DELTAWOLF UNDER SEAT STEERING MOD
Here is a simple modification for all you DeltaWolf and Marauder builders who would like to try under seat steering. This mod is based on some sketches I made, which I said I would upload for others to try. Rather than give untested advice, I have successfully made the modifications and will present them here for all my fellow garage hackers and bike builders. This modification would probably work for any recumbent with a 1.5 inch or larger main boom and linked steering as well.
Although you will have to make a few cuts to your frame, the good news is that you will not need to source any extra parts except for the handlebars, and the surgery can be done in an afternoon. Under seat steering allows the arms to rest in a more relaxed position beside your body, and allows the pilot to climb in and out of the bike without having the steering stem in the way. Under seat steering does however feel quite different than the conventional handle bars out front system, so think about this modification and read it through before you start up your grinder.
The original steering system must be completely removed from the frame before you can make this modification. Before you cut any tubing, make an "X marks the spot" mark on the main frame boom directly under the original steering head tube as if you were looking through it down to the frame. By transferring this mark to the frame, there will be a good chance that the original steering control rod will be the correct length after the surgery, saving you a bit of work.
Cut into the steering system tubing just above the welds so you do not damage the original frame boom when you are removing the original steering system. The leftover weld metal can be carefully ground clean using a sanding disk to avoid taking down any of the original frame tubing material.
The head tube will be recycled, which is logical since you already have all of the proper fitting steering parts such as bearings, cups, and the fork stem. By making a few rough cuts with a cut off disc, you can safely liberate the head tube from the frame tubing without the risk of damage. Avoid cutting into the head tube material when you are separating the parts, or you will have to repair the area later. The head tube will be getting a few inches cut from it as well, so don't worry about cleaning up the excess metal after separation at this point.
The head tube should be cut down to a length of 2.75 inches, so there is minimal tubing sticking up past the top and bottom of the main frame boom after installation. This is done so the under seat steering system does not interfere with the pilots legs, and keeps the ground clearance to a reasonable level.
If you tried to install a 6 inch tall head tube through the frame, it would either come dangerously close to the ground, or get in your way as you sat on the seat, so this shortening surgery is necessary.
As shown in the photo, mark off an area around the head tube so you can cut it down to 2.75 inches in length. If you have trouble marking a line all the way around the head tube, use a piece of electrical tape as a guide by wrapping it around the head tube to create a straight guide for cutting. After you cut the head tube down to size, grind away any excess material and then clean up the area so the tube is once again smooth.
Place the bearings and cups back in the newly shortened head tube so you can install your fork stem in order to determine how much it needs to be shortened. You could also measure the piece that was removed from the head tube, since all these parts once fit together perfectly. As shown, I have determined that I need to take out a 1.5 inch section of the original steering fork stem in order to have it fit back into the head tube.
The fork stem is shortened by removing a part from the center of the tube, where there are no threads. The best way to cut the tube, ensuring perfect alignment later is by using a pipe cutter as shown in the photo. A pipe cutter is an inexpensive hardware store tool that will come in very handy for cutting all tubing sizes up to 1 inch in diameter.
When you are cone cutting the tube with a pipe cutter, the two halves will line up perfectly, although with a little careful work, you can achieve decent results with the grinder or a hacksaw as well.
The fork stem will be rejoined once you remove the needed material, and if you have made a perfect cut using a pipe cutter, the two halves should butt together perfectly. A simple trick to ensure perfect alignment when tacking the two parts together is by shoving in a gooseneck stem, which will hold the two halves together perfectly.
The two halves are then tack welded in a few places around the perimeter as shown. If using the gooseneck to help alignment, be sure not to weld through the tubing or you will also weld the tubing to the gooseneck.
Once you have the two fork stem halves tack welded together so they are aligned perfectly, remove the gooseneck or any other guide tubing then complete the welding around the entire joint. make a solid weld, and don't worry too much about how it looks at this point, since the welded area will needed to be cleaned and ground a little bit in order to ensure the bearing cups can fit back over the tubing. This photo shows the completed weld after cleaning it up enough to get the bearing cups to slide over the area. Only clean up the weld as much as necessary, since you do not want to weaken this important joint. The completed area should have a hill, not a valley.
Install all of the fork hardware so you can make sure everything fits together and spins around with minimal friction. Don't forget the "balls into the cups" rule when inserting the fork bearings, or there will seem to be excessive friction when you hand tighten the hardware. The stem should move easily in the head tube.
The steering head tube will be inserted through the frame so it is on the same angle as the front head tube, just like it was in the original design. As we discussed in the original DeltaWolf design, the control arms and head tubes should all be at the same angle so there is no rubbing between the control arms and the ball joints.
To mark the frame where the head tube will go, trace a circle over the original mark you made using a marker on the inside of the leftover head tube stub. You can then transfer a line at the same angle as the front head tube down the frame to make the hole on the other side. In other words, the under seat steering head tube should be inserted through the frame so it is sitting at the same angle as the front head tube when you are done.
