Another "stealth bomber" build.

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j bjork   10 kW

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Posts: 743
Joined: Aug 31 2018 3:01pm
Location: Linköping, Sweden

Re: Another "stealth bomber" build.

Post by j bjork » Apr 04 2020 6:59am

I think the main issue with the frame is the soft steel, it is a problem especially in the dropouts. They are also a bad fit for the axle, so I think you will have problems with the shaft and dropouts if you don't do anything. Especially if you use regen. I used hard metal shims between the axle and droupout first, to get rid of the play. But the dropouts bended anyway. After my modifications they have been rock solid. I haven't been able to re torque any bolts or anything, and I have regen that can lock the wheel at full speed on asphalt.

The swing is heavy. I think the best thing would be to build a new swing, maybe keep just the part with the pedals and the part that mounts to the frame. After that I think it would be a pretty good frame.

It seems like most of these frames have metal bushings now, hopefully they are ok. Otherwise I think there are kits available to change to ball bearings, so I don't think it is necessary to make the parts for it as I did.

I think a better rear rim would be a good idea.. I think you will have a bumpy ride with a qs 273 :wink: For me there hasent been any problems with the china front rim so far, the sm pro rear rim has been ok too. I have almost pinched holes in the tire though, from hitting rocks and stuff.

More rear travel like you planned may be a good idea too. I don't think you should lean the frame more forward though, I think it will be nervous with steeper angle on the fork.

Are you planning to use 21" both front and rear? I think you should go smaller in the rear, 18 or 19" maybe. Both for the motor rpm and to be able to find sutible tires.

litespeed   100 kW

100 kW
Posts: 1433
Joined: Aug 11 2010 4:42pm
Location: O’Fallon, Missouri

Re: Another "stealth bomber" build.

Post by litespeed » Apr 04 2020 10:30am

Problem I see is with a 40 lb motor and a 21” rim is lack of tire. In my opinion you should go with an 18” rim and a 3.50 or 4.00 tire. From the Shinko web site it says that a 18 x 3.5 tire is 25.55 inches and the 18 x 4.00 is 26.42 inches. That is close enough to a 21” tire (27.68 with a 3.00 tire) with a whole lot more rubber. That will help absorb the motors weight during rough stuff and not transfer that vibration into the frame and you. I have the shinko 241 tires with a 17/3 inch tire on the back with a QS 205 and 19/2.75 front. Run at lower pressures it’s as soft as riding on a mattress.

I’m 6’-4” 210 lbs and with 10” travel in the rear I have only bottomed out on the hardest hits. I keep my suspension pretty soft (I have a lot of long suspension background) so I Statically sag in at about 3 to 4 inches which keeps the motor from bucking on all but coming off the ground. Just have to pay attention to peddle strikes. Bike rides/handles at high speeds (Over 60mph) very well. I have one of the “other brand” original frames with bearings and everything is as tight as the day I put it together. Picture of mine to show how big it is. In my opinion the two things that the bikes need is a dropper seat post and ability to put 2 speed cranks.

BTW I used 4 inch rise bars but they get kinda flexy riding hard. If you buy new forks leave the steer tube long and put your handlebar clamp at the top to get another inch or two. Just don’t cut it.

Tom
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I'm married so you know I'm no stranger to pain!

synics   10 W

10 W
Posts: 96
Joined: Apr 03 2020 11:18pm

Re: Another "stealth bomber" build.

Post by synics » Apr 04 2020 11:37am

Man, you guys are making my buyers remorse even worse! lol I mean, I don't have the means to make an entire new swingarm...how much do you think a fabricator would charge me for something like that?

18" Tire isn't an option with them apparently. I tried asking the company to put a 21" on the front and a 19" on the back, and they're telling me no, the bike will not function, and I'm like say what? I don't see any hub rims that are cross laced in an 18" either. Should I go with both 19" and worry about getting a 21" later down the road? Maybe put a shinko 241 3.5x19 on the back? I guess I could ask them to ship an extra 21" wheel if they refuse to put it on themselves. I just don't get why they're saying no to that.

