Home made HE

[gonzalo Senior Member Find all posts View Profile Close gonzalo]

Hi,

Some days ago I finished a HE I put together with some basic materials.
You may see some pictures attached.

It basically consists of a 50mm diameter steel tube, 1.5m of copper (6mm outer diameter), a big nut, 2 cappings (those used on fences), a thermo switch and the fittings.

First thing is coiling the cooper pipe using a stick. Donīt kink it. While coiling it you must keep the pipe in tension.

Then drill a hole in the 50mm tube a bit bigger than the size of the thermal switch. That way it can protrude.

Now you will have to file the nut so that you get a concave shape that fits with the tube. You will spend a good deal of time here.

Now weld the nut and check if the switch can be screwed properly. Needless to say that the weld must be water tight.

It is time to drill holes on the cappings to insert the 2 fittings. The size of the fittings depends on the diameter of the hoses that carry the hot water in your car.

2 additional holes have to be drilled in one of the cappings so that the copper pipe can go through. The holes must be as tight as possible.

Now you put everything together and seal all the joints with Nural 27 or something similar. Ensure everything is clean and degreased before applying the sealing compound.
You may notice I have fitted small bolts securing the cappings. This is because I donīt want the Nural to take any loads. This way the bolts take the load and the Nural simply seals. If one of the cappings was blown off, the rate at which the cooling water would leave the circuit would make it difficult to stop in time to prevent engine damage.

The thermal switch will let you know when the water is hot enough to change from bio to WVO. I have connected it to a small led in my dashboard. The light switches on at 70 degrees.

Now the bad news; The copper pipe is too narrow, so the injection pump prefers to suck air. My electric pump (Facet 8PSI) does not push the oil hard enough.
Solution: Bigger cooper pipe and a more powerful pump. The first part is done. It has improved the situation, but I still need the pump.

Regards
gonzalo

[gonzalo Senior Member Find all posts View Profile Close gonzalo]

Re: Home made HE

and the last one

[Guest Close David]

Re: Home made HE

Interesting Design.

Is there a reason you didn't weld the end caps on so the would be 100% watertight and have no chance of blowing off?

I take it you sealed the copper pipes coming back through the end cap with this Nural Sealant? Not familiar with nural but I would think that any type of sealant would have a hard job in this application where stress and vibration would put a lot off load on the joint no matter how tight it was. Personally, I would watch these joins very carefully.

You can "Weld" copper and steel by Brazing ( Gas welding) it with an Oxy torch and some Tobin Bronze filler rods. That will give a seal to your joint that will be completely sound and much stronger than any sealant compound.

You could Braze the end caps in the same way if they are thin metal as brazing is ideal here as it readily flows ( or can be made to) right into the joint and you have much less chance of burning through the metal.

The other way you could do this would be to use a length of threaded Plumbing pipe with a couple of screw on endcaps. You could Drill & tap these much thicker caps and use compression fittings to seal the copper tubes coming out. Your sealant on the threaded endcaps will work well here and ensure a watertight fit.

If you are going to use a larger diameter copper tube, You may have trouble Coiling it tightly enough unless you anneal it first. This is heating the tube to red hot and then taking the flame away and letting it cool slowly. Don't over heat it or you will get some flaking of the copper surface. It is a good idea to make sure you properly flush the tube to remove any scale after doing this.
Annealing the copper will make it much softer and you can bend it far more easily without having to worry about it kinking.

From Memory you are only running a small 4 Cyl Engine so I am surprised that 1/4" copper is not big enough. I use that on my 300D and it is fine. As the oil going through it will be heated and thinned, the flow should be OK. Perhaps you just need to check you connections to the copper line and where ever else you have tapped into the circuit because sucking air would show that there are weaknesses somewhere in your plumbing.

What Size are the fittings for the coolant in the end caps? They look kind of small so I'm wondering what size hose your car runs here. As there is an ineffeciency in any design of HE, the more water you can pump through the better the chances of getting full heat to your oil.

[gonzalo Senior Member Find all posts View Profile Close gonzalo]

Re: Home made HE

Interesting Design.

Is there a reason you didn't weld the end caps on so the would be 100% watertight and have no chance of blowing off?

I take it you sealed the copper pipes coming back through the end cap with this Nural Sealant? Not familiar with nural but I would think that any type of sealant would have a hard job in this application where stress and vibration would put a lot off load on the joint no matter how tight it was. Personally, I would watch these joins very carefully.

You can "Weld" copper and steel by Brazing ( Gas welding) it with an Oxy torch and some Tobin Bronze filler rods. That will give a seal to your joint that will be completely sound and much stronger than any sealant compound.

You could Braze the end caps in the same way if they are thin metal as brazing is ideal here as it readily flows ( or can be made to) right into the joint and you have much less chance of burning through the metal.

The other way you could do this would be to use a length of threaded Plumbing pipe with a couple of screw on endcaps. You could Drill & tap these much thicker caps and use compression fittings to seal the copper tubes coming out. Your sealant on the threaded endcaps will work well here and ensure a watertight fit.

If you are going to use a larger diameter copper tube, You may have trouble Coiling it tightly enough unless you anneal it first. This is heating the tube to red hot and then taking the flame away and letting it cool slowly. Don't over heat it or you will get some flaking of the copper surface. It is a good idea to make sure you properly flush the tube to remove any scale after doing this.
Annealing the copper will make it much softer and you can bend it far more easily without having to worry about it kinking.

