Suspension and Drivetrain Design Project

[intrepid44]

Just thought I'd share with everyone some screenshots of my just finished CAD model, and show that some of us student don't just drink!

Anyway enjoy and let me know what you think:





Now to finish my log book, currently on page 92!

P.S. I also have the rear of the chassis modelled, and the wheel/tyre etc. but I've made them invisible so you can see the more interesting bits.

[davepoth]

Why belt drive, if you don't mind me asking?

[intrepid44]

I decided that the belt drive was the easiest to maintain, it didn't require continual maintenance, like a chain requiring lubrication and a gearbox is quite heavy. Although I guess a chain/sprocket combination may be a bit lighter. Plus it'd be a bit of a pain modelling the chain!

[WhoseGeneration]

intrepid44 said:

I decided that the belt drive was the easiest to maintain, it didn't require continual maintenance, like a chain requiring lubrication and a gearbox is quite heavy. Although I guess a chain/sprocket combination may be a bit lighter. Plus it'd be a bit of a pain modelling the chain!

This is your answer to a question, your assignment, however, what was that question?
Any comments will have to bear that in mind, you see.

[maclf01]

Just some quick FYI. Since, you used a spherical bearing for your top and bottom attachments to the upright, you've made the camber adjustable, however, you have also put a rod in bending which is a big no-no in racecar design. I would suggest redesigning it a little bit with some kind of pressed in spherical and make your camber adjustable at the upright using shims. I believe this also improves compliance between parts.

Anyway, is this for FStudent?

[intrepid44]

maclf01 said:

Just some quick FYI. Since, you used a spherical bearing for your top and bottom attachments to the upright, you've made the camber adjustable, however, you have also put a rod in bending which is a big no-no in racecar design. I would suggest redesigning it a little bit with some kind of pressed in spherical and make your camber adjustable at the upright using shims. I believe this also improves compliance between parts.

Anyway, is this for FStudent?

Yeah it is for electric Formula Student, well that's what the assignment is for. I'm currently only second year so not on the design team yet, hopefully will be next year though.

And yeah you're right, I have put a rod end in bending, but for me personally it isn't worth redesigning it, obviously I'd redesign it if I was going to make it, but for the assignment I'll only lose a few marks if I declare it and say how I would change it.

As for the other poster basically the assignment was to design the drivetrain and rear left hand suspension of a small autocross single seater to go into a limited production run. So cost and maintenance are fairly improtant factors, and not so much outright performance. The parameters that I've been given, include wheel track, suspension travel, mass, and tyre coefficient, and we've had to calculate how it will perform i.e. acceleration (cornering/straightline), the forces through all of the components, breaking load, bearing life etc. So it's a fairly big project.

[vrooom]

Lot of wrongs this in this design.

1) those rose joints will snap, because it fitted to hub with no up/down movement available for rose joint. I suggest you turn the rose joint right way up which is vertical.

2) belt drive will come off the big 'gear' because there is nothing to hold the belt on.

3) those driveshaft has no CV joints...

[ShredderXLE]

It almost looks as if the whole assembly needs to be rotated around the hub by 90 degrees so that the bearings in the rose joints are rotating in the direction of suspension travel.

Edited by ShredderXLE on Monday 28th February 19:12

[wobert]

Are you sure the belt will transmit all the torque you have available without snapping?

Also the belt wrap on the pinion sprocket "looks" low, in terms of angle. You might want to consider an idler mounted on the "slack" side of the belt to increase the wrap angle and reduce tooth loading?

I use Pro/E Wildfire 4.0 on an almost daily basis!

Edited by wobert on Monday 28th February 19:18

[mickrick]

I'm always impressed by this stuff. I can send and receive e-mails, and copy and paste. That's about the extent of my computer knowlage!

I used to love Technical Drawing as a schoolboy, but back then we did it with a pencil!

I actually bought a Solidworks book recently, just to see what was involved. I got to about page 168, and I think I'd managed to understand how to model a square piece of aluminium!
If I was in the U.K. I'd be going to night classes for this, (I did City & Guilds Mechanical Engineering years ago at technical collage in the evenings)unfourtunately I live in Spain, and I'm afraid if there where such a place to go and learn this stuff in the evenings after work, it would be even more difficult with Spanish not being my first language.
I do however intend to get myself a powerfull enough computer to run Solidworks, and have a go with the help of books and tenacity.