Also, do you know what the crank bracket size on these frames are? The crank they're putting is total garbage with a shimano touring tensioner. I was gonna take all that out and make it fixed with a 32T front sprocket. Does it need a chain tensioner?

litespeed   100 kW

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Posts: 1433
Joined: Aug 11 2010 4:42pm
Location: O’Fallon, Missouri

Re: Another "stealth bomber" build.

Post by litespeed » Apr 04 2020 1:26pm

You will need a chain tensioner. No need for buyers remorse....you just may need to modify a bit. We all have small things we needed to do to get the build done. No big deal.

I have a 48 tooth front and 16 rear which is uncomfortable to peddle past about 22-23 mph. I’m guess you will struggle past 15 to 17mph?

The BB was fine on mine so I can not comment on these new ones. I bought semi decent square taper 175mm cranks Which have held up non-eventfully for many years now. I think if kept tight they should be ok, you just have to remember to re torque after every ride for the first 5 to 7 rides or so. I think you should try what you get before replacing everything. Same goes for the rear torque plates.....every ride for the first 7 check them and snug up. That’s the key to staying away from most issues.

As far as wheel goes the 19 will work but your always best getting a smaller wheel and using voltage or field weaking to get more speed. Mechanical advantage you’ll hear mentioned often with a hub motor....the more you have the happier your motor is. With a 273 3.5T I doubt you’ll need more speed. I have the 205 3.5T and have hit 65 mph with MaxE/20s and backed off because I was unsure of how it would handle faster. OK.....I was scared in my bicycle helmet and sweat pants! Speed was not a prerequisite for me I just got lucky with a brand new QS 205 3.5T V3 laced with a 17 rim and matching 19” front black spokes and all shipped for about $500. I wanted a 4 or 5 turn.

Run what you get and see how it does. Just keep the regen low and the torque blocks tight.

Tom
I'm married so you know I'm no stranger to pain!

synics   10 W

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Posts: 96
Joined: Apr 03 2020 11:18pm

Re: Another "stealth bomber" build.

Post by synics » Apr 04 2020 2:12pm

thanks for your response Tom, your info is very helpful!

I wanted to go smaller crank because I figured I would never be pedaling anyway and it would help to have that middle ground clearance. You pedal a lot? for exercise? I wanted the look that the small direct mount crank has, it just looks cool. LOL

Have you done a lot of off road riding? You're frame is different the the one I'm getting. I have the same one as Bjork.
So yeah speed is not my top concern either even though they're telling me this will hit 70 mph with no adjustments. I actually much prefer to have the most low end torque possible. I'd rather have the 5T wind than the 3.5 one I'm getting, same as you. But again they didn't give me the option. I really don't know anything about programming the 200A Sabvoton, but I guess I'll see how it feels. What is field weakening and will I have to enable that myself?

Will the 19" tire give me more torque than the 21"?
As tall as you are the 19's don't make the bike too small?

litespeed   100 kW

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Posts: 1433
Joined: Aug 11 2010 4:42pm
Location: O’Fallon, Missouri

Re: Another "stealth bomber" build.

Post by litespeed » Apr 04 2020 5:17pm

The cranks/chain wheel I chose is good for everything except going over big logs......I have had to get off the bike a couple times going over big logs to keep from damaging the chain wheel.

I do peddle a lot......basically I always peddle on the road/paths to keep a stealthy appearance. On smooth trails I peddle but once it get rough then it’s all electric power! Honestly for the last couple years I moved to an area with a lot of paved/groomed trails.....now I’ve moved back closer to some good single track trails......should get back 50/50 on road off road like in my past.

Feild weakening is where the controller can raise the RPM of the motor at the cost of efficiency. Uses more power and can cause the motor to get hotter than normal.

