The On-Line Magazine of Rideable Model Railroading
© November 06, 2011
©Discover Live Steam. This material may not be published, rewritten, or redistributed without written permission.
This article first appeared in the Orange County Model Engineer's Newsletter. Used here by permission of the author.
I Can Do That
The Development and Construction of a Velocipede
Written by Gary Sharp
Orange County Model Engineers
"I can do that!" How many of us modelers look at something someone else has done and said that? I said that once again and in October 2007, the odyssey of this velocipede began. It took me over 3 years, to develop the concept, design, and then build but yes I did it!
How it all began:
During the Train Mountain Triennials, all kinds of trains, cars, MOW equipment, and other critters in all types and conditions could be seen. Several versions of a rail bike or velocipede, (any human-powered land vehicle with one or more wheels) could be seen. Some were scratch built, some partially built out of a bicycle, one built out of several bicycles, etc. The only thing that they all had in common was a seat, pedals, and 4 wheels. I thought I needed one, so I started this project.
The goal of my design was to have a variant that was very simple, it had to have a clean look, be as close to indestructible as possible, be able to coast down the Serpentine at Train Mountain, and have a recovery system to allow a tired rider a way to get home. I decided that the simplest method was to design around a single speed drive system. Bicycle derailleur’s with associated mechanisms and chain tensoners get complex and tend to be finicky in operation. For the clean look I went with straight lines, very few welds, and parts made to look like they were only part of this design, not recycled pieces from another life. What is more indestructible than 1” x 2” steel box tubing, which is a little heavy, but solid? Additionally, what fun would it be if you could not coast down a long hill? For this I needed some kind of freewheeling mechanism. Bicycles have a ratcheting device that allows the wheels to spin in the forward direction without pedaling; there should be a way of incorporating this technology into my design. The thought of having a fixed drive, and being forced to continue pedaling downhill would be uncomfortable, or possibly dangerous if feet came off the pedals. On a long ride everyone needs a recovery system; so I decided to add a coupler to the front that allows a rider to hitch up to a passing train for a ride up any hill. For those who like company or a real work-out how about pulling a car? A rear coupler lets you become the locomotive.
The first item on any project agenda is to take inventory, what do I have to build with? I had 4 RMI 5 ½" wheels, bored ¾" and broached for a key. I also had a piece of 1" x 2" square tube, which any respectable metal shop can supply in 10 to 20 foot lengths. A basic design was required to attach wheels to a frame using 4 light duty bearing blocks, two ¼" thick X 3-1/2" x 4" plates, and some ¾" diameter keyed shafting, couplers, all standard car building items. The basics are available, now I need the fun parts. Every velocipede that I have seen starts with the following basic bicycle parts; the crank assembly, a chain, and a rear sprocket to get the power of the rider to the wheels, and there is a good selection available. All bikes have some sort of a freewheel that allows forward movement without pedals being used. Now I had to answer several more questions. Where do I get a crank assembly that I can adapt to box tubing? How do I mount the freewheel, break, and pedals? I noticed that many builders take a bike frame and cut out the threaded cylinder, or bottom bracket, or even use the frame as the support for the crank. This works, but did not appeal to my vision of cleanliness and simplicity. I found a website for bike builders and they had bottom bracket shells ready for welding. Freewheel assemblies come in several styles and tooth counts, eBay had several that had a large enough bore to fit a ¾" axle. Now that I have a freewheel, the next question was how to provide the rider a way to stop this contraption on that long downhill run. A little research on the internet provided the answer. Scooter parts are playing a big role in the small parts area for building our hobby, I found a simple band brake assembly with a drum, actuator, and housing that could work.
Crank/Pedal Assembly, with mounting structure and Bottom Bracket Shell
Surplus Center sprocket hub machined down to a threaded freewheel/drum hub
The basic fabrication of the frame was probably the easiest part. I was able to cut all the box tubing, and bearing plates with a small bandsaw and do the basic drilling and tapping on a drill press. With a lot of welding help from another club member, Steve Trom, I had the basic frame built. The length was based on my leg length when seated against a wall. This determined how far from the pedals my seat would need to be. I then added in a little extra to allow for couplers and rounded the whole thing off to about 5’. The crank support was a simple 45° triangle, again keeping the lines clean. This was welded to the box tubing so that the length of my leg would extend past the crank bearing to the pedals. The bearing plates are simple plate steel, match drilled and tapped for the bearings. So far I had 4 wheels, 4 bearings, and a method to mount the crank; it was looking like a simple project after all, (not). Trying to keep costs down, I found a nice aluminum crank set on eBay, with the largest sprocket possible.
