Hi everyone,

Long time lurker, first time poster here. My name is Justin and I currently live in Pittsburgh, PA. I am a mechanical engineer and work for Carnegie Mellon university building a prototype autonomous off-road vehicle for the military. I like to mountain bike a lot which is where my username came from. I also post on www.minibuggy.net as minibajaman.

I have never owned a Pilot or Odyssey but have always wanted one since I was a kid and had a go-kart. In college, I joined the Mini Baja SAE team where I worked on designing and building 4 different buggies over the years. Even though they are kinda slow, racing them against 100 other teams at the same time is some of the most fun I have ever had.

After I graduated, the SAE team went through a restructuring and needed to clear out space in the shop. I offered to take one of the older buggies out of the way in exchange for continued advice on the project, sort of as a consultant, since the team was now mostly made of new members with little experience. So now I had one of better buggies we had built, but obviously the 10hp Briggs was no longer acceptable. This was late fall of 2007.

Long story short, I decided on putting a sled Engine into my buggy along with substantially modifying the rear end to get it to fit and increasing the overall length for stability. I ended up with a '94 Polaris 440 liquid because it was cheap, designed as much as I could in SolidWorks, and worked on building it with my roommate/co-worker on weekends. Luckily we are able to use the facilities at work (machine shop, weld shop, waterjet) so that helped a lot with the build. Three weeks ago, I finally got the buggy running and driving again. It is not completely finished yet, still a bunch of little finishing items to do, but at least I can drive it now.

I would like to go to some of the races this summer if no one minds me joining the Pilot/Stadium Lite class. I think my machine is very similar to a Pilot in terms of size and top speed, but does have a quite a bit more horsepower. Racing is just as much about driving ability as power anyway. I was thinking of attending the GNCC events in PA and OH, and also some of the NOORA races and anything else that may come up nearby.

Anyway, here are some pictures and a quick video of my buggy.
http://www.youtube.com/watch?v=jrlXKf8tn8U

I have a full album of the build process here:
http://www.facebook.com/album.php?aid=2 ... 7bd9c3ae24

Welcome aboard Justin,

I'm quite the mountain biker too although I'm now mostly riding a hybrid on the Katy Trail here in Missouri. I just go a couple miles to the trail head and go North or South and make a 30 to max of 35 mile trip out of it. There are a few really cool off road trails off of the Katy but we need about 2 weeks rain free to enjoy them.

Your car looks cool. I like the way you integrated the chain/gear box into the design. Does it have forward and reverse, can't tell from the pictures but i do see a lever on the side of the box. You and your car will fit into any race you want to drive to, it's a really laid back atmosphere. Just make sure you have up to date safety gear and some sort of hand/wrist restraint......safety first! Talking safety though....you really should put a heatshield of some sort over that pipe or better yet consider rerouting it behind the seat somehow. That could really cause some serious burns in a bad situation. No offence ment!

Hope to see more of your car on the board.

Tom

I just watched your video, consider either going to a softer spring or using heavier arms because you have way to much wheel spin. You need to get the power to the ground and put more load on the Engine. When you spin a lot it just throws too much stuff in other peoples faces and you don't go any faster. Tires wear out quicker blah, blah blah

Looks like fun. Just throwing out some stuff. Again no offence ment.

Tom

Hi Tom, thanks for the welcome. No offense taken, I always appreciate constructive criticism. I came to this board because there are a lot of people that race on here, and also for the 2-stroke expertise because I don't know that much about them.

You bring up many good points, all of which are on my list of things to address because as I said, the buggy is not quite finished yet. The sled chaincase I am using does have forward and reverse, which is the main reason I did use it. I still need to make a shift lever for it. I have a helmet and neck collar and harness, but still need to get some wrist restraints. I have header wrap to put on the pipe, just haven't done it yet, and I have also added a firewall in between the Engine and seat since those pictures were taken. The pipe is not near the driver when in driving position, but when getting in an out it is possible to put your arm near it.

The clutch turning needs to be changed, as the current clutch is not the one that came on the Engine since I added electric start to it. You are right, it does not put power to the ground very well. I think I could really use some wider rear tires as well, the current ones are only 24x9 because I had them laying around, but something in the 10-12" wide range with a flatter profile should help as well. The suspension also needs to be dialed in, currently the rear is a little stiff and both ends could use some damping tweaks.