The smaller the wheel/tire diameter the more torque that will be available. With the 3.5T your getting you NEED the 18 inch wheel and no bigger! I’ll get a picture of 6’-4” me standing next to and me sitting on my bike when I get a chance. Think super motard!

Tom
I'm married so you know I'm no stranger to pain!

synics   10 W

10 W
Posts: 96
Joined: Apr 03 2020 11:18pm

Re: Another "stealth bomber" build.

Post by synics » Apr 04 2020 6:23pm

So Tom, I'm confused. Every other thing I read is telling me that if I'm going to be predominantly off road, the 21" wheels will be better for stability purposes and rolling over obstacles... no? will I really lose that much torque with a 21"?

Oh and yeah I hear you on the pedaling stuff. There's a 16 mile off road park here in Jersey that I ride in that allows MTBs, and this type of electric bike would still technically qualify, but if I got rid of those pedals then it's a "hit the pike" situation. I always slow up around people though when I'm on the scooter and act super humble. Not trying to piss anyone off. ha

j bjork   10 kW

10 kW
Posts: 743
Joined: Aug 31 2018 3:01pm
Location: Linköping, Sweden

Re: Another "stealth bomber" build.

Post by j bjork » Apr 05 2020 5:54am

I would surely go 18" if possible. It wont be much smaller, but a lot more rubber. You want a lot of rubber between the rim and ground :wink: I doubt you will be able to fit a 4" wide tire in the swing arm though.

Look at dirtbikes, 21" front and 18 or 19" rear. However, here the rear tires are 110/100 18" or 19". Those are wide, I measured one now to 125mm.
On this bike I have 3.00 16, that is 86mm wide on a 1.85" wide rim. The standard here on small dirtbikes with 16" is 90/100 16", I mesured one now to 110mm wide. That doesn't fit in this swing, it is about 100mm wide where a 16" tire "hits". Narrower with bigger wheels.

You don't need a chain tensioner. On some combinations of sprockets you may need a half link to make the chain fit, but I think that is available.

litespeed   100 kW

100 kW
Posts: 1433
Joined: Aug 11 2010 4:42pm
Location: O’Fallon, Missouri

Re: Another "stealth bomber" build.

Post by litespeed » Apr 05 2020 12:10pm

Like j bjork said, go as big as you can get up front and 18 rear, just like motorcycles. I had forgot we had different frames, sorry about that. Didn’t mean to add confusion to the mix.....some of these threads blend together after ready so many.

I followed this thread because j bjork did an outstanding job over coming all the flaws of the bike frame and an excellent job piecing the right components together. Stellar build.

Synics, I saw others trying to sway you to go mid drive on Facebook. While mid drives have their advantages in off road capabilities They will never be as stealthy as a hub motor simply because of lack of noise. If your on your own or private land I probably would have gone mid drive but being around bicyclists on public Streets/trails hub motor/sine wave is the way to go. My bike make absolutely not a bit of sound....nothing minus the tires on the pavement. It does well for me on the trails but to me it’s a light weight motorcycle. Coming from a 275 lbs DRZ400 dirt bike this feels like a bicycle in the trails at 120 lbs., very flickable. I also am not in hilly terrain....most trails having less than 100 feet of elevation change. If you wanna ride with regular bicycles and stay somewhat invisible then hub is where it’s at. 18 rear and 19 or 21 front and you’ll plow through anything the trail has to offer.

Tom
I'm married so you know I'm no stranger to pain!

synics   10 W

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Posts: 96
Joined: Apr 03 2020 11:18pm

Re: Another "stealth bomber" build.

Post by synics » Apr 09 2020 12:13am

Hey guys, somehow I missed your last replies. So yeah that is my thing, I need to be stealthy and still have pedals to not get hassled. The Sur Ron is so loud. I know a guy with one and I can hear that thing coming a mile away. And on the trails I ride at I don't need anyone calling the cops on me. (side note, NJ governor shut down the trails today, idiotic)

So I was able to convince the seller to give me a 19x3" back wheel and a 21x3" front, best I could do. Crappy chinese knobbies though. I plan to get the Sr241's and put those on. I hear lots of good things and it has a 4ply nice strong sidewall. Do you guys think the 19x3.5 would fit in the frame?

