1. Free Chopper Frame Blueprints
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MINI BIKE PLANS Page 2 4. Lay out 2 pieces of 7/8' tubing each 31' long. Mark and bend in shaded area as shown below. Cut 2 pieces of 7/8' tubing, with a 5/8' inside diameter, as shown in Figure 5. Set up blueprints in Catia v5 surface modeling tutorial v5 by Sketch Tracer tool. But here I have not much discus on plastic component design techniques but any way you can learn draft analysis and how to creating the parting surface which will help you to design plastic components. Addng Formulas In Catia. Feb 29, 2008 - A real chopper artist can chop any bike, even this crusty old codger cruiser. In fact, the more I looked at the bike, the more I thought it would be a sweet ride. Check out all that chrome, look at that long spindly frame, yeah, I could make this happen The how-to is a great a step-by-step and has dozens of.

This is an instructable on how to build a chopper bike on a budget. The main inspiration for this came from AtomicZombie and Koolkat's instructables. I've recycled as many parts as possible, and used scrap materials when I could. I took a 25 year old Raleigh Wisp ladies racing bike and converted it to something a bit out of the ordinary. Materials needed:.Donor bike.Welder (I used a gasless MIG welder - a Clarke 105EN).Steel tube(s) for the forks. These need to be quite heavy gauge as the forces involved will tend to bend the tubes.Steel tubing to extend the frame after chopping. The diameter of this tubing should be either slightly smaller than the existing frame tubing (to fit inside the cut tubes) or slightly bigger (to fit over the tubing).

Butt welding tubes of the same diameter is more difficult and will not be as strong unless your an expert welder (and I'm not!).Some sheets of steel. I had some 1.4mm thick sheet steel which is perfect for the plates I made.New chains - if you're extending the frame significantly, the chain length will also increase. Buy two cheap chains to join together.Access to a pipe bender - you may need this if your angles change significantly and you don't want to cut the extension tubes at an angle.

Read on for instructions on how I did it, and the mistakes I made along the way. Above all, enjoy building and don't give up! Right now, our forks are just two tubes. There's no way of attaching them to a wheel, so we need to make some drop-outs. Pic 1 shows what we want to achieve. The drop-outs need to be strong.

I used some scrap steel plate, about 3mm thick. This is ideal.

Universal keygen generator. Overlay one of the existing fork's drop-outs onto the steel to be cut. This will give an indication of the size and shape of the piece to cut out.

Use an angle grinder to cut out two pieces from the steel to form the drop-outs. Angle grinding is never exact, so the drop-outs were not exactly the same. I aligned the drop-outs in a clamp and used the grinder to get their edges identical.

Pic 4 Use the grinder to make the edges neat. Remember, the straighter the surface, the better the join will be.

Clamp the two pieces together and cut out the slots for the wheel axle.This way, you can be sure that when you use an angle grinder to cut the slots, both slots will be identical. Take your time here - don't cut too much of you'll risk the wheel popping out. Your aim here is to cut a slot just big enough for the wheel's axle to fit snugly. Keep trying to fit the wheel axle into the slots until they just fit. A tight fit is needed - not a lose fit. (Pic 6) Next, we need to weld the drop-outs to the forks. I used a magnetic mount to hold the drop-out to the fork.

IMPORTANT: I made a mistake when I welded my dropouts - I placed them right in the centre of the tube - I should have moved them closer to one edge. I only discovered this later during a test ride when a wheel's spokes were rubbing against the inner side of the fork tubes.

Luckily, I was able to use another wheel which fitted better, but take heed of this mistake! Tack weld the drop out to the forks. Check your alignment. When your happy that all is well, weld it securely. Here's where the time taken to make a straight edge pays off! Ok, we have our two tubes and we've welded drop-outs onto them. My plan is to be able to bolt a steel plate to the tops of the forks, so we'll need to work out a way of being able to screw a bolt into the forks.

