Early Ambulance body twist concerns.

[Bush Mechanic]

We are currently trying to recreate an early ambulance at our local Veteran Car Club workshop. The vehicle was built locally in the late 1800's and originally drawn by a pair of horses. The body later went onto a Model T chassis, and was finally fitted onto a '29 Dodge Bros, with the frame extended.

 

There is some concern regarding the effect of frame twist on the exterior cladding, which is intended to be marine ply. We have five frames down the length of the body, and I am concerned that they will rotate slightly, (viewed from end on), and cause issues with the fasteners. Currently we are thinking of three parallel panels on each side, with provision for some lateral movement between each. Ideas such as oversized screw holes and also sliding joints behind cover strips have been offered.

 

Does anyone have experience in panel sided wood frame construction, who could offer imput on this possible problem? Would the original horse-drawn affair have had solidly fixed side panels? I suspect it would, as the suspension worked differently on a four wheeled carriage. We currently have five cross members bolted to the frame, so any twist in the frame will be imparted to the bodywork.

 

The chassis has been nicely restored by it's current owner, Terry Jones. He traced the vehicle's demise to a local property, where the iron-work of the ambulance body was used in the construction of a chook house, (chicken house). The party allowed Terry to recaim the wrought iron in return for a new chook house. He also showed a coffee table made from a lower panel from the side of the ambulance. That was a Cedar slab of around 5/8" thickness. So we have those pieces as a guide, and some historical photos. These should enable us to build a fairly faithful recreation of our early Launceston ambulance.

 

Any suggestions would be appreciated.

 

 

Edited November 29, 2020 by Bush Mechanic
spelling (see edit history)

[Guest]

I would think if the panels were simply a friction fit into the frames there would be no problem. Sort of the same as a paneled door where the panels are a loose fit in the stiles and rails which are the only glued together parts.

[Bush Mechanic]

A nice idea, but the cladding is being attached to the outside of the framework.

[3macboys]

1 hour ago, Tinindian said:

I would think if the panels were simply a friction fit into the frames there would be no problem. Sort of the same as a paneled door where the panels are a loose fit in the stiles and rails which are the only glued together parts.

With my apologies to Matt and other engineers on my lack of scale diagram but I think Tinindian is on to something - the panels are free floating with the trim pieces hold them in the place with the only fasteners being through the trim into the frame.  Just make sure that the panels are slightly undersized to allow for some movement and swelling from moisture.  

[Guest]

 I don't know how far from original that you want to  venture but boxing the frame would help.   🤔

[gossp]

I would just make the box as rigid as you can and allow for some flex in the body mounts.  It seems like a lot of frame flex happens on brass era through early 30’s vehicles with little harm to the body. 

[ArticiferTom]

Are you taking back to horse drawn or on the Dodge chassis ? Maybe some one in Amish country could shed light . This seems like typical buggy design still built today .

[franklinman]

The problem you will likely have with the free floating panels will be anywhere the paint bridges it will end up cracking. We have done several panel type bodies on early brass vehicles and have had few if any problems making the bodies tight.

[PFitz]

In addition to having padded mounts, keep the body mounts closer together front to rear. Having them near the corners of the body just imparts more chassis twist to the body. 

 

Had this problem with the very flexible chassis of a 31 MG boattail that I was asked to rewooded the body of.  Someone had added body mounts under the corners of the firewall, in addition to the original front mounts further back. That added a lot more twist to the body. So much so that it would jam the doors if the car was not parked on level ground.  I was able to convince the owner to eliminate the firewall mounts and the chassis twist the body would be subjected to was reduced by about half. 

 

Paul

[Bush Mechanic]

22 hours ago, 3macboys said:

With my apologies to Matt and other engineers on my lack of scale diagram but I think Tinindian is on to something - the panels are free floating with the trim pieces hold them in the place with the only fasteners being through the trim into the frame.  Just make sure that the panels are slightly undersized to allow for some movement and swelling from moisture.  

Thanks for the diagram. This is our 'sliding joints behind cover strip' option. Currently our first choice.

