modifying an old VW splitscreen van, side impact risk

[dubin]

Hello,

First post. I would like some input from knowledgeable vehicle body structural engineers around a debate that is raging in the Splitscreen van community (whilst most of the people involved have been working with the vehicles for 20+ years none in my opinion have your level of knowledge).

Setting aside that a split screen van built in the 50's has little safety anyway as you are basically sat inched away from a head on collision with no protection, we are debating the safety of a side impact at the b-post area behind the front wheel!

why?

Well VW produce several different type of vans and a member wishes to convert their bulkhead panel van to a swivel seat van by removing the bulkhead and wonders what, if any, additional strengthening should be added.

To start the debate these where the models produced by VW and the bulkhead/strengthening used.

1. Panel van, bulk head side to side from B-pillars, raised rolled floor side to side under seats.

2. Walkthrough, 2 tubs around the rear of the front seats, raised floor cut in the middle and lower section added to from a walk-through area.

3. Swivel seat, same as above with the tubs cut right back to just form triangular support at the b-post.

4. Flip-seat, same as above with the triangular upright supports removed.

Below is a bulkhead model with the bulkhead cut out

At the B-post area is a metal hoop running up the b-post, across the roof and under the floor is one of the main chassis section cross members.

So if the bulk head of a Panel was cut out you would be left with 4(a flip-seat) model, how much weaker is this and did the original bulkhead offer any protection from a side impact or is it just stopping goods in the back of the van flying forward and hitting the driver?

What additional support should/could be added to provide greater protection?

I realise we have no data for any real calcs, but what engineering principles come into play here that could be used to guide a decision?

 

[MikeHalloran]

>>>When was the last time a NASCAR or Drag car had a head on crash while racing.<<<

The last one I remember is Mark Martin hitting a concrete wall at ~100 mph in a secondary collision after losing his brakes in the first collision. The television coverage was excellent, and included Mark holding his head post-crash. The TV guy asked why, and Mark said "If I hold myself where it hurts, you can't show it on TV", or words to that effect.

The one I remember before that was Neil Bonnett hitting the _only_ accessible wall at 180+. It was not survivable, and the coverage was rather subdued.





Mike Halloran
Pembroke Pines, FL, USA

 

[dubin]

In ‘Days of Thunder’ he drove his Nascar head-on into the side of another car that had spun!
Not trying to produce a race car here, just seeing if it is possible to make the front of a split van any safer. As it stands there are 2 walls of 1mm steel about 6” from your legs and then fresh air on the other side, there is also a bumper which bolts directly into the chassis. Working with the fact that it is impossible to build in any crumple zones you are left with 2 options:
1. Do nothing, leave it as it was designed in the 1950’s.
2. Re-enforce the front somehow to protect the area.
In either case I would think there is no crumple zone to speak of, but by doing number 2 if you where to survive then you might be able to walk away. I don’t know what sort of crash safety was conducted in the 50’s, perhaps they have already built all the strength you need into the chassis/bumper and I am worrying about nothing! But what about the lowered vans whose bumper is now below the main impact point, would re-enforcing the inside structure add back in the protection they would have had with their bumper?

 

[evelrod]

All this talk of roll cages in such a vintage machine is totally irrelevant to any safety concerns. It's a vintage auto...Drive it like any other antique or vintage auto and you will be fine. Drive it like a modern car, fast and furious, six feet off the next cars back bumper...Yeah, the roll cage may hold damage to the VW down a bit...Ain't gonna help you one little bitty bit!!!

Having seen a VW van with all the steel tubing added, while it was quality journeyman workmanship, did not impress me. Drive it like it was worth a million bucks and you'll be fine.

Related topic---Safety is all about perception. Relevant to the time period in question. Today, the van is not what I would call a safe ride. In 1950's, no one thought much one way or another. E.g., my first race car had a roll bar fabbed from water pipe...seat belt from a P-40...fuel cell was a five gallon Jerry can tied to the roll bar support in the boot. Personal protective gear was a pair of Levi 501's, cowboy boots, T shirt, a metal helmet with leather side panels, a pair of aviator goggles and, a pair of fingerless Italian driving gloves. State of the art mid America dirt track 1950's!!!

Many of you have seen the video of my crash in 2003. One of the most impressive things about it from my point of view was the sound. Clunka-clunka-clunka...No TV crunching sounds. No screeching of torn metal. Just the clunk of a solid rollover structure bouncing off the race track. That type of crash on the street would have been fatal to the driver. I had only a few bruises where my harness crossed my shoulders. It you think this VW van involved in such an incident would protect the driver without all the NASCAR type gear, you are delusional.

Rod

 

[patprimmer]

Days Of Thunder was a movie and fiction, not a race.

Walls and rules in racing are designed to avoid direct head on hits so there are tyres, sand traps, nets or angles designed so things slow or bounce off rather than come to an instant stop.

