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HPV FS26 Assisted with MAC 10T Hubmotor

Building the perfect beast for riding coarse pavement in rolling hills was a fun albeit a bit costly exercise. Final Specifications first:

  • HPV FS26 with Bodylink Seat on Big Apple tires
  • 26/39/52 triple front & 36/11 rear (19-124 GI)
  • Shimano Deore LX Trigger Shifters & Rear Derailleur
  • Shimano M785 Hydro Brakes
  • Rim Caliper Park Brake
  • Golden Motor 48V 10 AH LiFePO4 Rack Mount Battery
  • MAC 10T Hubmotor
  • Infineon 12 x 3077 FET Controller
  • Cycle Analyst 3 Computer
  • Thun Torque Sensing Bottom Bracket
  • DaVinci 160mm Cranks with Crankbothers Mallet DH Pedals
  • 67 lbs total weight

Taking an already stout trike and adding more weight is a hard thing to do. That is until you feel the benefit, which took all of about 30 seconds.

Mounting the 13 lb battery as low as possible and centered for-aft between the front wheels actually made the trike feel much more stable then before E-Assist (which was already very stable). 5" of ground clearance is plenty. Having the heavy duty springs and anti-roll bar is well balanced with the added weight.

The difference in weight between the MAC wheel and the DD3 wheel measured 8.1 Lbs, so the fore-aft balance works out pretty well.

One of trikes I tried in early testing had a Bionx 500 watt with the battery mounted on the rear rack. Not only was it slow to accelerate it was mighty top heavy. In comparison this trike rides like its on rails with boot-in-the-butt acceleration off the line and climbing capability that made uphills feel like downhills.

Compared to an HPV FS26 Pedelec with the Go-Swissdrive package it still has much more power and feels more stable. The added stability of the forward battery position is due to the stability triangle that forms between all 3 tires; further back is at a narrower point.

One thing I noticed with all the Direct Drive systems I tried is the motor feels like it isolates the rider pedaling force from the drive wheel. Maybe that's because you really don't want to pedal on Human Power only from the cogging drag effect, but even the Torque Sensing feature felt a bit dampened.

Hubmotors with built-in torque sensors measure the amount of torque applied to the cassette (or freewheel) gear from the chain and output power to the motor in a linear manner. Of course depending on the gear the cassette is in determines the actual torque force measured.

For example, if the rider applies 100 watts of power to the crank, and they're in a 36 tooth sprocket in the rear, the hubmotor sees a force equal to applying say 200 watts of power. However if the chain is on the 18 tooth sprocket the hubmotor only sees half that level of torque and accordingly only applies half the amount of power.

Using a Torque Sensing Bottom Bracket like the Thun, force is measured where its applied and therefore remains consistent with the rider. A far superior control measurement that results in a more natural and "connected" feel.

As a Torque Sensing Bottom Bracket can accurately measure the riders power input it also doubles as a Human Power meter.

Together with the freewheeling capability of a geared hubmotor like the MAC torque sensing has a totally natural feel with a touch of Superman legs. The riding experience is an unexpected improvement over the internal torque sensors without the cogging drag when riding without power.

Bionx, Go-Swissdrive and Falco systems suffer from the gear ratio turndown of Torque Sensing. The Thun was also tried with the Magic Pie 4 and delivered the same feeling under power, however without power also delivered the "flat tire" feel at normal cruising speeds.

The Cycle Analyst 3 (CA3) computer is at the heart of the "processing" system connecting the following items:

  • Thun Torque Sensing Bottom Bracket signal
  • 0-10X Torque Multiplier Trim Pot
  • Throttle
  • Battery (Voltage & Current draw)
  • Speedometer
  • Brake Switches
  • Controller
  • Intern Temperature Sensor for Hubmotor

The CA3 allows can provide a signal to the controller based on Torque Sensing level, Throttle, or Cruise Control settings. It measures and stores distance, battery power consumed, human power generated, battery charge counts, and has a GPS interface. Nice back light feature it stays lit at all times, very easy to see at night.

The screen is toggled through 8 different views very easily so you can keep up with what information you want to see. For example, want to know how many watts you're pedaling at climbing a hill or pushing your top speed? Some values like the 0.7 AH displayed with alternate every few seconds -in this case to Trip Miles.

The Human Wattmeter is a really nice feature along with an accurate measurement of Cadence. Connected to the GPS option all power data can be stored along with GPS data for an overlay that no other system can provide at 4x the price.

