Tri Cruiser

Build the TriCruiser Recumbent Trike Another Atomic Zombie™ Extreme Machines Adventure 

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TriCruiser Recumbent Trike

Table of Contents

Table of Contents Characteristics Characteristics....................... ................................................. .................................................... ..................................................... .................................. ....... 3 Main Boom ................................................. ........................................................................... ..................................................... ...................................... ........... 7 Rear Triangle................................................................ Triangle.......................................................................................... ............................................. ................... 13 Homebuilt Seat............................................................. Seat....................................................................................... ............................................. ................... 24 Back Rest .................................................... .............................................................................. ..................................................... .................................... ......... 32 Adjustable Bottom Bracket......................................... Bracket.................................................................... .............................................. ................... 35 Trim the Boom.......................... Boom .................................................... ..................................................... ..................................................... ............................ 44 Head Tube ................................................... ............................................................................. ..................................................... .................................... ......... 45 Front Boom ................................................. ........................................................................... ..................................................... .................................... ......... 51 Truss Tubes ................................................. ........................................................................... ..................................................... .................................... ......... 61 Steering ................................................... ............................................................................. .................................................... ........................................ .............. 63 Chain Management ................................................. ............................................................................ .................................................. ....................... 83 Final Touches, Painting and Adjustments Adjustments .................................................... ................................................................ ............ 95

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TriCruiser Recumbent Trike

Table of Contents

Table of Contents Characteristics Characteristics....................... ................................................. .................................................... ..................................................... .................................. ....... 3 Main Boom ................................................. ........................................................................... ..................................................... ...................................... ........... 7 Rear Triangle................................................................ Triangle.......................................................................................... ............................................. ................... 13 Homebuilt Seat............................................................. Seat....................................................................................... ............................................. ................... 24 Back Rest .................................................... .............................................................................. ..................................................... .................................... ......... 32 Adjustable Bottom Bracket......................................... Bracket.................................................................... .............................................. ................... 35 Trim the Boom.......................... Boom .................................................... ..................................................... ..................................................... ............................ 44 Head Tube ................................................... ............................................................................. ..................................................... .................................... ......... 45 Front Boom ................................................. ........................................................................... ..................................................... .................................... ......... 51 Truss Tubes ................................................. ........................................................................... ..................................................... .................................... ......... 61 Steering ................................................... ............................................................................. .................................................... ........................................ .............. 63 Chain Management ................................................. ............................................................................ .................................................. ....................... 83 Final Touches, Painting and Adjustments Adjustments .................................................... ................................................................ ............ 95

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TriCruiser Recumbent Trike

Characteristics

Characteristics The TriCruiser recumbent trike is a great all-weather vehicle and very comfortable cruiser. Because the seat is higher than most recumbent trikes, visibility in traffic is good, placing you at eye level with most vehicles. The recumbent position allows for more efficient pedaling, making the TriCruiser a great winter vehicle for staying in shape all year ‘round. The weight distribution of the long wheelbase configuration places traction in the rear wheel, and the rear suspension absorbs bumps for a very smooth ride. The nice thing about this trike is that you can build it using standard bicycle components, with no need to source special front axles or create complex steering parts. There is a ton of room for your own modifications, so feel free to experiment once you have read though the entire plan. Welding Hazards

All welding processes produce fumes and gases to a greater or lesser extent. Galvanized steels produce added fumes from the vaporized zinc coating. Fumes from welding galvanized steel can contain zinc, iron and lead. Use precautions, including high-velocity circulating fans with filters, good ventilation, air respirators and fume-extraction systems.