Public roads are VERY different and that was my point. What works for a race car does not work for a road car.

Like Rod says, the VW is an old design and was acceptable back then. Conditions, standards and expectations have all changed.

You have several options.

1) Do subtle mods that will have some minimal benefit.
2) Do major obvious mods that will work better, but still not to modern stds and will defeat the purpose.
3)Drive it with due respect for what it is. This applies on top of points one and two anyway.

I drive a 1912 model van on occasions.

It has a full wooden body.
It has canvas windows.
It has no windscreen at all.
It has a high centre of gravity.
It has suspension with very poor axle location.
It has wooden spoke wheels.
It has 2 wheel brakes on the back wheels only and they don't work all that well.
It has no working lights at all.
It is so slow, being rear ended can be a real concern if due consideration is not given to where it is used.
We drive it with a great deal of thought, care and respect.

Regards
Pat
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[profjohn]

Hi, I’m new to eng-tips so please forgive me if I take a while to get used to the custom and practice here. The whole subject of safety and older cars is something that interests me greatly as I compete in rallies and speed events and I’m building a V8 powered MGB GT. The VW camper question is particularly topical as my wife would like us to have a splitty to take dogs and grandchildren out in.
My view on this is to separate out the competition car requirements from the road car crashworthiness needs. The roll cage serves three purposes. 1. It creates a strong and stiff passenger cell that increases the survivability in high speed impacts and roll overs. This requires triangulation and high section stiffness from large diameter hollow sections. 2. It provides additional energy absorption by plastic deformation, buckling and collapse with limited displacement during a big accident – I know, I rolled my Escort rally car into a tree in Germany and bent the roll cage but walked away unscratched. This requires good ductility and toughness in both the steel and the welds. 3. It increases the stiffness of the bodyshell to the benefit of the suspension and the durability of the shell. This is much more limited on historic rally cars because of the restrictions on roll cage design. Again this is governed by section stiffness and triangulation. Nowhere in here is high yield strength important. It only comes into play with serious competition cars where the elastic stiffness is needed with low weight and so thinner walled high strength T45 tubing is used then.
In a road car, my view is that updating older cars is about reducing the likelihood of serious injury in a typical road traffic accident. So, apart from things like better brakes, tyres and dampers, and then trying to pad out the stiff structures in the dashboard, we are down to finding ways of increasing the energy absorbing capacity of the bodyshell and chassis. As you say, the problem with the forward control style VW vans is that there isn’t much to play with.
Thoughts:
1. Keep the front bumpers and the nerf bars. Unlike some scenes, de-bumpering doesn’t seem to be the fashion in Splitty circles. The inner structure that you’ve made will help a great deal.
2. Look at inserting mild steel tubing inside the A and B pillars and welding it in to as many places as possible. A relatively small section is fine. This was done in the A pillars of the works TR7 V8 rally cars in addition to the full roll cage.
3. Seam welding or brazing the bodyshell. Short, 1” lengths, of weld or braze, every 4” or so, helps to transfer load around the structure. Fully welding the seams will make it stiffer, but will also give a preferential path for tearing before getting the benefit of the plastic deformation of the larger area of sheet metalwork surrounding the welds.
4. Boxing in open channel sections helps by increasing the elastic stiffness, promoting plastic buckling and collapse and providing more steel to absorb energy by plastic deformation.
5. Tall, narrow vehicles like these vans are vulnerable to roll-over. A big steel roll cage will make it worse by raising the centre of gravity..... Strengthening the side window pillars by boxing, seam welding and inserting small tubes will all help to reinforce the upper structure.
6. Removing the bulkhead will reduce the capacity for energy absorption by plastic deformation on side impact. Some sort of gusset from the B post into the floor will help a little to transfer load into the floorpan.
7. More extensive work might include forming lengths of top hat section 16 gauge sheet mild steel and intermittently weld them into the cab floor. Is there any space underneath? Or even across the inside of the front panel to tie the A posts together. Similar sections on the inside of the doors might help too.
Hope this helps.
John

 

[evelrod]

Welcome, John. Your ideas will work just fine and yield a great little bug van that can survive a roll down a 200 foot hill with only a few 'minor' repairs....Bang out the tin, wash out the blood and, repaint....Sell to next of kin.

Rod

 

[profjohn]

Rod, I may have misunderstood the purpose of this thread. Apologies for straying into your play pen.

 

[evelrod]

Bad start, John. Never apologize for stating your opinion or belief if you are certain in it. You have just as much right to post as I do. If you are off in left field, you will certainly hear about it and PDQ at that. I'm really old and sometimes my likes and dislikes make me a bit intemperate and sarcastic. I like pretty much all that you posted except the V8/MGB deal. Even the factory screwed that up. That and I'm not a fan of making bug vans into hot rods.

Rod