Frame building, fork/head-tube question

spinningmagnets

spinningmagnets

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I'm investigating making a frame this winter, the only question left for me is...what is the best length and inside diameter of head tube?

Rather than choose a head-tube that accepts a specific fork I'm impressed with, what size allows the most options. I want a front suspension fork with a disc brake option, but if this works out well, I may make a couple more frames for the local market, and a buddy may want a lighter solid fork for a low-speed set-up. (but we both know he will want more speed soon, plus the upgraded fork!)

Or...are there 3 common and popular sizes? Thanks in advance.

Almost forgot, this will be a 26" wheel commuting cruiser, not a sport-bike, a recumbent site recommended a 62-65 degree head tube angle for a stable ride, thoughts?

roscoe_E2_tech.png


350px-Head_angle_rake_and_trail.svg.png
 
There is few standards in head tube bearings 1" (cheap bikes) 1 1/8" (most bikes) 1 1/4" and 1 1/2" (expensive DH bikes)
It is steerer column nominal OD. For ID check table I have attached.

For the lenght there is no standard because most todays fork came with stereer tube longer then needed. Common is 110mm. I use 130mm.
 
spinningmagnets said:
Almost forgot, this will be a 26" wheel commuting cruiser, not a sport-bike, a recumbent site recommended a 62-65 degree head tube angle for a stable ride, thoughts?
Click to expand...

Its a pretty 'aggressive' head angle its near to what i have used (~65 degrees) on the last two frames i have made, not sure how it
would go on a short wheel based bike perhaps Hal would have better idea i believe he made a frame for himself
with increased head angle to the rest he produced IIRC? Whatever you go with make sure the trail is adequate
or it will have a heap of flop making it potentially dangerous to ride...best of luck with it mate look forward
to see what you come up with :)

KiM

p.s if increasing the length of the wheelbase is an option, this will add to high speed stability also.
 
The widest range of forks come in 1 1/8" size. everything from solid steel to entry level alloy suspension to high buck DH forks.

The cheap bikes with 1" tend to use the same forks on just about all bikes, at least for suspension forks. The 1" forks are all cheap steel ones, good for front hubs, but not for actually soaking up a bump.

The bigger sizes like 1.5 inch are only going to fit really expensive DH forks.

Length is not much of an issue with threadless steertubes, they come long and get cut to fit. The stronger frames come with longer headtubes, my giant has one about 5.5 inches long, but other bikes I have may be as short as 4 inches. If strength is the issue, I'd go for long.

With threaded steertube, anything longer than 4.5 to 5 inches gets hard to find a fork for. Nearly all threaded headtubes have enough threads to be cut shorter, but no matter how many times you cut it, it never gets longer. ( old carpenter joke,I cut it three times and it's still too short)
 
Thanks for the replies. It sounds like 1-1/8" will be the type I'm looking for. I expect a few people will like the way mine ends up, but everyone has their preferences. I want to see how hard it is. If it turns out to be fairly doable, I would love to get methods and techniques documented that allow others to make a frame, but in the shape that THEY want.

Here's the wooden bike thread, DIY carbon fiber thread, home-made tube bender, and welding :

http://endless-sphere.com/forums/viewtopic.php?f=1&t=10697
http://endless-sphere.com/forums/viewtopic.php?f=2&t=10906
http://endless-sphere.com/forums/viewtopic.php?f=3&t=12581
http://endless-sphere.com/forums/viewtopic.php?f=2&t=10143

Steel frame lugs are available for purchase, can aluminum tubing (cut and bent by me) be brazed (or epoxied) into steel lugs? Plus, any favorite links to shop for a variety of 1-1/8" forks (solid plus suspension) ?

lugs.jpg
 
spinningmagnets said:
Steel frame lugs are available for purchase, can aluminum tubing (cut and bent by me) be brazed (or epoxied) into steel lugs? Plus, any favorite links to shop for a variety of 1-1/8" forks (solid plus suspension) ?

lugs.jpg
Click to expand...

It probably could how well it would work would be hugely debatable personally i wouldnt want to trust enough epoxy
got between the lug and the alloy tube though, stick with all alloy or or steel is my advice, personally unless your an accomplished welder
or have someone that is i wouldn't be attempting anything other than mild steel for your first frame definitely not aluminium.
Interestingly you can "weld" aluminium to steel using a method called 'friction welding' not your traditional welding really uses friction and heat to make the joins...If i were you i would pick up a 150-200amp mig, Lincolns are a proven name you will get one for
600-700 upwards they can do both gas and gasless (mate grabbed one few weeks back from Auction 300 bucks!) i would suggest .8 or .9 size wire with the appropriate tip for welding frames up. If you start using more 'exotic' metal you get into the area of having to 'heat treat' the frames after they have been welded. Something else you will need is a FRAME JIG to hold all the tubing square as you weld it, RatRod Bikes have some good exampled of DIY frame jigs basically you need a jig that holds the head tube bottom bracket and rear dropouts in place and square to each other. Without a jig your going to end up with a twisted frame that will 'crab walk' as you ride down the road fun to ride and funny to look at LoL..You can make a frame without but i wouldn't suggest it if you haven' got a lil experience with welding, you can tack or clamp the tubing to a flat surface to weld it up so as it doesn't twist/move but IMHO the best and easiest way is a jig, well worth the time and extra $$ to make one.