Keep it up! I think what you're doing is great!
You're lucky to be able to learn stuff like this.

[busta]

vrooom said:

Lot of wrongs this in this design.

1) those rose joints will snap, because it fitted to hub with no up/down movement available for rose joint. I suggest you turn the rose joint right way up which is vertical.

2) belt drive will come off the big 'gear' because there is nothing to hold the belt on.

3) those driveshaft has no CV joints...

Ever seen a cam belt? As long as the alignment is correct it'll be fine.

[anonymous-user]

I think the main problem is using an electric motor........ Where's the socking great V8 ????

[intrepid44]

vrooom said:

Lot of wrongs this in this design.

1) those rose joints will snap, because it fitted to hub with no up/down movement available for rose joint. I suggest you turn the rose joint right way up which is vertical.

2) belt drive will come off the big 'gear' because there is nothing to hold the belt on.

3) those driveshaft has no CV joints...

1) The rose joint can move with the small angles involved in suspension travel, according to SKF they allow for free movement to about +-15 degrees. The weakest part is at the thread of the rod end, this is due to the rod end being in bending, but it does allow for easy adjustment of camber/toe.

2) No it won't.

3) I wasn't required to model a CV for the project, just something that took the space of one, and had a flange/spline fitting.

[intrepid44]

wobert said:

Are you sure the belt will transmit all the torque you have available without snapping?

Also the belt wrap on the pinion sprocket "looks" low, in terms of angle. You might want to consider an idler mounted on the "slack" side of the belt to increase the wrap angle and reduce tooth loading?

I use Pro/E Wildfire 4.0 on an almost daily basis!

Edited by wobert on Monday 28th February 19:18

Yeah it will take the torque, I've looked at graphs from manufacturers catalogues and decided on a belt from that. I did write that in my log book as an alternative to tensioning the belt, although I've also made it so that the motors can be moved forwards/backwards to take up the tension that way. Of course that then effects the weight bias of the car/requires more room etc.

[intrepid44]

mickrick said:

I'm always impressed by this stuff. I can send and receive e-mails, and copy and paste. That's about the extent of my computer knowlage!

I used to love Technical Drawing as a schoolboy, but back then we did it with a pencil!

I actually bought a Solidworks book recently, just to see what was involved. I got to about page 168, and I think I'd managed to understand how to model a square piece of aluminium!
If I was in the U.K. I'd be going to night classes for this, (I did City & Guilds Mechanical Engineering years ago at technical collage in the evenings)unfourtunately I live in Spain, and I'm afraid if there where such a place to go and learn this stuff in the evenings after work, it would be even more difficult with Spanish not being my first language.
I do however intend to get myself a powerfull enough computer to run Solidworks, and have a go with the help of books and tenacity.

Keep it up! I think what you're doing is great!
You're lucky to be able to learn stuff like this.

Thanks, it is probably the best module at uni at the moment, certainly better than the law/business/accountancy/statistics that we have in addition to the more engineering related modules. We actually get this software for free from Autodesk being a student!

[Adam205]

vrooom said:

Lot of wrongs this in this design.

1) those rose joints will snap, because it fitted to hub with no up/down movement available for rose joint. I suggest you turn the rose joint right way up which is vertical.

2) belt drive will come off the big 'gear' because there is nothing to hold the belt on.

3) those driveshaft has no CV joints...

LOL! Classic.

[McSam]

I'm a first-year on Auto Eng, so all I can add is

[Alan Kee]

As it's for an off-road design (therefore not constrained by construction and use regs) can you do away with the outboard brake disc and use the electric motor for braking/regenerative effect? I'm assuming that a competition electric vehicle will benefit from less mass, certainly less rotating mass .. or is engineering a braking system in the design a requirement in the brief?

[Perra]

Alan Kee said:

As it's for an off-road design (therefore not constrained by construction and use regs) can you do away with the outboard brake disc and use the electric motor for braking/regenerative effect? I'm assuming that a competition electric vehicle will benefit from less mass, certainly less rotating mass .. or is engineering a braking system in the design a requirement in the brief?

Brakes stop a car faster than regen.

[davepoth]

Perra said:

Brakes stop a car faster than regen.

Depends on the brakes, depends on the motor, depends on the gearing.