Close ups of the US Pro Drive gearbox - Warning! 10 inline images all at just over 200k each, size 1280 X 960
Video's of the US Pro Drive unit running on the bench.
Most of the Currie Drive System owners are "happy" with their bikes, and don't think there is much room for improvement. But one woman in the stream of a ride yells out, "This thumb throttle sucks". We purchased the Magura Twist Throttle from Scott (EVdeals.com) that arrived in no time, and was simply installed. And this changed the bike ride completely. No more awkward thumb position, no more uneven increases in speed, a seemingly natural relationship with the power. (For a moment I thought I was back to the '60's with my power-assist 650 Trimuph.) I moved the gearshift to the left side to get right hand control, and wonder if a bike with a front and back derailleur may have some problem - ask Scott. The electrical connector was made to fit the Currie System. I recommend this Twist Grip idea for throttle control, but understand Currie's desire to keep the bike/kit price down. EV Global's SX has thumb throttle and sells for $US 1850, I guess they want to keep the price down too.
There have been so many posts on this that I decided to tell you all now. I put the PRO Drive on my road bike, and I don't like the looks of my throttle. It is made for a mountain bike and doesn't really fit right on the loop of the handlebars of my road bike. I wrapped handlebar tape over it but it is still a big ugly blob.
As a result, I designed a motorcycle style throttle with the variable resistor, spring, and everything up inside the handlebar. I will have to drill a hole in the middle of the handlebars for a wire to exit, but that is all the modifications to the handlebar. At the end of the my twist throttle is a teflon cup that shrouds back over the ends of the handlebar for 2". I will put foam over that, and foam over the rest of the handlebar. When I am done you should see nothing but handlebars with foam on them and a little space 2" up on the right handlebar separating the stationary foam with the foam that turns. I am still machining out the parts now. When I am done I'll put pics on the web and let you know. I am using a different variable resistor than what comes with the kit, because I need the wires to go straight out the back of it. So, I had to experiment with my USPD kit. I measured the variable resistor with an Ohmeter and discovered that the variable resistor in the USPD kit is very different from most. It ranges linearly from 0- 5K in 1/4 turn. It still rotates 280 degrees like any other variable resistor, but the 45-280 degrees does nothing. I discovered also that USPD must have originally designed their motors for stock variable resistors because 1/4 turn on a standard 5K variable resistor is full throttle. So really about 12 degrees of turn on all Currie drives are full throttle even though you can turn them 1/4 turn. So, all of you don't really need to push the throttle so far to get full throttle. That may help your hand, just push it about half way.
We did two things to reduce the "throttle hand" sensation:
1) took the throttle apart and overstretched the spring a bit so it requires less tension to activate, but still returns to zero position (about 5Kohm, I recall)
2) turned (loosened and rotated) the throttle assembly so that it can be held fully activated (almost 0Kohm) with the first joint on the thumb rather than thumb fully extended
Repositionng the throttle alone may make operating it much more tolerable.
We'll look at combining a kill switch linked to the hand brake with a full speed "button" on the throttle, combining an idea from a prior posting.
"Scott MacGregor" <smacgregor@a...> wrote: After spending lots of time writing e-mails and talking to customers on the phone, I've come to the conclusion that this public notice may be helpful to Currie scooter and bike owners. Although this problem has been addressed in earlier posts, I think it's necessary to restate the technical tip as follows: > If you are experiencing poor battery performance from your Flyer, Scoot-e, Phat-E, Phantom, or Pro-Drive Bike, (charging problems, slow speed, low range, etc.) there may be a simple cure. In some cases, I have found the "push-on" battery connectors on these products quite loose as they come from the factory. This loose connector problem can cause any of the above mentioned difficulties, as well as intermittent operation or losing power after going over bumps, etc.
