Long tail full suspension bolt-on frame

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Re: Long tail full suspension bolt-on frame

Postby BarkMau » Tue Oct 29, 2013 12:26 pm

Stevil_Knevil wrote:
BarkMau wrote:fat 20" on cast rim seems bullet proof. Right now I'm looking at Michelin gazelles 17x3.0 on moto wheels which should come a bit under a 24" bicycle wheel size. we'll see how that turns out.


Pedal strike will be an issue - if you pedal in turns - which seems silly @ 30+ MPH.

Looking forward to seeing how well this machine performs 8)


I pedal when turning, I pedal @ 30mph. Silly me.. :P
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Re: Long tail full suspension bolt-on frame

Postby Stevil_Knevil » Tue Oct 29, 2013 5:51 pm

BarkMau wrote:
Stevil_Knevil wrote:
BarkMau wrote:fat 20" on cast rim seems bullet proof. Right now I'm looking at Michelin gazelles 17x3.0 on moto wheels which should come a bit under a 24" bicycle wheel size. we'll see how that turns out.


Pedal strike will be an issue - if you pedal in turns - which seems silly @ 30+ MPH.

Looking forward to seeing how well this machine performs 8)


I pedal when turning, I pedal @ 30mph. Silly me.. :P


Me too, but it just feels wrong @ 31 MPH ..especially when the bottom bracket is 1+ inches lower :)
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Re: Long tail full suspension bolt-on frame

Postby Stevil_Knevil » Wed Oct 30, 2013 2:01 am

..and I am totally going to build one of these with 17 inch moto wheels :twisted:

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Re: Long tail full suspension bolt-on frame

Postby dogman dan » Wed Oct 30, 2013 6:03 am

I'm confused what the argument is about. If you build so you lower your bottom bracket much, you change fork angles. You don't want that generally.

You build it so your pedal height is what you want. If you corner at 30 mph, likely that will lean enough to pedal strike riding many stock bikes. FS bikes tend to be taller, and able to pedal through fast corners.

My longtail is quite capable of pedaling through corners at any speed I can handle. The BB is quite tall. But if I had built it with a small rear wheel, I would not have changed the pedals bb height any. That's to preserve the originally designed fork angle. Because I used a front frame with a fork angle designed for a shock, the bb is plenty high to pedal through corners all you want to.

But if you were to use a normal unsuspended bikes frame, and used a fork that raised the front 2" more than normal, you'd need to build your bike so the bb was also raised about 2 inches. In that case, the bb would go up, not down.

If you built using a small wheel lowering the rear, then you'd have to adjust the shock mounts or how the two frames were connected some how so you'd get the bb back to the normal height. If you didn't, then you'd again get unintended modifications to the fork angle of the bike.
Last edited by dogman dan on Wed Oct 30, 2013 6:09 am, edited 1 time in total. View post history.
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Re: Long tail full suspension bolt-on frame

Postby Stevil_Knevil » Wed Oct 30, 2013 11:43 pm

No argument here. The concept is solid and proven. What happens when ~24" wheels are introduced is my only concern.

Drilling, threading then cutting off the lower 20mm of crank arms -rendering ~155mm long cranks- seems like a good solution.
Last edited by Stevil_Knevil on Wed Oct 30, 2013 11:44 pm, edited 1 time in total. View post history.
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Re: Long tail full suspension bolt-on frame

Postby BarkMau » Thu Oct 31, 2013 11:25 am

dogman wrote:Love to see more FS Frankebikes. Though the shocks on mine are a joke, it's worked amazingly well for me.

Interesting shock mount bracket. Is that a repurposed caster? If you have not tuned it yet, this is how I did mine. I took the original frame and fork, and put wheels on it. Then I measured the height of the pedal crank from the ground. Then when I put on the rear assembly, I made sure the crank height was identical. This makes sure that you haven't ended up with a funny fork angle. Mine ended up riding perfect, with no funny handling issues.


But I do think you must center that swingarm in the frame. Id take a hacksaw to the long part of the BB, or find a cheap bb that is equal in length to install on the swingarm.

Love your bolt on shock mount. Much nicer that what I did, retaining a large chunk of the second frame.

Once I was happy with the connection, I welded my bb to the frames rear droputs. I didn't like relying on just bolts at that point. You can only do that if the front frame is steel of course.

But if you bolt it, which should work fine really, I'd think that some kind of torque arm like device might be good. What I mean is a plate with a round hole for the bottom brackets "axle" to pass through. This then attaches to the front frame. It's not to prevent rotation like a TA, but just to prevent a complete separation of the two parts of the frame. That way if your bolts slip, you get some chance of stopping and getting off before the rear wheel goes bye bye.

Most of the riding forces just want to make the bb jam into the dropout, but you might still have forces when you jump off a curb or whatever going out of the dropout.

