2004 Iron Horse SGS DH daily with a BBSHD

[Johnny A]

Thought I'd post this up and say hi.

Build it as a regular bike maybe 10 years ago, just finalising it as an ebike now really.

2004 Iron Horse SGS DH frame with a fox air shock.
Some old Rock Shox 140mm solo air front forks (yes I know this frame is designed for 180+mm dual crown - but they're expensive and I'm poor)
Hope Mono M4 brakes
BBSHD, 42T offset chainring, 33A Daniel Nielson firmware.
52V 12.6ah battery pack made from Molicell P42A 21700s and a Daly BMS (specced to output over 90A continuous should I switch to an aftermarket controller)
Dm03 display
Rear cassette reduced to 3 gears (30T, 24T and 16T) as these are all I need.

I use it for work (9miles and lots of hills) and charge it up in-between. It will do about 16miles with all those hills so I get maybe 3/4 of the way home before it hits low volt cutoff.

So I am charging to 80% at each end now, suits it perfectly. Just completed its first full week of commuting, only issue was a snapped chain link (tbf it's a 10 year old basic chain).

 

[Johnny A]

Little update:
I was popping links like a MF'r last week. One trip back home (which is more downhill then uphill) it popped 7 times! Luckily I knew what to listen for so I could stop and re-seat the link before total failure.

As I wanted to continue using the bike for work with this suboptimal chain I started leaving it in the 30T rear and reducing total output to 80% and so far it's holding. I plan to purchase a KMC 10sp E-bike chain very shortly.
Interestingly with the chain kept in the largest rear cog my top speed is now 18mph so i'd basically be wide open throttle everywhere and my energy consumption is dramatically less. Also the motor and controller are almost stone cold upon arrival. Just goes to show how maintaining the highest speed (30mph) creates a lot more resistance.

I also changed my seat for something far more comfortable for my big ass last week, it's called a Buchel Wittkop Medicus 3. It's very comfortable and makes the commutes a lot more enjoyable but it has one issue. The rails on the saddle are much shorter and further back which has caused my seating position to be moved forward quite dramatically to the point where its borderline awkward!
Nothing much can be done about the saddle rails themselves so I have opted for swapping out the zero-offset seat post for an offset one. Unfortunately most of them offer maybe 25mm of offset at most, but I found one developed in the 80's by SR Sakae and it offers enough offset.

But with all these niggles I think the worst happened on Friday just gone. Was riding back and I swear I could hear some subtle noises coming from the BBSHD motor. I couldn't tell exactly the noise, it might have just need the chain but as an engineer I had no issues deciding to completely strip it down for a 200mile inspection.

So this weekend I removed the BBSHD and totally dismantled it. Long story short everything was fine, if I wanted to be a bit picky I could argue the nylon gear didn't have enough grease on it so I painted some on with a brush.

But the biggest thing that struck me about the design of the BBSHD has how it's sealed from the outside world and this is something I would like input on (if people read this post? I dunno it's pretty long!).
So you have three main compartments:
Motor housing
Controller housing and
Secondary reduction gear housing (with the big granny gear in it that connects to the crank)

The motor housing and the secondary reduction housing use compressed fibre type gasket which is ok for light splashes of water but constant exposure they can't handle too well.
The Controller housing uses a formed rubber gasket/seal which is much better BUT mine at least was fitted very poorly and was pinched in a few places.

I mean Bafang obviously are aware of the flaws with using such gaskets as they have used white silicone to seal the wires/connectors from the motor housing into the controller housing. That silicone should not be necessary if the outer gaskets would do their jobs.

So what I have done is to trim the rubber gasket for the controller housing down so it can no longer pinch and cleaned up all mating surfaces. Also removed all that silicone sealing the wires as they pass into the controller housing from the motor but retained the original rubber grommets as they will stop any rubbing.

As the parts are reassembled the gaskets and seals are coated with something called Hylomar Blue. Its a gasket sealing compound that is very thick and sticky like silicon sealant is but it never goes hard so future dismantling is SO much easier as it can simply be cleaned off with some solvent. If there is enough interest ill do a how to video but it's pretty self-explanatory really.

 

[amberwolf]

Keep in mind that sealing is hardly ever *completely* perfect, so if you have a lot of water exposure, water can eventually get in...but the good sealing then traps the water inside, where it then does the things that water does to stuff that doesn't like it.

If you don't have much water exposure, there's not usually much worry.

(here in Phoenix we get flash floods that I have to ride the SB Cruiser trike home from work thru a couple times a year, sometimes over a foot deep in one 1/4-mile-long stretch, and the only issue so far was once I got intrusion into my battery compartment so I had to take my pack apart and dry it out as soon as I got home, as there was a small amount of water at the bottom edges of all the pouches. The rest of the time my system, which is not waterproofed, did fine. The only thing I've done is to use dieelectric grease stuffed into all the connectors down there where this could happen, and used a potted-sealed charger bolted to the bottom of the trike (the controllers are typical controllers with good water-resistance, but not waterproofed; under the trike they don't really get wet except in these specific conditions).


The places it most often gets in motors/casings is via the cabling inside the sheath between the wires or inside the conductors, if there is any point along the cabling that is not sealed, and via rotating bearing / shaft seals.

 

[Johnny A]

Yeah I've just got hold of some dielectric grease for the connectors.

I don't plan on riding the bike when it's really wet but I know I'm bound to get caught out at some point.

 

[amberwolf]

I didn't originally build SBC for really wet / flooded conditions either...but those flash floods happen in summertime and occasionally during my ride home...when they do there's not really anywhere sheltered I can get to that doesnt' force me to go thru some of the flooded bits to get there. :/ So the way I have it setup is the best compromise between easy access / serviceability and water intrusion prevention, after a number of years of working this out.

For the motors that can't be sealed up perfectly, I use ventilation holes to let them drain and/or evaporate out any moisture that gets in. So far, no rust or other corrosion.