Excellent suggestion ! In addition, when a fellow CTI owner of an eFolder here in Central NC complained of an intermittent problem we did two things:
1) cleaned all connections with a wire brush and used an antioxidation compound on the battery and switch connector leads in the battery pack and on the connectors (Ilsco De-Ox from a local electrical contractor supply store)
2) added a 40A fuse into the (+) 24V lead, but left it internal to the battery pack
The former seemed to enhance performance, the latter simply added the same fuseable link safety feature that is in the CTI frame mount pack. Interesting that the rack mount pack doesn't include a fuse.
We also thought about adding a small set screw to tighten down the connector to the battery lug (there is already a hole appropriate for #4 set screw), but should also put an insulating compound over the screw. We'll add this latter step if the intermittent performance problems creep up again.
Now we're thinking about doing
the same on the CTI frame mount battery pack. We'll wait
if/until we update batteries. Any experiences on warranty
issues with batteries if the frame mount battery pack
seal has been broken ? I have to admit, I've never
returned a gel cell (except for cracked in shipment) in
over two decades of dealing with them in numerous
very important that you do not clamp the rear fork
dropout hard against the USPD! I made the mistake of
mounting it tight at first and almost ruined the bearings
inside that shiney Al part. I put a 0.2" spacer over
the quick release axel so that the fork clears. I also
had to grind some of the black anodized aluminum away in
order to clear the side tube of the rear fork.
From a previous post: Thanks for the battery advice. The info on the Hawkers web site is very extensive. I tried looking for a "Long" battery web site, but couldn't find one. Do you know if there is one? I wanted to see what their technical info says, and I also wanted to get the precise dimensions of the batteries. I was hoping that I could reuse the battery case that came with my Currie.
The full name of Long is actually Kung Long. After a bit of searching around, I was able to find a few websites for them:
The main English page is at http://www.kunglong.com/
Here's one of their distributors:
http://www.globalsources.com/GeneralManager?&design=clean&language=en&action =GetSupplier&page=supplier/Showroom&supplier_id=6008800051271&showroom_type= &action=GetPoint&point_id=3000000149745&catalog_id=2000000003844&prod_id=186 45
I believe this is the specific battery that Currie uses, the WB12-12E:
http://www.globalsources.com/GeneralManager?&catalog_id=2000000003844&design =clean&language=en&action=GetSupplier&page=supplier/ProductDetail&supplier_i d=6008800051271&product_id=8811441628&action=GetProduct
I notice that at the 1C (12 amp) discharge rate, the capacity is only 5.4 AH on this "12 AH" battery. This makes sense to me. I have found that my Currie can only go full speed on one battery in rolling terrain for about 5-6 miles. At 24 volts, 12 amps is 288 watts, which is about what you would need to go 16-17mph.
At the 1C discharge rate , the capacity of the 13AH Hawker is around 10AH. Thus, the 13AH Hawkers will give you nearly twice the range.
A calculator for estimating battery capacity at varying discharge rates (and a good description of why it matters) can be found at http://www.geocities.com/CapeCanaveral/Lab/8679/battery.html
I can't remember how much extra room is in the case (I'll
open it up tonight or tomorrow and take a look, but it
doesn't look like the Hawker (6.9" * 3.3" * 5.2)
will fit in the spot that the Long will fit (6 * 3.9 *3.9).
Making a case out of plywood should be a pretty simple
thing to do.....
Currie Tech Batteries if all the post seems to use the Kung Long batteries. Here is the web site. I am not sure exactly which model it is though, but there is a list of them with technical spec, so it is possible to narrow down which one it is without opening the case.
Hawker G16EP from Rose Electronics Distributing is
going for $84. 408-943-0200 2030 Ringwood Ave, San Jose
.... A better solution might be to switch to a higher quality battery. The USPD uses 2 Long 12AH hour batteries. These are rather cheap SLAs. Switching to a pair of 13AH Hawkers would give you more range. They will have a considerably reduced voltage sag when under load, which means the speed will drop less. Also, since they can take higher loads, they will last longer.
You should be able to get them for about $70 each. I have 2 26AH batteries from them that cost me $90 each. This would give you even more range, but the batteries weigh about 23 lbs apiece. The 13 AH batteries are about 11 lbs.