Dogman's approach at keeping the original geometry (including bb height) should work.
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Re: Long tail full suspension bolt-on frame

Postby dogman dan » Fri Nov 01, 2013 6:55 am

Yeah, I get it that if you build it for 26", then change to 24" rear tire, you just created a problem.

Cool thing about this one, is the bike is still tunable by moving that shock mount. On my longtail, I'd have to change the shock length. Or re do the welding to re tune it. So I'm pretty much set with what I have for the duration, 26" rear wheel.

I'd never consider changing the crank length, unless it was to just replace cranks with footrests. Other than to comply with the local laws, the pedals on my frankenbike are pretty pointless. Even at low speeds, pedaling is not getting me much other than avoiding a sore ass. Mostly I pedal to keep the ass from getting numb.
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http://endless-sphere.com/forums/viewto ... cing+betty.

bolt on longtail viewtopic.php?f=6&t=74584

The mixte long tail. viewtopic.php?f=6&t=74384

Beach cruiser converted to long tail. viewtopic.php?f=6&t=67049&p=1045572&hilit=Longtail+beach+cruiser#p1045572
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Re: Long tail full suspension bolt-on frame

Postby gogo » Fri Nov 01, 2013 11:17 am

dogman wrote:I'm confused what the argument is about. If you build so you lower your bottom bracket much, you change fork angles. You don't want that generally. …

Experiments with rake and trail variations.

+1 For paying attention to BB and pedal height, especially in corners.

As the Tony Foale article suggests though, the effect of steering geometry is not as cut and dried.
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Re: Long tail full suspension bolt-on frame

Postby dogman dan » Fri Nov 01, 2013 2:07 pm

When I was building my longtail, I just wanted to be doing no experiments with rake and trail.

I figured that if my bb height was exactly the same as before, I would be close to same as before after getting on and adding cargo.

This was including the assumption that I could tune the shocks to get the same sag front and back on the bike in the end. What I mean is, when I load the bike and get on, the shocks front and back lower about the same amount. To get this to happen, my rear shock preload is stiff, while the front is less stiff. When I get on, the bb height lowers, but the fork angle doesn't change much.

My thinking was that the original frame fork angle was what I wanted to keep.
For those that still don't know, I work online, for E-bikekit.com

Frankenbike longtail
http://endless-sphere.com/forums/viewto ... cing+betty.

bolt on longtail viewtopic.php?f=6&t=74584

The mixte long tail. viewtopic.php?f=6&t=74384

Beach cruiser converted to long tail. viewtopic.php?f=6&t=67049&p=1045572&hilit=Longtail+beach+cruiser#p1045572
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Re: Long tail full suspension bolt-on frame

Postby Stevil_Knevil » Fri Nov 01, 2013 7:47 pm

Both of my ridged longtails are 69'ers. 26" rear and 29" front. Tried same size wheels, but found that the less steep (slacker) head angle makes them handle MUCH more stable @ cruising speed.

I read a head angle of 70.5 degrees on mine. What do Y'all see on yours?
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Re: Long tail full suspension bolt-on frame

Postby BarkMau » Sat Nov 02, 2013 7:50 am

Stevil_Knevil wrote:Both of my ridged longtails are 69'ers. 26" rear and 29" front. Tried same size wheels, but found that the less steep (slacker) head angle makes them handle MUCH more stable @ cruising speed.

I read a head angle of 70.5 degrees on mine. What do Y'all see on yours?


Slacker head angle, definitely something to keep in mind. How are u measuring the head angle?
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Re: Long tail full suspension bolt-on frame

Postby spinningmagnets » Sat Nov 02, 2013 12:34 pm

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Re: Long tail full suspension bolt-on frame

Postby Stevil_Knevil » Sat Nov 02, 2013 2:31 pm

Yep, ^that is the official way^

I stand the bike straight on level ground and put a roof framer's tool on the headtube. Different variation on 'head (tube) angle' measurement.

This tool has two straight edges @ 90 degrees, and a swinging dial that always points up->

Image
Last edited by Stevil_Knevil on Sat Nov 02, 2013 2:35 pm, edited 1 time in total. View post history.
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Re: Long tail full suspension bolt-on frame

Postby dogman dan » Sun Nov 03, 2013 7:33 am

I haven't measured the trail on my bike. I have a typical cheaper shock fork on it with some rake built in. So there is some trail for sure.

Using the same tool as in the pic above ( cheap at Harbor Freight) I get 70 degrees on my longtail, sitting on the wheels, but not me sitting on it.

I did not have the tool when I built the bike. But I assume that I did not change it that much, if the bb height was exactly the same, and the bike when loaded does not tip to the rear a lot. It's obviously not getting loaded evenly, so the setup is a very stiff rear shock, and a very soft front shock. Much stiffness on the front, and it would ride the same as a hard fork. If the bike does sag to the rear, then it gets slacker when loaded. Load it really heavy, like 100 pounds on the bike, and you can feel the front wheel lighten up. So it likely does slacken the angle some when a max cargo load is on it.

