Epsiode 14 – Connections, Pipes, Hoses

People visiting us regularly in the workshop don’t see big changes on the tractor and come to the point where they ask what we are doing all the time, since the tractor is basically ready …

All the major components are painted and back on the frame, engine, turbochargers, rear axle, … . So, we should be good to start it up an take it to the first pull. But it’s missing a lot of the small details, which are mainly related to connecting everything together. Time to get you a small insight, what has to be interconnected on such a machine:

The engine needs to be connected to the rear wheels through drive shafts. No U-joints allowed, so everything has to be perfectly aligned and will be connected with splined shafts and couplers accordingly. Since you can’t buy these of the shelf, they need to be machined. They have to take all the horsepower and you can’t just do them out of normal steel, so you need to find an appropriate material. The solution comes in the form of tool steel with the desired hardness and flexibility at the same time. The disadvantage of tool steel is, that you will have a hard time to machine it. Lots of researches and tips from other competitors lead us to a type of steel which comes in a normalized form, thus is easy to machine and will get it’s final mechanical characteristics in a specific hardening process.

Time to machine the outside and inside splines …

Each spline has to be cut individually, indexing the splines has a zero-error-tolerance and you often need to take several passes to come to your final dimensions and have a perfect fit … time consuming and you have a lot of time to think about all the other work in front of you to get the tractor done ๐Ÿ˜›

… all major drive line parts are finished and on their way to a specialized company for hardening. Finding a company which can and will harden the parts to the needed specifications in our area is a whole other story :/

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… still missing the long drive shaft between the clutch and gearbox. It needs some final touches on the gearbox (good topic for another episode ๐Ÿ˜‰ ), to get final dimensions. It will anyways be machined out of another material, since there is no way (at our hands) to harden such a long piece without a tremendous amount of deformation.

In parallel we are making all the fluid and gas connections. Let’s try to list all the needed gas (air, exhaust, breathers, …) connections, starting with the trivial ones:

  • Intake air to the turbochargers … easy, since there is just an opening to free airย  … well, NO. We need to run an air restrictor in our class and ETPC rules call for an intake protection (I think, I will cover all the safety stuff in a separate episode).
  • Exhaust gasses to free air … no problem neither, just a big pipe with an elbow and you are done … well, NO. There a rules for your exhaust pipes and further safety elements behind the turbos.
  • Compressed air goes from the turbochargers into the engine … sounds easy, some pipe, rubber hose and clamps … well, NO. In our case we didn’t want to go with full custom made intake manifolds from the beginning, so we modified the stock aluminum intake manifolds, welded some pipes and elbows to it and were good to go. Besides this, the connection between the turbos and the engine had to incorporate the following elements: throttle bodies, blow-off valves, holes (actually it was a little more complicated) for the fuel injectors, connections for temperature and pressure sensors, ports for vacuum connections (other elements of the engine management system need these), … I certainly missed some others ๐Ÿ˜‰
  • Exhaust manifolds from the engine to the turbochargers … sounds easy and needs just hours of work in stainless steel … cutting, welding, grinding an press forming adapters from a specific round to a specific rectangular shape :/

    … at some point you need to integrate connections to be able to disassemble your construction ๐Ÿ˜› V-band connections are great for this purpose

  • The turbo chargers, due to their basic function principle with hydrodynamic bearings (the shaft spins and is centered in a pressurized oil layer in the bearings) need their own oil supply and return, which we realize with a dedicated oil pump, filter and a separate oil tank for the turbos.
  • All tanks, in fact circuits with liquids, need a ventilation with a receptacle to catch any liquid exiting the ventilation and avoid contamination of the environment. Counting all these gives a nice number as well: rear axle, rear planetaries, gearbox, two braking circuits, hydraulic steering, fuel tank, turbo oil tank, crankcase ventilation, …
  • Hydraulic steering and brake systems … I’ll cover these and their function in a separate episode with the other controls of the tractor (clutch, throttles, shut-offs, …)
  • As we switched the engine lubrication system to an external oil pump, oil needs to go from the crankcase to the oil pump and from the oil pump into the engine … easy … well, NO. Connections were welded into the oil pan, after the oil pan was shortened and thus allow the oil feed to the two stage oil pump.
    2019-08-06-10.08.05.jpgActually they are not just pipes welded to the oil pan, but inside they are routed to the deepest point of the pan, incorporating filtering elements to avoid pump damage … hard to get a picture of it now :/

