TheSamba.com :: View topic - Mid-engine street buggy build.

Sat Dec 01, 2007 4:03 pm

OK guys.

This is the time of year when the northern Wisconsin weather forces us to focus attention on "indoor" activities.
My good friend, Bill (one damn excellent fabricator), and I have started our newest project - A mid-engine street buggy.

Today I'll start by posting some "before" pix. It's a 4-seat full-length car.

The first 5 pix is what our little jewel looked like when we found it.

Home in the shop, being dissected.

Here's what we were after.

And here's a leftover.

Our goal is to KISS the project. Even though some of the build will be elaborate, we want the end result to be very simple and clean.

I also intend to post a reasonably detailed spend-sheet that will track overall costs (excluding the engine).

This is all I have time for today. I'll post more later... when we actually get started.

Neil

Sat Dec 01, 2007 5:21 pm

Cool project, if your looking for mid-engine buggy ideas, have a look at;

www.deserterownersgroup.org and look at the links covering GS cars.

If you need an engine cover, I probably can help? Have a look at;

http://geocities.com/bim55_01747/GSENGINECOVER.html

Good luck

Boston Bob E.

Sun Dec 02, 2007 4:55 am

Found this in an issue of 'Dune Buggies the fun car journal'. Corvair mid-engine.

Sun Dec 02, 2007 3:44 pm

The body flipped upside down so Bill could start fabricating. The bottom frame will all be square tubing.
The roll cage assembly and the lower frame will sandwich the body.
The body will be removable, but the cage must come out of the car first.

The cage assembly will all be 1 1/4" chrome moly round tubing, creating a lighter look without compromising strength or safety.

The bottom frame is sitting on the floor right side up. It sits nice and flat, but needs a bit of tweaking to get it square.
The fiberglass firewall isn't flat or square, so we'll compensate for that with the nose pieces that come off the front to the beam.

Bolted the exhaust system on an old engine/trans for mock up.

The engine/trans sitting roughly where it will go.
Nibbling away at the fiberglass a little at a time.

The rear subframe extensions now on.

The engine/trans subframe mounts are on slides so we can tweak the assembly front to rear +/- 3 inches to allow for axle length.
The axle offset will be around 20 degrees rearward, so longer axles and different CVs will be in order.
The beam is tacked in and squared. It needs lots of bracing and gussets, but we're waiting for the rack and pinion.

The frame will be exposed from just behind the seats rearward, so lots of bracing will be in order.
The transmission extensions will be where the lower control arms will mount.
The upper control arm mounts will come vertically off of this and tie into the cage above the exhaust.
In addition to clearing the exhaust, this will allow the hubs and coil-overs to be quite tall, requiring less bracing.

The steel for the cage will be ordered tomorrow morning. Then progress will slow down considerably.
Lots of bending, tweaking and fishmouths for the tubing.

Mon Dec 03, 2007 6:47 am

Cool build. Interested in what you'll be using for the rear uprights? Custom made?
Using an upper/lower A-arm suspension in the rear?
Jeff

Thu Dec 06, 2007 5:27 am

Hey Jeff,
Yeah, the rear suspension is a double a-arm setup. We're gutting type 1 trailing arms to make the rear spindles and carriers. It'll be a total ground up rear suspension build. We experimented with a trailing arm from a variant (had one laying around) but decided to re-do the same procedure with type 1 stuff (have some laying around) so the mating of the inner and outer axles won't be quite as much of a nightmare. We backed off from the Stephen King level to a more manageable Dean Koontz nightmare build. Should be much harder, small chance of success, and tons of work. Right up my alley.
I'll see if I have a pic (not sure of how to post pics here. I'll question the vwnut) of the variant spindle I fabbed up just so we could look at it and drink beer ...
Bill
Quizzats@yahoo.com

Thu Dec 06, 2007 6:27 am

Here you are.

Thu Dec 06, 2007 9:40 am

OOooo - cool home-brewed! Kind'a massive, but should have the required beef. Seems a bit masochist-ish to cut down trailing arms for the hub carrier - when they're readily available and cheap from several off road vendors? Tool wear would negate the $$$ saved!
I like the layout though, being in the midst of my own mid-engine buggy build always interested in what others have dome for those pesky uprights.
I was going to suggest using a FWD hub assembly, but that doesn't help in the axle fitting dept.

Here's mine:

A set of NOS Chassis shop uprights - takes the standard T1 bearings and axles. I lucked into these a few years ago right here in the Samba - perfect for my build.