The external controller is an Infineon square wave driver chip driving 12 IR3077 FET's. OK so what's that mean?

Infineon develops small motor components for the automotive world with some of the best Brush Less DC (BLDC) motor driver technology available.

International Rectifier is a leading manufacturer of silicon switching systems like Field Effect Transistors (FET) and have the most efficient and robust FET's for the task; the 3077. FET efficiency is very crucial to prevent the system from overheating under heavy current draw. Moreover the number of FET's provide higher current capacity. It takes a minimum of 6 FET's and sets of 3 can be added to extend capacity.

12 FET's provide up to 2400 Watts Peak and 1800 watts continuous. The wires will burn before the FET's will.

Square Wave refers to the shape of the wave. BLDC driver chips can either drive a Square Wave or Sine Wave.

Square Wave abruptly turns on and then abruptly turns off. That tends to increase the audible noise level, but runs slightly more efficiently.

Sine Wave ramps on, then ramps off, not so abruptly. It is quieter but a little less efficient, not to mention about double the price. On a Geared Hubmotor the lower noise won't be much of a benefit.

You'll notice a lot of wires coming out of the Controller box; the 9 connectors are for:

  • 2 wires connect to the Battery
  • 3 wires connect to the Motor Phases
  • 5 wires connect to the Motor Hall Effect
  • 6 wires connect to the Brake Switches (not connected)
  • 3 wires connect to the Throttle (actually connected to CA3)
  • 6 wires connect to the CA3 Communication Port
  • 2 wires connect to the Reverse Switch (not connected)
  • 4 wires connect to the Cruise Control Switch (not connected)
  • 8 wires connect to the Programmer (not connected)

While this may seem more than you wanted to know, in case you did want to know, you now know.....

MAC offers their Geared Hubmotor with 4 different windings to tailor the motor to various different speed applications. Keeping it simple, more turns are down with smaller size wire. Less turns allow the motor turn faster but with less torque. Depending on the top speed you need and the tire size you have the option of selecting the best winding for your application.

Mac Windings

  • 6T - 400 RPM - Best for 16-20" wheel - highest speed, lowest torque
  • 8T - 320 RPM - Best for 20-24" wheel
  • 10T - 255 RPM - Best for 24-26" wheel
  • 12T - 200 RPM - Best for 26-29" wheel or Tandem - lowest speed highest torque

With the current limit set to 30 Amps and a 48V battery the 10T will push the HPV FS26 to 27 MPH without pedaling and can easily climb a 20% grade with a total weight of 255 lbs.

The green circuit board at the top mounts the 3 Hall Effect switches and a Thermister that relays internal temperatures to the Cycle Analyst. In the event the motor rises above a set point (160° F recommended) the Cycle Analyst can be set up to "Scale Back" power to reduce further heating. If it reaches a higher temp (190° F recommended) it can shut off power completely. Despite riding in 100° + heat on steep hills, I've never had the MAC reach "Scale Back" heat level.

The cover plates on both sides are easily removed with six T20 Torx screws each.

The MAC has a screw-on Freewheel rather than a Freehub with Cassette. The Sheldon Brown site does the best job of explaining the difference between these two designs.

As gear systems migrated to Freehub Cassette systems in the era of 8 speeds the availability of 9 and 10 speed Freewheel Gearsets became a bit sparse. However as most of the Hubmotors tend to use the screw-on Freewheels and that more people are upgrading to Electric Assist, there are more options available.

The MAC was designed to fit on a 135mm Dropout Spacing which is consistent with most trikes. 9 and 10 speed systems add about 3-4mm to the width and will need a spacer to fit on the axle which will clear the inside of the Freewheel Gearsets. Most Dropouts are elastic enough to be spread 4mm or so without causing any stress concerns. For that matter its not really that difficult to pull & replace the wheel in case of a flat repair on the side of the path either.

The MAC comes with special washers with a tab designed to lock in the dropout. Grind off one of the tabs and place that washer on the axle first, then use the second washer with the tab facing outwards to fit in the Dropout and that will give plenty of space for the gears and chain. As the second washer is supposed to go on the left side it will offset the wheel by maybe an 1/8" but that's not a problem unless you plan on having a rear disk brake. Few trikes need rear disk brakes.

