Mike builds a teardrop (doors, cedar strips, ironmongery)

[Mike G]

I've been hinting at this for a while, but things are now just getting under way. I am going to be building something along these lines:


This isn't met with unbridled enthusiasm by my wife, but she understands that the alternative was a boat. This is the lesser of two evils for her, and our motivation is that we can use it to cycle, walk and paddle in new areas at short notice.

The strategy is to build everything from scratch, including the chassis......but the chassis will be delegated to a local fabricator. Everything else will be by me. One of the deeply frustrating things in the design process has been the lack of accurate information. I have been ordering stuff "blind". There are a couple of critical dimensions I need for the chassis design, and one of those was the space needed for the bikes to sit on the "tongue" (triangular frame at the front of the trailer). So, I bought a couple of roofrack bike stands from Facebook Market-place, and rigged up something temporary to check on the minimum spacing:



DaveL of this parish printed me some plastic knobs for those stands. I took the necessary measurements and adjusted the tongue length to suit. The far bigger frustration was not knowing the ride height of the chassis with my chosen wheels, tyres and suspension units. In the end, I just had to buy the stuff and measure it for myself.

So, decision one.......15" wheels. I came to this not only from looking at my drawing, but also from measuring a friend's teardrop which I've had here for a week or two for some repairs and alterations. After liasing carefully with the company supplying all the trailer bits-and-pieces (suspension units, hitch, jockey wheel, corner stands, lights etc), this package turned up:



.........and was then fitted with a pair of 215/65 R15s (it turns out that's a standard size for vans such as Transits, so these are 8 ply tyres):



I then went to order all the stuff I just mentioned, and found out that the only hubs which would fit my wheels either had to be specially made, or had to be braked, which I don't need. For the sake of speed, I opted for the braked hubs, but empty of all brake components. A package of goodies turned up a couple of weeks later:



The guy at the trailer parts supplier had estimated the clearance between the inside wall of a tyre to the plate of the suspension unit at 35mm, and I could now measure to find out the accurate figure. Luckily, he was close, as it came to 39 or 40mm. This is a critical figure because the side walls of my caravan come down outside the chassis, and I need to organise for there to be enough clearance.

Now, to measure the chassis ride-height, I decided on an experiment. I decided to bolt the suspension units and wheels onto a board, and load it up. It was actually pretty straight-forward. I coach-screwed the units onto a pair of scaffold boards:







At this point I took a baseline measurement (mark on a stick). I then loaded up the planks with 50 bricks:



The design weight of my trailer is 650kgs, so, after I weighed a brick (I actually weighed 5 different bricks and took the average):



.....and measuring the deflection:



I was able to do some simple arithmatic and come up an estimate of the chassis height under a full load:



I will play with my drawing tomorrow, but I suspect that this will mean the suspension units will be packed down below the chassis. This is no problem.

I won't be producing the detailed drawings you're all used to for this build. There are quite a number of innovations in my design which will just be stolen/ copied immediately by others. Teardrops are actually quite a big thing in the USA, and although they are really badly built these things can cost an awful lot of money. I'm not planning on helping them out! However, I can let you see a plan of the 2.7 x 1.5m chassis:



You can see the bike rack on the front, and the framing for a "well" above the axle location. This is for a water tank and battery compartment. The big innovation in that drawing, though, are the plates with multiple holes, giving 4 locations for the suspension units. The big deal in trailer (and caravan) safety is having them properly balanced, with the optimum tongue weight (weight on the hitch). As I have never built one of these campers before, I can't be certain where the balance point should ideally be. The front compartment is just a bed, so is very light. The rear holds a kitchen, stacked with fridge, cooker, food, cooking stuff etc, so is comparatively heavy despite being small. Having the ability to move the axles backwards or forwards, in addition to being able to move the battery/ ies in the big well, gives me the best possible chance of getting this thing properly balanced.

Finally......what's it going to look like? Well, I am going to build it in the manner of a (western red-cedar) strip-built canoe:





......and it will be framed and detailed with bog oak. As with canoes, it will be fibreglassed and varnished.

So, that's it for now. The next progress to report will be when the chassis comes back from the fabricator. The basic timetable is to get the shell fibreglassed before the autumn gets too much underway, as fibreglassing is temperature and humidity dependant.

 

[AndyP]

This is going to be fun to watch. What is that on the roof, an awning?

 

[Mike G]

This is going to be fun to watch. What is that on the roof, an awning?

Yes. Actually two: one either side. They'll be home-made as well.

