Introduction: DIY Chainsaw-bike
Step 1: Introduction
I am going to help you design and create your own chainsaw bicycle. This is because when I was looking on the web for ideas and ways to create my own bike, there was very little information, which lead me to guessing most of the time (but this gave me a lot of experience). There are many guides on YouTube, but many are old, poor quality and just plain sketchy so I've decided to help you instead of doing my homework. This guide will should help you make your own, without having to restart over and over again (like I did). This is a guide though, and I need to mention that the method I will be using will not always work for everyone. But I am here to point you in the right direction.
Step 2: Tools and Other Stuff
This is a rough list of what tools you will need. There are other alternatives to some on this list so if you don't have something don't worry.
Dremel hand tool- I used one because I had it but a file or an angle grinder will do whatever this can
Chain link remover
Drill- including HSS drill bits (Drill bits that can drill through metal)
Arc welder- A MIG welder would have been better, but I had to work with what I got.
Hacksaw-(or just use the grinder)
Soldering iron and solder-(depends if you want a battery and lights)
GOGGLES, WELDING GLOVES AND WELDING MASK-safety first people
Latex gloves for handling motor oil-not entirely necessary, just helps keep your hands clean and reduces risk of cancer. They're super cheap to buy or just ask a proctologist for his ones.
Step 3: Engine and Bike
Well of course your going to need a bike and an engine.
For the bike, I recommend a mens mountain bike without rear suspension. This is because it provides the maximum amount of mounting points for the engine. Preferably an old Marin or a Raleigh from the 90's as people will have one laying around and they can be picked up for quite cheap on eBay. However it is possible to use a different type of bike, but your engine mounts will have to be different and sturdy. On my bike I have used a Marin mens mountain bike which I think is from the 90's or early 2000's.
The engine is more complex. For this design, the engine needs a working clutch which luckily most chainsaws have. Avoid Strimmers (weedeaters), leaf blowers, and hedge trimmers as their engines are just to small and they don't always have clutches.
The chainsaw you need should be above 40cc but a 35cc Ryobi may just be ok. For Chainsaws around 40cc, you might have to increase gear reduction for more torque and to avoid burning out the clutch.
If you've already got a Chainsaw that you want to d̶e̶s̶t̶r̶o̶y̶ give a new lease of life to, then you'll have to work with what you got. For those looking to get one for this purpose, eBay will be best. Avoid big brands such as Stihl and Husqvarna and go for less desirable ones. This is because second hand Stihl saws and blowers are still expensive. For my bike I bought a 45cc Qualcast chainsaw which I got for £40 ($52).
Also It is a good idea to get a Chainsaw that you know works, and always take what the seller says with a pinch of salt.
Step 4: Other Materials
The less important stuff...
Steel- as seen in the picture, I have used some quite heavy duty stuff. I salvaged this from an old ornate gate. Not everyone has an old ornate gate laying around though (weirdly) so I would recommend angle iron as it will be just as strong.
Spare bike sprockets-steel. For the clutch I used a 9 tooth that I made myself using the dremel and for the chain ring sprocket I welded a 13 tooth onto it.
Derailleur jockey wheel
Nuts and Bolts M6 M8 M10 but you can change these.
Nylon threaded nuts-optional, but I use these now because my engine nearly fell of during a test run.
Washers and Spacers(or pipe)
Bungie or spring
Step 5: Plan Where Your Chainsaw Will Sit and Remove Unnecessary Parts
Using the chainsaw and Bike that you have, roughly decide what you'll need to cut and remove from the bike and the chainsaw.
On the bike, I had to remove 2 bottle cages, but I relocated one to the back so I can still carry spare fuel.
On the chainsaw I had to remove the large handle and the engine cover, as this would be difficult if I needed to look at the engine. I also cut the throttle handle off using a dremel.
The area on the chainsaw where I have circled in red is one of the cuts I had to make to make it fit.
