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Building a full Suspension, BBSHD fat bike

gogreenpower

gogreenpower

100 mW
Joined
Dec 11, 2012
Messages
44
Location
Perth, WA, Australia
Hi guys,

It’s been a few years since my last build but I’m back and jumping straight into the deep end.

I'm building a BBSHD Full Suspension fatty, it has a 120mm BB with room to add a couple of 4.7" Vee Tire Bulldozers, then later on down the track I'm adding a Rohloff XXL 500/14 and if possible a Gates belt drive. It will be used nearly exclusively on the beach.

Here is the bike:

IMG_20160619_160343_1644373011.jpg

I've broken it down into 4 stages.


Stage 1:

First thing is fitting the BBSHD kit and battery. The chainline looks good and I don’t foresee any problems with fitting the BBSHD. Unfortunately it requires a custom made battery to fit what I want in the frame. I thought about backpack batteries but that’s not for me.

I want to have around 15Ah or more, it depends on what I can fit in the triangle, I have 11 different bags on the way so I will have a better idea when they arrive... I want to have another removable 10Ah split into two packs in a bag over the top tube.

I plan on using Sanyo NCR18650GA in a 14s5p with BMS for the triangle and for the removable top tube bag split into 2 packs of 6s3p and 8s3p to accommodate a BMS on one side.

I am using the Bestechpower HCX-D167's. 35A max continuous.

http://bestechpower.com/518v14spcmbmspcbforli-ionli-polymerbatterypack/PCB-D167.html


Now if I understand my battery theory correctly which is highly debatable, i have come up with this.

Given that the BBSHD controller can draw 30A continuous, unsure on the surge?, and the GAs are rated at 10A, 5p will give me 50A continuous limited to 35A through the BMS to feed the 30A controller.

Stage 2:

I plan on fitting a couple of 4.7" Vee Tire Bulldozers on the front and rear 100mm rims and going tubeless. The gap on the forks is 4.8" so I assume that's enough clearance? If anyone has run this sort of gap before, how did it go? I really need as much tyre as I can get for the sand. And if anyone has any ideas about a better soft sand tyre please let me know.

http://www.veetireco.com.au/#!product/prd12/1764633255/bulldozer---26%22-x-4.7%22


Stage 3:

My original plan involved fitting a Nuvinci N380, but with 190mm dropouts that won't work so I have found a Rohloff XXL 500/14 designed for my exact size.

https://www.rohloff.de/en/products/speedhub-xxl-fatbike-190mm/index.html


Stage 4:

Eventually a Gates belt drive system if possible.

I will research more when the time gets closer, haven’t looked into it that deeply yet except that the BBSHD and XXL have adaptors that will take a belt.


If anyone has any suggestions or wisdom they wish to impart and if there are any questions fire away. I'm evolving as I go.

I’ll update the post as I make progress.


Thanks for reading,

Green
 
I don't have answers for all your questions, but in regards to cycle life and stressing your battery, I don't worry so much about that anymore. You can probably track down some data on your particular cell and get a cycle life estimate based on how hard you plan on sucking the current out of them. Say you get 400 cycles drawing them at 10amps per cell, vs 1000 cycles at 7.5 amps per cell. Then think about how much you are going to use the bike. At 400 cycles and 1 charge per day, you would get over a year on those cells. In a year, battery tech will have changed enough where replacing the battery pack will not be much more than the hassles and costs of getting a bigger pack now. I used to think about longevity, but at the rate I'm always changing things on my bike, I won't be using my motors or battery anywhere close to end of life. Just my 2 cents.
 
Where does the motor hang, it looks like it might be directly below the BB. You should let the air out of the suspension and see how much ground clearance you have when fully compressed. There is no sense carrying around the weight and complexity of a rear suspension if you have to limit travel.......
 
StinkyGoalieGuy said:
I don't have answers for all your questions, but in regards to cycle life and stressing your battery, I don't worry so much about that anymore. You can probably track down some data on your particular cell and get a cycle life estimate based on how hard you plan on sucking the current out of them. Say you get 400 cycles drawing them at 10amps per cell, vs 1000 cycles at 7.5 amps per cell. Then think about how much you are going to use the bike. At 400 cycles and 1 charge per day, you would get over a year on those cells. In a year, battery tech will have changed enough where replacing the battery pack will not be much more than the hassles and costs of getting a bigger pack now. I used to think about longevity, but at the rate I'm always changing things on my bike, I won't be using my motors or battery anywhere close to end of life. Just my 2 cents.
Click to expand...