Next step - make a threaded top for the forks. First of all, you'll need to get some nuts, bolts and washers. I bought a pack of M10 bolts, nuts and penny washers.

All these are M10 size (10mm hole). These are really cheap from any hardware discount store. Assemble a bolt, washer and nut as shown in the first picture. Weld each face of the nut to the washer. Remove the bolt, so you'll be left with a welded nut and washer as shown in the second picture. Finally, weld the washer/nut to the top of the fork.

Now you should have a solid mount on the top of the forks This will enable us to screw a bolt into the forks. Let's move on. To recap - at this stage we have two tubes. Each tube has a drop-out on one end and a threaded nut at the other end. Next step: Build the forks Cut the legs off the forks.

Try and get the base at flat as possible. Using a bit of cardboard as a template, draw a semi circle around your new fork tubes.

Use a marker to draw the shape of the new forks on the fork crown. Use an angle grinder to cut the shape of the new forks out of the crown. Take your time here, try and get the shape as close as possible to the new forks. Attach the wheel to the ends of the forks. This will give use the correct width for the forks. Next, place the steerer tube / crown between the forks. If you've been careful, it should fit snugly.

Using another bit of cardboard, mark and cut holes where the three tubes fit. This will form the template which we'll use for the base plate and the top plate. Trim the cardboard so it's a nice neat shape.

Make the base plate: Using the cardboard template, cut a shape from some sheet steel. I used some scrap 1.4mm sheet steel.

Draw the two outer holes (where the forks go) onto the sheet steel. Use an angle grinder to cut the sheet steel so you have a base plate as shown in picture 3. Tack weld the base plate to the fork crown. Be careful not to get any weld spatter on the bearing races! Next we have to make a stem. If you like, you can cut the head off the existing stem.

Free Chopper Frame Blueprints

I've chosen to make my own stem, as I had some steel pipe which fits inside the fork's steerer tube. Use the angle grinder to cut a 45 degree cut on the end of the tube. Cut the tube so that its length is correct for the steering bolt and wedge. We've now made our own stem. If you cut the head off the existing stem, you can skip the above steps. Fit the new stem into the fork's steerer tube. Position the steerer tube / crown between the forks once more.

If you have a friend, they can help you hold everything together. I've used a strap to hold everything together.

The upper headset nuts should be about an inch below the top of the forks. When everything is nice and centered, weld the base plate to the forks. OK, now we have our two fork tubes which are welded to the steerer tube / crown.

Next we need to make a top plate which will clamp everything together. We will re-use the cardboard template we made previously to cut out a shape in sheet steel. Now we need to mark on the sheet steel the centres of the two forks and the stem bolt.

I'm using 10mm bolts so I drilled 15mm holes at the fork centres, and about 10mm hole for the stem bolt. It doesn't matter if the holes are bigger than the bolts, we'll be using washers when we assemble it. Picture 1 shows the drilled top plate. Picture 2 shows the plate bolted to the top of the forks. (Ignore the clamp that the bolt is holding - we'll discuss that later) Summary - we've now built our forks. Our tubes are welded to our base plate, which in turn is welded to our fork crown.

We've made a top plate and proved it fits OK by bolting it all together. Picture 3 shows the bike assembled with our forks. Well, the forks look OK, but we'll have to seriously modify the frame to make it rideable. Next step - the frame.

Think long and hard about what you're going to do with the frame. It took a lot of thinking to make sure that my frame chop was going to work. In the end, it worked out OK.

Chopper Frame Blueprints Pdf Writer Download

Picture 1 shows the frame before chopping (it's upside down on the bench) The frame was chopped to that the bottom bracket shell was towards the front of the bike. We'll be stretching the frame. Picture 2 shows the frame after the chop! There's no going back now! I decided I wanted to keep the twin top tubes as they're such a great feature, so I cut them as near to the rear hub as possible. Picture 3: The next step is to mock up the bike with the new frame design. It's important to put the wheels on so you can get the height correct.