 

10 hours ago, Roger Walling said:

 I don't know how far from original that you want to  venture but boxing the frame would help.   🤔

Not sure what is meant by boxing the frame.

 

8 hours ago, ArticiferTom said:

Are you taking back to horse drawn or on the Dodge chassis ? Maybe some one in Amish country could shed light . This seems like typical buggy design still built today .

Tom, they are actually the same box, transferred to different vehicles. We are trying for as close a copy of this as we are able, using the photos and iron-work for reference.

 

6 hours ago, PFitz said:

In addition to having padded mounts, keep the body mounts closer together front to rear. Having them near the corners of the body just imparts more chassis twist to the body. 

 

Had this problem with the very flexible chassis of a 31 MG boattail that I was asked to rewooded the body of.  Someone had added body mounts under the corners of the firewall, in addition to the original front mounts further back. That added a lot more twist to the body. So much so that it would jam the doors if the car was not parked on level ground.  I was able to convince the owner to eliminate the firewall mounts and the chassis twist the body would be subjected was reduced by about half. 

 

Paul

 Ha! It is the memories of excessive chassis twist on my '48 Morgan which leads to my current concerns.

 

We haven't any 'body pads' as such under the five cross members. The style of construction of the base is dictated by limitations of garage height at the owner's home, and work done previously which was incorporated into the restoration. Also by the blacksmith work on the chassis extension. While it would be simple to disregard flex and make a stiff box, I feel that some allowance is needed.

 

Thanks to everyone for the imput.

 

[Guest]

13 hours ago, Bush Mechanic said:

On 11/30/2020 at 8:18 AM, Roger Walling said:

 I don't know how far from original that you want to  venture but boxing the frame would help.   🤔

Not sure what is meant by boxing the frame.

 Boxing the frame is a method to make the frame less flexible.

 It consists of welding plates over the inside of the "C" frame and turning it into a 4 sided tube.

 Ask any hot roder how to do it.

[hidden_hunter]

They must have been pretty unlucky to run into another car in Launceston in 1924, cant imagine there were a lot of cars in Tassie at the time

[Bush Mechanic]

4 hours ago, hidden_hunter said:

They must have been pretty unlucky to run into another car in Launceston in 1924, cant imagine there were a lot of cars in Tassie at the time

 

Traces of the damage are still there, in some welding on a rear reinforcement. That intersection is still an accident hot-spot, despite the new roundabout. The streets are on a hill. 

 

There were quite a large number of good quality cars in Tas then. But they continue to drain away to the Mainland and Europe.

 

[jdome]

If you build the body to allow panels to float and joints to flex and twist then the body will flex & twist and will squeak & creak & rattle & wobble and wear lose and eventually fall apart. You will also have water getting behind the loose fitting panel joints and cause rot. Wood bodies were originally made rigid. I suspect your frame is more rigid than you think or it should be unless the rivets are loose which could be the case. The stiff body mounted on the frame will help stiffen the frame as well.  Most wood bodies were bolted to the frame with four or six - 3/8 or 1/2 inch bolts. You might want to do a search on line for Model T Ford Pie Wagon or Paddy wagon blue prints or search the model T web sites. You will probably be able to find prints for free or reasonably cheap. These prints will provide you with some good construction tips & techniques & a good basic design to follow.

 

Good plywood (Baltic Birch-best choice, poplar, maple) is very stable with negligible expansion & contraction, no reason for it to float lose. Most early cars used Ash for body structure. Very strong, hard & stable. Flat body panels were usually made of wide, solid poplar boards sometimes up to 20" - 24" wide and nominal 3/8-1/2"  or 5/8 thick and up to 6ft or more long. You can still find wide, kiln dried poplar boards today if you know where to look. Plywood was not commercially available until the 1920's although it is a good substitute if you can deal with the open grain edges. You will see "plywood" on brass cars that are actual thin, solid plies that were glued up for the specific body panels.

 

As I understand, you are using Cedar to build your body. Probably not the best choice. Cedar is not a hard wood and will likely dent & chip easily and wood screws won't anchor into soft wood under the stresses the body will be subjected to.