    Not using the original oil pump left us with the question how to get the oil into the engine. We ended up feeding the oil directly into the main oil galleries of the engine. Oil supply in an engine is just a work of art, when you consider that all the complete internal oil supplies can’t be cast with the engine block, but are machined and drilled afterwards.
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    Not using lots of the stock oil supply, we ended up without an oil filter and oil pressure regulator. The solution came in machining an oil filter according to our needs, integrating an adjustable pressure regulator with a return line into the crankcase. We integrated another feature, which is a transparent plate, in the filter, allowing us to inspect our filter element without the need to open the filter. This allows for a quick check on engine health between runs and eventually call it quit before a major engine damage.
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    Most of the hose connections are done with AN-fittings (Dash-fittings or whatever you are used to call them). This is an amazing system, common in motorsports, which allows you the realization of virtually any connection without the need of press fittings. Well, nearly any connections, besides those which are non-standard or you just forgot to order the correct ones … let’s just machine them :/

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With all the connections, the front of the engine becomes really cramped :/
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  • Then comes all the fuel stuff … fuel pump, fuel filter, fuel pressure regulator, fuel distribution, and fuel rails. I’ll try to cover this in a dedicated series of episodes on engine management.

What did I miss? … Aaah, all the electrical stuff :/

I think, one gets a pretty good overview what was and is ongoing in the workshop, without seeing major changes in the state of the tractor.

Talking about liquids, some of them have their containers, trough the way how they are constructed, as the engine oil or the rear axle oil, others need to have their containers build. With not a lot of space left on the front, due to overall vehicle length, time for old-school cardboard models ๐Ÿ˜‰

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Episode 13 – Feeding a bear

Building a pulling tractor with a big engine is like getting yourself a large pet … lets say: a bear ๐Ÿคฃ

It’s amazing to have one, but at a certain point you need to feed it and fulfill all it’s basic needs ๐Ÿ˜‰

In one of the previous episodes, we showed how we will feed the engine with air … the turbos will keep care of this. Having lots of air, you need lots of fuel and this fuel needs to get pumped somehow. Electrical fuel pumps have two disadvantages in our application: they don’t deliver enough fuel and they consume lots of electrical energy, creating the need to somehow get this electrical energy. The solution lies in a mechanically driven fuel pump, suited for methanol, as they are commonly used in racing.

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Nice little pump, has metric bearings in it but someone decided tho have an imperial hex shaft to drive it ๐Ÿค

A more basic need is the oil supply of your engine. As explained before, we wanted to use the stock oil pump in the engine, but were made aware (several times) not to do so. Investigating all this showed, that the original one stage, big displacement oil pump spins faster than the crankshaft, pumping to much oil at high engine speeds, combined with the risk of cavitation and the forming of oil foam. The main and connection rod bearings wouldn’t appreciate that foam and their life expectation would decrease drastically. So … how do other people tackle this issue? The solution lies in the use of an external oil pump and commonly people use specific modified, three stage, dry sump oil pumps, as they are common on high performance racing engines. For us the terms “motorsport”, “racing” and “high performance” are always related with high costs for solutions which don’t seem to be that much of rocket science as one would expect for the price. Not willing to spend that much money on “just an oil pump”, it was time to use the might of the internet to find out about the specifications of these expensive pumps. Well, long stories short, we opted for a three stage hydraulic pump, as they would be used on excavators and other industrial machines, with the same flow rates as the dry sump racing pumps, commonly used. We have no weight issue, and we will enlarge the pump ports, so that the pumps can flow without restrictions.

But why three pump stages? As mentioned before, single large displacement pumps appear to be problematic, so that the engine oil supply is split between two smaller pump stages. The third pump stage will be used to feed oil to the turbochargers in a completely separate oil system. This will avoid contamination and allow us to run different oils, best suited for methanol engines and lubricating turbochargers, without making compromises. I think, oil will be worth a complete episode on it’s own ๐Ÿ˜‰

Both pumps, methanol and oil, are mechanically driven … how do we drive them from the engine? The solution comes with a system, based on a timing belt …

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Everything will be driven from the front of the crankshaft, no problem. Well … we have to consider transmission ratios an everything has to fit between the chassis rails, due to the very low mounting position of the engine … total width of only 44cm ๐Ÿค”

For the transmission ratios, this meant the pulley on the crankshaft has to be as small ass possible, compared to a large pulley on the oil pump. The methanol pump should be fine with a 1:1 ratio, since the flow rate fits the target engine speed and maximum capacity of the used injectors quite well.