For this mock up, I supported the bottom bracket and extended the frame with some thin scrap tubes. I noticed that the twin top tubes were too low so I took a chance and bent them by hand to the correct height for the seat. If I damaged them (split the joint, etc), I would have had to weld them to repair them. As it was, I got away with it. I was happy with the overall shape and design of the new frame, so the next step was to extend the frame by inserting two new steel tubes from the bottom bracket shell to the bottom pair of tubes at the bottom of the seat post. For this task, I used the measurements from the mock up to cut two lengths of tube.

I used a pipe bender to make a slight bend near the bottom bracket shell. This was necessary as the down tube angle had changed.

Picture 4 shows this clearly. At this stage, the seat tube is not attached to anything - it's just floating. The next step is to secure the bottom of the seat tube.

Using a piece of cardboard as a template, I made a plate of sheet steel which I positioned underneath the seat tube. I welded the plate on top of the horizontal tubes. This strengthens the joint between the two new tubes and the rear tubes. I then welded the seat tube to the plate. Next, let's turn our attention to the top tubes. Again, these are just floating - they're not attached to anything yet.

Again, I made another plate from sheet steel. You can't see it, but I used the angle grinder to make a slot in the seat tube. I inserted the steel plate into the slot, then tack welded the plate to the seat tube. This slot means the joint will be a lot stronger and there will be less downward stress on the weld.

Next, I welded the two top tubes to the steel plate. The frame needs some more strengthening. The next step is to join a new piece of steel tube from the bottom bracket shell to the top tubes. This will replace the seat tube which is now towards the back of the frame. Using the same trick of making a cardboard template, I made a steel sheet plate and welded it to a new piece of steel tubing.

It took several attempts to get the angle correct, so use a small tack weld and be prepared to break / grind / re-weld. Be careful with the length of the tube - if it's too long, it will hit the bottom bracket axle.

Make sure the tube fits into the bottom bracket shell, but not too far in. Picture 2 shows the frame, fully welded. I'm going to take full advantage of the twin top tubes, and mount a seat on top of the tubes.

The seat is going to be a simple construction of scrap wood, scrap foam and scrap leather. Picture 1: I screwed two pieces of scrap wood together, then drilled holes in the wood through to the plates below. I used some bolts and nuts to check it fitted OK. Now for some upholstery! Picture 2: I used a heavy-duty staple gun to staple some foam to the wood.

Picture 3: Again, use the stapler to staple leather scraps to the seat. Next step is to fit the handlebars. You have three choice with the handlebars 1.

Use the existing handlebars. In my case, they're racing drop-handlebars, so they're not suitable. Make your own. If you have some steel tubing you can either make your own bars using a pipe bender or by cutting and welding into the right shape 3.

Use other bars. I had some scrap motorcycle handlebars, so I decided to use these. I used the seat from the donor bike, and removed the seat clamp from underneath the saddle. Picture 1 shows the seat clamp loosely assembled around the handlebars. It's a pretty good fit so we'll go with these. Picture 2: Next we position on of the seat clamp grips onto our top plate we made earlier. Picture 3: Tack weld the seat clamp plate to the top plate Picture 4: Weld the seat clamp to the top plate and assemble the seat clamp around the handlebars.

We now have a fully adjustable handlebar clamp. If you use the same wheels that came with the bike, you won't have to bother with this step.

I wasn't happy with the 27 inch wheels thats the bike came with. I decided to change them for sturdy 26 inch mountain bike wheels. For this to work, I had to alter the brake hanger.

IMPORTANT: Shield the tire with a wet cloth or it will be damaged by the heat from the welder! Picture 1: I worked out where the brake caliper had to be mounted and tack-welded a section of plate across the rear chainstays.

Note that the mounting hole is not central, this is due to errors in my frame alignment. Picture 2: Check the brake caliper fits and functions correctly by hand before final welding. Picture 3 shows the welded plate and the caliper mounted. I used a spare brake lever I had from another bike.

