Hopkins Baja Design / Build Thread

Hey guys,

So Baja is very interesting in the way that there is a lot of innovation, yet most teams are hesitant to reveal how they do something in fear that they will be copied and beaten with that respective technology.  As a senior this year at Hopkins, I have had a number of lectures on Intellectual Property and Patents.  One of the interesting things about a patent is that it provides a way for an inventor to get credit for their invention, while still revealing it to the public and adding to the overall body of knowledge.  This is why people patent things rather than just keeping them secret, it allows a way of getting credit for an idea.

Before this forum went up there was no way to have a central repository for ideas that were credited to your team.  But!! Now that we have this sweet forum, with the capability of having threads, it is now possible to make a long design/build thread which documents ideas that you had and simultaneously share them with peers.

I think we as a team come up with some pretty cool stuff.  Obviously its nothing earth shattering, but I think that as Baja continues to improve it will be nice to know who came up with an idea first.  A great example of where this did NOT happen is the great TTU vs. ETS wheel covers debate

So with that in mind, this thread will document our design/ build progress.  We pretty much have our car designed, minus some small stuff but it will give you a good idea of the stuff we did and why we did it.  Also once the car begins construction we will be uploading pics of our progress along with text on our methods.  I mean wouldn't it be cool if our car construction methods made it into the Baja vernacular, like bending tubes the "Hopkins" way !! probably not, but its possible.


So with that as an introduction to the Hopkins Baja 2010 Thread, Lets begin.........


Edited by jhu42 - 2009-Nov-12 at 10:50pm

Looks good man.  That's a pretty compact little ride.  We suffered from the same problem that you did in the weight distribution area although ours was slightly better at 36:64 :)  We're taking similar steps to fix the distribution, including shortening the driver area and moving the engine down and forward.

Just a tip from our '07 car, don't use the butt joints for the RRH, make them mitered joints.  If you run them like that you are far more likely to deform the tube in a "crushing" manner.  Our LC in the RHO is like that and after several hard rolls you can see visible deformation in that tube.  True it's easier to make, but in the long run it's my experience that the miter pays off.

Originally posted by CLReedy21 Just a tip from our '07 car, don't use the butt joints for the RRH, make them mitered joints.  If you run them like that you are far more likely to deform the tube in a "crushing" manner.

Edited by DrewT - 2009-Nov-11 at 3:18am

Have you run your frame through any FEA yet?  I'm asking because this is the first year we are not bringing out RHO down to meet the front of the car.  Instead it stops around where the shock mounts are like many other teams do.  I noticed that you don't have any other front bracing to distribute the forces (like from where the RHO meets the frame forward to the bumper) in a front end impact, which is what my concern is.  If you have run FEA what loads did you apply and what were the results?  Ours isn't 100% drawn yet otherwise I'd give our results to compare. 

Hey,

nice design, here is a little snap pic of ours and i cant help see the similarities! We are also reducing number of tubes and their respective thicknesses. My main design point this year is ease of fabrication, for example, we will machine two holes+insert in the bottom rear members in the frame before welding to mount the gearbox, less welding, less jigging,  this just requires a little foresight.
http://minibaja.mcgill.ca/?page_id=92


Edited by jeiB - 2009-Nov-11 at 5:55pm

Hey JeiB,

Yeah, we rebuilt the rear of the car.  It was not fun, but the car did turn a whole lot better with the improved weight distrubution.  but at that length we started to have problems with the length of the car limiting the turning cicrle.  I was looking through the Alabama competition car data sheets ( Horray for data mining) and found that there is a grey area for successful car's wheel base,  seeems about 65" is the upper limit and it goes down to 62"  or so.  I think being in that range for wheel base and having as close as possible to a 50/50 weight distrubution is the key to having a car that turns well. 


Oh also RobZilla, we do not have fea on that yet, but we're not going to hit any trees.  The competition is usually designed with that in mind.  I have the philosophy that if the rules don't say to have a tube, then not to have one.  But thats just me.

Originally posted by jhu42 ... there is a grey area for successful car's wheel base,  seeems about 65" is the upper limit and it goes down to 62"  or so.

I disagree.

