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modifying an old VW splitscreen van, side impact risk

modifying an old VW splitscreen van, side impact risk

modifying an old VW splitscreen van, side impact risk

(OP)
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?
 

RE: modifying an old VW splitscreen van, side impact risk

I have a friend that is nuts about VW vans.  He is a competent builder and has done several over the years.  After a minor front end crash he went about "strengthening" the thing.---(That's in quotes for good reason.)---Steel roll cage type construction around the front and side footwell areas along with a very nicely concealed rollover bar in the B pillar area.  I'm not sure that it might not be the van in your photos...I don't participate in that forum.

Now, my opinion is that all the work may be worth the effort in a minor crash incident...Anything over walking speed, the driver/passenger still being 'soft tissue', is much akin to playing Russian Roulette by choosing a .22 over a .357"!

Rod

RE: modifying an old VW splitscreen van, side impact risk

To get anywhere near a formal evaluation, you'd have to look at the transverse section of the various B-pillars.  (I.e., the section image when cut in a horizontal plane)

Any B-pillar whose transverse section forms a closed tube is going to be much stronger than a B-pillar whose transverse section is similar, but not completely closed, or channel-like, or angle-like.

It's probably easier to just insert a NASCAR style tube hoop.
... and a connected half-hoop in the front, protecting knees and hips.
... sort of.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: modifying an old VW splitscreen van, side impact risk

I was a real VW fan way back when they actually made a peoples car, but I never really got into vans.

To be frank the VW vans really frightened me for several reasons, not the least of which was the fact that the internal energy absorption media for the front crumple zone was the driver and passenger.

Crash bars only make the structure hard, they don't prevent injury, they simply transfer the injury from external body parts to internal organs.

Regards
Pat
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RE: modifying an old VW splitscreen van, side impact risk

Having said that a /good/ structure further back and a 4 point harness would be a step forward. Your thigh bones will still end up in your kidneys, and the steering wheel will pierce your heart, but at least your neck won't be broken.

Cheers

Greg Locock


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RE: modifying an old VW splitscreen van, side impact risk

Honest, I _was_ going to mention that the rollcage has to be far enough back that you can't possibly bump your head on it, _and_ covered with frangible foam for when you find out that's not far enough.

... and that the half-hoop going forward to protect thighs and feet probably needs to lie completely outside of the doors and front bumper in order to actually afford any protection.

... but I got distracted by something and didn't flesh out the message.


I was also not quite talking about boxing the B-pillars if they are not already closed, and it occurred that such boxing would work even better if the pillars were first tightly packed with fitted hardwood.


 

Mike Halloran
Pembroke Pines, FL, USA

RE: modifying an old VW splitscreen van, side impact risk

(OP)
Lots of replies already, thanks.
I understand the van is a huge risk anyway, but what is the best way to try to reduce that risk (obviously not including selling it and driving a modern vehicle!).

The van is quite high, by rally car standards, so I don't think there is a huge risk of hitting your head on a cage if fitted, but also it would need to be done aesthetically, no one is going to want to climb over a huge diagonal cross section over the front door! Is it viable to try to think about crumple zone! If the front seat area was protected would the force of an impact then be transferred into the rear or is the sub frame just too strong for that?

Here is a schematic of the van frame
[img = http://www.vintagebus.com/techinfo/dim1.jpg]
 

RE: modifying an old VW splitscreen van, side impact risk

(OP)
OOOpps, got my tag wrong.

RE: modifying an old VW splitscreen van, side impact risk

(OP)
There is obviously a trade off between what I would be willing to add to the van for strength and usability, for example, I am unlikely to consider cross bracing the doors something I can live with! It is also unlikely I am going to roll the van so maybe a full rollcage is not really adding full value.
I am primarily interested in adding some more protection against a head on crash, a side impact into the wheel well (increasing this side to side strength now the bulkhead is removed) and putting back any rigidity lost from the removal of the bulk head.

If I was to add a cage like this would it add much additional protection or is it a waste of time. Organs crushing inside your body aside, would I be more likely to still have legs left with this sort of additional protection?

RE: modifying an old VW splitscreen van, side impact risk

How about adding some airbag seat belts like we are seeing in small general aviation aircraft these days?

http://www.amsafe.com/

Seems to me the old vedub vans were underpowered already, what will be the weight penalty for your "beefing up"?

RE: modifying an old VW splitscreen van, side impact risk

I don't see a lot of advantage of the internal front cage.

The rear hoop looks good. If you want to retain walk through, the X bars could be raised where they meet the upright and drop diagonally to the floor on its side near the edge of the walk through. A heavy cross beam could be added below the floor to reinforce the walk through area and the diagonal buttresses could tie to that.

The doors should have side intrusion bars.

The front cage should be external and out front as far as reasonable. It should be relatively soft to absorb energy as it deforms.

Regards
Pat
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RE: modifying an old VW splitscreen van, side impact risk

Agree with Pat; you get the most added protection for the least cost by adding side intrusion beams to the doors.

On the external front cage, you could have fun with that and make a set of 'roo bars' with a giant VW logo built in.



 

Mike Halloran
Pembroke Pines, FL, USA

RE: modifying an old VW splitscreen van, side impact risk

(OP)
The original 1200 engines these things had are long gone, everyone runs at least a 1600 now and most people a lot more than that, so you are now flying along at 80mph in your metal coffin! Hence the advice being sort to try and make things a bit safer.

