Project MBT-8 914 (warning - big pics for dial-up), new build thread for my V8 tube car Options

[byndbad914]

So, I was updating my website and came up with a name for my car... though it is really more sarcastic than I would have wished for.

Project MBT-8 914 stands for (in military voice) Main Battle Tank 8 nine one four - or resembling the fact it is a V8 914 that is quickly becoming an M1 Abrams. It will be interesting to see what this puppy weighs when I am all said and done - I expect that the 2305lbs it went in at has been on a steady diet of burritos. I put a lot of cage in it for safety, so I am okay with that, but now that I am adding weight with a dry sump tank (not the tank, but the extra oil weight and hoses), a wing that feels pretty heavy, and door panels, etc (every little thing adds up of course) I am going to have to go to fiberglass decklids and lexan windshields to get back near that weight.

Let's see, how can I lie to myself... oh yeah, hey it will be more stable. Yeah, that's the ticket.

But, if you are going to war, bring a tank right? Lame metaphor for racing of course, but... well... whatever.

AJ made a bunch of progress again, from the rear iso it is starting to look like a 914 again


YEAH, we can preview pics finally!! And do multiples in one post!! Nice job to the admins!!

here you can see the upper pad set in place - notice the cut to get it in. Once it is screwed down, the seam will be noticeable but not bad.


the front will need rework to fit, but tacked into place for now until the front fiberglass is put on this week.


Also added in some midpoint mounts to the adapter plate for additional support - that 930 transaxle mounting setup is scary to me so this should take some of the load off of that area.


BTW, if you saw this link for the first time, here is the original link from the start
http://www.914world.com/bbs2/index.php?sho...p;hl=byndbad914
got messed up a little by the "great virus of 06" fiasco, so I started another here.

[Brett W]

Brett - The toe change shouldn't be too bad over a couple inches of bump - but that is left to be seen. All the links are adjustable, and I have to mess with the caster angle of the rear to tune it out. It shouldn't be anywhere near as bad as the trailing arms were. Also, camber gain is relative between the length of the upper and lower - so it is a short upper, but somewhat short lowers. I calculate 1 degree gain at 2" of bump and 1.5deg at 3" of bump. After that I drag the car on the ground, so gain becomes irrelevant. Remember, any suspension design will work if you stop it from moving laugh.gif

But good eye as it looks to be really short, but the tube diam and rod ends can be deceiving - it is around 8-3/8" long and the bottoms are like 9 - 9-1/2" long IIRC.

Actually I thought about it some more and you may have a decent design for a hybrid car. If you set it up so that the front links will toe the suspension in on braking and bump you can help stabilize the chassis. This will make the car much easier to drive for a non-professional driver.

You are right the less the suspension moves the more all suspensions become the same. That was something else that I studied with my design. In a race car with very limited suspension travel for instance, struts and dual a-arms have similar characteristics.

What does your roll center do in bump and roll? Where is it in location to the front? How is it in relation to the CG height in the rear?

Car is looking good. You plan on painting or powder coating the chassis when your are done?

[byndbad914]

Actually I thought about it some more and you may have a decent design for a hybrid car. If you set it up so that the front links will toe the suspension in on braking and bump you can help stabilize the chassis. This will make the car much easier to drive for a non-professional driver.

You are right the less the suspension moves the more all suspensions become the same. That was something else that I studied with my design. In a race car with very limited suspension travel for instance, struts and dual a-arms have similar characteristics.

What does your roll center do in bump and roll? Where is it in location to the front? How is it in relation to the CG height in the rear?

Car is looking good. You plan on painting or powder coating the chassis when your are done?

Brett - yous a smart kid and catching on to how I am setting the car up. The car will have toe change (AFAIK all indep suspensions have slight toe change through motion, it is all about minimizing it and choosing if you want over or understeer). I am going for slight toe-in to force understeer, which as you wisely mention, is easier to drive. The key of course is to not have it change from in to out or vice-versa - then the car is a mess to drive.

And you are mucho correct on the "non-professional" part of my driving (IMG:style_emoticons/default/mueba.gif)

Roll center on the front moves down (struts) and same with the rear on bump <both move up on rebound>. I have the RC set higher in the rear (not exactly calculated frankly, but drawn out on paper it is slightly higher and should roughly stay higher all the time at static settings) - again to force understeer. But that value will move around anyway as I set the car to the track (camber changes move the RC - the front will be more affected than the rear tho'). If I have to run a bunch of camber in the rear and none in the front to get tire temps correct, then maybe the rear RC would be lower than the front for instance. I don't expect that scenario of course, but the RC is a moving target; at static settings with same front and rear camber, rear is higher.

As for relevance to cg - I has no ideas unfortunately. This car has never been built, so there is no way of knowing where the weight lies until it is done - then I can weigh it and tip it if I feel so inclined (pun intended) and figure that out.

Why all the understeer tuning? Bcuz it oversteered like a mofo before at any speed. And it is the only car I have ever spun (IMG:style_emoticons/default/wink.gif) And in terms of trying to get all the RCs and ICs right - there will always be compromise and for a 914, it is space. I have 10lbs of (IMG:style_emoticons/default/stromberg.gif) in a 3lb - not even 5lb - bag.

So basically what I get is what I get and I will tune the suspension so it can be all it can be, not all it might have been if you catch my drift. I am not going for the track record with the car anyway, I just wanted to be as safe as possible because I love going really fast v. tons of corners (why I like Willow Springs), and if we could improve some things, then improve them.

BTW, I should check your blog... how is your car coming?