Land Mo:
1) 60" (RIT)
2) 66.5" (USF)
3) 62" (Louisville)
4) 60" (UMCP)
5) 59" (Auburn)
6) 60" (U. Mich)
7) 62" (Queens)
8) 57" (ETS)
9) 61.5" (Northeastern)
10) 70.5" (TTU)

S&T:
1) 60" (RIT)
2) 60" (UMCP)
3) 70.5" (TTU)
4) 59" (Auburn)
5) 57" (ETS)
6) 62" (Louisville)
7) 66.5" (USF)
8) 61.5 (UMBC)
9) 60" (Sherbrooke)
10) 61.5" (Northeastern)

Endurance:
1) 61.5" (Sherbrooke)
2) 57" (ETS)
3) 67" (Michigan Tech)
4) 60" (UMCP)
5) 62" (Louisville)
6) 60" (RIT)
7) 70.5" (TTU)
8) 63" (Kansas State)
9) 58.5" (Fairmont State)
10) 68.5" (Pittsburgh State)

It seems to me that all the successful cars happen to be 62" or less, with the notable exceptions of Mich. Tech, TTU, Pittsburgh State and USF (all over 65"). Which to me proves absolutely nothing except that wheelbase isn't really a big deal until the numbers start getting crazy.  I mean, if TTU can whoop up on 78 other teams on a tight twisty Land-Mo course in a car with a 70.5" wheelbase, then there are much more important factors at play.

But yeah, weight distribution FTW.


Edited by Old Greg - 2009-Nov-12 at 11:00pm

I'd also disagree with the criteria of wheelbase and weight distribution being the most important factors to a car's success in maneuverability.  Our last car had a 66" wheelbase and a 40/60 weight distribution, one of the lowest CG's you'll see in Baja, and a spooled rearend.  It was 3rd in maneuverability at Illinois and 17th in maneuverability at Oregon.  The biggest factors I see are the suitability of your vehicle to the particular course (it changes every year), and the skill of the driver.  Close behind those would be the simple performance of the car in acceleration and speed (getting from corner to corner faster is a big deal).  Our last car broke all those generic rules about the wheelbase, trackwidth, weight distribution, ect., but is a really nice handling car because the overall package is tuned to work together.  The anti-roll bar lifts the inside rear, the front cutting brakes provide a little extra turn initiation to get the power-on oversteer to happen, and the very soft but well-balanced suspension allows the driver to manipulate the car with all sorts of weight transfer tricks, and the low CG means the car can do all of that stuff, even when the course is off-camber, without having to slow down or risk rolling.

Originally posted by jhu42 Cornell's car will always have more carbon fiber

Did you see USF's car last year? We had carbon composite RIMS!!!


Build progress, will be up as soon as I can get the pics I have resized, and put on our website. Basically in a week we went from nothing to RRH and forward tacked in and in place.

The frame should come off the table and burned in this weekend.

If your wanna see the current progress www.usfracing.com click on Who's in the Shop > Fabrication Shop Cam


Edited by USF Stick - 2009-Nov-12 at 9:24pm

Originally posted by USF Stick Originally posted by jhu42 Cornell's car will always have more carbon fiber Did you see USF's car last year? We had carbon composite RIMS!!!

Dang!!!

Hey Stick!!

Can't believe I forget the coolest team that's better than us :)

CF Rims! How are we supposed to compete with that, lol. 

And you have a Bus!!  Oh well, 5th place is not so bad!!

Originally posted by Old Greg Endurance: 1) 61.5" (Sherbrooke) 2) 57" (ETS) 3) 67" (Michigan Tech) 4) 60" (UMCP) 5) 62" (Louisville) 6) 60" (RIT) 7) 70.5" (TTU) 8) 63" (Kansas State) 9) 58.5" (Fairmont State) 10) 68.5" (Pittsburgh State)

Originally posted by jhu42 There are of course going to be some that think this is a bad idea.  That's ok.  "Adam, your giving away your team's secrets!! "  Well, here are the facts, We're never going to win Baja.  Michigan's car will always be lighter, Cornell's car will always have more carbon fiber, and Sherbrooke's car will always be faster.  So at best I finish in 4th place, lol, just kidding.  However, even though my team will never win, I can get my team recognized by my baja peers for the innovation we have worked on.

Originally posted by USF Stick Originally posted by jhu42 Cornell's car will always have more carbon fiber Did you see USF's car last year? We had carbon composite RIMS!!! Build progress, will be up as soon as I can get the pics I have resized, and put on our website. Basically in a week we went from nothing to RRH and forward tacked in and in place. The frame should come off the table and burned in this weekend. If your wanna see the current progress www.usfracing.com click on Who's in the Shop > Fabrication Shop Cam

Carbon composite rims FTMFW. We used the same thing on last years car and will be transferring them to this car too.