We absolutely wanted to go with one of these aircraft, direct crank drive starters, so this has to fit somehow with our pulley system. Time to find out, what we can machine, on purely conventional machines out of chrome-molybdenum steel.

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Some other, minor stuff ๐Ÿ˜œ, had to go on the front of the crankshaft as well. The EFI system needs a trigger signal at crankshaft speed, which we will get from a toothed wheel. In our application, this trigger wheel needs to clear a pretty large external crankshaft counterweight. The tractor will get some electrical consumers, mainly the EFI system, and we don’t want to solely rely on battery power … a belt pulley has to go on the crankshaft and we will try to find a nice spot (or just space which is not yet overfilled) to mount an alternator.

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Timing belts have a lot of advantages, but are limited in the maximal torque which they can transmit per single tooth on a pulley. Therefore you need a minimum number of teeth from a pulley which engage into the belt at any moment to transmit the needed energy from belt to the pulley or vise-versa. Using small pulleys, we were able to overcome this issue by routing the belt in a serpentine pattern in combination with the needed tension pulley.

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With the pulley and belt system in place, time to find out if everything still fits in front of the engine.

After all the machining, time to think about connecting everything with hoses, content for another episode ๐Ÿ˜‰

 

 

 

 

Epsiode 12 – A team and small steps

With a project like this, it is amazing to see other peoples interest in your work and progress. Wherever you come, people ask about the current state and when the tractor will run for the first time.

You can prepare the nicest project plans but often it is just not in your hands. We were waiting to get laser cut parts delivered, which took 7 weeks instead of the usual two weeks, so that we were blocked in our progress on some parts. It came to a point were we even started to paint the first components … watching paint dry is definitely not one of our favorites ๐Ÿ˜‰

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Be assured, the tractor will not come completely in orange paint. We came up with a particular color scheme for the tractor, where orange is just one part.

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Talking about organizing parts, the material value of a tractor is only a minor part, compared to the value of the work going into such a project. Work which is done by the entire team, starting with cleaning parts, assembling/disassembling, measuring and finally designing, welding and machining all the parts. Not having a high-tech tool and machine shop with CNC controlled machines at our hands, every part is done the old-school way on conventional lathes and mills. In a team which started as a bunch of friends, everybody is learning skills from each other to operate the machines and is thus able to realize even more complex parts on his own. The principles in the workshop are clear: Don’t stop were you are, you grow with your challenges and if there is no solution, it is not a problem.

I think this is a good place to thank everybody for their motivation, devotion to the project, the time invested so far an the time you will invest to get the tractor running.ย  Another big thanks has to go to our families, girlfriends and so on, allowing us to invest so much time in our project, without their support it would just be impossible.

I missed another principle … if, after a long day at the job and a whole evening working on the tractor there is not a lot of motivation left, or something just didn’t work as expected, there is always time for a beer or two between friends.

What about the small steps?

Front and rear axles with the steering and brakes are done and just awaiting their final paint job.

The clutch and flywheel are ready and fit perfectly. A big thanks to Freakshow Performance for the amazing work.

We finally found a piece of large diameter steel pipe to get the clutch protection done. Looks like some more machining work ๐Ÿ˜‰

Rohr

The auxiliary drive for the oil- and fuel pump, incorporating the direct crank starter and trigger wheel for the EFI, comes together nicely.

Spark plugs are in and ignition coils mounted to the cylinder heads.

Fuel injectors fit the intake manifolds and we are currently machining the fuel rails.

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Turbos and throttle bodies are on and we are working on the intake and exhaust piping.

The gearbox housing is getting machined and the Fuller parts are getting the needed modifications.

Decisions are made on the material for the drive shafts … some more machining.

Seems like time to get back to the workshop. We are currently to busy to keep up with the technical episodes, but these will follow, with the tractor running. To close this episode, here is a picture what the italian power pack actually looks like ๐Ÿ˜‰

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Episode 11 – choo, chooo, choooo

Let’s just start with a statement of Jeremy Clarkson, which shows the basic understanding of most people about turbochargers:

“A turbo: exhaust gasses go into the turbocharger and spin it, witchcraft happens and you go faster.”

So before we show our turbo setup, which is currently still in the making, we thought it would make sense to go into the basics of turbocharging an engine.