[Bush Mechanic]

On 12/1/2020 at 4:54 AM, franklinman said:

The problem you will likely have with the free floating panels will be anywhere the paint bridges it will end up cracking. We have done several panel type bodies on early brass vehicles and have had few if any problems making the bodies tight.

And keeping moisture out of the joints could be a real issue.

 

I finally made contact with the brother who had a carriage building/restoration business in the 1980's and 90's. (He goes bush, prospecting). He was emphatic that it should be built as tight as we can make it. Also the frame can still twist in the span between the box and the firewall. So our thinking has come full circle, and that is the current plan (I hope). I will try to post some photos of the project, when we are more advanced.

[Bush Mechanic]

3 minutes ago, jdome said:

If you build the body to allow panels to float and joints to flex and twist then the body will flex & twist and will squeak & creak & rattle & wobble and wear lose and eventually fall apart. You will also have water getting behind the loose fitting panel joints and cause rot. Wood bodies were originally made rigid. I suspect your frame is more rigid than you think or it should be unless the rivets are loose which could be the case. The stiff body mounted on the frame will help stiffen the frame as well.  Most wood bodies were bolted to the frame with four or six - 3/8 or 1/2 inch bolts. You might want to do a search on line for Model T Ford Pie Wagon or Paddy wagon blue prints or search the model T web sites. You will probably be able to find prints for free or reasonably cheap. These prints will provide you with some good construction tips & techniques & a good basic design to follow.

 

Good plywood (Baltic Birch-best choice, poplar, maple) is very stable with negligible expansion & contraction, no reason for it to float lose. Most early cars used Ash for body structure. Very strong, hard & stable. Flat body panels were usually made of wide, solid poplar boards sometimes up to 20" - 24" wide and nominal 3/8-1/2"  or 5/8 thick and up to 6ft or more long. You can still find wide, kiln dried poplar boards today if you know where to look. Plywood was not commercially available until the 1920's although it is a good substitute if you can deal with the open grain edges. You will see "plywood" on brass cars that are actual thin, solid plies that were glued up for the specific body panels.

 

As I understand, you are using Cedar to build your body. Probably not the best choice. Cedar is not a hard wood and will likely dent & chip easily and wood screws won't anchor into soft wood under the stresses the body will be subjected to.

 Excellent reply, jdome. I like your thinking. We posted at the same time.

 

We have the cross members bolted down with eight 10 mm coach bolts. And the European car that I am restoring at the moment has one of those 24 inch x 3/8 boards across behind the front seat, and we all marvel at it, it being so unusual here. A pale pinkish timber. And still sound after 100 years of abuse.

The timbers used in carriage work here in Aus are different from those in the US, but the local equivalents. The old guy with the ironwork in his chook house called it cedar, apparently, but from talking to Greg, my brother, I think it would have been Kauri, a Queensland timber. Greg talked of the various timbers used here at the time. For the frame, we are using 'Tasmanian oak', a marketing name for a couple of Tasmanian eucalypt hardwood varieties. This is the timber usually used in Aus for car body construction. It has similar properties to those of Ash. And is sometimes available air dried. While cedar is an excellent timber for some jobs (house window frames and doors),  as you say, it is not for car bodies. The piece in question was cut from a lower side panel, originally about seven feet long.

[Rusty_OToole]

The whole vehicle will have an easier life with limited use at low speeds on good paved roads, compared to when it was new. Make the body strong and don't worry about it. If you can consult an old coachbuilder or find some old coachbuilding manuals so much the better. In the old days they made them rigid and added iron reinforcements as necessary. Weymann was the first to deliberately make a flexible body covered in waterproof fabric or artificial leather that could flex with the frame.  They had a certain vogue but never displaced the conventional body, before both were replaced by the all steel body.

[Bush Mechanic]

Rusty, the first wood frame that I looked closely at was a Wayman bodied Rolls. That probably infected my subsequent thinking, to a degree.

 

Brother Greg ( an old Coachbuilder), has dug out some construction plans for horse-drawn Ambulances, so everything is now advancing in the right direction, thanks.