Remember that most batteries are rated at the 20 hour discharge rate, because it makes their capacity look bigger. Electric bikes discharge their batteries much faster - closer to the 1 hour rate. At the current draw that you are putting on the Longs, these "12AH" batteries really only give you about 7-8AH before they are dead. The 1 hour discharge rate capacity on a really good 12 or 13AH SLA like a Hawker will be about 10-11AH
Some information on the Hawkers:
They also make smaller batteries in 2, 4 and 6 volt modules, up to 8AH each: http://www.hepi.com/monobloc.htm
I bought mine from Rose Electronics - see Hawker's
distributors page. They gave me the best price, even
though they batteries had to be shipped from California
Well, I just switched out the old Mac motor (smooth silver housing, purchased here in the US in Nov. 2000) for a brand new Morgan (black finned housing) on my friend's USPD equipped trike. The motor face is machined differently - you just have to remove the adapter plate used with the Mac and the motor fits perfectly. It came with longer bolts as the Morgan mounts go all the way through the end of the housing. The old motor had problems - intermittently would fail to respond to the throttle, and occasionally made a squealing noise like a clutch was slipping.
By my seat of the pants dynamometer, I would have to say the new motor is more powerful under acceleration. It is slightly larger and certainly looks like it is better made. From a dead stop there is still a pulsing effect when you feed in the throttle. Once you are moving a little this goes away. I guess this is just endemic to the way the speed controller is designed. I still haven't heard anyone's explanation of what is going on with this speed controller and why this should be the case.
It is good to see USPD improving the line - maybe the next version will have no pulsing and NiMH batteries . . .
Many people, including myself, would be curious to know full performance specs for the Currie motor, and also know exactly how this unusual motor works. Well, Pa Sunde from this list was so curious he sent me his Currie motor for me to "disassemble and do as I choose to measure and understand", just so long as I shared my findings with the Group. Last night I disassembled the motor and will report on the mechanical construction and operation, with full electrical performance to follow. Sell, Ken previously posted some excellent photos of the internals of this motor :- http://photos.groups.yahoo.com/group/power-assist/lst
As you can see from the photos, this is a brushless DC motor (BLDC), with the stator windings on the "inside", and the PM rotor on the outside, which is the reverse of how most BLDC motors are built. This is a 16 pole, 3-phase motor. The PM rotor consists of a single-piece ferrite cylinder, which has been cleverly magnetized to have 16 poles around the circumference. Innovative, cheap to produce, and effective. The stator has 18 "legs" around it's circumference, and there is a single winding on each leg. Again, this is unusual. Normally, there are many more legs than poles, each winding occupies several legs, and the windings are interleaved to obtain the 3 phases at 120 degrees apart. In this motor, each phase consists of a group of 6 leg windings wired in series. Each group of 6 windings consists of 3 adjacent legs, and the 3 diametrically opposite legs. In the photos, you can clearly see the 3 lengths of winding wire linking the diametrically opposite groups. I can elaborate on exactly how and why this arrangement works if anyone is interested. This winding design is very cheap and simple to wind, and performs quite well. The legs are only a bit more than 1/2 full of copper wire, partly because copper is expensive, and partly to simplify machine winding I suspect. A carefully handwound version of this motor could pack a fair bit more copper, and raise the power rating of the motor.
The 3 phase windings are connected in "delta". Usually the "Y" connection is preferable as this prevents undesirable circulating currents. I suspect that delta was chosen because each winding will then have a greater number of thinner gauge wire, which is easier to wind, especially on automated equipment.
The electronics (3-phase controller) is mounted on the front flange of the motor, and completely potted. There are 6 screws tapped into the flange, which I'll bet are for mounting and heatsinking the 6 MOSFETS in the 3-phase bridge. Judging from the screw spacing, these are TO220 devices. The small PCB on top of the windings connects to the 3 hall-effect magnetic sensors used for commutation.
