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Ain'tMisbehavin
2nd Aug 2008, 06:23 AM
Butz German Trailer - Concept of Dr Everhard Bunghartz

I have become fascinated with the idea of building a small, lightweight builders trailers using an 1933 chassis concept devloped by Dr Everhard Bunghartz of Germany. This chassis appears to be very cheap and simple to make indeed. It basically consists of one main chassis longways bar with the tow-hitch at one end and, rather revolutionary, each of the two trailer wheels welded to; and suspended from, an horizontaly welded and U-bolt tied down - 6 leaf - 6 leaf spring, with the usual floor support cross members welded on top of this bar. My Google reference search words ised were: Butz German trailers cars 1933, and the reply link given was: www.bungartz.nl/hist-bungartz.html (http://www.bungartz.nl/hist-bungartz.html)

May I ask would other members with better trailer building knowledge than myself, please comment on this idea and tell me if it's still got merit in today's market place. My concern is that the "leaf spring holding the wheels on " will eventually fail [it doesn't look very strong at the ends] and in theory one of the wheels could fall off. I will paste a 1933 drawing of this trailer [it may not post] if it doesn't appear then will members please look at the Butz www site mentioned to see what I'm on about: www.bungartz.nl/hist-bungartz.html (http://www.bungartz.nl/hist-bungartz.html)
Any advice and trailer building hints given would be greatly appreciated. May I add that this trailer had great success in the 1030s in Germany.



Bob. Leeds, England / Ain't Misbehaving

Yonnee
2nd Aug 2008, 01:14 PM
Hi Bob, and :welcome4:

Interesting article. To this day, the Australian Army uses a chassis design similar to that with one main beam down the centre of the trailer. However, they use an independent coil sprung axle set-up.

It all comes down to horses for courses. A small, collapsible, lightweight trailer would be perfect for someone wishing to move the odd lightweight article occasionally and doesn't have a lot of room to store it, or a large vehicle to tow it.

But if I were to build a car carrying trailer using the same type of design, it would have a huge tendancy to twist diagonally while towing fully laden. Also, a single beam drawbar could start a whipping action if it were not strong enough material. A triangular drawbar is much stronger using lighter material. And having the wheels mounted on the ends of the spring like the one in the picture would put a huge twisting force on those springs now that brakes must be fitted to all trailers over 750Kg.


May I add that this trailer had great success in the 1930s in Germany.
So did the Volkswagen Beetle... doesn't mean we haven't refined it over the years. And made different vehicles for different applications.:2tsup:

Ain'tMisbehavin
2nd Aug 2008, 06:32 PM
Thank you Yonnee for your well thought out reply. I thought this 1930 trailer chassis was ideal for a simple, easy to make 6' x 4' foot household trailer or camper, maximum weight loaded 750 kg. I was going to build a copy of this Butz trailer but in view of your comments am now hesistating. You mention in your post that the Australian Army used a similar trailer to this Butz, do you know how it differs chassis rails wise from this German model?

Speaking off army trailers, about 6 weeks ago I went to an British Army trailer dealers based 2 mile south of Grantham, England, looking for a trailer or spares. The place was enormous [you'd need a bike to ride around it] they had trailers everywhere, but the snag was their weight and size. It would take 2 men to lift the tow bar hitch in order to hook up. Pricewise they were for nothing £75.00 each, [A $148.00] I picked one out that was virtually brand new but the yard manager would not allow me to drag it away with a car - because he said it was an unsafe combination. Ex Army trailers mostly sell for scrap prices. Steel scrap here is currently £300-00 ton [£1 = $1. 98 Aus $] [ $594 per ton]

Once more thank you for your comments, I'm age 68 and going back to work because of the current worldwide credit crisis. My Apolgies for not sticking strictly to the post.

Bob.

Yonnee
2nd Aug 2008, 07:41 PM
There's nothing stopping you building a replica, but I just wouldn't put alot of weight in it. The wall thickness of your main beam would be the key to its strength, but then this adds weight.

The Australian Army trailers are built very rugged and heavy. One of their requirements for the suspension and axle manufacturer is that the trailer must survive a parachute drop from a helicopter.