As I said, lots of little things to do, but after working on it for so long I just needed to take it out driving a few times even it it's not really finished yet.

If your riding spot is close take it out after every change/update/rebuild/mod so you can see what it did and if it's going in the right direction. The more you ride the more you will notice....ask me how I know!

I watched a bunch of your video's on the car....your not far from where I believe you want to be. Keep the video's comming.

Going to a wider flatter tire will help but softening the rear suspension will do more for it. It will let the car squat shifting the weight to the back tires. I like a super soft suspension. In my opinion your suspension needs to be as soft as possible but strong enough to take the biggest jump you will come across. My Drakart is set up so soft that it will bottom sometimes when I go down a dune full speed at the bottom but still has enough spring to take a 40 to 60 (guess!!!) foot jump at some 10 to 15 ft up in the air. I'm not sure how much you have played with the Fox Airs but they have some major tunability.

Tom

Hi and welcome to the site.

What is the reduction ratio of the FNR box you used off the sled?

What is the reduction from the output of the sled box to the rear axle?

Going to install an air box? Ask OdyPilot on minibuggy site if he thinks you need one..

How about some specs on your buggy, length width height, suspension travel, weight etc.

Any idea on the HP ? Assuming its 70-90 hp in the sled?

Hi hoser,

Reduction of the sled FNR box is currently 39/21 = 1.86:1. I bought a 16 tooth sprocket for it, but need to get a shorter chain to use it.

The chain box to the rear axle is currently 40/12 = 3.33:1. I initially planned on a 10 tooth drive, but was worried about such a small diameter sprocket holding up.

The current overall gear ratio is 6.2:1. This is a little higher than I wanted as I was planning on around 8:1, but there is certainly no shortage of torque right now.

I may do an air box eventually. Depends if I end up riding in the mud/water or only take it out in drier conditions. I agree it's a good idea to have one, but it's not as high on the priority list as other items right now.

I believe the horsepower is around 70-75. The Engine, CVT, and FNR chaincase is from a '94 Polaris Indy 440. The air intake and Aaen exhaust probably allow it to make a bit more power than stock, but I have no way of knowing how much.

Specs are:
Overall width: 62"
Overall length: 92"
Overall height: 58"
Wheelbase: 65.5"
Front wheel travel: 12"
Rear wheel travel: 13"
Weight: haven't measured it yet, but estimating under/around 550lbs
4 gallon gas tank
Four wheel disc brakes, dual master cylinders
Rack and pinion steering, 1.5 turns lock to lock
Fox 2.0 air shocks all around, 8.5" stroke front, 10" stroke rear
Rear hubs, brakes, bearings, CV joints from Polaris Sportsman ATV
Front hubs, bearings, brake rotors from Polaris Predator ATV
All other suspension components and frame custom built

I am almost done working on my buggy. I have added in a few more tubes for better protection, and I am in the process of making new body panels and adding mounting tabs for them instead of using zip ties again. It still needs some fine tuning in the rear suspension, clutching, and possibly carb department but it is working good enough for now so I plan on doing the next GNCC race. That should certainly highlight any weak spots. Anyway here are some recent pictures.

Heat shield for sure I had a 250 once that when you reached back looking for the harness you burned your arm on the after market pipe only took me a few times then I installed a heat shield lol

If you don't get the air box done when you ride in mud or water just take a towel and some zip ties and make a shield or tent out of it to protect the filters the cloth will breath and let air in but help shield it from the brunt of the crap that might be splashed or flung onto the pod filters.

Yeah that is on the list of things to do eventually...for now I am going to wrap the pipe with header wrap so at least it's not exposed bare metal. I already touched my arm to it once when getting out, for sure, but didn't leave too bad of a mark.


That's a good idea, I'll keep that in mind, thanks. At the Mines & Meadows place I rode at the buggy got pretty muddy, but the filters stayed fairly clean. If it was more water then mud though I could see a potential problem. Here's a picture from after that ride, you can see the filters near the yellow dipstick.

that's a lot of mud where you don't want it I would work on something to minimize the mud in the Engine compartment, fenders, maybe something off a ATV can be used? Side panels like the Drakart has might help also? Problem with mud is most of it is acidic and corrodes everything it works its way into threads and electrical connections, gets past rubber seals, clutches wont last long... Fork seals off a motor (( Internal Combustion Engine ? )) cycle for the shocks?