PD: Primary Drive Make your own Generator

Robert Watson

Well Known and Active Forum User
VOC Member
I appreciate the Walkernator as being a very serviceable solution, albeit some what large and bulky.
I went at it a little more discreetly.
The alternator is a permanent magnet from a small John Deere tractor. It pivots on the through bolt for the footrests (the hole needed to be drilled out slightly and the battery tray mount shortened, I recall I made anew one) and the outer end is held by an automotive style slotted arm pivoting from the original generator hold down clamp. The jack shaft is a two piece part held together with a draw bolt in the outer end and suspended between two bearings, one in the opening which already exists and the other in a solid outer cover. As this seals up the primary I have a small breather fitted to the inspection cap. The pulleys are J section 6 rib poly V belt. The largest I could fit on the jack shaft and the smallest I could fit on the alternator. It has been running since 1992. It has had two major issues. Once due to pilot error - the screws holding the sprocket to the jack shaft were not installed correctly and even the lock wire couldn't hold them, This was on the original one piece jack shaft and disaster ensued. the other was that a wire fell off the regulator - twice. I run an 85W headlight and have switched most everything else to LED, and I also run a heated vest. It pretty much balances the load around 2K RPM.

These units come in 3 sizes...

200 watt units (which is what I have)

300 watt units are the same as mine but the regulator uses all three coil outputs. whilst mine only uses 2 of the three available.

400 watt units which use the 3 outputs and the alternator has stronger magnets.

I have run this for about 100K miles (yes 100,000 miles).

The belt drive has had the belt replaced once or twice and I carry a spare although it has never failed on the road. I don't crank it up too tight and it stakes the shock out of the permanent magnet system. I have never had it "eat" the rollers on the primary chain.

It was a bit of a PITA to make and install, but has been VERY reliable.






20190702_072936.jpg
 

oexing

Well Known and Active Forum User
VOC Member
Robert,
great reading. I guess the small belt drive type is a permanent magnet alternator. So you don´t have the triplex shock drama reaching the rotor via the belt at all. I absolutely don´t see the magnet "shock" symptom from the alternator magnets, definitely , my motors have 8 poles and I can tell by holding the motor in one hand in tests. They feel all smooth, and we are talking about some mere quarter of one hp and at speeds high enough !! This argument is OWT - old wifes tales.

Vic
 

Robert Watson

Well Known and Active Forum User
VOC Member
If you grab one of the permanent magnet types that is gear driven you can see the shock comes from the magnets passing the coils for sure.........The Kubota (and old style Alton i think) gear driven replacements do have some substantial shock value (Physical, not electrical) when driven by a gear train or direct connected. This unit is bigger in dia and therefore does not requires such strong magnets and spins somewhat freely by hand. the belt seems to take care of any slight shock loading.
 

timetraveller

Well Known and Active Forum User
VOC Member
That is looking good Vic. It will be interesting to see it working on a complete bike. One query. You mention one end being machined for an ignition pick up. On twins the generator rotates at 1.25 times the engine speed On singles it is at engine speed. Do you intend to make some sort or reduction gear for twins to reduce the rotational speed?
 

oexing

Well Known and Active Forum User
VOC Member
Norman,
that end is standard in that motor as its main purpose is most likely a servo motor with its magnetic hall sensor - that I removed, no use here. I just rememered someone asking for the Hegeler system and its generator at the mag position. Without any gearing up - that I´d hate to have there - with its own flaws - you would see twice the speed required to get my readings of course. I don´t plan to offer any sets, just messing around, mainly for own bikes - and discussions . But you are right, on a Comet this could be a great way having power plus electronic ignition from that end.
Forgot to mention: No need to reduce o.d. of the motor to the very end of the end cap to 68 mm, there is sufficient clearance to the engine case already. Just the drive end is critical, but 70 mm is doable on the engine case when you decide on that motor size. 68 mm are very common though.

Vic
 

JustPlainBill0

Forum User
Non-VOC Member
Following your work closely (and enviously) Vic, If I had your skills I'd be copying your work. Failing that, I'm going a slightly different direction. I've purchased a China made 143 x 60 mm brush type, 87 watt permanent magnet motor ( eBay item number: 401766275363) hopefully to reduce the need for custom machining and not stray too far from original looks. For non-machinists, the 60 mm diameter body permits more flexibility in mounting and positioning the generator than possible with a 68 mm body. That is, one can use a conventional steel, "L" style front motor mount or a spindle motor mount somewhat resembling the Vincent part; both of which allow some up/down, fore/aft adjustments. I have not thought through oil sealing yet; love your O-ring solution. My plan is to arrive at an inexpensive, largely do-it-yourself generator for the unskilled; with the same advantages in finding replacement parts as for the China brushless motors.
 

oexing

Well Known and Active Forum User
VOC Member
Instead of using a L-bracket I´d try to fix the cylindrical motor in the standard cradle by placing some sheet alu under it. The L-bracket seems to me vibration-sensitive, a bit too flexible on this application. To be open, meanwhile I got quite a collection of various motors for testing. Seems , the best bet is a 24 or 48 V motor to get a good voltage from low rpm and 14 V there.
There are a number of motors possibly suitable, a 57 o.d. mm is very common too. So, yes, some get some satisfaction from trying things in own workshops instead of just buying from well known sources.