Steel scrap here is currently £300-00 ton [£1 = $1. 98 Aus $] [ $594 per ton]
Wow, currently we are getting offered $400 - $450 AUD per ton.

Arthur Dyason
2nd Aug 2008, 08:01 PM
Cant see any problems with that type of light trailer construction. You are loosing the additional strength of the axle but you are also loosing its weight.

Should perform and be just as good as any of the light chinese made trailers available.

The reduction of weigth by replacing the axle with the springs would enable you to add a FULL chassis fully braced producing a far more rigit trailer.

If you are adding brakes I would recommend a light trailing arm on each hub from the chassis to stop any twist when braking with load.

Yonnee
3rd Aug 2008, 11:19 AM
The biggest problems would be sourcing the transverse springs, and setting up the suspension geometry so the wheels run straight with little or no camber.

The thing about the current 'run-of-the-mill' spring and axle setup commonly used these days is their simplicity and their cost. By all means, design and build something unique, but how do you replace it if it breaks?

Arthur Dyason
3rd Aug 2008, 12:47 PM
Yonnee

I do design work for Modular Vehicles who build specialist trailers. All designs are to regulations for the EU and Australia. Maybe for others but I dont have the specs for any other countries.

You would have no problems using standard springs but even heavy duty trailers tend to have springs which are less than 800mm center to center of the spring pivots. Using the standard springs would require the mounting plates for the stud axles to be designed with an offset to give the wider wheelbase required for a 6'x4' box trailer. It would still work fine and give you a very low floor. If you used a heavier spring you could get away with using only one. If using ony one spring you would definitly need a trailing arm system to keep the axle in line.

Any camber or not could be designed into the mounting plates by using elongated holes (cheapest but not the best) or a screw adjustment (recommended).

The suspension geometry would work similar to that of a 2CV.

bsrlee
3rd Aug 2008, 08:43 PM
The basic chassis setup is still being used for motorcycle trailers, but they have a more conventional suspension - again, probably due to the difficulty of getting the right size springs.

When you are looking for ex-military trailers, ask about ex-airforce ones - mate picked up a very nice on which was largely aluminium & had a very high ground clearance.

Yonnee
5th Aug 2008, 12:52 AM
Yonnee

I do design work for Modular Vehicles who build specialist trailers. All designs are to regulations for the EU and Australia. Maybe for others but I dont have the specs for any other countries.

You would have no problems using standard springs but even heavy duty trailers tend to have springs which are less than 800mm center to center of the spring pivots. Using the standard springs would require the mounting plates for the stud axles to be designed with an offset to give the wider wheelbase required for a 6'x4' box trailer. It would still work fine and give you a very low floor. If you used a heavier spring you could get away with using only one. If using ony one spring you would definitly need a trailing arm system to keep the axle in line.

Any camber or not could be designed into the mounting plates by using elongated holes (cheapest but not the best) or a screw adjustment (recommended).

The suspension geometry would work similar to that of a 2CV.

I'm not quite sure you got my point... why re-invent the wheel? Or in this case, go back to a wooden spoke wheel when newer, cheaper, off-the-shelf wheels are available.
If you set out to make a replica of the trailer in question, and were prepared to source or fabricate all the components required, then by all means go for it, I'd love to see it and even be involved. But if you're just making your own trailer for domestic use, then there's a wide range of off the shelf components available that are simple to set up, interchangable with other trailer manufacturers parts, and readily available for replacement should you break something down the track.

prozac
5th Aug 2008, 02:23 PM
[quote=Arthur Dyason;781182]

You would have no problems using standard springs but even heavy duty trailers tend to have springs which are less than 800mm center to center of the spring pivots. Using the standard springs would require the mounting plates for the stud axles to be designed with an offset to give the wider wheelbase required for a 6'x4' box trailer. It would still work fine and give you a very low floor. If you used a heavier spring you could get away with using only one. If using ony one spring you would definitly need a trailing arm system to keep the axle in line.
[quote]

Would it be possible to use 2 springs in place of the single sping, one each side of the centre spine? They could even be angled slightly to be their own trailing arm.

prozac