Sunday, June 14, 2020

Camping and Picnic Trailer

Here's something I finished during the Covid pandemic for my Heinkel Scooter: a single-wheeled trailer to tow my stuff. I had to cancel two big trips because of Covid. I'm not going anywhere this summer because of the pandemic, so I can take little picnicking, camping beer/food pickup or beach trips.  It's based very loosely on an East German "Campi" design that my friend Werner in Germany built. Since I'm also a woodworker I chose to make the storage area out of wood, reminiscent of a "woody" station wagon or wooden boat.
Travel Trailer and Heinkel Tourist Scooter
13 Feet of Scooter and Trailer!

Trailer with access hatch

This was a very challenging project- almost every piece is curved, bent or angled. From now on right-angled woodworking will be boring!

The trailer weighs about 80 lbs and runs on a single 4.80x8 tire. I've added some pictures below and a description of how I made it.

My friend Werner gave me some detailed measurements of his trailer and I used them as a place to start. I started scouring the internet for design ideas and found a lot of videos, but this one in particular was really helpful: Single Wheeled Trailer.  This gentleman provided good sources for the wheel and design for the U-joint.
Prototyping the metal frame of the Heinkel trailer
I learned some new and improved metal and woodworking skills. My welding is much better. Here's the trailer hitch I built for the scooter, which lets me keep the rack and spare tire:
Trailer Hitch with U-Joint
It bolts directly into the frame of the scooter using the existing holes. I raised the rack by topping the existing spare tire mount bolts with coupling nuts, and covered that assembly with 7/8" black water supply tube, which I left slightly long to act like a lock washer when I bolted down the rack:

I also learned to better cut and rout channels in complex shapes. I had to build several helper jigs to get the curves and channels correct:
Various routed and curved custom shapes
I added a kickstand so the trailer could stand on it's own and not have the woodwork damaged, since a one wheel trailer is not stable:
Kickstand, based on the Heinkel Scooter Kickstand

Kickstand in the Up position with return spring and toe grab
The trailer is made of Ash and Okume, Ash was the first choice of car body makers in the US for wooden station wagons. It is light in color and very strong. I used Okume for the rest since it looks like mahogany, is waterproof and can bend. Okume's natural color is boring so I used a Walnut stain to darken it:
Staining the pieces

Example of the color contrast on the hatch
I finished it with 8 coats of spar urethane. Spar urethane is flexible and contains UV protection. I could have achieved a glass-like finish with a few more coats, but I was afraid the wood would end up looking like the cheap plastic imitations you see in car interiors. This level of finish highlights the woodgrain nicely.

Next Steps:
I just got my license plate. It is registered as a "homemade" trailer, costs $20 per year and is covered under my homeowner's insurance. The total length is over 13 feet so it is not as nimble as a regular scooter. I've gone up to 35 miles per hour in my test rides to determine how it reacts at faster speed.  I'm learning how to load it to avoid swaying, and checking the welded joints to make sure they don't crack under stress.

I hope you like it. I've attached some other pictures of the build in progress below:
Figuring out the shape using a cardboard template
Using the cardboard template to do all subsequent measuring

Building the case supports and kickstand
Jigs to cut and rout channels in the front of the trailer

Checking the height of the rack. Hitch size is 1.25" (US "class 1" hitch" standard)

LED Taillight/brake light / turn signal

Underneath view showing frame and kickstand

Inside. it's quite large. I'm using a dog leash as a strap because of Covid-induced supply shortages
Big enough for a cooler, sleeping bags, tent 

Another inside shot
Door access to shock load adjustment

In the US you need front and rear side lights. These are LED too.

Here's a video!

Monday, August 12, 2019

The Best Carburetor Option Yet?

If you’ve read my blog over the years you know how fickle carburetors can be. I’ve tried several options; rebuilding existing ones, buying lightly used ones, buying a new Bing, using a Jetex- you name it I have tried it. In the spirit of trying to get my car to be the best it can be I have tried another option, and I’m happy to report results that are worth passing on.