The parts laid on the floor that are labelled are some of the items I had to remove.
DO NOT REMOVE THROTTLE OR THROTTLE LINKAGE AS YOU WILL NEED THESE
Step 6: Making the Sprocket
Yay the d̶i̶f̶f̶i̶c̶u̶l̶t̶ easy bit.
Unless you use a belt system, which I am planning to do in the future, you're going to need a drive sprocket.
You can salvage a sprocket from a bike cassette, but I decided to make my own using a Dremel tool and an angle grinder.
I drew the template by hand using some pi and good ol' maths equations and stuck it to a large washer. I then grinded it down to what it is now and welded it to the clutch. If you'd like to know more about how I drew the template write it in the comments.
When you weld the sprocket to the clutch, I would recommend only spot welds otherwise you'll warp the clutch drum and that'll make it useless.
Step 7: Mounts, Mounts, Mounts, Moun....
Ok, if you have made it this far, it is time to fabricate the engine mounts.
This is a simple but sometimes time consuming process which may involve some measurements.
Firstly, look around the chainsaw if you already haven't done so and look for the best possible mounting areas.
Then place the engine exactly where you want it to be. The sprocket you made in the last step needs to be aligned with the largest chain ring, otherwise chain issues will be caused. For this I would recommend getting someone to help you.
If you're using angle iron, create a bracket for the first mount, preferably the easiest one that you can choose. Attach this bracket to the engine and drill a hole through the frame where appropriate. I recommend M10 bolts as these are pretty much indestructible and are easy to weld. The first 2 pictures of this step is the first mount I created. Originally it was to just hold the engine in place whilst I made the other mounts, but it was strong so I decided to use it too.
Once you have done this, proceed to creating the other mounts you need. To make sure the engine is aligned with the largest chain ring, use spacers like I have. (I used copper pipe cut to size)
On my engine, the mounting area I used are:
- Part of the engine structure had 2 handy bolt holes that I used as mounts below the muffler. This mounted to the front of the bike. (1st, 2nd and 3rd Pictures)
- The bolt that held on the chain bar as one mount. This goes to the top of the bike frame. (3rd, 4th, 5th pictures)
- I mounted the bottom mount to an existing bolt hole on the plastic engine cover, which goes to the bottom of the bike.(last 2 pictures)
I only have 3 mounts but that is all that you need if you build the mounts strong. For these, I welded the bolts to the metal instead of drilling doles through them because my drill bits aren't good enough.
Once you have completed this, take a long shower because you'll stink of welding fumes by now :)
Step 8: Crankset Modifications
Time to weld a second sprocket.
I had to do this increase gear reduction as my clutch was burning.
To make this I used a piece of steel drain pipe and a bike sprocket. As said in a previous step, the sprocket is from a bike cassette, which is the selection of gears at the back of a typical bike.
Here is how I made this crank:
- I cut off the smallest chain ring as this would get in the way and I didn't need it anymore.
- I also removed the front gear selector because it will no longer serve any purpose.
- I used the angle grinder to turn a piece of pipe into a thin spacer that would fit into the narrow gap between the chain ring mounts and the centre. This will put space the sprocket away from the rest of the crank set so the chain would not touch it.
- I then placed the sprocket on top of the washer and after making sure it was centred correctly and ran true, I welded it to the washer.
- I then welded the washer to the chain ring mounts
- I then cut off the pedals as these were a hazard when riding as they spin too fast to keep your feet on.
- Once you've finished these, attach the crankset back onto the bike and attach the chain.
Step 9: Time to Throttle
Hooking up the throttle shall be somewhat easy unless you removed it.
By using the gear cable from the front gears that you removed you can get a working and secure linkage working relatively quickly.
The left twist shifter is what will control the throttle as this was what controlled the now gone front selector.
The cable still goes to exactly where it was but the only difference is that it is now bolted to a metal plate that is bolted on the other end to the chainsaw throttle.