The motor is well made, with the shaft supported on two generously sized ball bearings.Weight of motor only is 1650 gms. Overall, the design and contruction is rather clever, and lends itself to being produced VERY cheaply in large quantity.
Stay tuned for results of performance measurements.
As promised, here are more Currie specs. Firstly, a summary of the mechanical reduction system as posted previously by others, and some of the motor parameters measured by me.
Primary reduction: 4.75:1 planetary gear Final reduction: 19T:54T chain Total reduction: 13.5:1 No load speed: 3500RPM @ 24V Theoretical top speed: 32km/hr (20mph) No load current 1.8A @ 24V Torque constant: 0.065 Nm/amp Winding resistance: 0.067 ohms Controller resistance: 0.020 ohms estimated
A good first step is to calculate the "motor contant", Km, given by R/(Kt^2), as explained in previous postings. For comparison, I have included Km for 2 other popular motors.
Twin Revcor motors: Km=75 Currie motor: Km=20.5 (including controller R) Scott motor, Km=13.1
Remembering that a lower Km indicates a more powerful motor, we see that the Currie is no Scott, but certainly blows the pants off the twin Revcor motors used by Zap. The Scott needs to spin at a relatively high 3000RPM to produce 1HP so, as the Currie has a less favourable Km, we predict that it will also need to spin at least 3000RPM to deliver useful power. No coincidence then that Currie elected to use a 2-stage reduction, so their motor can spin at up to 3500RPM.
OK. So exactly how powerful and effiecient is the
Currie motor? Are Currie justified in claiming this is a
400W motor? Next posting will present detailed power and
Currie Silver Motor at 24V (30 km/hr) (ie, throttle control at max, 24V battery)
Currie Silver Motor at 12V (15 km/hr) (ie, throttle control at half speed)
The "rated power" is best defined as the maximum power output for which efficiency is usefully high, and for which the motor does not overheat. On the basis of efficiency, this motor can prodcue an honest 400W of power at 85% efficiency, or even a horsepower at a still respectable 82% efficiency. This is impressive for such a small (1.7kg) motor, and is a result of the very low winding resistance. However, things come a little unstuck when heat dissipation is considered. Such a small motor cannot be expected to dissipate more than about 70W on a continuous basis. It's ironical that a motor with such a desirable power-to-weight is heavily penalised precisely because it is so small! Even so, it is fair to claim this as a 400W motor, corresponding to a dissipation of 73 Watts. For SHORT periods of time, it can efficiently produce in excess of 1 HP.
Compared to a larger and heavier brushed motor of the same power rating, the Currie will rapidly overheat when overloaded. This is mainly just because the Currie is small and light, but the thermal design is also poor. Most BLDC motors are built like car alternators, with the stator on the outside, and able to conduct winding heat efficienty to the case, and thus to the air. The Currie design may be cheaper to make, but has a much higher thermal resistance from winding to case. Observations from Currie owners confirm all of the above - this motor feels quite powerful until you come to a long or steep hill, and then it overheats and cuts out.
Another observation is that this motor (and virtually all e-motors) can ONLY produce good power at rated RPM. To put it another way, the motor does NOT substitute for a gearbox. Look at the above specs at 1/2 speed (15 km/hr), which is the speed that you might like to climb a really steep hill. Maximum useable power output at this speed is only 235W at 77% efficient, and 69 Watts dissipated. Pump more amps thru the motor to produce 336W, and the motor dissipates 160W, and will rapidly overheat and cut out. Again, a theoretical analysis closely mirrors observed performance.
If this motor were used through multi-speed hub gears, you could have a first-class setup, with the potential for a 40km/hr or more top speed, and powerful, efficient and sustainable hillclimbing, and all from a 1700 gram motor.
Enough! I might give a few thought as to how
performance could be improved, but there are no easy-to-achieve
quantum leaps - if there were then Currie would have done
....... improve the performance of the Currie system.