Here's the carburetor: a 30mm Tiawanese OKO carb made for 250cc quads. I’ve put several hundred miles on one in a variety of conditions and I’ve been pleased with it. This carb solves several issues for me. Installation is not too hard (but not necessarily easy) but well within the reach of anyone who tinkers with their car on a regular basis (and who doesn’t; It’s a Heinkel!)

Here’s the carb as I bought it off of EBay:
Carb purchased from e-bay

Here are the issues with my existing setup that I hoped to solve, and how this carb stacks up:
Poor idling
Flat spot on acceleration
Running rich (black spark plug)
No bodywork modifications
Accelerator pump?
Easy to get parts
Easy to tune
Easy access to make adjustments
Mostly (use stubby screwdriver for idle)

General overview of the carb:
This is a 30 mm CVK Carb. It has a 30mm orifice with a 36mm (exterior) manifold mount.

Air intake view
Manifold side

Accelerator pump is cylindrical piece on left bottom

Electronic choke is in upper right hand section in this picture
It has an accelerator pump like the original equipment Pallas 22mm. It also has an electric choke, which means you don’t have to pump the gas to start it. It has a 46 mm intake opening for an air filter.  Don’t be embarrassed if none of these stats are familiar; not one of them is a standard Heinkel measurement.


Installation is a 5 step process: I've gone through each one below with plenty of photos.
The steps are:
1. Make a new throttle cable
2. Run a wire to power the electric choke
3. Make an airtight seal from the carb to the existing Heinkel intake manifold
4. Make a supporting bracket for the carb
5. Install an air filter

You may also need to re-jet the carb, but I'll talk about that at the end of the post.

Making a new throttle cable: The Oko carburetor has different ends than a Pallas. Not to fear, you can make your own cable quite easily. I used a Venhill U01-4-101-BK Universal Motorcycle Throttle Cable Kit - 5mm OD, made in the UK. Cost was $16.99 delivered to my house. The only trick is here is to determine the proper length of the inner cable. Loop the outer cable up and over the engine and then down into where the carb will sit. Then measure the distance from the top of the adjuster to one of the cable holding holes on the carb. That’s your distance.

Running a wire for the electric choke: The electric choke replaces pumping the throttle when you are starting the engine cold. The electric choke is temperature activated by an electric current that comes from the ignition circuit. The other end of the wire runs to ground. The easiest place to pick up the ignition circuit is where all of the black wires meet up under the dash, so you need to run a wire all the way back to the dash. I setup my carb with electrical disconnects so I could easily take it apart if necessary (and it has been necessary a few times).
Disconnects for electronic choke

You can see the black wire under the tube. It would be a tight
 fit in the tube but you could do it if you had time
Making airtight seals: The Heinkel carb intake manifold has a 28mm outside diameter. The new carb has a 30mm opening. There are two ways to bridge this gap- make a custom manifold adapter or find some off the shelf component. Luckily there is an off-the-shelf solution (sort of). I poked around my local motorcycle salvage yard and came up with a “spigot manifold”. The manifold solves the carb side of the problem. Here's an example of one I purchased from Amazon that is an exact fit:
Perfectly sized spigot manifold

Installed on carb
The other end I solved using 3 o-rings slid over the end the Heinkel intake manifold. I used 1 1 1/8” inside diameter 1 3/8” OD O-rings, which are a common size in the US and cost 50 cents each. I assemble everything with screw clamps and got a great fit.

1 3/8" OD O-rings - 3 required

Put one on the manifold
Put two more inside the spigot manifold

Installed - a really nice fit
Supporting the Carb: While the airtight fit was great, it was so flexible it would fall off quickly from vibration. The solution was to make a carb “exoskeleton” to support it and prevent if from falling off. I made a bracket. You can weld up one like I did or assemble one with nuts or rivets. Here’s a picture of mine. This is version 2.0: the first one allowed the carb to fall backwards off of the manifold, so I made an extra support piece that sits atop the speedo housing to prevent this from occurring again.

