Holmes' v3, Santa Cruz Bullit

[johnrobholmes]

I have had a ton of bikes over the years. When I was going through college I even worked at a bike shop for about 4 years, mostly to get good deals on parts. This was one of the bikes I got while working there, and it has just sat around for about four years since I can no longer ride it to the full potential due to a back injury and two shoulder dislocations. A much lighter XC bike is well suited for my size and terrain of the area too, so my 40 plus pound bike has been collecting dust while my Superlight has been getting all of the attention. Well no more!! This is my third Ebike build, and most arguably the most fun to ride. I get about 9WH/mile efficiency with very minimal pedaling and 20mph riding. I am really liking the Bafang setup with a lightweight 3 phase RC controller. It will start up from a stop, but isn't as smooth as a sensored startup could be. Generally I start with a bit of a roll before kicking in the motor, and I will gladly take a 5.3 ounce overkill controller if it means saving a pound or more of weight vs. a sensored version. It will pull a wheelie if I lean back too, so I think it syncs well enough. All kitted up it is right under 50lbs with 16 plus miles to a charge. I wrap a shin guard around the top tube just like I used to do as a kid when my legs would get hot. Hides the batteries quite well I must say, and protects them too.

Specs
Santa Cruz Bullit frame- 6" travel 2002 frame
Marzocchi Super T- 7" travel 2002 model
XT drive components
Hayes 6" rotor disc
Salsa Gordo rims
Big ass seat
Bafang Rear Geared motor, 6 speed freewheel.
Magura twist throttle
Castle HV110 controller (sensorless)
12s2p a123 cells, 36v 4.6ah
one huge grin all the time


It actually balances better with the rear motor on there as compared to how it used to ride. That front fork was a bit heavy for the bike. Sadly, I can no longer bunnyhop it 3 feet like back in my hayday. I am doing good to get up 6" curbs without bonking the rear right now. At any rate it doesn't matter much since I can actually ride up a curb and let the suspension do all of the work.

This is version one drivetrain. I have version two in the works that will be more offroad capable, and also lighter by about 3 or 4 pounds. I have taken this offroad a few times and jumping down quite a bit of stairs around town. So far the hub flange is holding up and the wheel isn't getting loose on me. My biggest concern is the drive side hollow axle. I may end up getting a hardened steel one made if the time comes.

 

[pwbset]

Sweet build. I really like the batts around the top tube idea.. been thinking about that for my Milwaukee packs as well. Nice re-use of shin guard as well!

 

[johnrobholmes]

It handles like a dream off road and on with the packs as they are. I might scoot them forward or backward an inch depending on conditions, but otherwise from my testing it is the best position for batteries. I wrapped the top tube with old innertube to keep the batteries in place and protect both the frame and packs from abrasion and bumps.


I have about 6 pairs of old shinguards. Seems like the best use for old torn up ones!

 

[Mark_A_W]

That's pretty sweet

I love seeing duallies with triple clamp forks.

My rebuild will be pretty close to this in setup - I think I'll fit a Bafang rear motor to my Jamis with a Headway pack.

 

[deecanio]

Hi Rob,

sweet build, bet it's a hoot to ride
im with Mark, duallies with tripple crowns rock for off road ebikes 8)
Rob are you considering the rc setup for drive number 2 ???? i think its the way to go for really top notch power to weight not to mention the benefits of a standard rear wheel.
seems to be a few of us now heading in the light powerful dh bikes, must be something to 'em
Great build, please,please post some vids if you can, i need my edh fix and my kona's away from home hehehee

Cheers,


D

 

[johnrobholmes]

I will be using an RC setup for drivetrain number 2. It will be geared somewhere around 15 to 20mph, plenty fast for in the woods and pulling me up a hill.

The RC setup can also be used with a hub motor, so fast speeds and a hill climber motor can be on the same bike.

 

[voicecoils]

Looks awesome. My Super T Pro forks are from 2002 as well.

I can't get over how TINY that rear Bafang PMGR looks. Even smaller then my front one for some reason.

Well done & enjoy the trails

 

[D-Man]

Wow. This one looks like a bike. Not hacked yet. Good job.

 

[Ypedal]

Nice rig !

I love the trails, i end up doing a detour every day after work thru the local nature trails, thru the BMX course, then zip home.. but as you discovered, big power and light weight make for a huge difference off the beaten path. lugging around 72v 20ah worth of batteries makes high-speed braking on soft stuff ... uhm.. interesting !

Over winter, i'm considering a BMX frame with dual crowns in the front, BMC on the rear at 72v and 10ah of PSI cells.. suspension seat post ( thud buster i'm told is the best out there )

Knobies and hydraulics = Yeah baby !!

