last sunday durring heavy rain, and without a doubt they're the bomb!! Yes, your right...it's funny how long we wait before forking out the cash for this irreplaceable item! Chris Walstow sent me a link a while back :http://www.motoren-israel.de/ They sell a high-output alt. cheaper than Moto-elec. Check it out. Good luck! |
Have just seen a 400watt alternator available from Motor Works for £235. I'm going to go for that, I think, it should make life a lot easier i.e. warmer.
My grateful thanks to all concerned John http://www.horizonsunlimited.com/ubb/biggrin.gif |
Thought I'd let you folks know that I've fitted the new Motorworks 400watt alternator and that it works just great.
It now powers the 65watt headlamp and two 50watt driving lamps, BMW heated grips and also my heated waistcoat (plus all the rest like sidelamps, instruments and ignition etc)and it does so when the engine is doing 3250rpm. You may recall that with the original 280watt alternator I had to maintain 4,000rpm (70mph in top gear) and that was before I had the heated waistcoat (40watt, I think). The kit consisted of a new rotor and a new stator and a new diode board, some new wiring plus heavier earthing straps. Actually, there was a bit of work needed with these (the straps) The terminals were slightly larger due to the heavier conductors used to carry the increased current, and I didn't like to bend them like the original terminals were bent to fit under the socket head bolt where they go in the recess in the chaincase casting. What I did was to use longer bolts, 50mm instead of 45mm, and made two 5mm long brass collars, 10mm diameter and drilled 6mm. (As it happened the terminals were 5mm and had to be drilled out to 6mm at this end) The terminals were threaded on to the bolt followed by the brass collars and then they were screwed into the casing. The terminals were now level with the casing and so there is no need to bend them, with the collars taking up the space in the recess. The two bolts holding on the engine front cover were just the right length so I used those for the job and used the original 45mm bolts to hold the cover on instead, they only had four turns of grip, but with a touch of Loctite they did the job fine till the proper 50mm bolt arrived a couple of days later. Incidentally, having the head of the bolts protruding does not appear to be a problem; although the original loom carrying three-phase output from the stator to the diode board was routed past the bolt I would say there was still plenty of room for it, but the new loom carrying the three phases plus the Y conductor is now routed differently and is thus well clear of this bolt anyway. Another small thing was that the spade connector of the lead to the voltage regulator from the middle of the back of the new diode board had to be pushed over very carefully to provide clearance from the casing. I also changed the rubber mountings for the diode board even though, surprisingly, the originals semed to be in excellent condition. With these two longer bolts, remember to put them back in their correct places if you take the chain case off in the future, all the other bolts are 45mm By the way, make sure that the lead from the trigger unit is tucked safely out of harm's way when you replace the front cover in case it gets pinched by the partitions forming the cooling channels at the side. I didn't do it myself, but my dealer managed it at my 600 mile service all those years ago. Total cost was £200 plus VAT making £235. I've done about 600miles so far, with 200 miles with full (electrical) load, no problems so far, the max. voltage is still the same at 13.8 or so, and with no worries about the battery running down, and the battery acid level still ok. I know that this isn't much of a trial but if I get any problems I'll let you know. If any one is interested I've taken a dozen or so pictures which are still in the camera. (Digital cameras? Nah, never heard of them) Thanks for everybody's advice, John ------------------ Johnefyn |
Sounds great John!
Only one thing I noticed http://www.horizonsunlimited.com/ubb/frown.gif - the rubber mounts should be tossed and replaced with solid aluminum ones. Originally the diode board was solid mounted directly to the engine. The rubber ones arrived somewhere on the scene in an attempt to reduce diode board failures. However, turns out that failures then went up - the board needs the heat dissipation more than the vibration reduction. And I think a higher output board needs it even more than the original. I thought I needed the ally mounts for my G/S - but turns out that for some reason mine has the orginal solid mount system. So I just happen to have a spare set of ally mounts (stil in the bag with instructions) from I think Motorrad Elektrik... http://www.horizonsunlimited.com/ubb/smile.gif US$20 including post if you can wait till mid-April. Sorry if that sounds like a sales pitch to get rid of some old crap... http://www.horizonsunlimited.com/ubb/wink.gif Grant |
Hey, I didn't know that about the solid aluminium mounts, in fact there's a reminder about changing these for new ones in the back of the Moto-Bins catalogue. Still, heh, serve me right for buying the uprated alternator from Motor Works! Oh, come to think of it, M.Bins don't do the 400watt ones anyway.