(a) Build your own controller This option is strictly for those with some electronics expertise, but a separate controller would have many advantages. Firstly, the controller heat would be dissipated separately from the motor. Secondly, you could use more and/or larger switching FETS to reduce "on" resistance, improve efficiency, and reduce controller heating, and finally a well built separate controller may be more reliable, and could be repaired without replacing the entire motor. The original MAC controller is totally potted so I don't know what is in there, but it appears to use just six TO-220 style FETS in the 3-phase switching bridge. There really can't be all that much in the way of complex circuitry or zillions of ICs and componenets, because there simply is not the space for them. Nonetheless, building a effective and reliable BLDC controller is quite a challenging project - certainly MUCH more difficult than for a brushed motor. Some of the additional complications relative to a brushed controller are 6 FETS vs. a single FET, commutation sensors and logic must be provided as well as PWM, need high-side gate drive, need circuitry to provide 'shoot through' protection, and current monitoring and limiting is more difficult. There are IC's available to provide most of these functions, so it is certainly not an impossible task. Giles Pucket has built one, and could advise on some of the available IC's. By the time you have finished, you will have spent a lot of time and a fair bit of money on power FETS and other parts, but the result could be very rewarding.
(b) Rewind the motor. For reasons of cost and easy winding, the windings in the Currie motors are not completely filled with copper wire. If you are going to build your own controller anyway then it would be only a small amount of extra work to carefully rewind by hand so as to completely fill the stator with wire. Rewinding would have many advantages. Firstly, winding resistance could be reduced so as to increase the power rating or, for a given power, reduce the motor heating. Secondly, you would have the option of choosing a different battery voltage. Serious electric propulsion systems are at least 36V or 48V, as this reduces current and voltage drop in controller and wiring. As an added bonus, this would require more turns of finer wire, which would be easir to hand wind, and would permit a better copper fill-factor. You also have the choice of using 2 parallel-wound conductors reduce wire gauge. Depending on how the wire gauge turns out, you also have the option of a "Y" connected stator which may be preferable to the original delta connection used in the silver MAC motor. Finally, you get the option of increasing the motor RPM for a higher top speed - an increase to 35 km/hr or so should be feasible. However, be aware that iron loss is already quite high in this motor at it's present top speed of 3500RPM, and attempting to greatly exceed this speed for long periods of time will make for a hot motor. However you look at it though, you have little to lose and much to gain by rewinding for moderately more RPM. You can always use the controller to reduce speed to 3500RPM or less if you want to, but it's sure nice to have the option for a burst of high speed when you want it.
(c) It appears that the later motors, with the stator on the outside and rotor on the inside, are fundamentally a better and more powerful design, and would probably be the better choice for those contemplating building their own controller and/or rewinding.
In summary, a keen and competent hobbyist could significantly improve a Currie assist system, with more torque and higher top speed. Eric is also right in daring to suggest that, if you could build a BLDC controller for a Currie motor, then the same basic design should work for the Ecycle motor. However, the Ecycle motor is a fair bit more powerful, with much lower winding resistance, so you would need considerably more power switching FETs to do justice to the motor. Maybe share a few thoughts about ecycle controller in another posting.
I appreciate the information you share and the effort you put in to being accurate and objective! Hope some of this is valuable in understanding the Currie motor issues.
I have read your description of the MAC motor and it's failure on the power assist group. I was very interested in the description of the failure and your thoughts on the causes. The motors used by Currie up to and including today (qualified by the early use of a couple of short runs of different design) are: 1: A high torque MAC motor for Left hand application. Bicycle 2. A low torque MAC motor for left hand application. Folding bikes, some cruisers and Early scooters. 3. A low torque Kollmorgen for rt. hand application. Next generation scooters 4. A high torque Kollmorgen for rt. hand application. Next generation scooters 5. A High torque Kollmorgen for Left hand application. To replace the HiMac on bikes. 6. A new MAC high torque for right hand application. To replace the HiKol on scooters. 7. A new MAC high torque for left hand application. To replace the old HiMac and HiKol on bikes
Note that the original application of the MAC motors was for a bicycle. It was exposed to much more air flow at higher bicycle speeds and somewhat constant assist from the rider, especially when climbing. The MAC performed extremely well under these conditions. It was quite reliable and powerful. Heat buildup was considerable and because of this I believe the lifespan is/was somewhat limited but certainly not so short as to cause wholesale failure of the motor.
