The RatRodRower - a Rowing Machine From Used Bike Parts

During the high time of the pandemic with working from home, restrictions of staying outside and so on, I needed a way to do sports inside on a regular basis. Also I felt a big urge to build SOMETHING, no matter what.

From an earlier time in my live I remembered that rowing on a machine could be a calming thing and then I saw one of this fancy water rowers built of wood at a friends home. So I thought, it should be possible to build one by myself instead of buying one, as even the cheap ones are out of my range AND look really ugly.

So I did some research online and ended up on the site of the Openergo Project, that gave me a lot of inspiration and ideas to come up with my own solution, that I present you here.

Supplies

A trip to the basement presented me with several options: wooden planks, steel railing, my Ikea hardware collection, various bicycle parts...

Totally doable!

Step 1: The Base

On the openergo site the "Green Machine" had cought my attention, as the design was much shorter than all the other ones. We (family of four) live in a flat and there is no spare room to store sports equipment. So I needed something that didn't take up too much space or could easily be stored away. The "Green Machine" met those criteria, so I decide to build my own version of it.

Still in the basement, I pieced together a basic mockup to check if I got enough materials and to leave in the basement what was not necessary. I decide to start with the railings, as it provided the most options to mount stuff to it in an easy way. To start building I used two pieces of wood as front and back plate (attached with some IKEA screws). I replaced those later with other pieces of railing.

First step was to mount the bike wheel into the frame. For that I cut and bent two shorter pieces of railing and enlarged the holes to make room for the axle. Later on I slotted the railings (a bit like bike dropouts) to make removal/mounting of the wheel easier. The total distance between the two bike mounting pieces gave me the necessary hight of the final base frame.

For mounting the other three axles, I made several L-brackets from shorter pieces of the railing.

The footrests needed a longer slot, as the holes didn't exactly match. The diagonals that hold the footrests serve a double purpose: first the obvious to give my feet something to push against, but second and also very important, these diagonals improve the stability of the rectangular frame a lot against going from rectangle to rhomboid.

The first installment of footrests incorporatet some old race bike pedals with straps.

Step 2: Pull Mechanism

First was this basic sketch on that little piece of red paper (later translated into that coloured digital sketch).

At the start I had the idea to use a bike chain to get the wheel spinning. But I soon found out, that the laws of gravity worked against this plan, as I couldn't provide enough constant pull to avoid the chain falling of the now horizontal gears and also the length of pull was too limited this way.

So I had to go all rope. That meant, that the gear cassette had to come off. A long lever and a chain wip took care of that and left me with the smallest gear and the bare freewheeling unit.

The first test showed, that the rope would wander off of the freewheel unit, so I made two "stoppers" from some of those clear CD-spindle thingies they put into the spindles as protection or fillers. The spacers from the cassette provided me wih the right measurings and a circle cutter did the rest.

The three additional bike wheel axles got mounted with my self produced and some IKEA brackets at their designated spots, a pulley was added to the rubber cord and the handlebar got some additional hardware, to be able to pull the rope.

Like this, the system became basically operational, I now needed a seat to start rowing...

Step 3: The Seat

As rails for the seat I used two wooden slats I had found in the basement. I screwed them onto the railings from the bottom side up and added stoppers at the back ends to avoid the seat rolling off.

The seat was quickly screwed together with pieces of wood found in the basement and eight little wheels from the furniture aisle of the DIY store. The bigger ones (should) hold my weight, the smaller ones on the sides keep the seat on the rails.

Sidenote: On the second pic you can get a glimps at my creative mess I produced in our living room...

For a long time I used the seat with a folded towel on it as padding. That worked, but it left a lot of room for improvement...

So when I saw a cheap (6,99 €) yoga mat, I bought it to make some padding for the seat. In my stash I found a fitting piece of jeans fabric and a strap. From my shed project I took some screws and washers.

First I cut 3 layers with the same size as the wooden board and stapled the first two to the board, the third I fixed with some doublesided tape on top. After that I cut the edge in an angle with a kitchen knife.

On top came a larger piece of the mat, that got stapled to the edge of the board and then trimmed off.

After that I covered the seat with the jeans fabric and finally wrapped the edge with the strap to finish it off with some crews and washers.

Step 4: Foot Rests

The first thing that quickly needed improvement where the footrests. The first version with the bike pedals just didnt work properly and was to complicated to get in. So I decided to got the simple way and put some wooden boards and packing belts in place. To let the boards sit flat on the railing frame screws, I drilled little recess holes where the screw heads were. The packaging belts are held in place by standard screws and washers.

Step 5: Break System - Additional Resistance V 1.0 / 1.1 / 1.2

The initial idea was to build an adjustable system to create additional resistance while rowing. I thought of a derailleur and magnets. So I ordered several strong neodymium magnets from my favourite retailer and mounted them into a piece of plastic mudguard, this mudguard then got attached to the derailleur. The derailleur was then mounted in way that allowed to move the mudguard as close as possible to the wheel without touching it.

The wheel I prepped with metal band, self drilling screws and pieces of plastic tubing as spacers.

When I put the pieces together, I realized that the derailleur setup wouldn't work, as the magnets where to strong (or the derailleur to week and wobbly) so that the magnets always got pulled to full contact. So version 1.0 was off the table.

For version 1.1 I mounted the magnets on railing brackets and as close as possible to the wheel. Here I realized that the main pull resistance came not from the metal band, but from the screws.

So for version 1.2 I got rid of the metall band and only used the screws. The big plus with this was that I could now easily adjust, if one screw was sticking out to far and thus touching the magnets. The downside was, that this setup was really loud when operated!