As stated in a previous episode, making more power out of your engine is just possible when you are able to burn more fuel. But you can just burn more fuel, when you get more air into your engine. Usually an engine is fed with air by means of the atmospheric pressure, which pushes the air into the combustion chamber(s). The amount of air for combustion is theoretically your engine’s total displacement for every two engine revolutions on a 4-stroke engine. This amount is limited trough airflow losses while the air flows into the combustion chamber(s) and usually further decreases with engine speed, since the air has less time to get into your combustion chamber.

To get more air into your engine, as trough atmospheric pressure, you have to force it in by increasing the pressure, or creating boost as tuners would call it . This is usually done by adding an air pump in form of a compressor. This compressor needs to flow large amounts of air without having to dramatically increase the pressure. Centrifugal compressors are a good choice for this task, working on a basic principle without a huge number of moving parts or needing complicated sealing.

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To drive such a compressor, you need mechanical energy. This mechanical energy can come directly from your engine via a special gearbox, stepping up the engine speed, to drive the impeller.ย  Another option is to use the energy out of the exhaust gasses to drive the compressor, as it is done in a turbocharger.

In a turbocharger, the centrifugal compressor is directly coupled (on a common shaft) to a turbine wheel. The turbine wheel is driven trough the energy still available in the exhaust gasses and transferring this energy to the compressor wheel and you can force more air into your engine.

In theory, this is pretty simple, but when it comes to choosing the right turbocharger, it gets a little more complicated, since the offer in turbochargers is huge. Basically you can make the choice for a compressor, based on horsepower numbers you “want” to make. Turbo manufacturers give you the numbers for the maximum amount of air, their compressors will flow. This is nice, but will you be able to get all that air through you engine? This is, where pressure an turbo speed come into the game. Two basic theories:

  • Your engine can not flow the air, the pressure increases, the compressor wheel slows down, less air is moved, …
  • Your engine can not flow the air, the pressure increases, the turbine delivers enough energy to keep the compressor spinning, the air heats up, boost pressure rises but you are not making more power, …

The two reflections lead to two extremes:

  • The compressor wheel slows down to a point where it won’t make any gain in pressure.
  • The compressor wheel over-spins and will not be able to make any gain in pressure neither.

Therefore, turbo manufacturers provide compressor maps for compressors.

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  • The horizontal axis shows the mass-flow of air, thus somehow proportional to the power you can make.
  • The vertical axis is the pressure ratio, compared to atmospheric pressure.
  • The islands in the map show the compressor efficiency.
  • The dotted lines show compressor speed in rounds per minute.
  • Everything on the left of the islands is above the surge limit of your compressor wheel. Basically your compressor wheel is to huge and you cannot keep it spinning with the energy you provide trough the exhaust turbine.
  • On the right of the islands, your compressor spins but you are not able to get the air through your engine and compressor efficiency drops. You are just producing hot air

As an optimum, you want to operate your compressor in the center islands. When you try to follow the basic thoughts, you come to the conclusion, that the compressor operation is in direct relation with the exhaust turbine, providing the energy to the compressor. Therefore, you can combine a given compressor with different exhaust turbines and exhaust turbine housings to make best use of the energy in your exhaust gasses for you application. There is a huge difference between low end torque for street driven vehicles and WOT (wide-open-throttle) as used in tractor-pulling.

Our class is limited with air restrictors, which every competitor has to use. The aim is to limit the maximum power for everyone to about the same amount. Running two turbos, we have to use two 76mm (~3 inch) restrictors. Our first thoughts were to just go with compressors of exact this size. But since we have to use the restrictors anyways, we decided to go with slightly bigger compressor wheels an target for high efficiency. Based on availability and budget, the choice was made to go with S400 clones equipped with 88mm billet compressor wheels.

Comparison with a standard turbo out of a 1.9TDI engine ๐Ÿ˜‰

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Based on the thought, that burning methanol in a high displacementย  engine will generate huge amounts of exhaust gasses, we went for the biggest exhaust wheel and housing combination available for this compressor.

Speaking about exhaust gas volume. What do you do with excess exhaust gasses, or can you even control the amount of exhaust gasses to the turbine of your turbocharger? Of course you can ๐Ÿ˜‰

Controlling the amount of exhaust gasses to your turbo allows you to control the energy you provide to the compressor, and thus you can control the amount of air the compressor flows. Basically you are using a mechanical valve to bypass exhaust gasses before the turbine, which will not drive the turbine. This valve is called the wastegate.