Figure 1 – Finding a rear suspension triangle and spring All content © copyright Atomic Zombie Extreme Machines. All rights reserved. www.ATOMICZOMBIE.com

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TriCruiser Recumbent Trike

Characteristics

The TriCruiser project uses the entire unmodified stock rear triangle from a typical suspension mountain bicycle. As shown in Figure 1, you will need the complete rear triangle (black section), the suspension spring, and at least the part of the main frame that contains the tube connecting the rear triangle to the frame that allows it to pivot. The front part of the frame is not important, so it can be in any shape as long as the rear of the frame is perfectly functional. Since you can purchase an entire bicycle about $100 (and sometimes even less), you might consider purchasing a new bike for parts so you can be assured that your rear, wheel, brake parts and shifting hardware are all in perfect working order. If you decide to consult your scrap pile or the local dump for parts, ensure that the rear brakes are working, and that the rim is not damaged in any way.

Figure 2 – The pivot tube and hardware will be needed

The only part of the bicycle frame that you need in addition to the rear swingarm and possibly the front head tube is the small tube that carries the plastic plugs allowing the swingarm to pivot up and down. Not all suspension frames are the same, but you can easily figure out which parts you will need even if they do not look like the one shown in Figure 2.

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TriCruiser Recumbent Trike

Characteristics

Basically, you will be taking any parts needed to re-fasten the swingarm to the new frame tubing, so cut them from the original mountain bike frame.

Figure 3 – Choosing 1.5 inch round or square tubing

The entire TriCruiser frame is made from 1.5 inch mild steel round or square tubing with a 1/16 inch wall thickness. This tubing can be ordered from most steel suppliers and is very easy to cut and weld. Steel suppliers like to rate tubing wall thickness using a gage number, so 1/16 wall tubing will be called 16 gage tubing, and although there is a slight difference between the two, your best bet is to tell them you want a length of 1.5 inch tubing with a wall thickness as close to .0625 inch (1/16) as you can get. If you are a heavy rider (over 250 pounds), then you should ask for the next size after that, which will likely be 14 gage tubing, or .078 inch wall tubing. Round tubing can also be found at most hardware stores that carry electrical conduit. Thin walled conduit (also called EMT) is perfect for this project, and is measured from the inside diameter, so it is slightly wider across the diameter than 1.5 inches. I will be using EMT to build the TriCruiser, but the plan is the same for round or square tubing. The main boom runs from the pivot point of the rear swing arm all the way to the front head tube. The main boom also carries the seat back, and also allows the sliding bottom bracket to adjust for just about any leg length. The overall length of  the main boom is determined by the size of the tallest rider that will use the TriCruiser, so it All content © copyright Atomic Zombie Extreme Machines. All rights reserved. www.ATOMICZOMBIE.com

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TriCruiser Recumbent Trike

Characteristics

can be cut down to a maximum length based on rider height rather than having a longer frame than you really need.

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TriCruiser Recumbent

Main Boom

Main Boom To start, cut a 6 foot length of the square or round tubing to become your main boom. Yes, 6 feet is more than you will ever need, and you will be cutting it down once the bottom bracket has been set up for your tallest rider. It's better to start with an extra long main boom, than end up an inch too short because you forgot to add the extra few inches added by the seat padding or something similar. Figure 3 shows a section of 1.5 inch square and round tubing for comparison.

Figure 4 – Making a fishmouth cut for the pivot tube

The suspension swing arm pivot tube that was cut from the mountain bike frame needs to be connected to the end of your main boom, so you will need to cut the appropriate "fishmouth" shape at one end of the tube as shown in Figure 5. A good way to do this is to use the pivot tube as a guide to mark the area to be ground as shown in Figure 4, this way you don't take out too much material. The goal here is to make a good joint that will have no gaps once the part is welded in place. Again, your swingarm parts may differ, but the idea is the same. Before welding, tap out the swingarm bearings, as they are likely just plastic plugs and would melt instantly during the welding process.

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TriCruiser Recumbent

Main Boom

Figure 5 – Fishmouth cut for the pivot tube

Round tubing is always more difficult to cut into angles and to make fishmouth cuts on, so take your time and use a round hand file to make the final touches on the joint. The fishmouth is shown cut into the boom in Figure 5 after a bit of rough grinding and then cleaned up with a round file.