I'm pretty uneducated about this stuff, it's why I tried to just keep it all the same as I made the cuts to weld my bikes into one.

Would it be just like a slacker head angle if you increased trail? Or can you slacken angle more and not need trail? I believe I heard trail helps stability at speed, while keeping easier steering at low speed you get with a steeper head angle. Mine seems to do good enough at both.

One bike I fooled with the angles with felt very twitchy to me, particularly at above 20 mph. Raising the front with a bigger rim and fork, the slacker head angle felt right to me. It created a wheelie bike though, so it was a fail.
Last edited by dogman dan on Sun Nov 03, 2013 7:41 am, edited 1 time in total. View post history.
For those that still don't know, I work online, for E-bikekit.com

Frankenbike longtail
http://endless-sphere.com/forums/viewto ... cing+betty.

bolt on longtail viewtopic.php?f=6&t=74584

The mixte long tail. viewtopic.php?f=6&t=74384

Beach cruiser converted to long tail. viewtopic.php?f=6&t=67049&p=1045572&hilit=Longtail+beach+cruiser#p1045572
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Re: Long tail full suspension bolt-on frame

Postby BarkMau » Sat Jan 25, 2014 12:48 pm

Frank's alive! I'm happy to report that the bike works. The rear suspension with the cheapest "shock" possible works great. Geometry seems similar to original. Still need to iron a couple of kinks but it should be ok. I'm looking forward to installing the rear rack, load it and fine tune the suspension.
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Re: Long tail full suspension bolt-on frame

Postby spinningmagnets » Sat Jan 25, 2014 12:59 pm

Glad to read about this progress. Expensive air-shocks are always an available future upgrade, but...going from a hardtail to even just a super-cheap low-end shock was such an incredible improvement.

Part of the reason I like the idea of a longtail frankenbike is that...any possible experiment concerning rake/trail/head-angle...they are all very easy, and super cheap to try.
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Re: Long tail full suspension bolt-on frame

Postby BarkMau » Sun Jan 26, 2014 9:12 am

I agree.
I'm leaning towards cheapo pitbike shock and lower the rear wheel to 20" max. A smaller scooter wheel could be even better on getting a low cargo deck.
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Re: Long tail full suspension bolt-on frame

Postby dogman dan » Sun Jan 26, 2014 9:31 am

Yay! Did you have to wait for a good thunderstorm? :D

Good to hear "It's alive, it's alive".

I just put a slightly longer, but much better front shock on my frankenbike. So I just slackened the head angle a bit. When I get on, it comes back down to about what it was before though. It's an air shock, and I'm running it a tad soft.

WOW. What a huge improvement. As winter came, the tired old cheap rockshock just gave up working and became rigid on a cold day. Still rode tolerable like that, but when I put a nice marzocchi air fork on it with a silky responsive deep travel, the ride on rough pavement got so much better, and the ride on crappy dirt roads is just amazing.

Anyway, the point is, it feels like the better front shock makes the crap rear shock have to work less hard. That's how I perceive it from the saddle. I'm feeling the bumps less through my ass.
Last edited by dogman dan on Sun Jan 26, 2014 9:33 am, edited 1 time in total. View post history.
For those that still don't know, I work online, for E-bikekit.com

Frankenbike longtail
http://endless-sphere.com/forums/viewto ... cing+betty.

bolt on longtail viewtopic.php?f=6&t=74584

The mixte long tail. viewtopic.php?f=6&t=74384

Beach cruiser converted to long tail. viewtopic.php?f=6&t=67049&p=1045572&hilit=Longtail+beach+cruiser#p1045572
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Re: Long tail full suspension bolt-on frame

Postby BarkMau » Sun Jan 26, 2014 11:30 am

Ha ha. Feeling the bumps less thru your ass gotta b a good thing..i guess
ya, the moment when u realize "it's alive" is epic!
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Re: Long tail full suspension bolt-on frame

Postby BarkMau » Sun Jan 26, 2014 5:43 pm

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Re: Long tail full suspension bolt-on frame

Postby dogman dan » Mon Jan 27, 2014 10:46 am

That is pretty clean looking! I love it.

Mine is much more kluged, with it's gigantic wooden cargo deck, and an obviously sawed in half rear section. And the welds a monkey could do better. Yours looks designed to be like that from the start.

Thread here, for those interested in mine that never saw it before. It was quite a figure it out as I went process. I'm amazed how nice mine rides to this day.

viewtopic.php?f=6&t=28389&hilit=bouncing+betty
For those that still don't know, I work online, for E-bikekit.com

Frankenbike longtail
http://endless-sphere.com/forums/viewto ... cing+betty.

bolt on longtail viewtopic.php?f=6&t=74584

The mixte long tail. viewtopic.php?f=6&t=74384

Beach cruiser converted to long tail. viewtopic.php?f=6&t=67049&p=1045572&hilit=Longtail+beach+cruiser#p1045572
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