Another couple of places that sell head tubes and other assorted parts for frame building are http://www.choppersus.com/store/ and http://www.firebikes.com/shopping.htm

KiM
 
those lugs are meant to be brazed on to steel tubes.

but if bond them you must. the parts must be supper, supper clean. then pre-treat the Aluminum parts with Loctite #7649 "Primer-N" would not hurt to prime the lugs with the same stuff. then use Loctite 660 to bond the parts.

temp limits for this stuff is 300F/150C so you would not be able to powder coat or bake your paint job.

rick
 
spinningmagnets said:
Almost forgot, this will be a 26" wheel commuting cruiser, not a sport-bike, a recumbent site recommended a 62-65 degree head tube angle for a stable ride, thoughts?
Click to expand...
For the head tube angle vs stable ride, it partly depends on speed. The faster you intend to ride it, the shallower the angle can be and remain stable.

For instance, my CrazyBike2 has a shallower angle than my road bike, and it gets *more* stable at much faster speeds (approaching 40MPH downhill it is like magic!), while the road bike gets *less* stable at faster speeds but is more stable at lower ones. Part of that is other frame geometry and rider height, etc, but part of it is definitely the head tube angle.

Early this year, I tried an experiment (which I need to someday get around to documenting on my blog) before I motorized CB2 where I put a 20" wheel on the front* and a 26" on the back, and coasted down the same hill I had previously done on both 24" wheels. The change in tire sizes made the head tube angle steeper, closer to the road bike's, and it performed less well in straight-line steering stability at the higher speeds, as the road bike did (although still much much better than the road bike, probably because of the rest of the frame design and profile). It felt jittery as I passed 25-30MPH, and I really didn't like it much at 40MPH. Not as scary by far as the road bike, but still not as much fun.

On the other hand, it was more stable at slower speeds; easier to keep going in a straight line without as much side-to-side flopping around, with the steeper angle.

I don't think I've ever measured either angle, but you could probably determine it from the side-view pics I have of CB2 on this site and on my project blog.




*Note that my 24" front suspension fork was modified for an earlier recumbent I never finished, so that it would take either a 24" or a 20" wheel and still have working brakes, by welding some rear dropout tabs to the front edges of the steel suspension tubes.
Some info about doing that is partway down this post:
http://electricle.blogspot.com/2008/09/pics-of-parts-and-progress.html

When I used *that* fork for this test, it was about as stable with either wheel size.

When I used a 20" suspension fork for this test, I got the results described.
 
the elise chassis for the tesla is bonded alu.
bonding made possible the use of thinner wall tubing than what welding would have required to prevent shoot-thru.
weight savings was something like a third also the frame is more rigid than welded which are the main reasons for going that route but it seems to hold up. :D
 
i'm not sure that what they do in aircraft or car building can be easily duplicated at home. it requires some pretty special techniques and tools. first you have to find someplace that does phosphoric acid anodising to prep the part and give the epoxy a surface to bond to. next you need a super clean oven big enough to bake the parts. first time to dry the rinsed and solvent cleaned parts (lots of smelly chemicals) and then to set the glue which is temperature sensitive.

closest would be the loctite 660. and i would only recommend it for cylindrical parts put into a hole. like the frame tubes inserted into some tight fitting lugs like those in thoe pictures.

an emergency repair can be made with a high strength epoxy like original JB weld as follows. 1. scrub the surfaces clean using a stainless steel brush. scrub until shiny. rinse using isopropyl. 3. mix the JB Weld and apply completetly covering both surfaces. 4. scrub both surfaces with the wire brush again through the epoxy. 5. clamp and let set of 24hrs.

Aluminum will oxidize the instant it is exposed to air. Covering it with glue and THEN scrubbing the glue in will cut through the very thin newly oxidized layer and the glue will prevent air from touching it to again oxidize it. this can be a very strong joint but it will fatigue quickly. i would not count on it for any length of time. it is meant mostly for emergengy repair of crash damage, reportedly it holds just long enough to fly the aircraft out of a remote or hostile area to wherever a permanent repair can be made. solidly in the "desperate to get out of this situation with McGyver at my side" category of emergency repair.

rick
 
I built an ICE intake and used welding and loctite hysol XXX.