Jeff

Thu Dec 06, 2007 9:55 am

You could look at the rear hub & A-arm components from a Mazda Miata or an RX-7 for suspension bits... Miata units are steel a-arms & I believe that 2nd or 3rd gen RX-7's had aluminum a-arms; you get a different rear bolt pattern, but gain disc brakes. Create a hybrid axle & Bob's your uncle...

And why stop with just a VW 4-speed, when you could go with a 914 5-speed? :wink:

bnc

Thu Dec 06, 2007 7:15 pm

WooHoo. The steel arrived today & Bill was on it like a bulldog on a bone.
Keep in mind that this is a work in progress.
We have a very solid game plan, but it's "tweak-as-you-go".

Nothing permanent here. We just have our toe in the water.
This represents how the upper frame-cage will sandwich the body to the lower sub-frame.

Again, much measuring to do.

Just a peek at the windsheild lay-back.

Much more to come. 8)

Thu Dec 06, 2007 7:19 pm

GS guy wrote: OOooo - cool home-brewed! Kind'a massive, but should have the required beef. Seems a bit masochist-ish to cut down trailing arms for the hub carrier - when they're readily available and cheap from several off road vendors?
Jeff

Your advice is well taken... and hub carriers were ordered today.
Thanks.

Neil

Fri Dec 07, 2007 6:15 am

Some other upright designs to consider:

Heres a neat idea from the Valkyrie US pages, a sheet metal style upright with welded in hub carrier:

Mazzone sand car upright:

Custom upright from a Mclaren kit car - looks nice!

Just some ideas to consider - I'm all for keeping things as light as reasonably possible.

Jeff

Sun Dec 09, 2007 6:02 pm

Bill and I have the rear suspension in rough design (on paper).

Does anyone have a recommendation as to who I can contact for purchasing our coil-over assemblies?

You know. Someone who actually understands the dynamics. :wink:

Thanks,
Neil

Mon Dec 10, 2007 10:22 am

Don't know about understanding the dynamics - not too many folks I've come across "in the know" regarding a high performance street buggy, custom A-arm suspension and coil-over shocks! This is definitely on the edge territory, where few tread.

I will say I'm using Chris Alston Chassisworks Varishocks on my car. Single adjustable, so I should be able to dial them in at various spring rates.

My friend used some coil-overs from McKenzies, I think they're older chrome steel-body Carrera's, non adjustable but less $$$.

There's also QA1, they make a number of different styles/sizes but are reported to be not very uniform from shock to shock regarding the valving and adjustments (ie: setting 2 shocks at the same setting but getting different dampening characteristics).

Also, Koni and Bilstein - both have coil-over versions if you've got the coin. :shock:

Jeff

Mon Dec 10, 2007 8:35 pm

Hey GS guy,
Thanks for the info and pics. When I sparked up our "test" spindle, I just welded on some bits so we could get some dimensions and play with a bit of geometry. Thanks for posting the pics. It really helps. I particularily like the Mazzone (sp?) upright, but with no more travel than we need for this car, the 4 link setup may be a bit much. I have seen 4 bar setups that were "pinched" at the front mounts. The forward end of the bars mounted closer together than the rears. This would give the car a bit of "squat" under acceleration as opposed to lifting the rear. That's what I'm trying to get to. We don't need a bunch of ground clearance for this beast. I've also been toying with the idea of using a setup like this, but with a 2 bar (wishbone) lateral positioner instead of the equal length 4 bar one shown. What do you think? I know it will have some torque reaction that the 4 bar eliminates, but I do like the idea of being able to adjust the upright in the fore/aft plane. Seems the torque reaction would not be nearly as severe as well, lessening the need for "massive" a-arms. I tend to "massiveize" all of my suspension stuff. It's a street car. Don't want anything coming apart at speed!
What do you guys think?
FYI: Neil ordered so much stuff for this beast that the ups guy is wearing a truss now. We got the rack and pinion stuff and the new seats on friday. I"ll be fabricating a temporary mount for the pedal assembly so I can fit the seats. Once that's all put to bed, I can weld up the cage assembly. I have most of the cage parts bent up and fitted, just need to position them fore/aft before final welding. After a conference with Neil, we moved the engine back about 5 inches to accomodate the seats and not set them on fire from the front exhaust heat. This preempts them from falling into the builders category TTHTAB. ("Things that happen that are bad".) We're also working out a firewall scheme that keeps the engine exposed (otherwise, what's the point?) without wrapping up hair, fingers, elbows and other misc body parts in the fan and moving bits. (see above explanation of TTHTAB) We've got some solid plans on that, but more ideas are always useful. You sand rail types (we have sand up here too! It's under the pine trees...) have probably grappled with that one already; like the last time you took Rob Zombie for a spin...
Bill