Step 6: Break System - Additional Resistance V 2.0

I realized that my magnetic braking system was somewhat wrong, so I did some research and finally stumbled over the above youtube video, that showed exactly what I needed: an eddy current brake. A magnet moved closely along aluminum gets slowed down. And as my rim was made of aluminum and I already had magnets, everything I needed was already there.

So I got rid of the screws and mounted the magnets as close as possible to the side of the rim (good thing that the wheel was true). I immediatly felt the additional resistance and the system was a lot quieter as before. So V 2.0 was the way to go!

In total I have now 8 magnets providing resistance. Four in front of the wheel and four in the back. The wheel is still touching the magnets frome time to time, as the whole frame flexes a bit while rowing (you can hear it sometimes in the video). It allready got better with the added diagonals in front of the wheel, but at some point I will have to adress that...

Step 7: Ground Control and Storage

To avoid movement while rowing, I added some rubber plugs to the bottom of the base cage.

For the upright storage I replaced the standard 6 mm bolts at the front end with four adjustable feet. I added an extra nut so I could tighten them firmly.

An eyelet screw was added to the bottom side of the seat and a hook on a narrow hinge to the cage. Like this the seat could be attached to the upright standing rower without falling off.

To hold the handlebar in place I added two magnets in front of the wooden rails.

Step 8: Setbacks and Improvment

The one part in this rowing machine I spent (and still spend) the most time and thought on is the routing of the pull rope around the freewheel.

It quickly became obvious, that the first setup with the CD spacers was ok but not final, as it produced extra noise and the rope crossing over itself on the freewheel ripped the rope apart very quickly.

The first idea was to switch from 1,5 turns around to 2/3 turn and improved tension with two eylet screws or an eyelet and another pulley, but always with the same results: either not enough friction on the freewheel or too much friction on the rope.

Usually the rope let go after around 30 mins of rowing, which became very annoying and dissatisfying. It became a bit better when I started to use thinner rope, as one part of the problem is, that when the rope is moving around the freewheel it wanders up and down with each pull and release and as soon as it reaches its upper or lower limit, it starts to cross over and therefore to rub on itself. The thinner rope made it through about one hour and a half of rowing.

I changed and rearranged the setup with various variations of pulleys and bare bearings on axles on different positions and also tried different ropes, but everything lead to the same frustrating result of a ripped rope after more or less 1,5 to 2 hours of rowing...

I also tried to add some bike tubing onto the freewheel to increase friction to be able to go with less turns but the tubing didn't hold up very long...

While repeatedly attaching, detaching and reattaching ropes I also changed from tying them directly to the frame to putting eyelet screws at the right places.

Step 9: Final (?) Solution for the Rope Routing

When I had published this instructable yesterday, my head got into problemsolving mode again and so I checked the various sites I drew inspiration from before one more time. A little detail on the site semistable.com got my attention. I had kind of overlooked it before. There was this picture of his freewheel setup that showed that he didn't go all around the unit, but routed the rope away after half a round and then back to give it another half turn. I immediatly went at it and after a few tweaks I had found my (hopefully) final solution.

I already had made the step with the horizontal limiters a few months ago: basically three custom bolts with a piece of brass tube on it that can spin freely, but the rope was still going around the freewheel and crossing over.

So I added three stacked up bearing units with washer to separate them (also already produced for other positions and tryouts before) centered in front of axle and limiters. The rope is now routed from the pulley around the bottom bearing through the lower gap, half around the freewheel then again through the lower gap around the middle bearing and thus guided upwards, through the upper gap, half around the freewheel again and through the upper gap towards the handlebar. Like this, there is no more diagonal pull while the rope is on the freewheel, so no more wandering and no more crossing over!

There is still some minor friction inbetween rope and washers, but as the washers move along with bearings and rope, the rubbing friction is down to a minimum now. Also does it keep the rope in the corrugated area of the freewheel and like that provide a bit more grip.

To hide the spokeholes in the rim and the holes left from first version of the magnetic resistance system I simply stuck some blue tape into the rim. Like this it also matches the blue rope.

Step 10: Final Thoughts and Future Additions

This was a fun project and I managed to get on the rower every morning for several months. But at one point I got so frustrated about constantly changing the rope even though I tweaked the rope guidance several times, I stopped using it. So now it stands in a corner, collecting dust. (<- hopefully this will stop now, with the new rope routing)

Every now and then I am still trying to improve the rope situation but haven't found a final solution (yet). Looks like I found one (see step 9)

The last thought was mounting a fixed gear bike axle as intermediary, to get more travel room for the rope and then transfer the power to the freewheel trough a short chain. This is off the table for now (see step 9)

In the comments came up the possibility to add fan blades to increase the resistance. As stated in my reply, I thought about that, but discarded the idea in preference of the magnetic solution. Another possible solution for more resistance just came to my mind:

As a former military cyclist in Switzerland I remember one way of pranking our superior officers: We filled the tubes of their tyres half way up with water and then pumped them up. That slowed them down a lot, even made cycling for them almost impossible. :-) So her comes the idea: mounting a tyre and tube onto the rim, then filling water into the tube and pump it up as much as needed to keep it stable on the rim. I might give it a shot at some time...

One other thing that is darely needed, is padding for the seat. For now, I usually put a folded towel on it before rowing for a longer time, but that is no way near a final solution.

If you build one yourself and come up with a better solution for the rope problem, let's hear it in the comments. You would make me very happy!

If I find one myself, I'll update this instructable with it! Promise! Until then: Row On!