Actually, one of the things that impressed me about the new diode board was that the power diodes were mounted on individual, proper, heat-sinks, so they will be better cooled, though, admittedly, as they are handling a greater current, they will need better cooling anyway. In my previous musings regarding increasing the output of the original 280watt BMW alternator I had considered providing better cooling for the alternator, the existing provision for cooling is pretty minimal, there's only the two little vents at each side at the bottom of the chain case at the front of the engine. The power produced (or dissipated) in any electrical item is generally limited by its temperature; the hotter it gets then the more likely the insulation is to break down; if you want more output, then cool it some more. So, what I thought was, drill a hole at the top of the front cover and put a little vent cover on it to keep the rain out, perhaps like the vent plug on the bevel drive casing, but a bit bigger. Going back to the solid mounts, they would be better for another reason, too. I found it difficult to tighten the earthing straps tight under the flexible mounts as it was not possible to grip the mounts while tightening the nut. As it turned out, however, it wasn't necessary to hold them as they didn't want to turn anyway. Hmm, some you win... Anyway, I did do this before actually putting the board in position because of the expected difficulty, and then put the board in its place on the chain casing and fitting the other nuts . (I keep on calling this the chain case-that is its name, isn't it??) I did take some measurements of the new kit before fitting it to compare with the original. The rotor resistance is the same at 3.5ohms, the slip ring diameter about a millimetre greater, the body diameter a couple of millimetres (I've got the actual measurements somewhere, but the difference is not really significant) There are no balancing drillings visible, unlike on the original. The stator is again the same dimensions practically, but the air gap is about a millimetre smaller which is probably significant. The conductor diameter is up from 0.045ins to 0.055ins, sorry, hang on a minute, that's 1.143mm to 1.4mm and is wound differently, the new one being wound approx eight??? turns around three poles and then on to the next three poles and so on, and the same for each phase with each phase being one pole further on. One end of each phase winding is commoned and brought out as the star (Y) connection and the other ends as individual connectors and labelled U,V & W. Total no of poles is 36, no. of laminations 25. Length of pole face is 21.6mm and the gap between 5mm. The old stator was wound with the conductor weaving over three poles and under the next three and so on, again with the three phases with each one pole advanced. My multirange meter was only able to give an approximate reading of the phases, of 0.1ohm for the new and possibly 0.15 ohm for the old. I couldn't count the number of turns on the poles without cutting it up, sod that, the original is still in good working order. I've given all these dimensions in case there's another freak (that's what my daughter calls me, anyway) out there. (Oh, she also calls me a sado. As in sad) Sigh. Cheers J ------------------ Johnefyn |
Hi, Grant
Just read your last reply again and am worried by your comment re using FOUR solid aluminium pillars. This would be absolutely OK with the original type of board but just in case there's somebody out there planning on getting the Motor Works kit then I think I'd better point out that you can use two such pillars for the top pair of mounts but you will need two INSULATED pillars for the bottom pair as the bottom half of the circuit board is live and connected to the battery +ve and MUST therefore to be insulated from earth. No pillars (of either type) are supplied with the kit. For that matter, no instructions are supplied either, but it wasn't too hard to figure out, and to be fair Motor Works did say so when I placed the order. And, yes, it's still working great. Cheers J ------------------ Johnefyn |
hmmm.... bad design there; mine for instance has ONLY cast one piece solid mounts - NO option to insulate, and no room to add in insulated pillars!
Grant |
In the original there is an insulated bush provided around the mounting hole on the board whereas there is none in the Motor Works one, only a bare patch of printed circuit conductor. I think I'll let Motor Works know and perhaps they could at least point that out to customers even if they still won't prove full instructions.