Figure 6 – Pivot tube tack welded to the main boom

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TriCruiser Recumbent

Main Boom

Figure 6 shows the swingarm pivot tube tack welded to the main boom on all four corners. Once you have the part tack welded and it has been checked for alignment, you can continue welding the joint starting with the top and bottom and then the sides. To ensure that the tube is welded inline with the boom, place a straight edge across one end of the pivot tube and check it against the length of the boom.

Figure 7 – Checking the pivot tube alignment

The straight edge placed over the end of the pivot tube should line up perfectly parallel with the boom tubing as shown in Figure 7. If your pivot tube is not aligned properly, then your rear swingarm will lean to one side, causing your final bike to not track properly, so get this angle as close as possible. With a few good solid tack welds in place, you could even reinstall the rear triangle to visually check alignment before doing any more welding.

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TriCruiser Recumbent

Main Boom

Figure 8 – Weld the top of the joint first

When welding a joint, the first weld will always be the one that introduces the most distortion due to the contraction of weld metal when the parts cool. To ensure side-to-side alignment, weld the top and bottom of the joint first as shown in Figure 8. This order of  operations is very important when welding, and becomes second nature when you have been at this hobby for awhile.

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TriCruiser Recumbent

Main Boom

Figure 9 – Pivot tube completely welded

The entire joint can be welded as shown in Figure 9 once the top and bottom of the joint has been completed. Once the parts have cooled, you can tap the plastic bearings back into the pivot tube, and then bolt the rear suspension triangle onto the main boom. The pivot tube may have been warped slightly due to heat distortion, so it may take a bit of effort to get the bearings to fit back into the tube. If distortion is extreme, you may need to work the tube back  into shape using a large hammer; you know the routine!

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TriCruiser Recumbent

Main Boom

Figure 10 – Pivot tube shown on a square tubing boom

The square tube version is shown in Figure 10 after completely welding the pivot tube to the boom. From here on, I will only be using round tubing, but the dimensions and steps are exactly the same.

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TriCruiser Recumbent

Rear Triangle

Rear Triangle

Figure 11 – Install the rear triangle on the main boom

The rear triangle is bolted onto the pivot tube, completing a large chunk of the building process. As shown in Figure 11, the installed rear triangle can pivot up and down freely, and it should be inline with the rest of the boom when viewed along the length of the main boom. Currently, there is nothing to connect the suspension spring to, so the next tube to be installed will hold the suspension spring and create a seat back support.

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TriCruiser Recumbent

Rear Triangle

Figure 12 – Checking the angle of the seat tube

The seat tube is a 16 inch length of tubing that will connect near the rear of the main boom in order to connect your suspension spring, as well as create a mounting place for your seat back. The actual placement of this tube on the boom will depend on the shape and style of  your rear triangle, and the seat angle of 30 degrees can also be altered if you think that you want a more reclined or a more upright position. The 30 degree angle is great for most people, but it can certainly be altered if you know how it will affect the overall feel of your completed bike. Figure 12 shows the approximate position on the main boom where I will have to mount the seat tube to attach the suspension spring so that it is just less than parallel to the ground. Read ahead a little to see how the spring angle will affect the suspension system. The goal is to place the spring in the same position relative to the rear triangle and pivot point as it was on the original bike before you chopped it all up.

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TriCruiser Recumbent

Rear Triangle

Figure 13 – Testing the seat tube joint for gaps

The seat tube gap should be carefully ground out so that there is minimal gap as shown in Figure 13. The adjustable square shown in Figure 12 is set to the desired angle so that it can be used as an angle reference as you clean up the joint for welding. A few degrees out will not cause any noticeable difference, so military precision is not necessary.