If you want to do some of the cool stuff, try to get helpful sponsor(s), we're looking at the possibility of doing a 3 piece steel/CF axle this year.

Originally posted by Old Greg Adam, all I mean is that correlation is not causation.  62 inches may be the end all, be all of wheelbases, I don't know.  But don't mistake the fact that a lot of fast cars are in that ball park with the idea that it was their wheelbases that made them fast.

Right, there are other things at play that make the fast cars fast, of course.

CVT tuning, Weight, Driver skill.

I understand what your saying.

 

Again it is all speculation, but assumingTTU and USF used the same swingarm setup,   had the same weight, same tires, etc., with a higher cg TTU would probably oversteer more IMO than USF in terms of actual inches of lateral slide in a turn, but because of TTU's longer wheelbase, the measured "degrees of oversteer" would be about the same. Further proof (speculation) that you can reach the same end result in a variety of ways.

The big thing with composite rims it they are able to deflect elastically, and then return to their original shape, and thus not bend and cause the bead to break and loose air. They also typically come with bead locks to keep the wheel on the rim at low tire pressures and when 'flat'
We are looking into them right now, but are still trying to determine if it is worth it. Any other teams have experience with either composite rims, or even just a bead lock aluminum rim? 

Agreed. Someone can start a new thread about carbon composite rims if they want to continure discussing it.

Originally posted by dillon_b12 What's the obsession with carbon composite rims?  From what I've heard from sport ATV guys, they leak, aren't as light as Douglas(depending on label), and cost about 3x more than Douglas.

The main cons of the rims are Cost and Weight, but the big pro is the durability.

Last year, across all 3 races we changed ONE tire. A sharp rock pierced the tire sidewall within the last hour at Wisconsin.  That includes hitting the railroad ties in Auburn at full boar EVERY LAP.

More pics dammit!

looks like you don't have the 12" required that extends from the lowest point of the seat to the upper LC on the RHO.

Hi guys!

I dont have more pics of the car :( sorry, because we are still finalizing stuff like the suspension and steering.  However, when its done I'll upload the SW model for you to check out.

Answers to the questions from before.

Wheelbase is -> arg! I forgot, will check tomorrow
Seat is the Jegs Highback Pro II with the seat cover
http://www.jegs.com/p/JEGS/JEGS-Pro-High-Back-II-Race-Seats-and-Seat-Covers/1118147/10002/-1
Really cheap seat that is quite comfy!  Really low for the cost report.

tire size: fronts 22x7 Holeshot XC , rears 22x8 Mudlite AT

Charles ->  Good catch!!  I see what your saying!  Thanks for the note.  I will make sure to change that :)



Ok!!

We started construction back on Jan 3, and have just finished day 5.  Hopkins has a nice Intersession period.  Class for us starts back up again on Jan 21, which gives us a lot of time to work on the car

Putting in some long days but its paying off, we are moving ahead quite rapidly with car construction.

Below are some pics along with some captions of how our construction works.





Here's our setup for jigs.

We use a smooth pressed cardboard with high quality wooden blocks.  Pretty simple.  This is our RRH being constructed and assembled before being welded.





Here was our main step today.  One of our guys had the idea to use ratchet straps to hold the notched frame pieces together for tack-ing.  He saw it on the USF website, thanks guys! 

I guess I should mention that we do our tacking with a small portable MIG welder in our labspace, but do the actual welding in our Welding room with a really nice TIG.  I think its a great combo, the trigger style of the MIG makes it really easy to get a lot of tacks down vs trying to balance a foot pedal for tacking with a TIG.




Here's where we are at so far.  Lots to go for sure, but hey, its progress.

Cool, ok well I need to get some rest....

Catch you guys later,
Adam

Looks great so far!  We use the method to jig the frame of the car.  Same tube bender too!

We started fab work this Monday and here is our progress thus far:

Edited by Redhawk_Racing - 2010-Jan-10 at 3:14pm

We use a plane of bend bracket for 3D bends, very simple (I made our team's) to make and use.  http://www.offroadfabnet.com/forums/showthread.php?t=924

Helps for 3D bends, and we also use it to make sure we have notches on either end of a long tube in the exact same plane.  Or if notches need to be in specifically different planes, whatever.  Way better to just turn the tube a known amount than to tilt the head of the mill.

Hi guys,

Edited by jhu42 - 2010-Jan-25 at 3:53pm