The 1.5" 6061 al tubes were bonded into pockets on the plenum side. There was
really no clearance to get a tig torch in there. We didn't use super
sophisticated prep. But we hit the ends of the tubes and the id of the pockets
with scotch brite, acetone and applied glue to both surfaces.

It would be interesting to see how this has held up over the last four years.
I know that it still works, but I don't know how strong the bonds are at this point.

I do know that in ICE intake is exposed to a huge number of vacuum induced
forces and cycling of those forces. Any time you hit the gas, vacuum goes down,
and then when you release it vacuum goes up which will stress the structure
thousands and thousands of times. It wasn't not a structural part of the chassis of course,
but was still exposed to it's own stressed environment.
 
Thanks for all the great replies. I think I'm going to get a MAPP-torch and play with brazing on scrap tubing this winter. I'll play with wood a little too. I'm going to have my own garage again soon, so then I'll start stockpiling trash bike frames to experiment with...

I'm certain I'll be making one of those tube-benders.
 
spinningmagnets,

Steering angles;

Assuming your builds are typical uprights, then I suggest you stick with well established head tube angles - 72-75 degrees. Head tube angles outside the aforementioned range will invoke difficulties in finding forks with the correct offset (rake). For example; Assuming a head tube angle of 73 degrees, a wheel Radius of 13" and a typical fork offset (rake) of 1.5", will produce 2.4" of trail. With your purposed HT angle of, say 63.5 degrees in combination with typical, off-the-shelf fork offsets of 1.5" and the same 13" wheel radius wheel, your trail will be double at 4.8" - resulting in massive fork 'flop'. The only fix in this case would be to build custom forks or plan on bending the existing blades to eliminate the excessive trail.

Frame fabrication;

Lugs, will severely restrict your geometry choices, I suggest you consider 'fillet brazing' instead. Mapp/Air will work, but you'll experience difficulties heating larger mass pieces such as BB shells, especially if your donors are made of cheap, mild steel tubing (read thicker walls). If you plan on more than just a few builds, then spring for an Oxy-Acetylene or Oxy-Propane setup.

There's better brazing rods available, but you'll do fine with just off-the-shelf LFB from your local supplier. Just use bare rod and Harris Stay-Silv Black paste flux.
 
dontsendbubbamail said:
Tube Miter is a good little app if you go lugless.

Bubba
Click to expand...

There the ones you plug in the angle of the join, tube diameters and it spits out a printable template to wrap around the pipe correct?
I tried them myself, took me longer to work out the software than it did to do one by hand but im not too bright LoL. You can also get notching tools for tubes if you want too splurge, once you have done a few...(dozen) you can knock them out with angle grinder without drawing a line on the tube, my mates a boilermaker (over 20 years working with metal) he can eye it of do it once with the angle grinder and it fits perfect 99% of the time...take me one or two "adjustments" get the same end result though hehe

KiM

p.s you been quiet lately Bubba you got anything on the go i can perve at?
 
you could also clamp the tube at the correct angle on a drill press and using a bi-metal hole saw of the same diameter as the intersecting tube just cut the notch.

limit your tubing to a couple of diameters and you only need to buy a couple of different sizes of hole saw.

rick
 
AussieJester said:
dontsendbubbamail said:
Tube Miter is a good little app if you go lugless.

Bubba
Click to expand...

There the ones you plug in the angle of the join, tube diameters and it spits out a printable template to wrap around the pipe correct?
I tried them myself, took me longer to work out the software than it did to do one by hand but im not too bright LoL. You can also get notching tools for tubes if you want too splurge, once you have done a few...(dozen) you can knock them out with angle grinder without drawing a line on the tube, my mates a boilermaker (over 20 years working with metal) he can eye it of do it once with the angle grinder and it fits perfect 99% of the time...take me one or two "adjustments" get the same end result though hehe

KiM

p.s you been quiet lately Bubba you got anything on the go i can perve at?
Click to expand...

That's the program I am talking about.

I have been blowing up controllers, so I have not had enough ride time to figure out what needs to change mechanically. Just got two 18 fet controllers, so expect new stuff in the near future.

Bubba
 
If your just planing the one frame i wouldnt be spending alot of dollars on tube notchers or benders you can build a frame without either. The program Bubba linked to will work fine.

dontsendbubbamail said:
That's the program I am talking about.

I have been blowing up controllers, so I have not had enough ride time to figure out what needs to change mechanically. Just got two 18 fet controllers, so expect new stuff in the near future.

Bubba
Click to expand...

Good too hear...well not the blown controllers bit ...you know what i mean lol Shall keep my eyez peeled :)


KiM
 
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