Trikes being Unstable

Dave31 · Sep 11, 2010

I just saw a older gentleman dump his trike down my street making a turn (un-motorized).

I dont have much experience with trikes but the ones I have ridden are very unstable and easily tipped over when making a turn.

While I was watching this poor guy get up off the pavement I thought why not add a little negative camber to the rear wheels? I wonder if this would help in cornering?

Kevlarr · Sep 11, 2010

It might help a little bit. The wider something is the more stable it is but the extra few inches of width you'd get really wouldn't help much besides the fact of adding negative camber opens up another whole can of worms in the form of needing u-joints or some kind of CV joint in the rear axle.

Trikes would be way more stable if they could lean into a turn and while in a lean shorten the distance between the front and outside wheel but that's getting way to complicated.

2door · Sep 11, 2010

Dave,
Anything with three wheels, or legs, is inherently unstable. Airplanes, tricycles, ladders and the infamous all terrain vehicles that the government banned. They can be made safer but will never be as stable as a four wheeled/legged device of the same design. The rider/user of three wheeled, or legged devices must use caution and respect of the fact that there is the potential for a fall.
Ask any tricycle geared pilot why he doesn't taxi and make fast turns on the ground or a worker who has experienced the tipping of a three legged ladder in spite of being careful.
My trike has its unstable tendencies and I'm quite aware of them and never exceed those limits...at least I hope I never do.
The only way I can see to prevent tipping of a trike would be to add outrigger wheels which would then make it a five wheeled vehicle. I wonder what the DMVs would think of that?
Tom

motorbiker · Sep 11, 2010

It helps to lean to the right when turning right and leaning to the left when turning left.

Some ride better than others that is for sure.

corgi1 · Sep 12, 2010

The out rigger wheels wouldn't need to touch the ground ,just ride 4-6 inches up to catch you if you tip,and older grown-ups don't have near the aversion to safty devices (some call them training wheels) as some of the still learning younger people do ,and when I was young an old guy told me the ways to avoid turning over 3-wheelers(speed is one)

city of angels · Sep 12, 2010

this is the reason why i changed the front forks on the trike they were way to weak i could turn a lot easier with these forks than the original

silverbear · Sep 12, 2010

I've wondered about the stability of a three wheeler as I have tentative plans for converting a 1942 Schwinn step through with a rear adapter axle such as the one available from Spooky Tooth. I'm anticipating the day when I'm too old for a two wheeler and want to be able to keep riding. Tom, or anyone else... what kind of speed are we talking about when turns can get ugly? I'm thinking that there's no need for gears on a trike since overall I imagine you would run it at lower speed than a two wheeler. A larger rear sprocket might even be a good idea for climbing hills, etc. without pedal assist. I'm picturing a pretty simple setup with a pull start HT 2 stroke mounted in frame. What would a sensible top speed be for straight running and what for turning (realizing the sharper the turn the slower the turn)? Seems like a four stroke or gears would be a waste on a three wheeler if you never tap in to it's potential.
SB

city of angels · Sep 12, 2010

i have a trike convertion on my bike i will suggest changing your front fork for better steering i only have one gear on my tirke i m running a 44 tooth sproket since thats the highest i could go on my bike my top speed is roughly around 20 to 25 mph i wont go higher than that my mechanic has told me around 30 mph bike starts to wobble i really like my front forks they are from the gt 1 bike if you go to the search and type upgrades you could see a pic of my trike the 25 mph that was going down hill with my brake gently apply when it comes to turns i slow way down and lean to which ever direction i need to go

Fulltimer · Sep 12, 2010

The instability is why I'm getting rid of my trike. Top speed = ? I cruse at about 20 to 25 with it. What worried me most was if I had to make a fast turn to avoid something in the road. It would roll over for sure. To make a right angle turn I had to slow down to just a crawl. From the outside of a tire to the outside of the other is 27". Front tire is 26" and the back ones are 24". I think a wider stance would help some.

Terry

motorbiker · Sep 12, 2010

silverbear said:
I've wondered about the stability of a three wheeler as I have tentative plans for converting a 1942 Schwinn step through with a rear adapter axle such as the one available from Spooky Tooth. I'm anticipating the day when I'm too old for a two wheeler and want to be able to keep riding. Tom, or anyone else... what kind of speed are we talking about when turns can get ugly? I'm thinking that there's no need for gears on a trike since overall I imagine you would run it at lower speed than a two wheeler. A larger rear sprocket might even be a good idea for climbing hills, etc. without pedal assist. I'm picturing a pretty simple setup with a pull start HT 2 stroke mounted in frame. What would a sensible top speed be for straight running and what for turning (realizing the sharper the turn the slower the turn)? Seems like a four stroke or gears would be a waste on a three wheeler if you never tap in to it's potential.
SB

Almost as fast as a bicycle.

Lean into the turns.

When you get good at it you can do turns on 2 wheels !