A little over a year ago I took a bicycle frame building class through the. I attended the chromoly brazing class at their Portland campus. Since then I have wanted to build more bike frames.

I am interested in making money doing it, and perhaps someday, making it my sole source of income. On the path to becoming a bicycle frame builder one of my biggest obstacles is acquiring a frame building jig. They are expensive, arguably the most expensive single tool you need to accurately build quality bicycle frames. So I, like many bicycle frame hobbyists, decided to build by own.

My personal goal for my frame jig however, was to build a professional quality frame jig. I wanted something I could potentially start a business with. In Portland I learned to build using an. The simplistic, functional and approachable design seemed like an obvious choice for me. I scoured the internet for photos of bicycle frame jigs, in particular Arctos jigs. A handful of people have posted photos of Arctos style jigs that they have built. Built a very close replica he called the “Arctos Clone Frame Fixture”.

His photos and descriptions were helpful and inspiring. With the Arctos model at the core of my design I started out to make changes to suit my specific needs. Some of the changes I wanted to implement included the option of simple attachments to make a tandem frame as well as room for extra long chain stays (for cargo bikes). The room for long chain stays was easy. I simply left the main spine of the jig as long as possible. I will discuss the the tandem attachment I came up with later in this instructable.

I designed specific parts of my jig as I built them. I prototyped as I constructed so you wouldn’t have to. I did not draw the entire jig in CAD. I used a variety of specific drawings and views to produce everything. I have attached all my CAD files both as original technical drawings and dimensioned labeled PDFs.

This instructable will be broken down in to one step for each sub assembly of the Jig. Aluminum Extrusions: I decided to build the majority of my jig using 80/20 brand extrusions. There are a variety of aluminum extrusions available, Arctos jigs use brand extrusions. Because many bicycle dimensions are given in metric, and I think it is a better system, I went with Metric extrusions. I went with the 40 series metric extrusions.

A little information I learned about 80/20: 80/20 comes in a variety of metric and SAE sizes. Their naming system give the distance between channels on all extrusions in that series. For example metric 40 series is 40mm between channels and the 1.5 series (the approx. Metric equivalent to the 40 series) is 1.5 inches between channels. The individual extrusion options are named for their dimensions. 40-40 (the skinniest option in the 40 series) is 40mm x 40mm.

It has one channel in the center of each face (20mm from each side). The 80-40 series is 40mm x 80mm. The 80mm face has two channels and the 40mm face has one channel. Each extrusion series is designed to use a specific hardware.

40 series is made for M8 bolts. The channels take M8 bolts and the end holes are the right diameter to be tapped for M8 threading. Therefor I used almost exclusively M8 bolts for this project. Detailed CAD drawings of lots of the available 80/20 extrusions can be found on.

However, McMaster did not have all the specific extrusions that I wanted so I ordered all of my 80/20 on Amazon. See the attached.pdf of all the specific extrusions I purchased (as well as what lengths I used). Aluminum Stock: The specific parts that I milled were almost entirely 6061 aluminum. It is fairly light, fairly cheap and I had access to lots of scrap. I used flat stock from 1/4” up to 1 1/2” and round stock with a diameter of 1.5”. I also used some 3”x3” angle aluminum (1/4' thick).

Handles and Hardware: I bought all my hardware from McMaster Carr. Other: I bought dummy axles from the United Bicycle Institute. Note: My Jig is designed to work with the specific dimensions of these dummy axles, modify yours if you use different dummy axles. Tools (at least some of the important ones): Bridgeport 1 Series Manual Vertical Mill for milling parts Sharp Manual Lathe for making cones and BB shell mount Omax Waterjet for cutting parts from stock Cold saw for cutting stock and 80/20 Horizonal and Vertical Band Saws for cutting stock. As I mentioned in the introduction, I wanted to keep the main spine long enough for long chain stays.