 

[AndyT]

Sounds like the rest of us will be too "busy watching" to do any woodworking ourselves - I know I will!

 

[Dr.Al]

This is going to be fun to watch.

Wot 'e said

 

[Lons]

Interesting Mike, I wondered when you might be starting. It had better be good or you'll be doing a lot of solo trips by the sound of it.

As you've deduced, the balance point is hugely important but you should be able to work that out remembering that for good towing it needs to be correctly weight biased at the hitch but your car will have a maximum towball limit usually around 100kg and for stable towing you need to be around that really.
Your carrier and bikes will take care of most of that and depending on what you take with you it's possible to shift the weight around a bit. What you don't want is it to be tail heavy.

I'll be very interested to see how you manage to keep the u/w down to 650kgs as at a guess the chassis and running gear would be a good 200kgs

Quite right to be wary of sharing too much detail on an open forum

 

[Mike G]

........ at a guess the chassis and running gear would be a good 200kgs

It's almost as though you've a bit of experience of this industry!! The trailer parts supplier quoted to build the chassis, and estimated the total running weight to be 205Kgs.

 

[Lons]

It was very much a guestimate Mike though it's not difficult to add up the component parts. Does his figure include the jockey wheel and hitch etc.?

I'm looking forward to seeing how you progress. One safe bet is that there won't be another one like it.

 

[Mike G]

It was very much a guestimate Mike though it's not difficult to add up the component parts. Does his figure include the jockey wheel and hitch etc.?

I believe so.

One safe bet is that there won't be another one like it.

I certainly hope not. The agreement I have with my wife is that we'll give it a go for a year, and if it doesn't suit us we'll just sell it. Looking a bit special might just help with that.

 

[Lons]

When we decided to sell the motorhome last November my wife agreed that we would revert back to normal holidays again but now she won't go.
I wonder if I can claim damages for breach of contract or maybe it's grounds for divorce?

 

[AndyP]

This is going to be fun to watch. What is that on the roof, an awning?

Yes. Actually two: one either side. They'll be home-made as well.

My mother-in-law made an awning that fitted into a channel that went around the sides and top of their little van and was held up with tent poles. This of course has to be stored in the car or van when being towed but offered far greater protection in lwind and rain than just a top fixed awning.

 

[Mike G]

Yes. Actually two: one either side. They'll be home-made as well.

My mother-in-law made an awning that fitted into a channel that went around the sides and top of their little van and was held up with tent poles. This of course has to be stored in the car or van when being towed but offered far greater protection in lwind and rain than just a top fixed awning.

Mine will be a 180 degree bat-wing thing with removable sides. Neither of us are reliable sleepers any more, and having somewhere sheltered to sit if we get up in the night is just a necessity.

 

[duke]

Are you planning to haul the canoe on your vehicle Mike?
Looks like a nice plan, I have seen more tear drop caravans (campers) on our roads this year than ever before.

 

[Cabinetman]

I’m sure you will remember Mike, there was a thread on here a couple? of years ago I think it was an American firm making caravans with wood strips as you are intending to do. I will be following this with great interest.
You are correct that with a van you are able to just get up and go and do things in the great outdoors. Have you ever been a caravan person?

 

[Mike G]

Are you planning to haul the canoe on your vehicle Mike?

Short term, the plan is to get an inflatable. If we like that, in the longer term I'd build a cedar-strip canoe, and that would then go on the car roof.

 

[Cabinetman]

I’m not a metal worker so take this with a pinch of salt Mike, I feel the chassis is a bit – not quite right. If it were me, I would have two more long lengths running underneath, front to back level with that sort of box section in the centre, the back rectangle where the heavy stuff is looks a bit unsupported to my eye.

 

[Mike G]

......Have you ever been a caravan person?

No, but I've camped my way around Africa (in home made roof tents). The theory is that this little camper is a step up from camping, without having the time, money and space invested in a caravan or camper van.

 

[Mike G]

I’m not a metal worker so take this with a pinch of salt Mike, I feel the chassis is a bit – not quite right. If it were me, I would have two more long lengths running underneath, front to back level with that sort of box section in the centre, the back rectangle where the heavy stuff is looks a bit unsupported to my eye.

I know what you mean, but I've got a commercial teardrop in my driveway at the moment. It has C section steels at the front and back and down the sides. Only. That's it. No cross members anywhere. It makes me feel very confident.