2door · Sep 12, 2010

Better stability can be acheived by lowering the center of gravity. Using an adult trike (plant trike) makes this a challenge by virtue of the design. The answer would be to design a three wheeler from the ground up and keeping the center of gravity as close to the ground as possible. There are many relatively stable three wheelers out there, the tadpoles and delta trikes designed for pedal touring are examples but they often don't lend themselves to motorizing without extensive work and fabrication.
To answer Silver Bear's question about what is considered a "safe turning speed", that could only be determined by experimentation on a particular trike and that could get dangerous. My trike sits close to the ground compared with the most adult trike designs yet I can feel the instability, especially at speeds approaching 25mph. I typically don't ride it that fast and keep it down to a reasonable, and safe speed in the mid to high teens. On a long flat stretch I'll let it wind out but due to the small front wheel and lack of road contact I take curves with a lot of caution.
I'd like to see, or be involved with, a good three wheel build that takes the instability question in mind and see what could be achieved. Maybe one day when I get all these other projects finished, I'll give it a go.
Tom

The_Aleman · Sep 12, 2010

Years ago when I lived in Alaska for a time, I bought a 3-speed Huffy trike with 24" wheels for my crash-prone girlfriend. She got mad at me because she thought I was making fun of her, but that trike was a lot of fun! It had a cool little differential which had a bit of posi effect on frozen puddles with moderate power. It was possible to do donuts on that thing lol

Anyway, being a former sidewalk terrorist from the Gen-X BMX era, I found the best way to bend a tight corner with that trike was to get it on the inner wheel instead of taking it flat. Of course that method is worthless if you have a heavy rear load or you are trying to power through a turn (one wheel will just spin), but it works with light trikes pretty well as long as you have good rear wheels and tires.

I don't think I'd try it with a 26" wheel trike, tho!

Upper Class White Trash · Sep 12, 2010

The_Aleman said:
Years ago when I lived in Alaska for a time, I bought a 3-speed Huffy trike with 24" wheels for my crash-prone girlfriend. She got mad at me because she thought I was making fun of her, but that trike was a lot of fun! It had a cool little differential which had a bit of posi effect on frozen puddles with moderate power. It was possible to do donuts on that thing lol

i have the same rear end!!!
you failed to mention that when one of the back tires come off the ground you loose all braking function till both tires are touching again..

that is a task in itself when you are turning to avoid hitting something

only way to remedy it would to disc brake both sides of the axle.

corgi1 · Sep 12, 2010

The Recumbent Bicycle and Human Powered Vehicle Information Center lots of explaining here

The_Aleman · Sep 12, 2010

Upper Class White Trash said:
i have the same rear end!!!
you failed to mention that when one of the back tires come off the ground you loose all braking function till both tires are touching again..

I didn't lose all braking function. The trike had a front brake.

only way to remedy it would to disc brake both sides of the axle.

That's not the only way. Sturmey Archer makes a few different left and right hubs with internal drum brakes.

corgi1 · Sep 12, 2010

a spring loaded sliding seat would move the center of gravity by moving body weight back over the rear wheels for higher speed cornering

2door · Sep 12, 2010

corgi1 said:
a spring loaded sliding seat would move the center of gravity by moving body weight back over the rear wheels for higher speed cornering

Sorry, corgi, but its not front to rear weight distribution but heigth. You'd have to lower the weigth in relation to the ground or centerline of the axles to gain stability. The lower the weight to ground the less moment arm there is to act in tipping the vehicle. Think of a lever...the longer the lever the less force there is needed to lift/move something. The higher the center of gravity the longer the lever to tip it over.
Front to rear will only benefit traction, not balance.
Tom

corgi1 · Sep 12, 2010

I understand the lower thing,center of gravity,there is imfo in the site on # 16 that gives the figured out ideal position for 3 wh balance on a reverse trike (similar to cat-trike's),the height is a problem but weight placement changes the pivit point a great deal as does the sharpness of turning,I was a great fan of Human Powered Vehicle sites before I discovered this grand site. In a sitting position legs forward as on a shwynn OCC chopper the center of gravity will be located in an area where a 12 inch ball would sit in my lap,the ideal location for that center of gravity on a trike is about 70/30% favoring the two wheels w/the 30%
,the height increases tipping as COG increases heigth keeping the most efficient front to rear COG in place: moving the 70/30 COG forward increases it more

Upper Class White Trash · Sep 12, 2010

The_Aleman said:
I didn't lose all braking function. The trike had a front brake.
That's not the only way. Sturmey Archer makes a few different left and right hubs with internal drum brakes.

duel sturmey hubs would work on some new trikes with left side and right drive but

most are only one side drive and we were talking about the one you had and i have.

for me to do duel hubs would be as much work as doing duel discs.

2door · Sep 13, 2010

Corgi, Good points, all.
Let's build the ultimate trike. Low COG and the proper front to rear weight distribution, four stroke and gears... Let's shoot for 35mph, tops

Tom

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