The longer the main spine the longer chain stays you can make. The length of the main spine is very roughly the max chain stay length plus the max effective top tube length you want to make. (this simple approximation does not account for BB drop, HT and ST angle or the width of the vertical spine piece but it is adequate). A size large Surly Big Dummy has chain stays that are 827mm long and an effective top tube length of 614mm.

With my simple formula that gives a spine length of 1441mm. The longest pre-cut piece of 80 - 160 extrusion that I could find came in a 1220 length. I bought this piece and left it uncut. The vertical spine is made of 80 - 80 extrusion. It needs to be long enough to allow the head tube to be held at various heights. Head tube height is not a primary measurement from frame design.

However, with the Arctos design it is used to set up the jig for a particular frame. I decided on 700mm for the vertical spine. This should allow me to build bikes as large as I will need to. Because head tube height is a measurement used for setting up the jig, I wanted to inlay a measuring device. I ordered adhesive backed metric measuring tape from McMaster Carr.

I used the Bridgeport mill to mill a grove of the same width as the tape up the majority of the vertical spine. Alignment of this tape is based on the Head tube assembly, I will discuss it further in that section. Attaching the vertical spine to the main/horizontal spine was done with.

Get the right size for your extrusions. To use this hardware you need to drill a hole though the vertical spine so you can get a hex wrench in there. You can cut the holes through only to the center of the vertical spine and use a ratchet in the cramped space or you can drill all the way through so you can use a straight wrench with a convenient handle from the outside. I drilled all they way through. These holes don’t have to be tremendously accurate especial if you drill larger diameter holes so the wrench fits loosely. There are 8 possible holes in the end of the main spine that can be used to attach the vertical spine. I decided to just use the outermost 4.

You must place the holes in the vertical spine so they line up with the holes in the main spine. I measured the location of these 4 holes in the end of the main spine with calipers. I measured, marked and center punched their corresponding location on either side of the vertical spine.

I drilled from each side through to the center, that way I didn’t need a 80+mm long drill bit. I used a bit diameter with plenty of space for the 6mm hex wrench (my M8 bolts use a 6mm hex). Ensure the end of the main spine is cut square to its channels so that the vertical channels, once attached, will be perpendicular to the horizontal channels. This could be hard to do with such a large piece of aluminum extrusion. Thankfully mine came square enough from the dealer.

Now tap the end holes on the edge of the main spine you will attach the vertical spine to. As I mentioned earlier the 80/20 is ready for a specific tap, in my case M8 x 1.25. Slide the hardware in and sequentially tighten it down. Before you snug it up make sure the face of the two spine pieces are flush and they are perpendicular to one another. I made this piece with a scrap piece of Aluminum stock that was lying around. It is 1.25' thick and 80mm x 100mm. I squared it up with an end mill on the Bridgeport.

Drilled two through holes for 8mm hardware (I used a.316' drill bit). These two holes need to be centered on the block and 40mm apart (to match the channel spacing). I ordered 1/4' stainless dowel pins from McMaster. I used these throughout the jig for keeping the various parts alighted in the 80/20 channels. I drilled 4 holes in the dummy axle block for these pins. I used a.312' drill bit for the dowels.

This dimension seems tight enough that they don't fall out once you press them in but not too small. These 4 holes need to be in the same line as the 2 hardware holes so they line up with the channels. The holes only need to go part of the way in to the piece. I drilled them in 1/2 the length of the dowel pins.

After the four holes were in I got the block ready for the dummy axle. I mounted the axle block vertically in the mill vise and used a 1/2' end mill (the diameter of the center part of the dummy axle) to mill out a grove for the axle to sit in. I then flipped the block back to a flat position in the vise and milled either side to give the clearance necessary for the dummy axle. See photo descriptions to make this clearer. I bought a compact holding handle from McMaster to hold the dummy axle in place.