Vic

57 mm motor:
DC motor 125 W
 

JustPlainBill0

Forum User
Non-VOC Member
There are gusseted L brackets available, but in general I agree they aren't so good for this purpose. This mount (next to the Vincent cradle):

DSCN8338.JPG


is for a 52mm spindle motor . That style is available in 57mm and other sizes, but the mounts tend to get wider as the bore diameter increases, so attachment to the engine case gets more difficult since you have to offset the mount (rearward) to center the motor in the engine case opening and you run out of room on the top of the case for the mount.

I'm acquiring a nice motor collection too Vic. While I was awaiting an answer regarding bearings used on the 60 mm China motor, I ordered a 100x52 mm 50 watt 24VDC brush motor that I will try with the spindle motor mount above. You can see I'm moving away from high output generators. My experience with the 12K rpm 200 watt motor at high RPM was not good. At 60 psi to the die grinder, and a 55 watt bulb, I recorded 60+ volts (upper limit of my meter) before the meter died and fried a couple of 12V sealed beam headlights along the way. My earlier test at 60 psi showed 18 volts with a 55 watt load.

Two things I learned using the air die grinder to test the generator: First you need to be pretty damn sure you know the relationship between air pressure to the die grinder and voltage output by the generator before seriously testing. I've been using a linear model: for example, if the motor needs 12VDC to spin 3000 RPM, I calculate that each additional volt will turn the motor an additional 250 rpm. And that when the motor is used as a generator, each additional 250 RPM will generate one more volt when turning the generator with a drill or die grinder. So to estimate generator speed, I measure the voltage produced by the air die grinder at a set air pressure and calculate motor speed by multiplying voltage times 250 for my estimate. That process can be repeated at different air pressure levels to the die grinder and you can determine approximate power output at different RPM and then at different road speeds. The purpose of this is not only academic, but it allows you to limit generator speed to real world levels during testing so you don't blow out your test equipment. Crude, but as a friend said "it's good enough for who it's for".

This leads to the second thing I learned: New carbon motor brushes for inexpensive China motors are made with barely concave surfaces that need to be "seated" to match the commutator shape before they deliver full power. Seating is done by running the motors with light or no load for a period of time?? to let them wear-in. If the brushes are not seated, power reading and generator performance will not be peak until they are. My failure to let the brushes seat probably accounts for the higher than expected power outputs that fried my test equipment. Lesson learned.
 

Martyn Goodwin

Well Known and Active Forum User
Non-VOC Member
Norman,
that end is standard in that motor as its main purpose is most likely a servo motor with its magnetic hall sensor - that I removed, no use here. I just rememered someone asking for the Hegeler system and its generator at the mag position. Without any gearing up - that I´d hate to have there - with its own flaws - you would see twice the speed required to get my readings of course. I don´t plan to offer any sets, just messing around, mainly for own bikes - and discussions . But you are right, on a Comet this could be a great way having power plus electronic ignition from that end.
Forgot to mention: No need to reduce o.d. of the motor to the very end of the end cap to 68 mm, there is sufficient clearance to the engine case already. Just the drive end is critical, but 70 mm is doable on the engine case when you decide on that motor size. 68 mm are very common though.

Vic
The idea of a single unit as generator and ignition, especially on a Comet is not new. When I first took over the Comet I have it was fitted with one of these units, which I still have in my 'parts bin".
 

Attachments

  • Miller DH1 - 1.jpg
    Miller DH1 - 1.jpg
    133.9 KB · Views: 37
  • Miller DH1 - 2.jpg
    Miller DH1 - 2.jpg
    152.9 KB · Views: 35
  • Miller DH1 manual.pdf
    12.7 MB · Views: 12

Robert Watson

Well Known and Active Forum User
VOC Member
The idea of a single unit as generator and ignition, especially on a Comet is not new. When I first took over the Comet I have it was fitted with one of these units, which I still have in my 'parts bin".


Gee Martyn. I posted up a while ago pictures of a DH3 I acquired, I couldn't figure out why there is a set of points in a generator. The cover says 6V 30W 1700 RPM. Look here, where you responded with a brochure...


Now I am going to have to delve deeper into the magic of Miller
 
Top