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Wastegates are eather integrated in the turbochargers turbine housing, called an internal wastegate or, as shown in the image above, they are positioned on the exhaust manifold before the turbocharger, called an external wastegate.

Basic wastegate control is done trough the wastgate spring, which counteracts against the exhaust gas pressure. The wastegate opens progressively when the exhaust gas pressure rises, reducing the energy delivered to the turbocharger and thus regulating the boost pressure generated by the compressor. This is just a very basic control and most wastegates are build with an additional pneumatic control, having a membrane under the spring, so that you can add force to the spring or counteract against it by applying pressures trough the two additional control ports. These pressures can either be directly your boost pressure or controlled trough your engine management system.

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But what about the “choo-chooo-chooo” in this episodes title. This describes the distinctive sound, lots of people directly relate to a turbocharged engine. But it is neither generated by the turbocharger, nor the wastegate. This sound is generated, and often ridiculously amplified, in the so called blow-off valve. A turbocharged system does not necessarily need this valve and one usually does not find it on Diesel powered engines and low boost gasoline applications. But why is it needed and extensively used on tuned, mostly spark ignited engines?

The need comes from the fact, how the engines power delivery is controlled. Generally speaking this is throttle control. On a spark ignited engine, you have a throttle, which controls the airflow to the engine. This throttle is placed between the compressor and the engine’s intake. A Diesel powered engine is controlled through the amount of fuel, the fuel injection pump delivers, thus it does not need a throttle controlling the airflow.

Now the blow-off valve’s main purpose is to prevent pressure peaks and avoid excessive wear of a turbo charger. The pressure peaks are generated, in a spark ignited engine, when you shut your throttle after high boost operation. With the throttle shut, the exhaust gasses are still delivering energy to the turbine and the compressor pumps air. The throttle allows just a marginal amount of air to travel to the engine and the pressure between compressor and throttle body rises, well over the surge pressure of the turbocharger and excess air would push back out of the compressor intake. This results in high thrust bearing wear or failure of your turbocharger.

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Basically the function of a blow-off valve is identical to that of the wastegate. The blow-off valve is positioned, as a spring loaded valve, in the intake manifold, between the compressor and throttle body. To help the opening of the valve, the pressure chamber in the valve containing the spring, is connected to the intake manifold, between the throttle body and the engine. Shutting the throttle results in a vacuum between the throttle body and the engine and thus helps in the opening of the blow-off valve. Releasing pressure through the blow-off valve sometimes results in an oscillation of the blow-off valve, resulting in the distinctive “choo-chooo-chooo” sound ๐Ÿ˜‰

A basic turbocharger setup then looks as in the following picture. The picture shows no intercooler. We will do intercooling with additional fuel or water injection (topic for another episode ๐Ÿ˜‰ )

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Our system will be setup exactly like this. Well, we have 8 cylinders, 2 turbos, 2 throttles, 2 wastegates, 2 blow-off valves …

The plan is to build a separate turbo setup for each side of the engine. Time to figure out, where we will fit all that stuff …

A mock-up is a good idea to find out if everything works as expected, but after all we still imported everything into CAD to design the needed flanges and supports. Oh, and you need some piping ๐Ÿ˜‰

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Time to get all the parts build and we will keep you updated in the following episodes.

Episode 10 – engine assembly

Since most of the parts for the engine were lying ready on the shelf and blocking storage space, why not just put everything back in and on the block.

We pulled the bare block which was “stored” in the chassis and got it back on our engine stand … time for a final cleanup of the interior and the complete oil circuit. The camshaft with the plungers come in first (sorry that we have no pictures of this, even when we got the camshaft in and out 3 times, due to various reasons), followed by the oil spray nozzles under the pistons. Time for new main bearings …

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After the bearings were in, let’s put the crankshaft in. The crank is a heavy bastard, even without the counterweights … or our engine stand is just to high to carefully lift the crankshaft with two people into the block. Easy task for the crane, but wait … find the error … ๐Ÿ™„

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Main caps on, bolts in an then it’s time for some serious tightening. The needed torque on the main caps and on most of the other parts which will follow feels like the bolts (mostly fine threaded M20s) will shear off any second ๐Ÿ˜

The counterweights are bolted to the crank … but before mounting these, let’s put them on the scale and do some math about the forces the bolts have to hold. The heaviest counterweights have around 7kg, let’s assume 3000rpm and the weight traveling at a radius of 12cm around the crank … thus the weight travels 0.75m per revolution and 37.7m per second … physics tell us that the centrifugal force calculates as: F=m*vยฒ/r … resulting in 82.9kN … or ~8.5tons pulling on the crank .. there are 6 weights and we will attach 8 pistons with steel rods to that same crankshaft ๐Ÿ™„

Let’s not further think, what will happen when one of these parts comes of … oh, and the centrifugal forces are proportional to the square of engine speed.