I wanted something that could be quickly opened and closed. To mount I simply drilled four holes (used a size 30 drill to be tapped for M4 machine screws) and screwed it to the plate. You may have to make some modifications to the holding handle so that the clearance is right for the dummy axle. In my case I sanded the rubber part that touches the dummy axle down a bit as the handle was designed for 0 offset from the surface it is bolted to. The purpose of this piece is to securely hold the dummy axle holding block at the centerline of the bike frame. I used both 80 - 80 and 80 - 40 extrusions for this piece.

The Arctos jig uses blocks of solid aluminum for the top and bottom pieces but like I didn’t want to drill super deep holes. So, like Alex, I used the 80 - 40 because it has a hollow center. After lots of thinking I decided to place the centerline of my jig 105mm from the face of the spine. This offered enough clearance to get a torch in and worked with the 3” angle aluminum I bought for the cone brackets discussed later. See my centerline CAD file for detailed drawing of this layout. The length of the two pieces of 80 - 40 are based on this centerline distance.

In my case they are 58mm and 131.75mm. I rough cut these with room to spare first. After this assembly was put together I used the Bridgeport and end mills to make sure the surface of these pieces were square, equal and of the exact length I needed them to be.

The length of the 80 - 80 is based on BB drop. This is a design factor in frame building and a measurement used to set up my jig. If you only want to build bikes with BB drop (most bikes) and aren’t building bikes with BB rise (BMX bikes) like me than this piece need only extend as low as the BB shell center. I go in to the BB assembly later but in my design its center sits 150mm below the base of the main spine. The top piece of 80 - 40 gets drilled in a similar way to the vertical spine but with no special hardware.

It gets bolted directly to the 80 - 80. Line up the four holes with the holes in the top of the 80 - 80 but inset from the front face by the thickness of your 1/4” stock (7mm in my case). This time the holes are for M8 bolts and must be more accurate than the tool access holes. I used the Bridgeport. Countersink the holes with an end mill for the bolts to sit in. Also tap the holes on either side of this piece of 80 - 40 (wait to do this on the back side until you have assembled and milled this surface.

Tap the holes in the top of the 80 - 80 (M8 1.25), ensure it is square. Cut out and drill (or in my case, water jet) the 1/4” plates. One for the front of the top piece of 80 - 40 and one for the back of the whole assembly (see cad files). I also inlayed a measuring tape on this piece. It is used to set up Bottom Bracket drop. It is measuring the distance the axle is above the fixed location of the BB (or how far below the axle line the BB is).

To achieve this you put the '0' on the measuring tape at the same distance below the spine as the BB center is (150mm in my case). The caveat is that you need to offset the tape slightly so that the reading you get looking at the base of the dummy axle block is actually the location of the dummy axle.

Simply measure the distance from the center of the dummy axle and the edge of the dummy axle block. Move the tape down this amount. Perhaps the most difficult part to design and build is the pivot assembly for the seat tube support. The difficult but critical element is that the BB stays at the same location when the seat tube angle is changed. In other words the center of the Bottom Bracket needs to be the pivot point for the seat tube support.

The reason you want the BB center at a fixed location is so that you can use it as a reference point for setting up the jig. The measuring tape installed on the dummy axle support and the vertical spine measure distances above this point. Fixing this point as the pivot could be done with a arm that extends down from the main spine and supports the BB assembly at its center. However, I chose to use the “floating pivot” design similar to the one used on the Arctos jig. This design uses pins riding in a track such that the BB assembly is the center of rotation yet it is not directly fixed to anything.

To achieve this I designed the channel in the mounting plate and the channel in the pivot block to share the same center point. This center point is the center of the BB. I chose to have the BB center 150mm below the base of the main spine. This allowed for the BB drop range that I wanted yet kept the BB close enough to the spine and mounting plate such that it could be securely locked in place (remember BB drop is actually achieved by raising and lowering the dummy axle not adjusting the actual BB height). The further the pivot from the mount the more play you will likely get in the assembly, keep it close. After lots of prototyping and design changes I settled on something that worked. I cut out the mounting plate from 1/4” 6061 using a water jet.