 

[johnrobholmes]

I was thinking about my winter bike. Something where my ass was lower would be better, for ease of putting a foot down and skidding through turns. The Bullit could be modified, but I have another bike with a 24" rear tire and marzocchi DJ1 fork that would be quite nice I bet. Hardtail motored cycle in the snow will be very interesting. I used to have the Super T fork on this bike....

 

[paultrafalgar]

Now promise me you won't ride that thing into any drive-in banks! :wink:
(Oh I suppose it's different now that they don't have any money in them!)

 

[TylerDurden]

Now promise me you won't ride that thing into any drive-in banks! :wink:
(Oh I suppose it's different now that they don't have any money in them!)

Ja, the bike-bomb confusion could become a problem... there was another in Iraq yesterday.

 

[paultrafalgar]

I know you won't tell me Tyler, but why three toes and a Maple Leaf?

 

[johnrobholmes]

I soldered up a few more battery packs for the Bullit yesterday. Added another 12 cells a123. I can either put them in parallel with the other packs for 6.9ah at 12s3p or hook em up 18s2p for 59.4v of nominal power! Fully charged at 66.6v. Hopefully this doesn't ruin my 50v hv110.

Bafang makes noise about 2/3 throttle, then gets quiet. I can feel it through the aluminum frame. I need to open her up and check the factory grease and gears. I will mess with the timing on the controller and see if that helps.


Now I can pop wheelies!! But I might need a better torque arm.

 

[Mark_A_W]

What speed cluster have you got fitted? I have picked up a rear Bafang and I'm struggling to fit it in my dropouts with a disc and 7 speeds - it'll fit, but I'd have to dish the wheel past vertical - like a cone.


Your noise sounds like a timing oscillation - my current direct drive motor growls when going very slow, then again at about 26km/h.

 

[johnrobholmes]

A standard 6 spd cluster. Some cheapie, I don't know the brand.

 

[Mark_A_W]

And it fit ok?

Can you please take a picture from the rear showing the cluster and the wheel?

Thanks

Mark

 

[johnrobholmes]

I did a bit of work to the bike in the past few days.

Re-tensioned the wheels.
Installed new 8" rotor front brake.
New rotor and pads for the rear.
Non-indexed shifter for the rear 6 spd.
New Andersons plugs for the packs. No more arc welding.


I found a digital meter that displays voltage from 6 cells at once. I may put two on the handlbars to watch all of the cells as I drive. I will also convert the rear to a single speed setup and just keep my front three gears. I really don't think I need more than three. One granny, one mid range, and one flat and downhill speed gear.

 

[johnrobholmes]

Some pics of how the bike sits. I took it offroad for an hour, used 2 amp hours total. The trails were quite steep and rugged, it is a tough set of loops. While I exerted about the same over the ride as normal, my top speed was much faster and I rode for 15 minutes longer than usual. Basically I covered a lot more ground.

 

[Fishmasterdan]

Looks like alot of fun.

If you dont mind me asking did you use a commercially available throttle?? How did it work with the castle esc??

 

[johnrobholmes]

I use the Magura throttle, coupled with a throttle tester where the pot would normally sit. Works very well, even offroad.

 

[johnrobholmes]

Time for more work on this build. I finally brainstormed an easy solution for mounting a drive system. I will be using front and rear 17" motorcycle rims.

I should be able to get the parts to restart this in a few days. Spokes are on the way, just need the steel for the drive mount. Lace up a rear wheel, clearance the cranks around the drive unit (maybe some profile cranks), and mount up the drive. Then I can work on subframes for my batteries.

 

[etard]

Nice platform to start with here, I have a few questions....

Can you give more details on this motorcycle rim and tire ( what size, where from, price)?
I am debating buying that exact fork (same year) with a Cove G-Spot frame for $400, would you recommend it?


Can't wait to see this build pan out, you definately have talent and very nice bikes.

 

[johnrobholmes]

I can highly recommend the fork. Either 2002 or 2003. The 2003 version is stiffer, I have one of each year here. I would pay $250 for a used fork if it wasn't beaten to a pulp.

The rim is a Pro-Wheel 17"x something for mini bikes. Tire is a Shinko 17x2.5 DOT rated dual sport. Search google for Pro-Wheel and you will get the company that imports them. You will need to call directly to get a 32hole, as the website lists rims by the bike instead of size.

 

[docnjoj]

That is a clever idea to use just the front chain wheels for shifting gears. I may consider that too, John Rob, as you are surely right about only needing 3 gears (provided the batteries dont fail) I would probably need 15 gear/inches to get home if mine shut down.
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