------------------ Johnefyn PS I should add that there would be no problem with the above if you still used the flexible rubber mounts as they would provide the insulation required. One solution would be to use two solid pillars and two rubber mounts, there wouldn't be a lot of weight on the rubbers, but then again they wouldn't last forever. As for me, I'll just leave the four rubber mounts in for now and if I and the bike are still around in ten years' time, I'll do something about it then. [This message has been edited by John Roberts (edited 30 March 2005).] |
The 400W alternatot kit as sold by Motorworks is made by the same company as the kit sold by Rick.
Airhead BMWs have no problems being ridden at low revs. remwmber that Airheads ahave been used by many police services who do escort duty at low speeds and low revs. Charles |
Just read this thread as it came up with todays postings. I feel I have to say something in defense of this bike as "the best tourer". I owned one in the mid-80s when I worked as a despatch rider based in Leeds. I was averaging 2000 miles a week and in 2 years covered over 200,000 miles on a 1977 R100RS motosport, with very little down time due to mechanical failures. I frequently did trips of around 1,000 miles in 24 hours when we were delivering advertising copy to newspapers around the country and I have never ridden a bike either before or since which I have found as comfortable over such long distances in one go. Unfortunately by the time I finished my despatch riding the bike had over 220,000 miles on it and needed a complete rebuild so I ended up breaking it for spares. I was so impressed with it that when an identical bike came up for sale a couple of years ago I bought it. 70 mph is around 3,750 rpm and everything seems very much in harmony and comfortable at anything up to 80 mph. It's also quite capable of sitting at over 100mph for hours on end as well, although sadly that's not really possible now. The only criticism I would level at it is the excessive wind noise and buffeting which seems aimed directly at the riders helmet from the screen.
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Wind noise: yes, that's just about the only real grouse I have with the bike. One possible solution is a BMW System 4 (or is it System 5?) or a Schuberth, and then there are earplugs, which I've only come across after decades of riding. I've posted threads on both quiet helmets and earplugs and both attracted a lot of very useful replies, my current solutions are earplugs, the cheapo ones rather than the custom-made ones but that's only because I haven't got off my backside and actually got some made and fitted.
Otherwise, I still think it's a belter. John ------------------ Johnefyn |
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I debated the whole upgraded charging issue for a few years too. I decided to go with the new kit from http://euromotoelectrics.com/
Here's a link with a write-up from my install: http://tinyurl.com/bncde Nov 4, 2005 I just returned from a test ride with my R80RT after installing an Enduralast 450 Watt system from http://www.euromotoelectrics.com/enduralast.html The bottom line is that from about 1200-1300 rpm onwards, the system puts out 14.1 to 14.2 volts. At idle, it’s between 12.4 and 12.6 volts. I installed a Datel volt meter to give me a constant read-out during riding. I puttered through town this evening and briefly hopped on the freeway. At all points the voltage was constant between 14 and 14.2. Yesterday, after ensuring I had rigged everything up correctly, I wired up an electric vest and a 70 Watt power inverter to the battery. Flicking the high beam on and off at idle makes the voltage blip, but it returns a steady number after a second or so. Since the inverter and jacket didn’t seem to make a difference in the voltage readout yesterday, I did not wire them up for the test ride. The kit contains a rotor (solid magnet) and stator, a mounting bracket, a rectifier and a bewildering array of little wires and connectors, of which you end up using a fraction. There’s even a rotor puller bolt included. The installation is relatively straightforward, but you do need to read the manual carefully. The wiring diagram is a no-brainer. Since I am going to move this system to my G/S in a few months, I did not bother removing any of the original wiring. Since none of it is needed in the meantime, I taped up all the ends and left them where they were. Installation: First job is to remove the original stator, rotor, diode board and voltage regulator. I left the voltage regulator in place courtesy of two spun screws. Mounting the rotor is the same procedure as a regular one. Since we’re dealing with a solid magnet rotor, you want to make sure your wallet and credit cards are not in the vicinity. I wondered about the Hall sensor with this thing