I put this design out to 3 different trailer manufacturers. They were all happy with the design, and the steel sections I'd specified. Indeed, they suggested I reduce from 3.2mm steel to 2.5 in places. So, whilst I don't know much about engineering design, I'm confident that this is OK. It has to go through an "IVA" process, where it is assessed (effectively licensed) by professionals, and all the manufacturers said there'd be no problem getting it through that.

 

[Cabinetman]

I know what you mean, but I've got a commercial teardrop in my driveway at the moment. It has C section steels at the front and back and down the sides. Only. That's it. No cross members anywhere. It makes me feel very confident.

I put this design out to 3 different trailer manufacturers. They were all happy with the design, and the steel sections I'd specified. Indeed, they suggested I reduce from 3.2mm steel to 2.5 in places. So, whilst I don't know much about engineering design, I'm confident that this is OK. It has to go through an "IVA" process, where it is assessed (effectively licensed) by professionals, and all the manufacturers said there'd be no problem getting it through that.

Well that’s all brill! I knew you would have done your homework.

 

[PAC1]

This looks interesting fun.
On your load calculation you had the far end of the plank resting on a stack of scaffold planks. Surely you would need to know the point load resting on the stack of scaffold planks as this would impact the load on your axles?

 

[TrimTheKing]

Love it, looking forward to seeing this progress Mike.

 

[Lons]

This looks interesting fun.
On your load calculation you had the far end of the plank resting on a stack of scaffold planks. Surely you would need to know the point load resting on the stack of scaffold planks as this would impact the load on your axles?

That shouldn't affect the weight over the axle which is a pivot point and certainly would have no bearing on suspension travel. The front end of the trailer would be fixed to a towball which is similar though not exactly the same as resting the plank end.

 

[PAC1]

It might not make much difference but it must affect it. If Mike had put all the bricks between the axles and the stack of scaffold planks creates a different point load on the axle to if he had placed all the bricks at the opposite end of the plank to the stack of scaffold planks or if he had carefully distributed the load evenly along the plank.
I agree that the stack of planks needs to emulate the towball connection. My understanding was that there is a limit to the vertical load applied at the towball.

 

[Lons]

Mike
How does the certification process work there days? Does the IVA process include weights or do you need to take it to a local weighbridge to confirm and submit U/L weight and axle weight. Just out of interest.

Our motorhome, as common to most, was close to the permitted MAM (GVW) especially close on the rear axle so I had it uprated which meant I had to do that process as part ofthe process.

We had to do it all those years ago in the caravan industry but everyone cheated by stripping out the prototype before it was wieghed so they could get a decent payload. One of the reasons so many are overloaded though hopefully it's better policed these days.

 

[Lons]

It might not make much difference but it must affect it. If Mike had put all the bricks between the axles and the stack of scaffold planks creates a different point load on the axle to if he had placed all the bricks at the opposite end of the plank to the stack of scaffold planks or if he had carefully distributed the load evenly along the plank.
I agree that the stack of planks needs to emulate the towball connection. My understanding was that there is a limit to the vertical load applied at the towball.

Mike will have to answer the question really but my understanding is that he needed to load the axle and suspension to see how much it deflected as the bodywork sides will be low and as far as I can see he achieved that.

As far as vertical load on the towball, that's correct and I mentioned it in an earlier post. On a normal family car the ballpark is usually around 100kg. Different for something like a landrover of course. You will find that the car manufacturer states a limit but so does the towbar manufacturer and they sometimes differ. A heavier load on the towball is better for towing stability and experienced towers will often excede it especially if they use spring assisters or assited stabilisers.

Caravan and trailer manufacturers set the axles to create an unloaded hitch load often aroung say 50kg and the balance is changed by the user by careful loading.

 

[Mike G]

This looks interesting fun.
On your load calculation you had the far end of the plank resting on a stack of scaffold planks. Surely you would need to know the point load resting on the stack of scaffold planks as this would impact the load on your axles?

Very true, Peter, but it was really just the weight of the scaffold boards. Trivial.....just a few kg. The bricks were centred over the axles, and even when it was fully loaded I could easily rest the scaffold board on my fingers at the other end.

 

[Mike G]

Mike
How does the certification process work there days? Does the IVA process include weights or do you need to take it to a local weighbridge to confirm and submit U/L weight and axle weight. Just out of interest.......