Good point, realistically I'd probably be charging twice a week and not all my riding will be using the full 30A.
 
WoodlandHills said:
Where does the motor hang, it looks like it might be directly below the BB. You should let the air out of the suspension and see how much ground clearance you have when fully compressed. There is no sense carrying around the weight and complexity of a rear suspension if you have to limit travel.......
Click to expand...

I don't have the motor yet, I need to get the battery sorted then I'll order the motor. I've had a quick measure and it will be lower than the BB but not by a huge amount.

It won't do any downhill riding, just beach and a little road. I can't see the rear bottoming out in it's intended use.
 
Exciting build!

Sounds like you are going to building something very similar to this:

rambo-bikes-r750c.png


https://rambobikes.com/motor-bikes/

http://www.cabelas.com/product/RAMB...xYTjlPQk9Wus5toVGSZfgaAldz8P8HAQ&gclsrc=aw.ds

But will yours be piloted by a bow wielding blockbuster action star!?!!?!!

http://makeagif.com/i/sKyJ8l

Hehe, well, yours sounds like it will be much more interesting, even though it is great to see E-Bikes being more main-stream, we had a customer bring one into the shop the other day (I didn't get to be there, was on a job) so I think you're on a good start for a great beach ride, just curious, how fast you plan on going? With such large/wide tires maybe they will provide most of the "suspension" you need unless you're going over rough rocky beaches or dunes?
 
If the chainline looks good between your fat BBSHD and a fatbike rear hub, it probably won't be compatible with any NuVinci hub. Plus, they're all spaced 135mm and your fatbike is, um, not. It's probably a through axle frame, which means no internal gear hubs of any kind for you. And no belt drive, since you have no way to adjust belt tension.

By the time you're out in 5 inch tire land, many normal bike drivetrain parts won't work. If that's for sure the bike you want, accept it the way it is. It will not be compatible with major changes from its original configuration (apart from the BBSHD).
 
Chalo said:
If the chainline looks good between your fat BBSHD and a fatbike rear hub, it probably won't be compatible with any NuVinci hub. Plus, they're all spaced 135mm and your fatbike is, um, not. It's probably a through axle frame, which means no internal gear hubs of any kind for you. And no belt drive, since you have no way to adjust belt tension.

By the time you're out in 5 inch tire land, many normal bike drivetrain parts won't work. If that's for sure the bike you want, accept it the way it is. It will not be compatible with major changes from its original configuration (apart from the BBSHD).
Click to expand...

Disappointing but good point. The dropouts are 190mm, so I guess the nuvinci is out of the question but I did find this little gem.

https://www.rohloff.de/en/products/speedhub-xxl-fatbike-190mm/index.html

This is maybe a sign of things to come from other manufacturers.
 
gogreenpower said:
It will be used nearly exclusively on the beach.
Click to expand...

I'm not sure why you need a FS fattie on the beach? Isn't it overkill?
 
gogreenpower said:
The dropouts are 190mm, so I guess the nuvinci is out of the question but I did find this little gem.

https://www.rohloff.de/en/products/speedhub-xxl-fatbike-190mm/index.html
Click to expand...

The Rohloff hub is super awesome; I have one on my year 2000 custom made proto-fatbike. (That was back when I could afford one.)

Even the big fatty Rohloffs have conventional axles, but 197mm through axles are becoming common for fatbikes.

A beach bike could certainly benefit from a belt drive too, but the belt requires that the rear triangle break open to allow installation of the belt, so it pretty much has to be in the bike's original plan.
 
WoodlandHills said:
Bikes with motorcycle type swing arms are also good candidates for belt drives:
Click to expand...

Belt drives have to be tight to work, meaning that you have to have horizontal dropouts or sliding dropouts or an eccentric adjusting BB to put correct tension on the belt.

Also, a belt remains the same length, while a high pivot swingarm causes the BB-to-rear-axle length to change continuously as the suspension moves.