Sunrace makes a pretty good 36/11 tooth 10 speed and is available on Amazon for about $100. You'll also need a tool to remove the freewheel Park FR1.2 and possibly a 9/16" drill to bore the hole in the tool so it fits past the 12 MM axle. As the axle on a Hubmotor is larger diameter than standard the center hole on the tool may not be large enough.

The Sunrace freewheel works pretty well, shifts very nice as it has the sprocket faces cut to allow the chain to lift or drop as needed.

With 120 Newton Meters (88 foot lbs) of torque on hand for the MAC 10T a quality Torque Arm is an absolute must have. If you rely only on the supplied tabbed washers its just a matter of time before the motor twists out the dropouts and spins until it rips out the wires.

One of the best Torque Arms comes from Grin Technologies and is often available from other Hubmotor suppliers as well. Made from 1/4" stainless steel plate it slides onto the axle having the proper size flats to hold the axle. The Torque Arm V4 is actually the part shown coming off the axle at about a 2 o'clock position. As the HPV has a caliper mount a 1/4" thick x 1" wide aluminum bar was cut to about 3-1/2" and with holes drilled and tapped to fasten the Torque Arm. After this picture was taken the bar was cut to the contour marked for aesthetics.

The cable that exits the motor is tied down to the swingarm with cable ties. After this picture was taken a white sleeve was installed over the cable with plastic twist locks to enable easy removal in the field in the event of a flat.

The built wheel came with a Schrader valve rather than a Presta Valve. As most Mountain Bike tubes are Schrader that simplified finding thick walled puncture resistant tube which is highly recommended for any Hubmotor. Puncture resistant tires are also recommended, after all, what's another 1/2 pound of weight at this point?

Keep an eye on the tightness of the axle nuts and Torque Arm screws, at least daily for the first week or so, and then every couple weeks afterward. The good news with a Geared Hubmotor is it only produces torque in one direction. Direct Drive Hubmotors produce torque in both directions due to Regen and have a nasty habit of coming loose.

Also keep an eye on the Motor Cable connectors where they plug into the controller to assure they don't get pulled loose.

It took a bit of home-engineering to assemble the perfect beast, but it was well worth the time and expense.

Most of my rides consist of 12-25 mile routes with anywhere between 300 to 800 feet of altitude change; figure about double that for total climbing as there are many roller coasters in between. Average speeds are between 10 and 12 MPH. I use the motor mostly to augment hill climbing and most often ride on torque assist with the multiplier set to 50%; every 100 watts I pedal, the motor supplies 50 watts. On some of the longer uphills I'll either set the multiplier to 2X or sometimes just hit the throttle. Most of these times I'm with my riding and life partner who is unassisted. On these rides I consume about 3-4 watt hours per mile.

With a 48V 10AH battery discharge to 80% gives me (48V * 10AH * 80%) = 384 Watt-Hours (WH), and at 4 WH/Mile for a 96 mile range.

When I ride alone, I kick things up a notch. Same routes but higher average speed of about 15-16 MPH. I'll see some bursts to 25 MPH on the flats, and sometimes have some fun with roadies. Riding about 15 MPH and watch them approach in the mirror, and when they're about 100 feet behind I'll pick up the pace never letting them get closer than about 50 feet. This will keep up for less than a mile when they fall back. After they're out of site I'll pull off in an indiscrete place and watch them ride by. Not every ride but maybe 1 in 3. In any event these type of rides burn about 10-15 WH/mile.

With hard pedaling Human Watts at 400 Watts (which I can maintain for just about 1 minute) top speed will peak 30-32 MPH on the flat.

Mac 10 E-Assist Parts List (Includes shipping)

GM LiFePO4 48V 10AH Battery (Golden Motor)
(2) 2.5" OD Pipe Mount Brackets (Battery mount)
Thun 116mm Torque Sensing Bottom Bracket
Cycle Analyst 3
Cycle Analyst Torque Multiplier Pot
Cycle Analyst Programming Cable
Go-Pro Roll Bar Mount for CA3
Infineon 12 FET Controller
MAC 10T Hubmotor laced to 26" Alex Rim
Torque Arm V4
Sunrace 36/11 Freewheel
Electrical Connectors

This system blows the "FET's" off any other system even at twice the price. Powerful, efficient, durable, and ultra user friendly.

HPV FS26 - MAC 10T Hill Climb Example

Yes it really is that quiet and powerful!