Also, what is the ideal spring stiffness in poundage for this heavy back end? Stiffer the better?

synics   10 W

10 W
Posts: 96
Joined: Apr 03 2020 11:18pm

Re: Another "stealth bomber" build.

Post by synics » Apr 23 2020 11:55pm

j bjork wrote:
Apr 04 2020 6:59am
I think the main issue with the frame is the soft steel, it is a problem especially in the dropouts. They are also a bad fit for the axle, so I think you will have problems with the shaft and dropouts if you don't do anything. Especially if you use regen. I used hard metal shims between the axle and droupout first, to get rid of the play. But the dropouts bended anyway. After my modifications they have been rock solid. I haven't been able to re torque any bolts or anything, and I have regen that can lock the wheel at full speed on asphalt.

The swing is heavy. I think the best thing would be to build a new swing, maybe keep just the part with the pedals and the part that mounts to the frame. After that I think it would be a pretty good frame.

It seems like most of these frames have metal bushings now, hopefully they are ok. Otherwise I think there are kits available to change to ball bearings, so I don't think it is necessary to make the parts for it as I did.

I think a better rear rim would be a good idea.. I think you will have a bumpy ride with a qs 273 :wink: For me there hasent been any problems with the china front rim so far, the sm pro rear rim has been ok too. I have almost pinched holes in the tire though, from hitting rocks and stuff.

More rear travel like you planned may be a good idea too. I don't think you should lean the frame more forward though, I think it will be nervous with steeper angle on the fork.

Are you planning to use 21" both front and rear? I think you should go smaller in the rear, 18 or 19" maybe. Both for the motor rpm and to be able to find sutible tires.
Quick question, the attached pics aren't my bike, but if I fabricated the same raised bottom shock mount that's on the silver bike, and put it on the frame of the black bike, do you think that would be an efficient shock angle so that I coudl get an 11.5" pitbike shock on this with a 1000lb spring? ImageImageImage

john61ct   100 GW

100 GW
Posts: 6678
Joined: Dec 18 2018 2:06pm

Re: Another "stealth bomber" build.

Post by john61ct » Apr 24 2020 1:59am

Can't see pics, not in Tapatalk, not in Chrome

synics   10 W

10 W
Posts: 96
Joined: Apr 03 2020 11:18pm

Re: Another

Post by synics » Apr 24 2020 9:50am

john61ct wrote:
Apr 24 2020 1:59am
Can't see pics, not in Tapatalk, not in Chrome
that's weird, I just looked at them in chrome on my computer, my phone, and ipad and it shows up on all three. hmmm

john61ct   100 GW

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Posts: 6678
Joined: Dec 18 2018 2:06pm

Re: Another "stealth bomber" build.

Post by john61ct » Apr 25 2020 3:46am

In going into quote mode, copying and pasting the URLs, I get

"The selected attachment does not exist anymore."

for all three.

Your machine is showing you a locally cached version of the files.


synics   10 W

10 W
Posts: 96
Joined: Apr 03 2020 11:18pm

Re: Another "stealth bomber" build.

Post by synics » Apr 25 2020 9:18am

how about now? can you see them?
F755C54C-A7D5-4909-A0B0-183F6D105E39_L0_001.jpg
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FluxA1-ES.jpg
FluxA1-ES.jpg (242.14 KiB) Viewed 727 times
FluxA2-ES.jpg
FluxA2-ES.jpg (229.95 KiB) Viewed 727 times

john61ct   100 GW

100 GW
Posts: 6678
Joined: Dec 18 2018 2:06pm

Re: Another "stealth bomber" build.