The location of the crank support required the crank set to be installed and clearance checked with the front wheels. I left about 1” for clearance in the normal operating orientation, but the pedals will hit if they spin freely. Now it gets complicated. How do I install a bicycle freewheel on a ¾” axle? I had two choices in freewheel mountings based on threads, English and Metric. Since I have an antique LaBlond, I went with the English, 1 3/8” x 24 TPI. This limited me to a minimum size 16 tooth sprocket that is a standard for motocross usage. As a scrounger and someone interested in odd items, m\y two favorite types of catalogs to peruse are McMaster-Carr and any surplus store catalog. For this application, Burden Sales came to the rescue. They have a selection of weldable hubs for making large sprocket assemblies. They are bored and keyed to whatever shaft you may need. For me, the ¾” with a 3/16“ keyway was perfect. I machined the small diameter to 1.375”, faced the large diameter to minimize the thickness, and then single pointed the required thread. The final product was a nice clean hub that was not too tough of a job, but did take some time for an amateur.
As it turned out, this thread that is common in bicycles is also used on scooters. The drums for the band brakes take the same thread, so back to the lathe to make an additional threaded hub. I now had a way of mounting the sprocket and brake drum on the axle.
The initial plan was to build the drive system just like a bike, with the chain on the right side. The chain as it comes off the crank is about ½” from the frame. If you try and install the sprocket on the right side, it would not line up and interfere with the bearing and would offset the chain about 1” from the frame. To get the sprocket closer to the frame, it would have to be installed backwards and then the sprocket would freewheel or unscrew from the hub and not provide drive. I decided to put the sprocket and chain on the left side, and reversed the crank. Everything seemed to line up. Good enough for this project. As it turned out, the brake had the same type of issue and needed to be installed on the right side to prevent it from unscrewing when used. All is well or so I thought. It is now time to install the chain. I wanted the chain to run along the frame and out of the way of the rider. This would require an idler at the base of the crank support. To get the chain out of the way on the top, a second idler was needed to hold the returning chain away from the drive side.
Freewheel and Brake Drum with hub
Brake details, Actuator and Stamped Housing
At the time I was able to find small scooter sprockets that I installed on a ½" diameter shaft. I used small bearing blocks to allow the whole sprocket and shaft to rotate. By adjusting the spacing between the idler shafts, I could use them for tensioning the chain. It was crude but it worked, (sort of). The brake was another learning experience. The basic assembly comes with a drum and housing. The housing has the band and a lever mechanism to activate the brake. It is a stamped steel part that has two holes, one for the axle and one to prevent rotation. I took the unit and drilled it out to clear the axle. I used plumbers tape to make a bracket to secure the housing and installed the assembly. I added a piece of wire and a lever, and I had a working brake.
Version 1 is complete, now it was time for the test ride. With a boat seat added, it was determined that one size would not fit all. I am 5’ 10", my wife is 5’ 4" and kids at the club are shorter than 5’, so it was time for the first modification. With the addition of a couple pieces of aluminum channel, and some plywood and I had a seat that would slide about 4 inches. First obstacle overcome. The test ride was relatively successful; many people rode and found it workable. I decided to take it to Train Mountain for the 2009 Triennial. Mechanically it worked, but just didn’t seem to be smooth. I received lots of advice and was queried on all aspects, but did not come to any new insight at the time.
Version 1 with Boat Seat and Channel Aluminum seat adjuster
Chain Idlers with ½” Bearing Blocks, New Sprocket Configuration
As it turned out, my idler and tensioning system seemed to be the root of the performance issues. After returning home, the velocipede sat for a few months. I did more research on bicycles trying to figure out how they handled chain tensioning and routing. Recumbent bicycles are a study in handling chains over long distances. All kinds of idlers and tensioners were found, but nothing that would bolt on. It was time to modify the standard part to fit my application. Most of the idlers for bicycles are plastic with no bearings.