Welded L-shaped bracket 

Top of bracket attached to convenient throttle spring mounting holes
Extra support keeps it from tipping backwards
Installing the air filter: This is easy! Just buy a standard Chinese 46mm ID air filter from eBay and mount it on to the end of the carb. In an ideal world you would actually run the air intake up to the original spot, but I tried to make an adaptor for this and the air cleaner kept falling off. They are only $5.00 each but that adds up after a while!

The air cleaner- 2 for $8.99 on Amazon
Air cleaner from back- I safety wired the air cleaner to keep it from falling off

My abortive attempt to connect the air cleaner to the original housing; it kept falling off!

Jetting the carb: I spent time jetting the carb to avoid flat spots and hesitation. Jetting is a bit time consuming, Paul Spakov has a great series on YouTube on how to tune GY6 carbs(a reference to the ubiquitous Chinese engines that use this type of carb); here's a link to one:  that explains the process.
I think I'm running one size of jets down from the stock. Chinese carb jets are standard and super cheap (at least compared to a Heinkel Bing jets); I think a whole set was $12.

Get this Jet Set along with the Carb

Performance: I've been running the carb since April and it has met all my objectives. I have yet to do a top speed test yet, although I have run it up to 45mph and felt there was still more power available if I needed it. I've been getting about 50mpg (US) which might be a little less than I used to get, though when I check the plug the color is good.
Plug color is light brown- a good sign

 On the whole I'm happy and would recommend this improvement to anyone.

Monday, March 25, 2019

Defroster/Heater Switch

I’m restoring an early Heinkel with the air vents in the door and I was missing the heater/de-mister switching piece.  This is a hard to get item, and I’d been looking for a few years to find one. Since I’d been doing all sorts of metal work to fix my car, I thought I had the skills to reproduce my own piece. It took a while but it wasn’t that hard, and the materials were basically free. An enthusiast with a little bit of skill and perseverance could do it, so I’ve made up the instructions below in case anyone else wants to make their own.

Pictures and Drawings:
I didn’t have the piece and didn’t know anyone with one (in the USA there aren’t many Heinkels), so I posted a question on the Facebook Heinkel Trojan Club page. Mark Fisher came up with some pictures for me:

Heinkel Kabines and Scooters
Heinkel De-Mister Photos
It was time to put my 7th grade mechanical drawing skills to work! Based on the one measurement I knew (the pipe opening of 45mm), I could determine the other measurements from the photos and produce a drawing of the most complicated parts. Here are my drawings of the main pieces for your reference (I’ve simplified a few things based on the materials and tools available):  
Heinkel Cars and Cabin Scooters
De-Mister Main Tube

Heinkel Cars and Cabin Scooters
De-Mister Backing Plate
Materials and Tools Required:
I scavenged most of the materials, and you probably can too. Here’s a list of the materials and tools you need to make the parts:

·         1 foot length of 1 ¾” (45mm) exhaust pipe
·         3” wide steel stock, 1/8” (3mm) thick and about 8” long
·         4” length of ¼” (6mm) smooth steel rod- zinc plated if available
·         2 rubber grommets that fit around the rod
·         3mm screw and washer

If you are restoring a car you probably have most of the tools you need:
·         Drill press or cordless drill with vise
·         1 ¾” (45mm) bi-metal hole saw
·         8mm drill bit
·         1/8” (3mm) drill bit
·         3mm tap
·         Angle grinder with cutoff wheel, grinding wheel, and 40, 80, and 120 grit flap disks
·         Pipe center finder
·         Welder

Once you have the parts and the tools you are ready to go. There are five metal pieces you will need to make:
  • Backing plate
  • Main Tube
  • Heater nozzle tube
  • Air deflector
  • Valve

Let’s walk through each one:

The Backing Plate:
This piece attaches to the car body and sits snug against the door when it’s closed. The original piece was stamped; since I don’t have a metal press I substituted 1/8” thick steel stock. The strength should be more than adequate for the purpose intended.  

