Single Seat SolidWorks Design Review

[NorCalBuggy]

Hello All,

This is my first post, but I have been a part of this club for a little while. Currently I am finishing up my Mechanical Engineering Degree in Sacramento CA, and I want to share a single seat buggy design that I have been working on for the past couple of months. I have attached two isometric views (front and rear) for your review. I look forward to any constructive critisim and especially any helpful ideas that will help me improve my current design to be more robust and efficient.

A little info on my current design:

Tubing - Main (rollbar and hoop) will be 1.25 inch 0.063 chromoly, A-arms are 1.25 inch 0.120 chromoly. All other tubing will be 1.0 inch and 0.75 inch 0.063 or 0.048 chromoly.
Front end - Hubs/Spindles/Brakes from Honda TRX450R.
Rear Driveline - Hybrid ATV Axle Carrier (Concentric Chain Adjust) with high angle U-joint & Slip joint axles connected to custom Hubs and Spindles.
Controls - CNC Pedals and Cut Brakes
Body Panels - either fiberglass or carbon fiber.
Suspension Travel - Measured to be 21 inches, but will probably be limit strapped to 18-20 inches.
Shocks - King or Fox. Current configuration is Emulsion, but with such a steep ride angle will probably for with coil over and external reservoir.

Please let me know what you guys think of my design. This site and everyones suggestions have helped me greatly in understanding what is needed to make a nice buggy and my design should show it as to date.

Cheers

Eddy L. (NorCal Buggy)

[jersdunz]

So are you going to be building this buggy? .. I like it.

[yoshi]

I would do at least .95 wall tubing for the main roll bar above your head, and .83 wall for the rest of the main chassis tubes. The 1" is fine for cross bracing, but I would not go smaller than .063 wall.

You can use thinner material for a chromo chassis but one thing most people don't think about is that it's harder to weld and easier to thin out in places making weak links.

I use .120 wall for my entire chassis, it allows me to turn the heat up higher and get good penetration and smoother welds with a mig, but not worry about blowing holes in it. You will need someone with good skills on a tig to handle your chassis...

I also run 1018 and 1020 for my rails, not chromo....

[250r05]

I like the design

[NorCalBuggy]

Thanks Yoshi,

Until I've completed FEA on all the load bearing points on the chassis, the tube thickness is going to be constantly in play. I agree that too thin tubing is a BTCH to weld. I was part of our school's Mini Baja team last year and we were melting holes in the tubing all the time, so much so that I believe there was an extra 15 lbs of excess weight just in weld filling! I really want this frame to last....one that will take a good roll and keep on rolling afterwards. Only way to get that much safety factoring into play is to not be cheep on the tubing sizes/thickness. But that being said, weight is always a factor, and since I'm already limiting my power plant to 125hp, the total weight of the vehicle will play a bigger factor then if I was using a 200+ hp busa motor.

As for building.......nothing short of money is going to stop me. I want to do it this year...but it may have to wait until I graduate and find a job to pay for all the toys that I have been waiting (iching) to get.....including a good rig to haul it with.

Does anyone have any suggestions of a good source for finding high angle u-joints that will handle the loading to be used for driveline applications? I want to try this route over the 930 CV application that is both common and expensive. (Not that common is a bad thing....common = tried and true)...usually.

EddyL.

[Bullnerd]

This is just my opinion,dont take it too seriously!
Looks cool ,easy to get into.
This is what "I" would do,
Spread out the rear(and front if you can) "a"-arm mounts on the frame.
Forget the u-joints,I think it was Standfast,that did a good comparison
between u-joints and cvs.(have to look for that)They have too much
stiction under load.Not the u joints ,the shafts.
Lower the ride height.
Mount the rear shocks to the lower control arm,and at a better angle.

Can you put up some more pics?

[Gene]

Welcome to MBN and nice work.

I too would make the A-arm pivot mounts wider (further apart) both front and back. Having a radiator over my head and a boilover raining into the cockpit was something I disliked about one of my cars, so I'm moving the radiator to the rear and will build a wing around it.

Rear shock angle at full compression is contrary to much discussion on the board. The shock should be close to 90* to the A-arm while at full compression. Also it is seemingly better to mount the shock on the lower arm although I have a car with it mounted on the upper arm too. Mine is mounted further inboard allowing a shorter stroke. See Another Mini for details.

Have you determined how much plunge is created during rear A-arm cycling? My rear A-arm setup has under one inch plunge and uses plunging axles with front wheel drive CV's. You might consider that option and eliminate potential U-joint disaster.

[K-fab]

Looks good. Appears to be well thought out and room for a larger power plant later?

I agree - the rear shocks and where they mount needs to be addressed. The rear end will be uncontrollable (in a suspension manner, not driving) with the setup you have right now. It will blow through the valving and be a bounce monster.

Widen out the lower a-arms and put the shock mount about 1/3 of the way in from the hub towards the frame, in front of the axles.

Have you determined max droop angle of the shocks? If it's not over 22 degrees at the CV, a type IV will work well. They're light, durable and can handle the hp. The axle's smaller than a 930 setup too and much lighter. The trick is finding Type IV CV joints. Porsche 944's used them - so I've been informed...

The closer you can get the CV flanges on the chassis, the longer you can make the axles and the more travel you'll be able to get from the setup.

Radiator - you'll probably need a larger unit than drawn - and put it on the down bars in the back of the chassis, not the roll cage.

[jersdunz]

If your going to hang a radiator that sits over the cockpit do this so it won't spray you even incase of a boil over, then you can leave it up in the air..

both inlet and outlet have a section of pipe that makes all the hose connections to a point that would blow water down and away from passengers.

Also I wish I had taken a picture. If your hanging upside down in the car..lol which i was the maiden day. ( locktight on that rack-pinion set screw ok )

The head breather if mounted on top the head will allow oil to run out and down your neck...which could burn..

[standfast]

Rear lower shock mounts need to be moved in to get good control over the rear travel. Valving will be a PITA to try to make it work like that. Would be better to be about 75% of the arm length out from the inner pivot. It would be much of an issue if the shock wasn't as layed over as it is but being layed over like that and mounted all the way out near the tire will make the shock get real soft when you want it to be getting stiff.

The current rear a-arm width is going to be hard on the bushings, the rear section of frame, and the arms. Spread out those mounting points, especially on the lower arm.

If you have very little axle plunge requirements due to your use of rear a-arms, (less than an inch or so) you may be able to get away with UJ axles.

Cutting brakes aren't gonna do much of anything without a differential and based on your ATV rear carrier description, it sounds like you will have a a locked axle.

I sure can appreciate the time you put into the design. It is a lot of work and you are doing the right thing getting input on the design. It will save you a lot of headaches in the end and leave you more time to enjoy instead of fix. Lets see a pic of your rear drive setup.