Pros & Cons of A Tube Chassis?

Please go up to the search bar at the top of this page (looks like a spy glass) and enter into the search window the following:

tube frame vs pan based

You should get a ton of hits (because I just did).

Also, I was always under the impression that Tube frame IRS cars just used the normal VW diagonal arms from the frame to the wheel hub.  They should be readily available and someone on here recently posted a thread about narrowing a pair, if that's what you need.

Good hunting.

I was thinking the same thing, Gordon. The trailing arms would work great with a welded-in stock torsion housing.

If the OP is looking for fabricated trailing arms with coilovers that does narrow things a bit. In that case look at Ron Lummus racing, there are tube kits for VW Bug drag racers that use a fiberglass shell front end that COULD(with a ton of fabrication) be adapted to a light and stiff Speedster chassis.

This is what I considered when I was looking at a coupe, with either a Kitman or Ralph Albiter 356a coupe body.

IRS trailing arms are pretty easy to come-by, even on Amazon.  Here is a whole kit:  Amazon.com: Pacific Customs Irs Rear 3X3 Trailing Arm Kit with Type 1 Beetle to Type 2 Bus Stub Axles : Automotive

Just about all the aftermarket VW parts suppliers that cater to the dune buggy crowd offer fabricated IRS trailing arms such as the ones on Amazon; and they offer "narrowed" versions as well.  As an alternative that is probably more than adequate for your purpose, there is the stock VW IRS trailing arm available "anywhere".

If the tube chassis you've been looking at are constructed for torsion bar/swing axle, then obviously converting to IRS will require some cutting and welding.  If you are contemplating building the whole car yourself, then this would be the least of your challenges.  As another choice, shop around the dune buggy suppliers and you might find a tube chassis "vw pan" that is already constructed for IRS trailing arms (or they will make one for you).

@RS-60 mark posted:

IRS trailing arms are pretty easy to come-by, even on Amazon.  Here is a whole kit:  Amazon.com: Pacific Customs Irs Rear 3X3 Trailing Arm Kit with Type 1 Beetle to Type 2 Bus Stub Axles : Automotive

Just about all the aftermarket VW parts suppliers that cater to the dune buggy crowd offer fabricated IRS trailing arms such as the ones on Amazon; and they offer "narrowed" versions as well.  As an alternative that is probably more than adequate for your purpose, there is the stock VW IRS trailing arm available "anywhere".

If the tube chassis you've been looking at are constructed for torsion bar/swing axle, then obviously converting to IRS will require some cutting and welding.  If you are contemplating building the whole car yourself, then this would be the least of your challenges.  As another choice, shop around the dune buggy suppliers and you might find a tube chassis "vw pan" that is already constructed for IRS trailing arms (or they will make one for you).

Thanks for the link and I have seen similar offerings from others. This might be a n00b question but aren't these type of aftermarket arms missing the cups for the lower strut connection? That's why I thought these wouldn't work and the dune buggies don't use them.

PAN - A VW pan with title is often easier to register (and sell OCONUS) than a tube chassis.  All the parts are there from the start and functional BUT you'll want to refresh everything.  You'll want an adjustable front beam, anti-sway bars and at least front disc brakes. Old pans usually need new floor pans welded in.  I've seen them with rusted (inside out) rear engine mounting forks and rusted out front sections - even the main support tunnels can be rusted out.  The shortening process is not that bad.  Just measure multiple times and check diagonals for proper alignment.  You want it flat and squared up.  Best to have an experience welder weld it as pans are thin and the center tunnel is thick (easy to burn thru pans and not get proper penetration on center tunnel. Many front beams are rusted out so you end up buying a new beam with adjusters already installed (Brazilian). An old VW pan will be rusty and crusty so plan hours scraping of old tar boards and rust - wire brushing, priming and painting follow. Used to be you could get a complete rusty VW for free or a couple hundred dollars - with engine, trans and wheels - NO MORE!

Here's example of rear rusted frame horns - difficult to detect if not this bad and hard to repair-

If I were contemplating a speedster/coupe build, I would contact Dave Barrett.  He has been building flat dune buggy chassis forever, and will build it any length, BJ or LP front, IRS or swing rear.

www.Manxchassis.com

@LI-Rick posted:

If I were contemplating a speedster/coupe build, I would contact Dave Barrett.  He has been building flat dune buggy chassis forever, and will build it any length, BJ or LP front, IRS or swing rear.

www.Manxchassis.com

That chassis is a beauty for sure.

What do you think of the Kitman chassis?

The unanswered question here is safety. I know we don't want to devolve into who builds the safest chassis. Or even the general question of replica safety/survivability.

The safest Speedster chassis I've ever seen is Cory's car. It is tubular and triangulated and has X braces in the door openings. All the pan-based Speedsters don't have any substantial upper structure. Lane's Beck coupe(and Beck Speedster) and IM tube-frame Speedsters also have decent structures.

The reason I was looking at a coupe is so I could put a light and strong cage inside and build a somewhat safe track car. In the end I bought something else for track use(Cayman).

In fact, one of the reasons I ended up with a Vintage Spyder is due to the space-frame structure, with front and rear hoops, side intrusion bars and good spots for proper belts. Having survived a head-on crash at 60 mph in a Spyder is a pretty surprising thing for me, even 6 years after. The fact that I bought another car from the same company says it all.

@LI-Rick that is a gorgeous chassis. It would be great to include an upper structure that thoughtfully made.

@RobertCalifornia posted:

That chassis is a beauty for sure.