From Memory you are only running a small 4 Cyl Engine so I am surprised that 1/4" copper is not big enough. I use that on my 300D and it is fine. As the oil going through it will be heated and thinned, the flow should be OK. Perhaps you just need to check you connections to the copper line and where ever else you have tapped into the circuit because sucking air would show that there are weaknesses somewhere in your plumbing.

What Size are the fittings for the coolant in the end caps? They look kind of small so I'm wondering what size hose your car runs here. As there is an ineffeciency in any design of HE, the more water you can pump through the better the chances of getting full heat to your oil.

Hello David,

Thanks for all your comments.

Initially I thought of welding the end caps, but finally preferred to keep the assembly "disassemblable", just in case.

Yes, Nural 27 was also used to seal the exit of the copper pipes from the end caps. During the first drives I would stop every 5 minutes to check on leaks. It has been more than 2000km now and the joints are still water tight. However I agree that this is not the best way to go. I wish I could get my hands on some proper welding equipment.

I have been thinking a lot about the restrictions in my system. The narrowest part was the 6mm diameter (outer) copper pipe and that was removed. However, there is still an air leak in the pump, even with a new filter and some new pump seals. I am now thinking of the solenoid valve, but some time ago I put it apart for another reason and the internal cavities seemed quite big.
Are you really running your Merc with 6mm outer dimater pipes without starving the engine?? If thatīs the case I think I just need a powerful fuel pump, which my car doesnīt have. It only has the lift pump contained inside the injection pump body.
The transparent tube going into the injection pump doesnīt show a single tiny bubble. The problem is in the pump itself.

Iīll let you know how I go

Regards
gonzalo

[Guest Close David]

Re: Home made HE

Hello Gonzalo.

My fuel system has several meters of 1/4" line in it and runs fine. The plastic hoses I am running from the tank are 1/4" and so is the 1M of copper line I am using in my HE.
This is another one of those things that people tell me is wrong and will cause problems but I have had no difficulty with.

Normally horsepower is a requirement of fuel flow but in diesels with a return, you would need more fuel than that again. My car is very low power ( about (80 Hp on a good day) so it's demand even with a surplus flow would be less than a lot of other cars. That said, flow in a pipe is also directly related to pressure so pushing your fuel harder will give you more where it is needed.

I would suggest either a hi flow, low pressure pump or a higher pressure pump with a fuel pressure regulator on it before the IP.

For your HE, you could always take it to a welding or engineering shop and have them weld it for you. Shouldn't cost much for a small, easy job like that.

[TroyH Senior Member Find all posts View Profile Close TroyH]

Re: Home made HE

Perhaps do a test to see if a shorter section of copper pipe will fix your suction head problem, rather than going for a larger diameter.

Was this test done with the HE connected? as reduced viscosity may also help your pump (however you ideally want it to work when there is no heat applied also.
A larger coil radius may also help reduce the pressure drop. Also, increasing the length of straight pipe between the coil and the pump may help.

Is the pipe in the coiled section round, or flattened slightly? Use of a bending spring will maintain the round cross-section and most likely help with flow issues.

[timo360 Biofuels Forum Newbie Find all posts View Profile Close timo360]

Re: Home made HE

Gonzalo,
How long does this system take to bring the oil up to operating temperature?
Cheers,
Tim

[gonzalo Senior Member Find all posts View Profile Close gonzalo]

Re: Home made HE

Hello Gonzalo.

My fuel system has several meters of 1/4" line in it and runs fine. The plastic hoses I am running from the tank are 1/4" and so is the 1M of copper line I am using in my HE.
This is another one of those things that people tell me is wrong and will cause problems but I have had no difficulty with.

Normally horsepower is a requirement of fuel flow but in diesels with a return, you would need more fuel than that again. My car is very low power ( about (80 Hp on a good day) so it's demand even with a surplus flow would be less than a lot of other cars. That said, flow in a pipe is also directly related to pressure so pushing your fuel harder will give you more where it is needed.

I would suggest either a hi flow, low pressure pump or a higher pressure pump with a fuel pressure regulator on it before the IP.

For your HE, you could always take it to a welding or engineering shop and have them weld it for you. Shouldn't cost much for a small, easy job like that.

Hello David,

I think I am fitting a high pressure pump with the regulator. I hope Clack can give the details of his pump.

Thanks
gonzalo

[gonzalo Senior Member Find all posts View Profile Close gonzalo]

Re: Home made HE

Perhaps do a test to see if a shorter section of copper pipe will fix your suction head problem, rather than going for a larger diameter.

Was this test done with the HE connected? as reduced viscosity may also help your pump (however you ideally want it to work when there is no heat applied also.
A larger coil radius may also help reduce the pressure drop. Also, increasing the length of straight pipe between the coil and the pump may help.

Is the pipe in the coiled section round, or flattened slightly? Use of a bending spring will maintain the round cross-section and most likely help with flow issues.

Hello Troy,

Yes, the test was done with the HE connected. The pump was sucking more air than ever before.
Reducing the length of copper pipe would propbable help, but then I am not sure if the heat transfer would be enough.
Thatīs the problem of not having measuring equipment; I am always gessing whatīs going on.
The coil section is round. Your point is a good one. This is the first thing I checked.

Regards
gonzalo

[gonzalo Senior Member Find all posts View Profile Close gonzalo]

Re: Home made HE

Gonzalo,
How long does this system take to bring the oil up to operating temperature?
Cheers,
Tim

Hi Timo360.

The thermoswitch I have fitted in the HE closes the electric circuit at 70 degrees. Thatīs when the led light in the dashboard switches on. In city traffic conditions it takes around 10 minutes for the water to reach that temperature. I assume that the oil temperature is very close to that. The fuel line is very hot to the touch.

Regards
gonzalo