Thu Dec 13, 2007 3:52 pm

Hey Bill/Neil,

I know you guys have been mocking up with a VW trans, but kind'a wondering how you're doing a later model IRS trans in a mid-engine application. Can the ring gear be swapped side to side to work mid-engine like the swingaxle? I know most formula car transaxles (based originally on the VW case - Hewland and Webster to name names....) inverted the trans to work this way. Can a dual side cover IRS trans be modified for mid-engine?

Something you might be interested in..... What about running a Subaru transaxle? Bremar makes a conversion kit to adapt the 4WD WRX trans to 2WD/FWD, and some just out conversion flanges allow using T2 CV joints and 33 spline axles..... Wouldn't that be something.. VW engine pushing a Subaru 5-speed transaxle??!! It would definitely be different!

I've got pics of the trans and more info on this if you're interested. I think the cost would be comparable to a nicely built T1 trans - including a good used WRX trans, the flanges and 2WD kit. You'd still have to work up your own cable linkage and mounts, but????? Tricky part might be the adapter kit necessary, but the Subaru engine to VW trans is common - seems like a reversal of the idea might be doable?? Cool idea in my mind at least! It's just too bad there's no (good) way to use this trans in a rear engine buggy!

Cheers,
Jeff

Thu Dec 13, 2007 5:53 pm

I have often thought of using the whole drivetrain out of a Prelude/ Civic or similar in a midengine layout. Or an Acura TL drivetrain (5 Cyl, 170 hp..170ft lbs of tq)as it has a transaxle similar to a VW layout.

If someone would make a frame to use a civic drivetrain they would sell like crazy......think of the hop up possibilities

Fri Dec 14, 2007 8:45 am

GS guy wrote: Hey Bill/Neil,

I know you guys have been mocking up with a VW trans, but kind'a wondering how you're doing a later model IRS trans in a mid-engine application. Can the ring gear be swapped side to side to work mid-engine like the swingaxle? I know most formula car transaxles (based originally on the VW case - Hewland and Webster to name names....) inverted the trans to work this way. Can a dual side cover IRS trans be modified for mid-engine?

Something you might be interested in..... What about running a Subaru transaxle? Bremar makes a conversion kit to adapt the 4WD WRX trans to 2WD/FWD, and some just out conversion flanges allow using T2 CV joints and 33 spline axles..... Wouldn't that be something.. VW engine pushing a Subaru 5-speed transaxle??!! It would definitely be different!

I've got pics of the trans and more info on this if you're interested. I think the cost would be comparable to a nicely built T1 trans - including a good used WRX trans, the flanges and 2WD kit. You'd still have to work up your own cable linkage and mounts, but????? Tricky part might be the adapter kit necessary, but the Subaru engine to VW trans is common - seems like a reversal of the idea might be doable?? Cool idea in my mind at least! It's just too bad there's no (good) way to use this trans in a rear engine buggy!

Cheers,
Jeff

Yes, the ring gear can be flipped in a dual side cover IRS trans - and that is what we are doing.
I know there are a lot of very kewl engine/trans combinations that can be done.
We're not adverse to that (as Bill's Fiat powered Laser 917 will attest to), but as I mentioned in the opening post...
"Our goal is to KISS the project. Even though some of the build will be elaborate, we want the end result to be very simple and clean."

Love all the input, however.
Neil

(more pix this weekend)

Sat Dec 15, 2007 3:57 pm

OK. Just a quick update on the cage fabrication. Bill has been busy.

After the main hoops are tacked, it's time to get out the masking tape.

Many of you have done this stuff before, so you know...
the body centerline is usually "not" the same as the thrust line.
So some tweeking is in order to make it all look correct.

A plywood mock-up to position the pedals.

Then confirm the seat locations.

The reservoirs will be accessible under the hood. We will not be using a stock VW fuel tank.

The pedals installed. This pic also shows how the cage assembly and the lower frame secures the body.

Stay tuned. More on the entire cage and frame soon.
Neil & Bill.

Thu Dec 20, 2007 7:16 pm

Quick update...
Bill tacked in the shifter mount.

And... woo hoo
Coil-overs arrived. Now comes the fun stuff. 8)