The motor was then placed on a scooter where it had no assist from the rider, it had far less air flow and was subjected to continuous loads like it was a motorcycle. Here shutoff caused by heat was frequent, especially among people who live in hilly areas and or hot climates. Repeated overheating eventually failed many of these motors. It is worth noting that not all failed. Motors in use in flat terrain, cool climates, light riders, and or short distances had far fewer problems.
At this point the Kollmorgen alternative was introduced as the solution to these problems. Unfortunately most of the original low torque Kollmorgens failed because of heat. The failure most commonly on the controller. Currie continued to replace the LoKol failures with new LoKol motors but since it was not a flaw but over-utilization of the motor without sufficient protection, motors continued to fail. About this time the HiKol or high torque Kollmorgen was introduced on the Flyer. This motor was overbuilt enough that heat buildup was vastly reduced and it seemed from the ground up a superior motor to the LoKol. People have for the most part been happy with the performance of the HiKol. With the passage of time however failures appear to be increasing on this motor now also. As Currie does not give us sales statistics our estimates of failure rates is based on cells of product at various dealers around the country.
The bicycle motors have always suffered fewer failures than the scooter motors, however in the last few months failures of the motors on bicycles especially in hilly locations has increased sharply. These failures are mostly the new HiKol left hand. I feel this failure rate is too high and heat I suspect is the problem here also.
Now Currie has introduced a new HiMac that it says is the best motor so far. Scot at EV Deals gives it high marks. I do not have much opinion on it yet as it has very little time in the field to prove itself. It is certainly more powerful than any of the other designs by reports and costs less to buy from Currie, (if you can get one). I like the general performance of the MAC better than the Kollmorgen but it is too early to tell much about this motor until it is thoroughly tested by the market. We will soon learn of it's performance. Our Service Center takes over one hundred calls a day! When thing start to go wrong we hear about it!
We are currently using a new motor that is a good replacement for the Currie right hand drive motors. It is smaller but approximately as powerful. Current is limited to 30 amps but the performance is almost exactly the same as the old Silver Can Mac at 40 amps. It seems like a very good motor. I will know more about this motor after additional testing and use.
Thanks again for all of your hard work and information!
Currie has used motors from two sources.
The most common and most successful one is the MAC BMC motor, which is manufactured in India and China by an American company. This is the "original" motor and most of them were in shiny silver cans. This is a remarkably good motor and is well respected by the industry. In my opinion, it is the best cylindrical motor available for electric bikes and scooters. It is not unique to Currie, and the manufacturer can be reached at email@example.com
The other motor, which is unfortunately not as successful in the Currie application is the Kollmorgen motor. Most of these are in black cans with cooling fins -- but so are some of the MAC motors. Again, not unique to Currie. KM is one of the largest and best respected motor houses in the world.
With all the talk
of improving the heat dissipating qualities of the Currie
motor, I thought I might add a note: I've put close to
2000 miles on one of the older silver can MAC powered
systems, and have yet to have it cut out due to
overheating or overcurrent. Maybe because of the way I
use the system (power assist on hills and into the wind
only) this has never been a problem, but even after a 25
mile ride the motor is seldom more than pee warm!
I just came across a picture of a US Pro Drive gearbox that looks very > different to mine shown one at. (warning - several inline pictures) http://www.recumbents.com/qldpprix/uspd/uspd.htm It looks to me like it doesn't have the planetary gearbox connected directly to the motor as mine does but a chain runs back to a cog before then going forward. http://www.wisechat.com/images/ebike_motor_detail.jpg Other pics at http://www.wisechat.com/carl/e-bikes.htm
That's the older version of the design. My 1999 model is like that. The primary reduction chain makes quite a bit of noise, and is somewhat prone to getting thrown off. The gearbox is a much better solution.
