Topic: engineering/design question on suspention

[ieism]

This is not motorcycle related at all, but I hope you can help me out anyway.

I'm building a full carbonfibre babystroller (yeah, I know it's a stupid idea) but I have a few issues with fitting some type of suspention.

It going to use rather small solid wheels from a roller-ski fitted to a single carbon fibre tube each. The small wheels are mainy to save weight but also to keep it as compact as possible when folded. But this means it's a pretty rough ride.
I planned on fitting small coil over shocks (from an rc car) to each wheel. But I have no idea what type of linkage to use: A-arm, I-beam or some type of other linkage? It needs to be simple and lightweight. I've found a few places where I can calculate springrates, but I simply don't know the best design to use. Or how long or short the arms need to be for it to work.

[Flying J]

Pictures please.

[grcamna2]

   That  sounds like it's going to be a Marathon runners stroller.

[ieism]

 

Not really, it's just that all the stuff out there isn't very good at all.

I currently have a stroller I borrowed from a friend that cost a fortune, but still weights 23 lbs and won't really fit into a small car. I thought that was ridiculous and I could easily just make something better myself.

I'm aiming for my design to be 6.5 lbs, and half the size folded. It also has to be cheaper, that's actually the easiest part because it's not that hard to build a full carbonfibre model for less than $1000 myself.

It will be less comfortable and have no fancy gimmicks and stuff, but I figure it really only needs wheels and a seat to work.

No pics yet, I need to finish it completely before I show anyone.

[754]

Sometimes you can use runner bands for suspension. Inner valve sprimgs could work.
 I saw a cool skateboard tonite with wide trucks with a spring, and they turned..probably 14 inches wide with the wheels.
 The smaller the wheel, the rougher the ride and more feedback from bumps.. hard to mount curbs too. Lwnmower size id getting small.

 If you mounted the wheels rigid or fairly rigid, you could suspend baby platform, inside carriage body from bungies or rubber bands

[Gordon]

Not trying to discourage you from building your own, because it sounds pretty damn cool, but from what you say you're looking for in a stroller it sounds like you just need a basic umbrella stroller.  We got a big, expensive stroller from my parents when our first child was born, and then I bought a cheap ($15) umbrella stroller a while later, and it gets a lot more use because it fits in the car easier and only weighs a few pounds.

This isn't the exact one, but it's pretty much the same:

http://www.coscojuvenile.com/usa/eng/Products/For-Travel/Strollers/Umbrella-Strollers/Details/195-US042AVT-Umbrella-Stroller

[ieism]

 

Good point, but I have one of those simpler strollers as well. But they're not as cool looking, and I have to walk behind it sometimes.  And they still are a lot bigger when folded than what I have in mind.

I just thought it was possible to make something much better than anything available right now, so I've challenged myself to do just that.

[Skunk Stripe]

You will need stronger springs but have you thought about a cantilever style actuation? This way you could ay the shocks down to keep them out of the way.

[Gordon]

Good point, but I have one of those simpler strollers as well. But they're not as cool looking, and I have to walk behind it sometimes.  And they still are a lot bigger when folded than what I have in mind.

I just thought it was possible to make something much better than anything available right now, so I've challenged myself to do just that.

That's fantastic!  I love when I have the rare opportunity to do something like that.

May I make a suggestion?  If you're already using RC car parts for the suspension, just go ahead and throw in a receiver and a couple of motors while you're at it.  That way you would never have to push the stroller again!

[ieism]

You will need stronger springs but have you thought about a cantilever style actuation? This way you could ay the shocks down to keep them out of the way.

Thanks, I'll definately look into that. It will also give me more options to finetune the springrate/travel since the kid is obviously going to get heavier over time.

Gordon, I sense a slighty sarcastic undertone in your reply. I'm well aware that this is a ridiculous project, but it's not as much work as it seems because i'm using mostly of the shelf parts for it. The aim is to get it done before the baby can walk, so I'm not sure your suggestion will be used. Just out of curiousity, do you think electric or nitro powered is the better option?

[dave500]

a stroller with two wheels and a sohc engine,,now your talking.

[Gordon]

Gordon, I sense a slighty sarcastic undertone in your reply. I'm well aware that this is a ridiculous project, but it's not as much work as it seems because i'm using mostly of the shelf parts for it. The aim is to get it done before the baby can walk, so I'm not sure your suggestion will be used. Just out of curiousity, do you think electric or nitro powered is the better option?

I don't think your project is ridiculous at all, seriously.  The motors were just the first thing that came to mind when you said you were planning on using rc car suspension parts, because I know I would try to do it if I were building my own stroller.  

Nitro would be far better for speed, longer jumps and doing wheelies, but I think most moms would have a problem with all the exhaust, noise and fire hazard so close to their babies, so I think you'd have to go with electric.