Tensioner Spring and Lever
I wanted this project to last so I used roller blade bearings and bored out the scooter sprockets, these worked great, I made up three sets. I used two sets for the idlers, with the existing bearing blocks for mounting only. The chain moved much easier, but the tensioning was still an issue. It was time to go back to the bikes. I finally decided to use a tension arm, and after much trial and modification. I found that it would mount on the bottom idler shaft and a spring and lever on the opposite side would keep the chain tight and in place.
Velocipede Beta Testers
Version 2 is complete, and an almost unanimous success. My test pilot, Lori Tolan, her son, and a fellow enthusiast from New Zealand, spent the President’s Day Meet doing laps around the Bittercreek and Western. After a few months of breaking it in, many miles, and beta testing at Bittercreek and Western as well as my home track the Mackerel Flats and Goathill Junction, the velocipede was deemed a success.
The basic design worked, now refinements can begin. One of the issues that cropped up was the scooter brake housing constantly squeaked. The stamped metal design would not stay aligned with the axle and squeaked. The housing was scrapped and an angle bracket fabricated to hold the brake band and the actuator. It was mounted to the bearing plate using the same hardware as the bearing, very simple, very rigid, and no longer required the front screw to keep it from rotating. The seat was an interesting addition. It is a small tractor seat, which is heavy, but has a built in slide that is adjustable at the touch of a lever. This seat is sprung so rail defects are not transmitted to the rider, and the arm rests add a nice touch. One other item that may need to be addressed at a later time is the chain tensioner; the arm would need to be shorter if a larger front sprocket is used.
Once all the parts were fit checked, the velocipede was taken apart and painted. I used basic black for the frame, the fixtures for brakes and lights were painted red, and a bright yellow seat was added. The wheels were painted bright yellow to match the seat and make a nice contrast to the frame.
Like any project, this one is only finished for the near term. Future upgrades include taller gears; everyone who has ridden it thinks it should fly. A cutting lever to allow disconnection from a pulling train once the rider is rested. A horn, something obnoxious comes to mind. Who knows what else?
What I Did Wrong:
Why did this project take 3+ years? Hindsight is always 20-20 and the mistakes made are now obvious:
Bearings, the original bearing looked good on paper; they were small, cheap, bushings instead of balls, stamped metal bracket, and rubber mounting. For the velocipede everything but the rubber mounting worked. When version 1 was tested, the constant shifting of the rider’s body caused a rocking motion that made the wheels pivot and even rub on the bottom of the seat.
Chain tensioner, I probably went through 3 or 4 variations of my own concoction before I looked into what was available on bicycles. I could have saved a lot of time and frustration. So when in doubt talk to the experts.
Length of frame, which was a pure lucky guess. Had I made the frame 4 to 6 inches shorter, there would have been clearance issues with the pedals and the front wheels. Talking to other builders or riding their machines would have given much insight.
Below is a list of the suppliers I used for this, and other projects. I have had good luck dealing with them and would recommend their services to any builder.
Source Website Item Part number RMI Railworks www.rmirailworks.com 5 ½” Wheels SWHL-007 McMaster-Carr www.mcmaster.com Bearing Block 5913K63 Burden Sales Co www.surpluscenter.com 3/4” Keyed Shaft 1-2982-75-3 3/4” Bore Hub 1-2342-E EBay www.eBay.com Crank and Bottom Bracket Your Choice Freewheel 16T, English, 1 3/8” x 24TPI reliableaftermarketpartsinc www.eBay.com Tractor Seat Nova Cycles Supply www.cycle-frames.com Bottom Bracket Shell NOV_LLBB_BMX All Electronics Corp www.allelectronics.com Band Brake Assembly BB-90 TNC Scooters http://tncscooters.com 9 Tooth D-bore Sprocket 106020 ElectricScooterParts.com http://electricscooterparts.com Any Bike Shop Standard bike parts, pedals, chain, etc.
Written by Gary Sharp
Orange County Model Engineers
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