After installing the pistons, all the parts were “in” the block. 3 pistons missing in the picture ๐Ÿ˜‰

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To close the block, we will just put the oil pan on. Actually not. Since we wanted a low center of gravity on the tractor, we are putting in the engine nearly as low in the chassis as we can. Without wanting to build a complete new oil pan, we just shortened an original pan. No problem, until you want to install the oil pump with the original suction tube …

Just a quick check and adjustments for clearance and we were fine.

In fact we came a little forward to make the engine race-ready and were meanwhile advised several times not to go with the original oil pump and setup, and will now go with an external oil pump. The newly build suction tube might become a nice candle holder ๐Ÿ˜›

Putting the cylinder heads on should be no big deal. Well, it is not, but there are a lot of parts going in the heads after installation and again lots of bolts to torque to the specifications.

Just get the timing gear on in the right position and the engine is back together. No worries, with the turned down pistons, the engine is a free runner (the valves won’t touch the top of the pistons in any position) and we don’t need to install the timing gear before the installation of the valve train.

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All nice and shiny …

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… hard to believe, regarding the state the engines were in before, and that we had to disassemble this particular block with a sledge hammer.

Time to move on with the auxiliary drive and work on the chassis, which will be covered in future episodes.

 

 

 

Episode 9 – Preparing engine parts

Parallel to the build of the chassis we are approaching the assembly of the engine. As stated in the episode about the engine tear-down, we had one engine in a pretty bad shape, but nonetheless we decided to rebuild that engine and keep the good block in stock. The rebuild will start anyway with a bare block, so that this shouldn’t be a problem. After the complete disassembly and a good clean it was time for a fresh coat of paint.

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After tearing down two engines, we had enough cylinder sleeves which are in the specs and only needed a good pass with a honing brush. One could say now: just use new sleeves and new components where you can when you are doing a complete rebuild. You are completely right, but spare parts cost you a lot of money and working on a limited budget … we will just reuse whatever we can.

The original camshaft out of this engine had just to much wear and damage, so that we were forced to use our spare. Camshaft bearings were fine, so that they just got a bit of a polish and were reused.

With the camshaft and cam followers back in place it was time to focus on some other parts, starting with the disassembly of the complete cylinder heads. Some of these were flooded with water and in really bad shape, the others were “just” full of oil coal and other residues from a probably more than 500000 km service life. So we needed to find a way for a good clean inside and outside, which (after first trials) none of us wanted to do by hand. We found the solution in electrolysis. Some hot water, soda and an old battery charger are good for a near miracle on such parts.

The cylinder heads got the needed machining to fit a spark plug and then it was time for a valve job. Valve and valve seat wear was at a point, that it was nearly impossible to just regrind the valves in their seats with grinding paste. The valve seat material is much softer than the valves themselves, so that grinding with paste would just wear the seats with nearly no impact on the valves. Since we don’t have a valve grinding machine, we became creative with a fixture to regrind the valves on the belt grinder. To drive the valves in the fixture and for the following grinding in the cylinder heads it worked just great to hot glue two valves with their faces together and use a power drill.

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Before reassembling the valves with their springs, it was time to test spring pressure. The specs for the valve springs give you a minimum spring pressure at a given length of the compressed spring. This is usually done in a special machine. The keen reader of this blog will know us well enough by this time … we build our own test fixture ๐Ÿ˜‰

A scale with a maximal load of 5kg, a well calculated lever and the Z-axis of the mill in combination with some special calibrated counter weights …

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Some tests for repeatability and we were able to select the needed 32 valve springs within the manufacturers specs.

The cylinder heads, together with the valve covers, got some new paint and after a good clean of all the bits and pieces, the valves were reinstalled.

During the machining of the pistons we already found out about different pistons designs. Getting the parts ready to reassemble the pistons with the rods for the installation, we found out that even the piston rings had slight differences from one piston version to another. Resulting from the stuck pistons, lots of the piston rings were damaged to a point that they couldn’t be reused. Somehow we managed to find 8 complete and fitting sets.