This piece requires three different operations; drilling, cutting and bending. Here’s how I did it:
I transferred the drawing to the steel plate and then used a center punch to mark the hole locations. This piece has 3 holes. The largest hole is 45mm (1 ¾”) and can be cut with a bi-metal hole saw. 
Hole Saw

Layout of Backing Plate

After you cut the hole save the little blank, which will probably be stuck up inside the saw; you can use that for the switch piece! The other holes are 8mm (for the door hinge) and a 1/8” (3mm) hole.  
You can drill the big hole by making a small starting hole and then using either a drill press or a cordless drill, provided you can mount the bar stock securely. Use a low speed (I used 625 rpm on my drill press) and some sort of cutting oil or lubricant the keep the temperature down and prevent the heat dulling the tool.

Once I drilled the holes I cut the backing plate to size using a grinder and cutoff wheel. It’s crude but effective. Once I got the approximate shape I used a 40 grit flap disk to get close to final shape, followed by 80 and 120 flap disks to finish it up.

Bending a 3mm thick steel plate is not easy! I put it in my vise and used an 8 pound sledgehammer to get the angle to 45 degrees.

The Tubes:

You need to make 2 tubes; the main tube and the heater diverter. The diverter tube needs to be scribed to fit the main tube. Before the internet, determining how to do this was tricky; now all you have to do is go to a website, enter some calculations, and voila you have exactly what you need. I use the website to produce a graph that I then attached to the tube. Once you do that you can cut away the excess metal with a standard 36 grit grinding wheel attached to your grinder. 
Graph wrapped Around Tube

You can also cut the diverter tube to length with a hacksaw or cutoff wheel, then sand the cut smooth. I made mine about 5mm longer than my estimate because it looked a little short.

The main tube requires several operations. The first is to cut the tube at an angle for where it will be welded to the base plate. I eyeballed about a 12mm difference in length from the photos that Mark provided. I also knew (or hoped!) that if I was off I could just bend the base plate into a final adjustment. Then I drilled a 45 mm (1 ¾”) receiving hole into the tube using the hole saw. If you have a drill press you should use a center finder to make sure you have the exact middle. If you need a center finder they’re available on the internet for about $8 (6GBP).  They look like this:
A cheap center finder
The last operation on the main tube was to drill holes for the switch part. Once again use the center finder to find the center of the tube, then mark and drill the holes straight through the tube and come out the other side.

The Switch:
Since I didn’t have any information or picture of the switch I had to make it up (of course I found one later!). I decided to put the switch in place past the heater outlet, since most of the time I thought I’d need heat rather than defrost in cold New England.

Remember the blank from the base plate? That is the perfect size for the switch valve. You need to attach the blank to some sort of lever so you can operate the switch. I decided to use a piece of bent ¼” tubing and attach it to the switch as shown below. I drilled a 1/8” hole and tapped it for a 3mm screw.

You need to do a little shaping of the switch as shown in the picture. 
The switch parts

I used rubber grommets to seat the metal lever. I thought they would keep the lever taut but still easy enough to move with a finger:
Zinc rod with grommets

When you’re done with these steps you should have a set of parts that look like this:

The parts ready for assembly

Once the parts have been made and test fit it’s time for welding. Weld the heater tube to the main tube first, then clean up the weld:

The first weld

After that weld the tube assembly onto the base plate:
Using magnets and a block of wood to position the weld
When you’re done it will look like this:
The completed piece, except for foam gasket
The next step is to find a foam or rubber gasket to use between the door and the switch. That will have to wait for the car to come back from the shop.

That’s all there is to it. I spent about 8 hours over a couple of days making this start to finish, but I got the satisfaction of making my own part. You can too!

If you have any questions feel free to drop me a line at