Post by john61ct » Apr 25 2020 2:10pm

Yes those work great

synics   10 W

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Posts: 96
Joined: Apr 03 2020 11:18pm

Re: Another "stealth bomber" build.

Post by synics » Apr 25 2020 3:20pm

you're talking about the shock mount right? What are you running on yours?

john61ct   100 GW

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Joined: Dec 18 2018 2:06pm

Re: Another "stealth bomber" build.

Post by john61ct » Apr 26 2020 9:25am

meant the photos

synics   10 W

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Posts: 96
Joined: Apr 03 2020 11:18pm

Re: Another "stealth bomber" build.

Post by synics » Apr 26 2020 11:57am

So any thoughts to my question about the mount?

ossivirt   10 W

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Joined: May 18 2016 2:08pm

Re: Another "stealth bomber" build.

Post by ossivirt » Apr 26 2020 1:19pm

synics wrote:
Apr 26 2020 11:57am
So any thoughts to my question about the mount?
Hard to say. Even small changes to suspension geometry can have big difference how it will feel/work. I have eeb enduro frame and suspension always felt like there is way too much weight for suspension to handle. I moved the shock just 1.5cm away from pivot point at both ends and now it feels a lot better. I lost some travel distance and 12kg hubmotor is a lot of unsprung weight but it is better than it was. I am 85kg person so for tiny people it maybe would have been ideal setup out of the box..

If possible make it adjustable from as many places as possible so you can find what works best for you.

N31L   1 mW

1 mW
Posts: 12
Joined: Apr 27 2020 11:08am

Re: Another "stealth bomber" build.

Post by N31L » Apr 28 2020 4:58am

Hi chaps,

Really interest in the geo talk ok here as I'm near the point of assembling my "bomber" build after gathering parts over the last couple weeks.

Geometry as in the rear shock set up an riding position has been a massive point that I keep going back to.

What are you over all rear shock lengths?

Cheers.

Sent from my SM-G960F using Tapatalk


j bjork   10 kW

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Posts: 743
Joined: Aug 31 2018 3:01pm
Location: Linköping, Sweden

Re: Another "stealth bomber" build.

Post by j bjork » Apr 28 2020 5:35am

I think mine is 200mm, it should be specified earlier in the thred. (the first one I had was to long I think)

Edit, checked. It is 200mm.

N31L   1 mW

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Posts: 12
Joined: Apr 27 2020 11:08am

Re: Another "stealth bomber" build.

Post by N31L » Apr 28 2020 5:58am

j bjork wrote:I think mine is 200mm, it should be specified earlier in the thred. (the first one I had was to long I think)

Edit, checked. It is 200mm.
Just me being blind then. Well there is alot to read thought. I will have a look thanks for the reply tho bud.



Sent from my SM-G960F using Tapatalk


N31L   1 mW

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Posts: 12
Joined: Apr 27 2020 11:08am

Re: Another "stealth bomber" build.

Post by N31L » Apr 28 2020 6:14am

synics wrote:how about now? can you see them?
F755C54C-A7D5-4909-A0B0-183F6D105E39_L0_001.jpg
FluxA1-ES.jpg
FluxA2-ES.jpg
Another real quick one, So after asking about rear shock length what size wheels are being used here 26" including tyres?

I really like the look of the bike an have my no e-bike rides real nice this is now my frame sits that's all.

Cheers Neil.

synics   10 W

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Posts: 96
Joined: Apr 03 2020 11:18pm

Re: Another "stealth bomber" build.

Post by synics » Apr 28 2020 8:46am

So after thinking about it more, maybe I'll have a mount fabricated like the one in this pic. It provides more stability to the shock mounts, and if done right the bike can be kept at the same angle and you can put any size shock on it you want as long as you have an idea of the size before hand, just fabricate to spec...
IMG_20150514_072626.jpg
IMG_20150514_072626.jpg (204.86 KiB) Viewed 661 times

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