For these reasons, the only suspension bike you'll ever see with a drive belt is one that's been specifically designed for belt drive.
 
Sounds like an interesting build, but:

Bulldozers measure around 115mm on a 100mm rim. your 4.8" spacing works out to 122mm. that leaves 3.5 mm clearance on each side of the tire. If your rim isn't running perfectly true, or you over inflate the tire a little, or you get something stuck in your tread, that tire could rub the frame or even get jammed in the frame, and send you flying over the bars.
Also, fat tires tend to walk side to side on the rim as you ride, which will cause them to hit the frame, acting like a brake each time.
A half inch of space between tire's sidewall and fork or frame is about minimum. so for a 4.8" spacing, 3.8" is about the widest tire you should run.

Tubeless fat bikes make as much sense as screen doors on subs. I know it's a trendy thing, but remember that mullets were once considered a trendy thing, too. Some do it believing they are saving weight, as you get rid of that 400 gram tube. However, you then have to add 200 grams of sealant back to the tire, and you can't do it to a drilled rim unless you add a heavy rim liner to seal up the rim. Some of those liners weigh as much as a tube. The actual weight savings is small if at all, and with high trade offs.

Also, Going tubeless means your tire can't be run as low pressure, and you'll be chasing leaks constantly at the normal pressures a fat bike runs. Tubeless tires need air pressure to stay sealed and keep the bead seated. Where a fat bike really shines is when running down at 5lbs. At those pressures, you can walk over the top of snow, sand, mud, anything you want. Most tubeless setups need to stay above 10lbs, and start to deflate below 8.

The Rohlolf hub looks like a great setup. you may need to fabricate your own lower swingarm to fit it, but for sandy conditions, it might be worth the effort. A carbon belt makes no sense, though. Belts need a large amount of tension to work right. the distance between the front and rear sprocket change constantly on a full suspension, and the belt needs to maintain a constant 40lbs. that means you would need to fabricate a custom belt tension idler that could maintain 40LBS through it's full range of motion, and then change out the shock for one that could handle 40lbs of preload and an extra 40lbs of rebound to compensate.
 
I am sorry, but that's a load of baloney. While it is convenient to have all the misinformation and old wives tales in one place, it is a disservice to claim that it all is not just opinion.

Tubeless tires work just fine under 10psi IME and in fact low pressure is where they shine compared to tubes: no worries of getting a pinch flat from your tube. I run mine at 7.5psi and I use a couple wraps of packing tape to seal the rim: only a few ounces. I use the split tube method with no issues and it is noticeably lighter and quicker handling. I have never had my tires move from side to side on the rim once the bead has been seated so I have no idea what that is about. Ditto on the necessary clearance: my 4.8" Maxxis FBFs have 1/4" or less between tread and fork or frame, a dimension that has not changed in several hundred miles off-road.
 
Drunkskunk said:
Sounds like an interesting build, but:

Bulldozers measure around 115mm on a 100mm rim. your 4.8" spacing works out to 122mm. that leaves 3.5 mm clearance on each side of the tire. If your rim isn't running perfectly true, or you over inflate the tire a little, or you get something stuck in your tread, that tire could rub the frame or even get jammed in the frame, and send you flying over the bars.
Also, fat tires tend to walk side to side on the rim as you ride, which will cause them to hit the frame, acting like a brake each time.
A half inch of space between tire's sidewall and fork or frame is about minimum. so for a 4.8" spacing, 3.8" is about the widest tire you should run.
Click to expand...

The bulldozers also come in a 4.25" width, does having a smaller width on the front work well? I have 4.0" on at the moment running 6 psi and the gap is quite large. The 4.8" measurement is the narrowest part at the top of the forks where the very top of the tyre passes through.

I was under the impression tubeless allowed lower pressure to be run which was the only reason I wanted it for the sand. If this is not the case then I'm happy to run tubes.
 
gogreenpower said:
The bulldozers also come in a 4.25" width, does having a smaller width on the front work well? I have 4.0" on at the moment running 6 psi and the gap is quite large. The 4.8" measurement is the narrowest part at the top of the forks where the very top of the tyre passes through.

I was under the impression tubeless allowed lower pressure to be run which was the only reason I wanted it for the sand. If this is not the case then I'm happy to run tubes.
Click to expand...