nearby, but a timing light check confirmed nothing had changed. The stator is mounted between two aluminum brackets and screwed into place with 3 screws in the same location as the original. No brushes here … this is a “contact-less” system. As with the original stator, you need to slowly easy it into place and tighten the screws in turn. There is one big wire going up and out of the front cover cavity, that’s it. The only other wire under the front cover after the install is the wire to the timing can (for post-81 machines). Lots of space to mount a small box with tools where the diode board was… hmm. I ended up mounting the rectifier to a frame tube and ran a car-size ground wire to the battery negative. This was pure laziness on my part, as others have installed this rectifier under the tank after removing the voltage regulator. It fits in that space. The wiring is simple: The voltage regulator plug ground and blue wire are used (with spade connectors), a wire (with provided 30 amp fuse) to battery positive. Two plugs connect the rectifier to the stator, one wire connects to a switched positive. For the latter you need to bare a (small) wire that gets “hot” when the ignition is on and splice one in. That’s about it. I spent most of my time trying to figure out where I wanted to mount the rectifier … the RT has less space than other configurations and I could not remove the voltage regulator. In hindsight, I preferred it that way. During riding I noticed not much difference, except that my stock voltage regulator was reading much higher than before. It’s nice to know that even when you’re loitering through town you’re not draining the battery. I was somewhat concerned that given the strength of the magnet, there would be more drag on the motor and hence I’d have to adjust idle (more fuel consumption…) but that proved to be unfounded. As well, the rotor weighs less than the stock one. I touched the rectifier at the end of the ride to see if it had heated up, but it was cold. I’m going to eye-ball this setup for a while and decide whether I want to move this over to the G/S. This whole thing started when I contacted John Rayski (Euromoto Electrics) and quizzed him on whether he wanted to have a “guinea pig” for his new system. He was happy to provide me a system, gratis, for which my thanks. Next April, I’m off for a LONG trip across Europe to China and beyond. In order to eliminate the need for carrying an extra rotor and diode board, as well have better charging, I want to take this setup. Since it’s on the RT, I’ll put ample mileage on it between now and then to provide me with enough comfort to put it on the G/S. Another (small) benefit of this system is that the charging light, although powered as with a stock setup, is not required to function for charging to take place. ------------------ Kevin http://www.nohorizons.net [This message has been edited by kberetta (edited 06 March 2006).] |
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Ahem, AFAIK the /5 had a 180W alternator, at least mine did, according to the w/shop manual... Quote:
http://www.horizonsunlimited.com/ubb/redface.gif</font><HR></BLOCKQUOTE> good catch beddhist! http://www.horizonsunlimited.com/ubb/smile.gif you're absolutely right on the alternator of the /5 - I was thinking slightly later model (and clearly not that well): "The /5 alternator output was rated at 180 watts, the /6 at 280 watts, the very slightly smaller diameter rotor of the fast-spinning R90S was rated at 238 watts, and the later models rated at 250 or 280 watts, depending on year." BUT - "Everyone else" being MOTORCYCLE manufacturers, mostly do mount it on the crank where it turns at double speed compared to the airheads, OR indeed off a pulley, as do car manufacturers for even higher speeds. |
Grant,
Why do you say that airhead BMW don't like low revs? What breaks and why? My R75/5 rarely gets above 4500, but often down to 2000, as I cruise through town in top gear at 50 km/h. The engine has done over 100000km without any bottom end work. The barrels got replaced, because it was burning a little oil and I had spare ones lying around. however, if it gets thrashed it throws oil fumes out of the exhaust and the rear of the bike gets covered in oil spots. My girl friend has two R100 and rides them similarly. Both 100000km. The people who I have met here in Europe who have exploded engines thrashed the bikes. Courier riders come to mind. |
the slightly cheaper option is to get the police spec voltage regulator, which charges the bettery at lower revs, better for trail riding and round town work. hope this hasnt already been mentioned.
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Police spec Voltage Regulator
I did try one of those a few years back but I must say I didn't find any noticeable difference.
John |
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