Those seatbelt airbags look great, wonder if they have ever fitted them in a vehicle? Any idea on price? With an air bag to protect your soft internal organs then I guess making the van exterior more rigid is a good proposition to protect your limbs and such!

Under the floor where the roll cage sits is one of the two main chassis cross struts in the van, this is where the outriggers and jacking points are located so I think it is pretty strong, but could be re-enforced if people think that is required?

As for the X-cross between the B-posts I am happy this will not get in the way too much when walking from front to back and will allow the seats to swivel into the back and be useful without bars in your face! but if they are offering no additional later support and protection (?) then I would prefer to not have them, smaller triangular struts could be used instead which would also not interfere with swivel seats. (I have added these in red here)

It is possible to brace across the door (again shown in red) without it getting in the way of being able to get in and out of the van easily. Would this add significant strength improvements to the cage? Or is it just to protect against side impacts?

As for the front, this is where we need the most protection; I really want to try to make that as strong as possible. The original bumper location was ideal when the vehicle ran at stock height, however now a days we all lower then bus at least 4" so the impact area, in a head on, would most likely be above the line of the main chassis where the bumper attached.

The idea I had with the front was several vertical bars, more than the 2 I have shown in red, to try to stop the front of the van folding around your legs. Then the diagonal red bars braced up from the chassis to assist in keeping the whole thing vertical and the horizontals coming off the two main up and over side bars.

Obviously I am not a automotive structural engineer so just working with designs I have seen of how a roll cage fits together and trying to work that into the space we have available in a van. It is not ideal, but will it offer additional protection, or is it a waste of time and money?

An external front cage is not an option, aesthetically no one would go for this, so we are left with working with the inside as best as possible.

RE: modifying an old VW splitscreen van, side impact risk

You will always be compromising space and convenience for safety. That is just how it is. Maximum safety is gained by large crumple zones with soft structures and a hard structure that is a close fit to the occupants.

Being held in place with a device that allows controlled deceleration with the load spread evenly over the body.

Retrofit airbags are a problem from what I can see. Full harness seat belts are good bur a reasonable inconvenience and mostly illegal due to not being automatic adjusting.

Regards
Pat
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RE: modifying an old VW splitscreen van, side impact risk

Well all the talk about crumple zones etc, has me thinking about the average nascar roll cage, and how many folks walk away just fine from 150 plus mph crashes. As well as the drag racing, crashes. Personally I say make the structure as solid and resistive to deformation as possible. Problem is then weight plays an important part. If you had the proper restraints and you were in an army tank, you could do a head on crash with most anything and survive just fine with no injurys. Just curious what the crumple zone would be of 4 to 10 inches of reinforced armor plate?   

RE: modifying an old VW splitscreen van, side impact risk

The crumple zone is entirely in the _other_ vehicle.

... except maybe for the paint.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: modifying an old VW splitscreen van, side impact risk

(OP)
My thoughts exactly, although didn't want to say I was planning on using the other vehicle, which is bound to be modern, as the crumple zone!

Weight wise it depends on the material used. A typical full cage used in motorsport is made with CDS and weighs around 45kg, obviously in the van I would not be going this crazy so expect the weight to be around 30kg.

As for material to build the cage from, all these cages you see use round tube, either T45 or CDS, both of which are expensive and bulky; T45 is the lightest and strongest but suspect out of my budget.

Mike you said
"Any B-pillar whose transverse section forms a closed tube is going to be much stronger than a B-pillar whose transverse section is similar, but not completely closed, or channel-like, or angle-like."

What are the benefits of using a true circular tube over a closed curved box tube? I used some curved edge box tube, the same as they use for making kit car chassis, for an inner hidden bumper on my split. Why? It was the strongest material I could fit in between the panels. This stuff is relatively cheap and you can form it yourself around curves easier than circular tube which is a lot more prone to kinking. If I made my sudo cage in this material it would be easier to get it butted up to the van and thus easier to hide. Here is a photo of the inner front bumper I had made and a sample of the material can be seen on the bench:



Can you also give a bit more detail to your comment:
"and it occurred that such boxing would work even better if the pillars were first tightly packed with fitted hardwood"
 

RE: modifying an old VW splitscreen van, side impact risk

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

In my observation, they all travel in the same direction and reasonably parallel or tangent to the walls. They also wear very well designed harnesses and helmets and often wear neck protection restraints and sit in very well designed seats.

They also do have softer sections at the ends of the structure.  

Regards
Pat
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RE: modifying an old VW splitscreen van, side impact risk

For any closed tube, some improvement in buckling resistance is possible by stuffing the tube with hardwood to support its walls, just as a mandrel in a bender helps a tube resist buckling.

So, stuffing a stock pillar should add some intrusion resistance.

Sistering a stock pillar is likely easier and more effective, but harder to hide.

 

Mike Halloran
Pembroke Pines, FL, USA

RE: modifying an old VW splitscreen van, side impact risk

>>>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

RE: modifying an old VW splitscreen van, side impact risk

(OP)
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?
 

RE: modifying an old VW splitscreen van, side impact risk

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
 

RE: modifying an old VW splitscreen van, side impact risk

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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RE: modifying an old VW splitscreen van, side impact risk

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
 

RE: modifying an old VW splitscreen van, side impact risk

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

RE: modifying an old VW splitscreen van, side impact risk

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

RE: modifying an old VW splitscreen van, side impact risk

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  

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