This part needs to be accurately machined (CNC). The arc location and radius is critical. After cutting it out I tapped the hole for the handle (M8 x 1.25) and pressed in 3 pins in to the pin holes. The pivot block is cut from 1 1/4” 6061 using the water jet as well.

I used the water jet to etch little “+” marks on the block to indicate where the pin location would go. The pin location is critical to the “floating pivot”. After cutting it out I cleaned it up a bit with sandpaper and drilled the holes for the pins (remember their location is critical, a CNC mill would have been a better way to make the block than the water jet but I didn’t have time to learn how to use one). I later discovered that the surface of the 80/20 is not flat. There is a angle down to the channel from the edges.

When I mounted my pivot block, because it is only 1 1/4” thick, it sat at an angle on the support. To solve this you could make your mounting block out of a thicker piece of aluminum. Or you can do as I did and make little support pieces. I put the block in the mill and milled out grove for support pieces that would span the full width of the support piece You need to drill two mounting holes for attaching this block to the seat tube support. I did this on the Bridgeport.

The holes need to be 20mm from the face of the block that will rest against the mounting plate so that they line up with the channel in the ST support. I counter sunk these holes for aesthetics.

At this point you can permanently mount the block to the support. Because the BB assembly can be slid up and down a bit you don’t need to be terribly accurate in the location of the block on the support. Look at the plans for the BB assembly and you will get an idea for how much play there is.

Remember the important distance is from the center of the channels to the center of the BB. Look at the CAD files for this dimension. Perhaps it is best to skip forward and build the BB assembly and then come back to this last step on the ST sub assembly.

Mount the block to the support, correct location? The critical distance is from BB center to centerline of the channel.

When you secure it to the support make sure it is dropping slightly below the support. In other words once it is attached if you lay the block-support sub assembly flat on a table the support should not quite touch the table only the block. I did this so that I could ensure they were perfectly flush. To do this I put the sub assembly in the mill and slowly milled down the block until it was exactly flush and parallel with the support. Once the support-block sub assembly and the mounting plate are done you can connect them.

The mounting plate gets three handles connect to t nuts on the main spine. The block-support sub assembly gets mounted with one handle threaded in to the tapped hole on the mounting plate. See my CAD files for details of this components used in the seat tube assembly. Attachments. The BB assembly is fairly straight forward.

I used a 1/4” back plate (cut out on the water jet) to mount the assembly to the jig with two bolts/t-nuts. I turned three different parts on the lathe. One is a simple cylinder for holding the support rod (5/8” steel rod).

The other two are “cones” for supporting the bb shell. I designed this assembly to work with 73mm and 68mm wide BBs. To adjust the BB shell width you slide the lock collars that are mounted tot he 5/8” rod. Make sure the center of the BB shell lines up with the centerline of frame. To secure the cylinder that holds the 5/8” rod to the back plate I drilled and tapped the back of it. I drilled corresponding holes in the back plate and screwed them together. I also drilled and tapped the cylinder for small set screws.

These will hold the rod securely perpendicular to the ST support. The cones are held in place on the rod with locking collars from McMaster. The big mistake I discovered once I started building with this jig was that I made the BB cones out of aluminum. The tight fit of the steel BB shell on to the big cone causes issues once you start heating. The aluminum expands differently than steel and gets really stuck in the BB shell. I need to make new cones out of steel.

Mount the BB assembly to the ST assembly at the correct position (distance from BB center to channels in the ST assembly, see drawings). If you are planning on making the Tandem attachment, make two of these assemblies. The head tube assembly is similar to the seat tube assembly except that it has a fixed pivot instead of a floating one. The pivot should be located directly under the bottom of the head tube. My design accounts for two of the common head tube diameters 1' and 1 1/8'.