Measure the inside width of the forks at the point of the sidewall. You want about a half inch clearance between the sidewall and the fork. Don't trust the tire's stated size as it's true width. they rarely are. But plenty of places have the actual measurements of various fat tires on various rim sizes published.

There is a school of thought that you can't run tubed tires as low as tubeless because of the risk of pinch flats. it is a valid argument, however it mostly a pointless valid argument. if you're in conditions where you need to worry about pinch flats, you're generally not in conditions that need the lowest pressure. But for actual low pressure riding, you can run a tubed tire down much lower than a tubeless. At low pressures, the tubeless doesn't have enough pressure to keep the bead seated. On a tubed tire, the bead can come unseated and you still maintain pressure and can continue on.

As for actual pressures, I've peeled tubeless off the bead at 10lbs. I've done the same to a tubed tire, but the tubed tire didn't go flat. I've had a tubed tire down to 4 pounds on the sand ( no pinch flat risk on the beach :D ) and found the bead packed with sand after a week of riding. Sand in your bead would end your riding day on a tubeless.
 
Also, if you're using pressures so low on surfaces so hard that you have to worry about pinch flats, you also have to worry about flat-spotting your rims and otherwise smashing up your wheels. Since tubeless buffs are not using cheap sacrificial rims and replacing them often, I have to regard this argument for tubeless as ill-founded and/or disingenuous.

Personally, I think tubeless tires on bicycles are fetishistic, a manifestation of the quasi-religious motorhead supposition that whatever works best for a car/motorcycle/bulldozer/helicopter/etc. is indisputably best for a bicycle.

If you want the benefits of sealant without fouling your wheels and tires with sticky crap, and without having to use an air compressor every time you do anything with your tires, just put the sealant inside the tube. This is not a hard problem to figure out, and you don't have to make more problems for yourself.
 
Whatever...... Tubeless is easy for me to do, has never caused me any on-trail issues or failures and best of all I really like the way it makes a 120tpi fat tire feel. If I ever have any of the problems you all mention I can just put a tube in, but until then I guess I'll have to stick what has been working so well for me....... As opposed to what the experts on the internet say. :wink:
 
WoodlandHills said:
If I ever have any of the problems you all mention I can just put a tube in,
Click to expand...

Well, you could do that... but your tire would already be like a big dirty diaper, only stickier. I put tubes into tires that have been despoiled by tubeless sealant more often than you'd think.

A decent person doesn't ask someone else to service the nasty tubeless mess that he chooses to make. But there are many who do.
 
E-geezer said:
gogreenpower said:
It will be used nearly exclusively on the beach.
Click to expand...

I'm not sure why you need a FS fattie on the beach? Isn't it overkill?
Click to expand...

No, no. Overkill will be when I add a thudbuster suspension seat post as well...
 
Chalo said:
WoodlandHills said:
If I ever have any of the problems you all mention I can just put a tube in,
Click to expand...

Well, you could do that... but your tire would already be like a big dirty diaper, only stickier. I put tubes into tires that have been despoiled by tubeless sealant more often than you'd think.

A decent person doesn't ask someone else to service the nasty tubeless mess that he chooses to make. But there are many who do.
Click to expand...

What a bummer, the OrangeSeal I use dries out after an hour or so in the sun and it all just rolls up in a ball in a few seconds. Very clean and easy......... Maybe you are using the wrong stuff? I always wear work gloves so maybe a bit of a mess doesn't bug me as much. Anyway it's no big deal to put a tube into the tires.
 
Sorry for the delay but I finally have something to update.


I have managed to upgrade the tyres, the 4.7" Bulldozers fit perfectly. Here's a few pics of the tyres

https://www.dropbox.com/sc/rvbqs5c5xsulbzb/AACLhyut1uuoDK-Imh3WFiKUa


I have purchased the BBSHD, but haven't fitted it yet... but what I have managed is to build the battery (almost).

https://www.dropbox.com/sc/27vyj0f6nvdrapb/AADvPLxu9DNmMLuHUkRike-Ca


I have an issue with the battery which I have started a thread about over here

https://endless-sphere.com/forums/viewtopic.php?f=2&t=84850


I will have the motor fitted soon, more to follow



Green.
 
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