Chances are, you do not have a drill bit even close to the size needed to cut the hole in the frame boom for the head tube, so the "can opener" method of hacking out a round hole can be used. Center punch a bunch of holes around the area marked and then drill a bunch of smaller holes in order to pop the "lid" out of the hole like a can opener would open a tin can. I have used this method many times to make huge holes, since my hand drill only holds a 3/4 maximum size inch drill bit.
Yes, you will need to clean up the area with a round file, but this is unavoidable anyhow, since the hole will have to be slightly oblong to take the head tube at an angle anyhow. This drilling and hand filing takes less than an hour to complete both sides.
After an hour of filing with a hand held round file, I had the head tube fitting perfectly through the holes in the main frame boom at the correct angle. If I stood back and looked at both head tubes, they were very close to the same angle, which was the original goal. A few degrees either way is not going to be a real problem, but it would be difficult to align the ball joint hardware if this new head tube were inserted straight through the frame at 90 degrees. When using the round file, it is easy to file away both side of the frame at the same time, so you can keep the gap to a minimum for a better weld.
Once you have the head tube fitting snuggly through the main frame boom, weld it in place using a small weld bead around the entire joint. When I say small weld bead, I mean you should try to keep the heat down as much as you can, only using enough weld metal in order to fill the gaps. You should also work around the joint by switching sides after an inch of weld bead so you keep heat distortion to a minimum.
The welding done to my frame boom and head tube did not cause any noticeable distortion to the main frame boom when completed. Also, do not install the bearing cups while you weld, or you may damage them accidentally.
If all went well, there is a good change the original control rod will be the correct length, or so close that is does not need any adjustment, which is why the line was transferred to the frame from the original head tube before it was removed. If your control rod hardware is threaded and adjustable, then you do not have to worry about this, but because mine was not, it was nice not to have to cut and re-weld the rod.
If you were using any washers or spacers to lift the ball joint off the surface of the control arms, make sure you replace them in the same position they were original installed.
The surgery is almost complete! Now that your handlebars will be held from the underside of the steering boom, a gooseneck must be installed so that is faces the ground. Obviously, an 8 inch long gooseneck is not going to work because it will seriously compromise your ground clearance, creating a dangerous "hook" under your trike that could become an issue every time you rolled over a speed bump or curb. By cutting down a standard gooseneck, the resulting ground clearance is no different than before, with the guide pulley being the lowest object under the bike.
To shorten the gooseneck, I just cut out a section (shown above the bolt) at the same angle as the original end so that the wedge shaped bolt would still work properly. I then cut and re-welded the original bolt so it was the correct length. I would recommend you simply purchase a new bolt unless you are extremely confident with your welding.
The handlebars that you choose should allow you a full range of steering motion, not interfere with your body when pedaling, offer room to mount the levers and shifters, and just be all around comfortable. I found these big old "ape hangers" from a chopper style bike that fit perfectly. You may have to hunt around for the perfect handlebars or simply fashion your own by bending up some 3/4 thin walled conduit. The best way to approach finding a set of handlebars is to first decide where you want to hang on rather than using bars that force you to some uncomfortable position. Keep all of the leftover bits for some other project - you can never have a large enough pile of scrap metal.
Once the handlebars are functioning properly, it's time to touch up the battle scared frame and add all those shifter and brake cables back where they belong. Since the handle grip area is now a little lower on the bike, the cables will not have to travel as far so you will not have to install longer cables. The extra two or three inches of cable slack can easily be taken up by a little creative cable routing and some zip ties here and there.
As usual, make sure no cable is allowed to rub on any moving part of the bike and that the steering can make a full range of motion without putting any of the cables under extreme tension. A cable should not be forced around a sharp corner, so make all your bends at least as large as the curve of the large chain ring to be safe. As for the chain, the drive side goes above the handle bars and the return side is below the handlebars - this leaves adequate clearance so there is no chain rubbing on the handlebar tubing.
So there you have it, the under seat steering modification is now complete, and my DeltaWolf is ready to hit the streets at speeds that would make most trikes cry. I must admit, the first test ride felt a bit faster with the new steering system, but that may just be due to the fact that I have been eagerly awaiting the return of my DeltaWolf. The turning circle is still extremely tight, and the new relaxed handlebar position felt very comfortable.
I am giving this modification a two thumbs up, and must say that it was well worth the effort. I like both steering systems an equal amount, but this new under seat steering system will allow easy access to the pilot's seat if I were to add a full streamlined fairing later on. Maybe that will be the next DeltaWolf modification, we will see.
Thanks for visiting our site! If you have some of your own cool modifications to show off, please drop by our forum and send a few photos. We are always interested in what others are doing with our designs, and might want to feature your ideas and modifications in one of our newsletters. Well, that's all for now, with a trike this to ride, I just don't have the time to hand around and chat... I have cars to race and upright bicycles to pass!
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