The different diameters will cause the head tube to sit in different places on the support cone, you must move the support cone to adapt to the two sizes. Like the seat tube assembly; water jet the mounting plate, water jet the pivot block, drill the mounting holes (20mm in), clean up the block, counter sink the holes, slot the block for the support piece, mill the surface parallel/flush to the support 80/20, mount the pivot block. The fixed pivot was created using a pice of a bolt and some set screws. I cut the threaded shank of an M8 bolt off so I just had an unthreaded rod with a cap at the end. I used a grinder to grind this cap down to make it thin. The idea is the pin cap will be inset in to the base plate and protrude out the top. The 80/20 will side on to the this pin and set screws will hold it in place.

This pivot is located directly under the base of the head tube. The placement of the pin isn't important just move the cone in to the right position. In my case I make a score mark on the 80/20 to indicate the two location of the cone (1' and 1 1/8'). Attachments. Based on my centerline offset of 58mm I needed angle aluminum that was long enough to support a cone with its center that far from the support 80/20. 3' x 1/4' aluminum works great, I ordered from McMaster. The L bracket part is simple.

I made them 40mm wide to match the with of the 80/20. Each bracket gets four holes drilled in it, all in the centerline. One hole 58mm from the outside corner to be tapped for the M8 x 1.25 hardware that will hold the cone in place. This is the only hole on one side. The other side gets three holes. The two outermost holes are for the M8 dowel pins, I used a.312' drill bit for these pins.

The last hole is for the adjustment handle to go through (I used a.316' drill bit). Tap the hole that needs to be tapped. And press the pins in to the pin holes.

Now for the cones. The cones don't need to be complicated.

As long as the larger diameter of the cone is bigger than the biggest internal diameter tube you want to hold and the smaller diameter of the cone is smaller than the smallest internal diameter tube you want to hold, they will work. I made two different sizes one that will work with 1' and 1 1/4' head tubes and one that will work with 27.2mm - 31.8mm internal seat tube diameters. I center drilled them for M8 hardware (.316'). I later decided to countersink the holes for looks.I also used the lathe to turn some cones for the BB assembly. I ended up making two different kinds. One was a cone very similar to the ones I made for the HT and ST but larger (1.5' large diameter, 1.25' small diameter). The other was more of a cylinder than a cone.

I used a smaller diameter of 1.375' and a lip with a diameter of 1.5'. The 1.375' part of the cylinder snugly fits the BB shell. This is the one that caused problems with expanding and will hopefully work better out of steel. For the BB shell cones I drilled a 5/8' hole so they would slide over the steel rod on the BB assembly. The tandem attachment was a simple idea I had. I wanted to have a somewhat small jig that I could make tandem frames on.

Why not use the standard jig to make the front triangle of the tandem. Then, using a special addition to the jig, move the front triangle forward.

Mount the front BB shell in to the additional BB shell mount. The original HT mount now becomes the front ST mount and the front triangle just protrudes from the jig. Then you could make the rear part of the tandem.

This is not going to be the most accurate way to build a tandem but it certainly is simple. I have not yet tested it but I hope to soon. Building the attachment was simple.

I cut an extra piece of 40-40 80/20. Using I bought on McMaster you can attach this assembly to the base of the HT support (first remove the bottom HT support cone/L bracket). The hardware requires that you drill holes in the HT support and the tandem support. Measure the hardware to determine the right diameter hole. The base of the tandem support gets another, identical, BB assembly (see the BB assembly step).

Pretty simple! Once you install the tandem support you need to slide the HT support plate up unit the tandem BB is at exactly the same height as the main one. You should be able to use the tape measure on the vertical spine to set this. (photos coming soon). The way I use the jig you need two measurements from your drawing to set it up; Head Tube height (measured vertical distance from BB center to the bottom of the center of the HT) and Bottom bracket drop the rest is slid in to place based on tube miters that I make accurately on a mill.

This was long instructable that covers a lot of details, I am sure I missed some. Be sure to look through all the photos and read all the photo descriptions.

Leave comments, send me a message and I can add information and fill in any details I missed.