What I mean by bolted is that I drilled a large hole on each end so I can thread the ends of the cables from the shifter and the engine through a hole on each end and put a nut and bolt through the holes, clamping the cables.
To make sure the throttle would return, I attached a spring to the top of the plate that goes further up the frame. This other end of the spring is attached by a plastic bike clamp.
You can see this plate with the bolts in the last 3 pictures on this step.
I weirdly effective but simple method.
Step 10: Diagnostics and Chain Issues.
Nearly done......or not.
So you've assembled the last step and put it back on the bike.
You're eager to give it a test run and you think to your self I'm gonna look badass on this fine motorbike.
You put your helmet on and you fire up the engine. You look amazing. You push away and give the engine some power.
It's working and you think to your self-thanks Complete maniac
But 5 seconds later you hear *clank* *clutter*
You look down,
The chain has fallen off.
Not disheartened by this you put the chain back on and go for another test ride.
Chain came off again.
The morale of this story is this happened to me many times. After I would modify it, the chain seemingly never wanted to stay on. The chain still does occasionally come off, which is why want to use a belt system instead.
In this step I will give you some advice about why a chain may come off and ways to prevent this.
- Chain Slack
If your chain is loose, then it will jump around a lot and will jump off the chainring.
To fix this you need a chain tensioner, Which I made from a derailleur jockey wheel. (2nd and 3rd pictures)
I used a long piece of metal bolted to the frame which has another bolt pointing out. This is what the jockey bolts onto. There are also spacers to make sure that it is aligned with the chainring. This whole "swing arm" structure is able to move towards and away from the chain. To provide the tension, I used a bungee which holds the jockey wheel firmly onto the chain. This reduces chain slack causing less chain issues.
However if there is too much tension, then the chain will be hard to move. This is undesirable.
And yes springs can be used instead of bungees.
2. Chain vibrations
If you made a chain tensioner but the chain still falls off. Firstly make sure the jockey wheel is aligned with the chainring and the clutch sprocket.
If this fails then:
Start the engine
Left up back wheel
Give the engine some throttle and watch the chain closely.
You are likely too see a lot of chain vibration, especially on the section that does not have a tensioner, (in my case on the right towards the front of the bike.
I noticed that this type of high frequency vibration caused my chain to jump off.
A way to stop this is by building a chain guide. (LAST PHOTO)
I built mine using 90 degree aluminium. This runs next to the chain and holds up the pipe that the chain runs through. This mostly stops vibration from occurring and was relatively simple to make.
This part of the build can be frustrating, and I nearly gave up on multiple occasions. But this step involves trial and error so you'll just have to grin and bear it.
Step 11: Foot Pegs
Finally an easy step
There are no more pedals anymore but you need somewhere to rest your feet.
All I did was drill a 1cm hole in a comfortable place and put a large m10 bolt and nut through it.
A nice and easy way to rest your feet.
Step 12: CIRCUITS!!!!!!!!!!!
This wouldn't be an instructable if it didn't include some kind of circuit.
This is an optional step but I thought I would show how I did it anyway, which is why I havnt included any of this in the parts list.
I drew a circuit diagram of what I did.
The lower switch doesn't do anything yet (I kinda want a horn)
Headlight I bought on ebay and I put a 3w led into it
Tail light is a section of pipe with a red led inside with a red filter on the end.
The battery is clamped to the frame beneath the saddle.
Step 13: Finished! Although Improvements Can Be Made
WOW that took long.
You now have officially completed your own chainsaw bike. WELL DONE.
Well not really, improvements can always be made.
On my machine I plan on adding:
- A belt system instead of a chain and clutch system
I really hope you have enjoyed this instructable as much as I have making it. I am open to any questions you may have so feel free to comment. There are probably somethings I have missed so be sure to ask.
This is indeed my 1st instructable ( if you couldn't tell by the poor grammar and rubbish photos) so if there is any advice you would like to give me, please do.
If you read this far then you are awesome.