What do you think of the Kitman chassis?

Unless I'm mistaken, I believe the Kitman chassis is made by Dave Barrett. A definitive answer is a phone call away.

@DannyP,

I agree some side impact protection would be nice.  I am not a fan of full cages in street cars though.  I think they are dangerous, unless a person wears a helmet at all times.  The also make the car cramped, and hard to get in and out of.  

Here's one of my old drag cars, full tube chassis.

I agree Rick. That's one of the reasons my direction changed to the Cayman. And then I shelved my 356 coupe idea.

The beauty of the Vintage Spyder chassis is the side protection and hoops are there, but not obtrusive. And for those rare track/cage occasions, the 4 point bar can be bolted in and a helmet and arm restraints used.

I'd love to see a non-pan-based Speedster with some side and front protection with triangulation and good places to mount some belts(even a 3-point shoulder/lap is better than just a lap).

The best thing for Robert to do is to start with intended usage and go backwards from there.

Safety - true with the pan-based steel sub chassis there isn't much structure.  I have seen some where steel is used in the front kick panels instead of fiberglass - that would add some strength.

Anything is possible with a good subframe and rear points for 3 point IVR required high above the shoulder mounting shoulder belt area.

it would be nice thought if the inner doors had some side protection too.

Or…. I have to remember to keep singing that song this is a motorcycle this is a motorcycle or is it a mantra.

@DannyP posted:

In fact, one of the reasons I ended up with a Vintage Spyder is due to the space-frame structure, with front and rear hoops, side intrusion bars and good spots for proper belts.

This was also the same reason I went with Vintage for a Spyder. Though, mine was built by SM. It's still just a roller skate with a motor.

Here are some things to consider that have not been mentioned (unless I overlooked them).  

Registration can be different.  in some cases it can be harder and in other cases it is actually easier as some states are starting to ban "dune buggy" type builds where a pan is rebodied.  Assuming your handle is related to the state you are in, CA seems to be easy for a pan, but it can be done for a tube chassis as long as you follow the proper steps.

Quality and strength of the "tube chassis".  I've seen some that looked like they were welded with a Harbor Freight 110v flux core DIY welder and I've seen some that were beautiful.  Likewise, look at the engineering.  I've seen some of these tube chassis that were an absolute JOKE with nothing more than a few 1/8th wall tabs holding a torsion housing to the "chassis".  Center tunnel: Yes, a low profile center tunnel is a neat touch, but the center tunnel of a VW is also the MAIN structure of the chassis.  This is why our low center tunnel sits on two 0.120" wall 1x2 on edge that run the full length of the chassis and continue under the frame horns!

Geometry.  Now this one can be a hard one because some of this the average person cannot "see" and it needs to be measured or tested, AND I'd say it mostly applies to the front suspension,  but it COULD apply to the rear.  Before designing our own a-arm front suspension we tested several others.  Some just weren't a good fit for my chassis, but several had geometry that was a joke.  Literally had a few that we looked at with reverse Ackerman and bump steer off the charts!

In short, do your homework.

FYI this is not a plug for my own chassis, we don't sell a chassis alone and likely never will, I am just using mine as an example because we addressed all of these concerns while engineering it...

@Stan Galat posted:

Unless I'm mistaken, I believe the Kitman chassis is made by Dave Barrett. A definitive answer is a phone call away.

According to this article it is not. It is made by Ed Fenn

https://www.rcnmag.com/garage/...F7w0oPmkhasy8kQ8awuQ

@RobertCalifornia posted:

According to this article it is not. It is made by Ed Fenn

https://www.rcnmag.com/garage/...F7w0oPmkhasy8kQ8awuQ

Good info. Sorry to have steered you astray. I put two and two together and got 22.

@Stan Galat posted:

Good info. Sorry to have steered you astray. I put two and two together and got 22.

No worries. I'm willing to listen to all feedback and thoughts and its up to me to "trust but verify" and all that. Appreciate the help.

@RobertCalifornia posted:

According to this article it is not. It is made by Ed Fenn

https://www.rcnmag.com/garage/...F7w0oPmkhasy8kQ8awuQ

@Chris Kleber, KitMan Motors Is this still current info?

Yes, the article is on my personal coupe and it is accurate.

Ed Fenn of Fenn's Chassis Research builds my subchassis and tube chassis ( they fit either the Speedster of Coupe bodies that I sell) for Kitman Motors.  Ed is a master welder and began his career as an aeronautical frame manufacturer.  Ed is now is building for me his other passion is making 200- 300 MILE AN HOUR salt flat streamliner racers from the ground up.  He knows his craft very well and is an authority that I deeply respect. His ethics are of the highest caliber and I consider him a good friend. He is a very busy guy.

The reason particularly for the subchassis ( Ed Fenn designed it) is that in our overseas sales to Australia, Canada, Columbia, Chile, France and others  it is almost impossible to import an old VW bug into these countries.  late 1960's early 70;s VW Beetles             ( Germany made 21 million of them!) can usually be found in those counties...... so the subchassis acts as a template and verification jig for the shortening of the VW pan.  That way, the original VW registration can stay with the vehicle as it is "recreated" into a Speedster or Coupe.

The Kitman Tube chassis has an integrated VW rear horn, "tunnel and tubes" and front end mounting.  It does carry a VW VIN from the donor Bug pan.  Sometimes we can obtain previous registration papers and sometimes we cannot. Hope this helps with your questions.  Please PM me if you have additional questions.

Cheers,

Dr. Chris