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TriCruiser Recumbent

Rear Triangle

Figure 14 – Determining suspension spring placement

The rear triangle will connect to the main boom tube so that the chain stays are parallel to the main boom tube. In other words, if the main tube is on the ground flat, the rear triangle should also be sitting flat on the ground. This is important so that the chain aligns properly without rubbing on the rear triangle tubing. A look ahead to Figure 23 shows how the chain stays on the rear triangle are in a straight line with the main boom tubing. The position of the suspension spring should match the original position that it was in before you hacked up the bike for the rear triangle. If you do not have the original frame, then it is not difficult to figure out the correct placement of the spring. As shown in Figure 14, the spring will work fine if it is parallel to the ground as the chain stays sit flat on the ground. A few degrees lower than parallel is actually optimal since the pivot point creates an arc around the point at which the spring is connected to the frame (shown in Figure 14). Again, this is not rocket science, nor is deadly accuracy important. If your spring is too high or low as compared to the arc, then your suspension will become too soft, but depending on your weight, this could become an advantage. Once you calculate the basic placement of the seat tube, draw a mark on the seat tube and frame where the parts must connect as shown in Figure 14. Remember to keep the angle of  All content © copyright Atomic Zombie Extreme Machines. All rights reserved. www.ATOMICZOMBIE.com

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TriCruiser Recumbent

Rear Triangle

your seat tube correct when doing this. A helper might be needed to hold the seat tube at the correct angle and position as you mark the three points.

Figure 15 – Tack weld the seat tube to the main boom

Place a few solid tack welds on the seat tube and main boom joint as shown in Figure 15 so you can re-check the seat angle before welding. Beside the seat angle, you also need to ensure that the seat tube is inline with the main boom when viewed from the end.

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TriCruiser Recumbent

Rear Triangle

Figure 16 – Checking seat tube and main boom alignment

As viewed from either end, the seat tube and main boom should be perfectly inline. Also shown in Figure 16 is the rear triangle, which is also inline with the other frame tubing. If your seat tube leans, tap it into place with a hammer or break the tack welds and try again.

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TriCruiser Recumbent

Rear Triangle

Figure 17 – Start welding on the top of the joint

The same order of welding operations will be done on this joint to ensure inline alignment. Start with the top of the joint as shown in Figure 17, and then complete the rear of  the joint.

Figure 18 – Welding the sides of the joint All content © copyright Atomic Zombie Extreme Machines. All rights reserved. www.ATOMICZOMBIE.com

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TriCruiser Recumbent

Rear Triangle

Once the top and bottom of the joint have been welded, check the inline alignment by looking down the length of the frame. If the seat tube seems to be leaning a bit to one side, then weld on the opposite side of the joint first, as the contraction may actually help to pull the parts into alignment. Both sides of the joint are to be fully welded as shown in Figure 18 to complete the joint.

Figure 19 – Cutting spring mounts from the frame

The suspension spring is held to the rear of the seat tube using a pair of 1/8 inch bits of  flat bar, or you could simply slice them out of your donor mountain bike frame, keeping the original drilled holes. As shown on Figure 19, the suspension mounting tabs can be cut from the donor frame, bypassing the need to drill the appropriate holes for the mounting bolt.

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TriCruiser Recumbent

Rear Triangle

Figure 20 – Suspension mounting tabs and bolt

The suspension mounting tabs are shown in Figure 20, salvaged from what was left of the original mountain bicycle frame. If you decide to use flat bar to make the tabs, then just make sure you make them both the same size and drill the appropriate hole in each for the suspension spring bolt.

Figure 21 – Lining up the suspension mounting tabs

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TriCruiser Recumbent

Rear Triangle

The suspension mounting tabs should end up in the approximate place you originally marked as shown in Figure 21. The tabs should also be evenly placed in the center of the tube to ensure that all parts are inline.

Figure 22 – Tack welding the suspension springs

Since you have already calculated where your suspension spring needs to be mounted, it's  just a matter of installing the tabs on the suspension spring, then using it as a guide to make the first few tack welds as shown in Figure 22. The spring can then be removed and the tabs completely welded to the rear of the seat tube.

