Month: August 2017

Recumbent trike handlebars

Looking at the upturned handlebars in the plans and the comments about twist grip shifters being hard to use, I was not surprised. You would naturally grip these thumbs up. You have to grip the shifter with your 2 smallest fingers against your palms.   Poor grip and leverage. Below is the photo of the handlebars from the Warrior plans.

I want to do a flatter arrangement so that I can reach down and have my thumbs toward the center rail and a normal arrangement of the brake lever and twist grip shifters.   I had purchased an aluminum mountain bike handlebar, but it did not turn up far enough for my liking. So it made a number of passes through the Harbor Freight roller tubing bender and ended up in a decent upwards arc. It was a bit tough at first to keep it from turning as it went through, but then shallow grooves wore into the center section and it stayed centered. The rollers I used are for 1″ diameter tubing which matches the ends but he center is 30.8 mm (approx 1.25″).

To make the pivot, I used another of the same bearing sets I used for the front wheels. The center post is fixed. The post is 1 1/8″ steel tube and has a step ring brazed on as I did for the wheel bearings. This was then tack welded to the frame for a test fit to see how it felt. The distance from the tail end of the rail is 7″ rather than the 10″ in the plans. After testing, I solidly welded it all the way around.

The center section is 1.5″  OD steel tubing that is bored on the lathe  to fit the bearing cups as before.  To this, I welded 2 steel shaft collars. They held a piece of tubing while I did the welding to make the alignment right. The collars were a bit undersized for the handlebars (it would have been better to test fit BEFORE welding up the assembly). So  I had to bore them out on the mill for a perfect fit. I placed some washers as shims between the halves before boring to make the opeing a bit elliptical for good clamping pressure. The soft Chinese steel bored easily.  Here is the view from the underside.

Next comes the linkage from the handlebars to the front wheels and hooking up the brakes.

Recumbent trike brakes and seat

The trike is set up with disk brakes. The fronts are new Avid BB7 mechanical and the rear is a used Avid Juicy 5 hydraulic.  All have 160mm rotors.

Mounting the brake assemblies requires fabricating some odd shaped pieces of steel to weld to the front wheel assembly and the rear fork. The easiest way to do this is to make templates from paperboard. First the template is attached to the brake assembly and successively trimmed while fitting the brake on the rotor.  Make sure that the brake is out far enough so it does not rub on the peaks of the non-round rotors.

For the mechanical brakes you can adjust the pads to hold it in place, however this is sensitive to slightest movement of the bike.  The mounting plates were cut from 3/6″ steel flat stock. My bandsaw has a 1/2 ” blade so the curves to a number of passes and a lot of grinding. The grinding was done on the bench grinder, some 1.5″ sanding drums and the combination belt / disk sander.  The mounting holes are 6mm diameter.

Once the shape appears close, then more test fitting is done (and more grinding). The plate is then clamped in the correct alignment with a small c-clamp.  The clamp is important as otherwise it is too hard to hold at the right position to get good solid tack welds. Then the plate gets tack welded in place. Now spin the wheel and actuate the brake. It should spin nicely and stop nearly instantly with hand pressure on the brake actuator arm.   At this point, the wheel and brake are removed to complete the welds. You don’t want to damage the brake with excess heat, weld splatter the rotors or tires. In the end the Philips screws will be replaced with socket head cap screws and properly torqued. These were just easy for testing and not tearing out of the paperboard templates

This is done for each of the brakes. The mounting will vary for each wheel although I was able to reuse and trim one of the front templates for the rear. Note that the rear brake is mounted behind the fork, not under it as the plans show

The next step was to modify the rear drop-out to fit the rear derailleur.  The derailleur is a used long cage SRAM X-9. This involved quite a bit of grinding to fit the recess in the derailleur for the original bike drop-out.  Comparing to the other side,  you can see how much had to be removed. In the background, you can also see the profile of the rear brake mounting bracket.  I still need to drill a hole and make a new bushing for the retaining bolt for the derailleur. (there is probably a more proper term for this, but I don’t know it). At this point it would fall off each time I remove the wheel.  The derailleur travel still covers all of the sprockets when moved by hand.

The seat needs to have mounting tabs to secure it to the frame. These are about 3″ long and I had the ends drilled with a 5/16″ hole.  The brackets are welded to the frame and ground flush. The seat is placed on the completed brackets and the holes marked. The were then drilled for 1/4-20 T-nuts which are mounted from the top. This makes for a very secure mount.

Once the seat is mounted then a small “backrest” bracket must be made form 1″ tubing and fitted. This an be seen below. I had test fitted it, in the process of setting he angles and after tacking, but it seems a bit steep right now. It may be  cut and adjusted after the padding is on the seat.

In addition to these items I did a fair bit of weld grinding and clean up today as well. Overall, it was a productive day.

Recumbent trike front wheels

The fit-up and welding for the front wheels was the most taxing process in the build of the trike  by far. There are multiple factors to take into account when creating the front steering geometry.  The pivot point for the front wheels should be under the contact patch of the wheels. For the axles I had made this meant that the steering tubes had to be at a 15.5 degree angle with respect to the plane of the wheel. If this was not enough, the same steering geometry had to lead the tire patch by about 10 degrees to make the wheels (caster) to naturally track.

The instructions said to fit the steering tubes directly to the struts.  Then adjust the strut angles with the rest of the frame to get the correct geometry.  I think the plan authors must have been rolling on the ground laughing at how much fun this would be.

Problem 1:  The tires need to pivot on the contact patch as you turn the front wheels. If this is mis-aligned you scrub of tire and lose cornering control. So, you need to fit the axle to the steering tube and held it in place at an obscure angle so that the projected line through the tube lands under the center of the contact patch of the tire.  Check.  With my axle configuration and hubs this as about  a 15.5 degree angle.

Problem 2: Now that the wheel can turn without scrubbing, you need to set the forward angle of the pivot such that the trike will track on its own. On a car, this is referred to as the Caster.  Think of the fact that hands free steering is “really nice”. So how do you accomplish this? It requires that the steering tube be inclined at about 10 degrees forward such that the imaginary line through the tube lands in FRONT of the tire contact patch. The tire is then automatically following the steering direction and tracks nicely in the forward direction (not so much in reverse) .

To achieve this , there was a lot of measuring, template making, cutting, grinding, cutting and grinding again and cussing. Making all of this fit, is a 3 dimensional puzzle with pieces that keep turning, throwing off the angles,  as you play with them.  The plans are basically saying “make it fit” rather than giving good guidance for the angles which may be hard given all of the variables in play. On top of this, as you dig into the AZ website you see  the slogan on the of:  “weld, cuss, grind, repeat” —  I did a few cycles of this …

Eventually I ended up with a reasonable facsimile of the angles and arms that are needed and they even fit the bearings I had purchased. The FSA ” the PIG” bearings have so far worked out well  (but I am still worrying about losing pieces).

So now, I have front wheels for the trike.  I have also tacked on the pieces to connect the wheels so they turn as a single unit. The Ackerman geometry seems to be working with the inside wheel turning more sharply than the outside wheel. However my testing in the shop is limited by available space.

Next, will come the brakes and the rest of the steering components.