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In our application, the engine will take a lot more abuse than it was initially designed for. This results in a lot of stress of some key parts, which can result in a major engine damage. One of the worst case scenarios is your engine getting stuck due to gripping piston rings. The rings are designed with a ring gap when installed, so that it will allow the rings to expand when they heat up. On the other hand you want that gap to be as small ass possible to get no compression leakage. To be on the safe side, we added some ring gap. Again time for a fixture …

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The ring gap is measured, by just installing the rings in the cylinder bore, with a feeler gauge.

When it comes to major changes in the basic engine design, we also decided to go for a slightly bigger main bearing clearance on the crankshaft. The argument is the same as with the piston ring gap … avoiding your engine getting stuck. Grinding and polishing a crankshaft, you might have guessed it … we need a custom setup and machinery.

Handheld belt grinder, with an old dryer motor to use it on the lathe.

The results came out better than we imagined. We were able to reduce the main bearing diameters by an exact value and the measurements for all five main bearings ended within 0.5/100 of a millimeter.

Before …

… after …

After the polishing you can see the finest grinding marks ๐Ÿ˜ฆ , but this should be up to the job.

Cleaning some more pieces, including 64 cylinder head bolts and we can proceed to the engine assembly in one of the next episodes. Stay tuned …

 

Episode 8 – ROP

… Roll Over Protection

As one of several mandatory safety devices, the ROP is one of the most important parts, but on the other side it is also a big part of the tractor’s appearance. Thus there needs a lot of thinking to go into the ROP, but it is also a challenge in terms of manufacturing.

The first problem starts when you want to organize the needed material. ETPC rules ask for a seamless steel tube and gives specificationsย  on the dimensions in relation with the material you use. The use of chrome-molybdenum steel (25CrMo4) is recommended, but you can use normal seamless tubes, used by boiler makers, when you go with a thicker wall thickness of the tubes. Knowing that we wouldn’t have a weight issue on the tractor, we could have accepted the 20% extra weight of the ROP and just go with the boiler tubes … well, sometimes you have to set yourself a challenge ๐Ÿ˜‰

How tough can it be? In the literal sense, talking about chrome-molybdenum, we learned our lessons.

Knowing what we want, it was time to call about every steel supplier available in our area. None of them was able (or wanted) to sell us the material we needed. Even a call at a specialized steel supplier in Germany wasn’t successful. With the help of the internet we located a web-shop in the Netherlands, which would even sent the material to us.ย  Apparently, the well known shipping companies are not to excited to ship seven meter long material, so we had it directly cut into the needed pieces, with some spare material … that might be useful, regarding our non-existing knowledge about tube bending.

Tube bending is the next keyword. To bend tube, you need what? Exactly: a tube bender.ย  Not being to confident about buying a tube bender from the PRC, plans were made to build one ourselves. On Youtube and in the deeps of the internet you can find very useful information and creative solutions … or you just know someone in town having and old-school tube bender made in western Europe.

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After some measuring and calculations we felt confident and started with the first pieces. Just to have a good feeling, we filled up the pipes with fine grid sand, compressed on both sides of the tube with a wooden plug. The two rear loops with a single 90 degree bend came out perfect, and we were able to take some more measurements to get a good setup for the front loop with it’s multiple bends.

We figured out, that it was all about the perfect alignment of the tube in the machine, doing multiple bends. This said, we marked a 3 meter piece of tube and the disaster started. Here we learned our lessons with chrome-molybdenum … once it’s bend and twisted in the bend, you are f****d. It’s nearly impossible to fix or clamp the tube well enough to correct your bend in any direction.

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One piece for the scrap container, of to the next one. We had a steep learning curve and with some corrections the next part came out just perfect.

Time to do all the other little pieces, to finish the complete roll cage. Having all the parts bent, it was time to start assembling. Assembling just works with lots of adjusting, measuring and of course tube notching. Not having a special made tube notcher, we just made a jig for the lathe. This setup is certainly not the safest, but even with doing small steps, you can reach your target.

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By the way … even the best hole saw learns it’s lesson the hard way in chrome-molybdenum steel ๐Ÿ˜‰

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We were finally able to complete the ROP and we think that it came out pretty well.

Everything is tag-welded in place and will be welded with the rest of the rear axle.