There's something of a light-touch regime for light trailers (sub 750 kg) such as this. I will have to show that it's below 750kg, but after that they'll pretty much just check the lights and warning triangles, and check that the chassis is suitable. My understanding is that this is just a visual check, but if in doubt I could be asked to provide steel sizes, and even a calculation. As I said, though, this chassis is more heavy duty than most commercial trailers of the size, so I doubt they'll be asking for extra information. Obviously they also check on number plates, and the VIN plate [there has to be a serial number permanently on the chassis (welded, engraved etc) which matches the VIN plate].

 

[AJB Temple]

Sounds challenging. As a matter of interest are the wheels set in line or do they have to have a lean angle and toe in to prevent weaving?

I'm intrigued as to how you will build the frame and by how you will prevent the fibreglass cracking from flexing on the road.

 

[Mike G]

Sounds challenging. As a matter of interest are the wheels set in line or do they have to have a lean angle and toe in to prevent weaving?

No, they're set straight and vertical. The stability of trailers is about weight distribution, and I think I've got that under control.

 

[MattS]

The build project I’ve been waiting for. Intrigued by the unique features you have planned. Chassis looks plenty strong, amazing how much of the external ring under our Eriba is 1” box with very thin wall thickness. Before I read the text I thought the centre section was a footwell, often teardrops have that.

 

[Phil]

MG, looks like a good project, reading and watching from down South.

How many nights would envisage staying in it? Might get a bit cramped for a long holiday.

The nose weight – we used to pack the Jurgens with a nose weight of 80 – 100 KG and it also had a pair of hook-on stabilizers. Towed without any effort by VW Microbuses.

Not to highjack Mike thread, if the weight is at the back it can be extremely dangerous. I was once asked to tow a trailer for a school group to build floats rowing down the Vaal river. The trailer was packed (large drums & wooden poles) and hitched and I was assured that the weight was correct for the nose. As we went down the on ramp to the highway it started swaying and just got worse and then started throwing its load all over the highway. Fortunately the cars on the highway backed off. It was no good applying brakes as that would have aggravated to situation. When we eventually could pull of to the side we were all a very white shade of pale. I had visions of the Microbus overturning, wife, son and 6 other kids. The person who loaded the trailer was driving behind us and I explained to him all about his ancestors and he could find someone else to do the towing.

 

[Mike G]

Let's post a clip showing the effect of weight distribution:

The alternative to shifting the weight from back to front is to shift the wheels backwards. It's about weight distribution around the pivot point (the axle).

 

[Mike G]

How many nights would envisage staying in it? Might get a bit cramped for a long holiday....

Long weekends, mainly, so 3 or 4 nights. I guess it isn't out of the question to do a trip in France now and then, so maybe a week. Don't forget the awnings. They'll double the capacity. People actually live in these things full time!

 

[Lons]

A good simple video for those who aren't aware Mike.

I lived in Beverley close to the main factory but often travelled back to the north east so was occasionally persuaded to take one of the prototypes and drop it off at the Consett factory. I was very experienced at towing and had a big heavy company car but some of those caravans were very difficult especially the big 2 berth rear end luxury models which in prototype concept form were heavier than normal and not properly balanced so when empty were very rear end heavy and would have had people with less experience or lighter cars off the road in no time.
Going down Sutton Bank (now off limits to caravans) could be exciting.

 

[Mike G]

I've just sent the final chassis drawing off to the fabricator. It has taken 8 hours today to work it up into a proper drawing ready for them to use, mainly because of all the holes, and because of a series of details which can't be seen in a 1:20 drawing. So now we wait.....

 

[Lons]

What's the fabrication time estimate Mike?

 

[Mike G]

He's saying 2 or 3 weeks. Some of that will be because of the galvanising, and some because of some laser cutting. Both of those are all about securing a place in the queue. The cutting and welding is only a few days of a process, and I booked my place in his queue 3 or 4 weeks ago.

 

[PAC1]

So how much of the creature comforts will this contain shower, WC, cooking?

 

[Mike G]

It's essentially a bed-on-wheels with a kitchen. The kitchen is surprisingly better than you'd imagine, with fridge, cooker, sink, running water, and a good amount of storage and worktop. We're still pondering on whether or not to include a microwave. We'll have a portable loo for night-time use, in the awning off my side of the teardrop (there's a door on each side of the camper). Other bathroom facilities such as a shower are possible, but not in the immediate plans as most campsites provide these.

If you want an idea of what teardrops are like and what they provide, here is a clip which might help. Mine will have a lot more going on in the kitchen (we're supposed to call it the galley, apparently) than this example, and is a bit longer and taller, too:

 

[PAC1]

Do you have a floor plan of the layout?