Custom Build Gallery, Drunkskunk’s Full Suspension Fat Bike

May 18, 2013
6,347 Views

Gavin (from Dallas, Texas) is a full sized E-biker (His endless-sphere username is “Drunkskunk“), and he felt somewhat cramped on most of the available frames. Plus he wanted a fat bike, which are not yet available in full suspension.  So…since he owns a welder…he did what any other garage builder would do in that situation. He built his own full-sized fat bike off-road frame, that he designed to be a hub-motored E-bike, with a large battery pack built into the downtube assembly.

The motor he chose is the Crystalyte motor (read our review), which he plans to run 5-10,000 watts through in gradual increments (as he works the bugs out).

 

Drunkskunk2

 

Gavin decided that rectangular tubing would be much easier to weld. The swingarm shock below is a Marzocchi Roco, which is 9-inches long with 3 inches of travel.

 

Drunkskunk3

 

Paint day…there’s nothing stealth about this Ebike!

 

Drunkskunk4

 

“…Here’s what I’m stuffing it with. Twelve 6S/5-Ah packs, grouped into three strings of 4, with the mains and the balance taps wired in parallel, then stuffed into my bike’s extra tight hole. And I do mean tight. It took 10 minutes to squeeze these things into that hole. It’s 18S, peaking at 75.6 volts right now…”

The large 1332-WH pack Gavin wanted almost required him to make his own frame.

 

Drunkskunk7

 

The tires are Surly Larry 3.8-inch fatties riding on extra fat 65mm-wide rims, using 12-Ga spokes laced by John Rob Holmes, who is partnered with Volt Riders in Columbia Missouri. This beautiful custom red frame was left exposed, and the battery compartment panels were covered with a pebble-finish truck-bed coating. Since the bike is proportional to Gavin, it may not look that large…until you read that it has a 57-inch wheelbase! The front brake disc is 9-inches in diameter.

“…It seems my tire circumference is 91 inches, exactly. And…I’m doing 39.7-MPH top speed at 75 volts…”

The front has a full 12-inches of travel provided by a set of Marzocchi Super Monster forks. The black shape just in front of the bottom-bracket is a Lyen 12-FET controller, which is known to handle 45A well. Gavin specified cool-running and efficient authentic 4110-FETs to get the most out of this popular controller.

 

Drunkskunk5

 

The centralized location of the large battery is a great place to locate the pack, and it minimizes the impact of the added weight. Rear-mounted batteries are easy to mount to an existing frame, but they make an E-bike tail-heavy, which affects the handling.

A full-sized bike needs a full-sized hub, and Gavin chose a Crystalyte 5404 (X5-series 40mm wide stator, 4-turns per tooth). Says Gavin: “…Riding the bike is Simply Amazing. It floats over speed bumps, curbs, stairs, small Hondas, the screaming fleeing masses. Its a Monster!”

For this bike to NOT be subject to scooter laws, it has to have pedals. The single-speed chain uses a 36T/22T gearing.

This is one of the first full suspension fat bikes, and the first full suspension electric fat bike we have heard of. Electric fat bikes have been popular lately in the DIY community (read our story on electric fat bikes).

 

Drunkskunk6

 

Non-hub builds have the weight of the motor more centralized, so they are more nimble. Also, giving the motor some gears increases efficiency while reducing motor/controller heat. However…some builders simply love the near silence of a powerful hub. Silently gliding through an off-road path on a powerful full-suspension E-bike is an experience that I highly recommend.

Here’s the build thread for this impressive E-bike:

http://endless-sphere.com/forums/viewtopic.php?f=6&t=38667&start=100#p716192

 

xxx

Here is the beast parked next to a common 26-inch bike from a big-box store.

 

 

Grew up in Los Angeles California, US Navy submarine mechanic from 1977-81/SanDiego. Hydraulic mechanic in the 1980's/Los Angeles. Heavy equipment operator in the 1990's/traveled to various locations. Dump truck driver in the 2000's/SW Utah. Currently a water plant operator since 2010/NW Kansas

4 Comments

  1. I am interested in making my own electric bike. Is there any way you can put me in touch with Gavin? I wanted to pick his brain about the batteries, controller and motor. Thanks

  2. Well done!! Alternatively, check out Carver Trans Fat. A production F/S fat bike.

  3. Ya I wish I could get the specs and where to buy the parts like controller batteries and wiring stuff, up here in Canada these things are rare right now.

  4. Very nice build…super clean.

  5. very nice!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!!

Leave a Reply