From: Tom Genereaux firstname.lastname@example.org
This is the old two-chain model of the USPD. As a relatively early adopter, this is the same model that I have on my MTB. Works fine, lasts a long time. There are some drawbacks with it - adjustment requires loosening the motor and clutch - a total of 4 bolts. The planetary gearbox design is newer and allows a single adjustor.
Bottom line: the heat sink
(without using heat sink compound) reduces operating
temps 9-10 degrees F.
I have a tube of super heat sink compound called Artic Silver on order that should improve the efficency even more.
All you have to do to mount the heatsink is to remove the front and top screw that hold the motor on, place the heat sink on top of the motor flange and reinstall the two screws. You do not have to remove the motor. The motor flange is the hottest point in the system, so coupling directly to it seems to work best. I tried mounting it behind the motor, using the top and the bottom screws but it was not in the airflow, being shielded by the motor can.
Mary and I have been riding a Greenspeed tandem since 1996. However one of us has a neuropathy resulting from a bout with cancer and the other has Parkinson's Disease. Each of these conditions has progressive deterioration of the muscles in the legs. Several times a week we do short jaunts of 10 to 15 miles but during the last couple of years the places we can go have become more limited because the small hills involved are becoming harder and harder to climb. Recently we got in touch with Tom at Tom's Bike Annex in Mt. Carmel, IL who had installed Electric Pro Drives on some E-bikes. After setting up an appointment we loaded the tandem on the Thule rack on our car and drove from Northern Indiana to Mt. Carmel where Tom installed the Electric Drive. Here is Tom's brief description of the installation. For pictures of an installation visit his web site: http://www.BikeRoute.com/BikeAnnex Here is how Tom described the installation:
"This was the first time I had the opportunity to do an installation on any trike, let alone a tandem. This would be a test of the U.S. Pro-Drive's power. Each installation presents a different set of obstacles to overcome, and the Greenspeed was no exception. Usually, the most difficult problem is to mount the 20 pound battery low enough as not to compromise stability, but that is a non-issue on a trike. We simply strapped it to the rack. The "fun" came with mounting the motor onto the rear wheel. Since the motor plate and the cassette gears each require a certain space on the hub axle, it works best to have wide rear frame spacing. This trike was equipped for a Sachs 3x7, therefore it did not. Since the frame on the Greenspeed is heavily built, it is impossible to make space by setting the frame (bending), so careful modification of the rear axle cones and spacers was required. After some trial and error, I was able to squeeze the loaded wheel into the frame. I then placed the throttle and added six feet of extension wire to connect it. The result was worth the trouble. The motor pulls a single rider along very wellâ¦almost as well as on a two wheeled, single bike. Adding the stoker took some of the snap out of the power, but the assistance provided was undeniable, especially when squirting out into traffic. I believe the U.S Pro-Drive really has great potential for helping less fit, or less capable riders achieve, or maintain their health. For that matter, it can help anyone extend their range."
Thanks Tom. In the week since he installed it we have found that it works very well. Used with the 20 inch wheel the maximum speed is 12 mph. Since the power can be applied incrementally it works perfectly to aid our efforts over the tops of the hills. Our first test run was over rolling terrain that we had quit riding because the hills had become too tough. We stopped at the bottom of a grade that is estimated to be a 10 to 15 degree climb of about Â¼ mile. Using only the motor it took right off and climbed the grade at 10 to 11 mph. The loss of the internal gears in the Sachs 3x7 hub was not a problem. In fact for most of the last half of the ride we put it in our highest speed ring and used only the 7 gears of the cassette on the rear wheel. When we hit the lowest gear of these we added a bit of motor assist and breezed over the hills. The other place it proved to be a godsend was in taking off at the intersection with US 33. By hitting full throttle on the motor we quickly moved through and out of the way of the line of cars we had been holding back. We hope it will extend our riding years by many years.
Thursday, 29 January 2009