Figure 23 – Rear suspension tabs installed All content © copyright Atomic Zombie Extreme Machines. All rights reserved. www.ATOMICZOMBIE.com

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TriCruiser Recumbent

Rear Triangle

The rear triangle is shown installed on the frame in Figure 23 after welding the suspension spring tabs to the seat tube. Notice how the chain stays form a straight line with the main boom tube. This is important for chain alignment. It is now necessary to create your seat so that you can calculate how long the main boom needs to be in order to accommodate your tallest user. The boom is much too long right now, and there is no point in having an extra long frame since everything past the reach of the crank  arm is wasted space. You don’t need to upholster your seat right away, but you will need to create the seat with the same padding thickness that you plan to use in the end.

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TriCruiser Recumbent

Seat

Homebuilt Seat

Figure 24 – Making a wooden seat base

The seat base and seat back will be made by cutting some 3/4 inch plywood as shown in Figure 24. My seat base is 11 inches long and tapered so that the rear of the seat is 11 inches wide and the front of the seat is 8 inches wide. The seat back is 16 inches long to fit the seat tube length and also tapered from 11 inches at the bottom to 8 inches at the top. I also rounded off the front and back of the seat base and back so that the material wouldn't rip while stretched around the wood. The six 4 inch lengths of flat bar (or bent shelf brackets) are used to fasten the seat base and seat back together to become one solid piece. This construction is extremely strong, especially once mounted to the seat frame.

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TriCruiser Recumbent

Seat

Figure 25 – Seat base fasteners

Figure 25 shows the six seat fasteners cut from the same 1 inch flat bar used to make the seat mounting tabs on the seat frame. Each fastener was placed in the vice and pounded until they were all at the same angle as the seat. You could also use shelf brackets by simply bending them to the correct angle, and they will already be drilled for woodscrews.

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TriCruiser Recumbent

Seat

Figure 26 – Connecting the seat boards together

The seat base and back are held together by the fasteners as shown in Figure 26. The fasteners are so thin that they will not have any effect on the foam covering once it is glued into place. If your seat angle is not perfect, simply bend the two seat halves to the desired angle. Imagine the nice adjustable seat you could make by using a few hinges in place of the fasteners!

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TriCruiser Recumbent

Seat

Figure 27 – Padding the seat

When choosing a seat padding material, avoid that typical yellowish sponge stuff that you find in seat cushions because it is way too soft to be of any use. It should be somewhat difficult to squash a thick piece of good seat foam to half its thickness using only two fingers, yet not be so stiff that it has no give at all. The 1.5 inch thick blue foam shown glued to the seat in Figure 27 is designed for wheelchair seats, and has the ability to conform to your body after a few minutes, yet retain its original shape once you are off of the seat. A visit to an upholstery shop will likely yield you some decent leftover material for your small seat padding needs. To cut the foam, trace the seat onto the foam, rough cut it just outside the line with a razor knife, glue the foam to the wood with a spray adhesive, and then trace the perimeter with a sanding disc using the angle grinder. The result is a perfect fit every time.

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TriCruiser Recumbent

Seat

Figure 28 – Covering the seat

The seat can be upholstered by simply stretching some vinyl over the material and stapling it to the back of the wood as shown in Figure 28. A fitted and sewn seat will always look better, but this easy method can be done in the garage in a few minutes and looks decent as well, although there will be a few wrinkles at the corners. Stretch the material as much as you can and empty the staple gun!

Figure 29 – Finding plastic to cover the seat back All content © copyright Atomic Zombie Extreme Machines. All rights reserved. www.ATOMICZOMBIE.com

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TriCruiser Recumbent

Seat

The back of the seat does not look very professional with the bare wood strewn with hundreds of staples, so some type of cover will be needed. Some plastic or even sheet metal cut to fit the seat will hide the mess as shown in Figure 30, and an old plastic tub (Figure 29) can be cut to make a nice seat back cover.

Figure 30 – Completed seat

The seat back cover is shown covering the staples and wood in Figure 30, held in place by a bunch of thumb tacks. The simple wood and vinyl seat looks pretty good, considering how simple its construction is.

Figure 31 – Making seat mounting tabs

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