CNC-wizard Harald Grillhiesl with his fuel-injected 260cc Serveta
CNC-wizard Harald Grillhiesl with his fuel-injected 260cc Serveta

CNC has revolutionised engineering in the last 20 years in the same way that 3D Printing (additive manufacturing) looks set to do the same in the next 20 years.

Harald’s firm specialises in the former. CNC is subtractive manufacturing, in that you start with a big solid lump, known as a billet, and you carve away everything that you don’t want.

 

Old joke intermission

Q: “How do make a statue of an elephant?”

A: “Get a giant lump of marble and chip away everything that doesn’t look like an elephant”

VIDEO | CNC in action

Elephant Stone

This carving is done using a combination of machine tools following a pre-programmed routine. CNC stands for Computer Numerically Controlled. Essentially, it’s any cutting machine controlled by a computer.

While we were visiting, along with SLUK’s German correspondent Boris Goldberg, we were able to see most of the process of production of the CNC basket for a BGM Superstrong clutch.

A selection of MMW handlebar pumps for Lambretta and 'Linke Nummer' left-hand inlet manifolds for the TS1 kit.
A selection of MMW handlebar pumps for Lambretta and ‘Linke Nummer’ left-hand inlet manifolds for the TS1 kit.

MMW

Harald is a man of many names, probably best-known on the German Scooter Forum under his pseudonym ‘Gravedigger’.

MMW stands for Mangold Maschinenbau. The ‘W’ is for Werkzeug – a Worb5 addition because most scooter parts manufacturers use three initials. They are a CNC company primarily concerned with producing parts for industry, but under Harald’s direction now turning over at least 20% of their machine-time to producing scooter parts. During the corona-virus crisis scooter parts actually represented a larger proportion of their production as normal businesses shut-down, but the demand for mail-order scooter parts remained remarkably stable.

The MMW scooter business started around the year 2000 when Harald bought another Vespa after a period in the wilderness riding motorcycles. It occurred to him that he could make previously unavailable scooter parts.

The first products were CNC-machined cylinder heads. At the time, when you bought a Polini or Malossi kit they came without a suitable cylinder head so Harald designed and made some to suit. He also filled the gap in the market when Piaggio could no longer supply heads for the Vespa T5.

“Now Malossi and Polini all produce heads for their kits”, Harald explains. “When the automatic scooter market went down they looked at their old products and revised them. They had to do what they could to support their businesses.”

Thankfully, Harald has no shortage of inspiration for other products to make.

When I ride I have the ideas”

Round billets await initial machining
Round billets await initial machining

Supplying the shops

 

Over the last 20 years, MMW has been a regular parts producer for pretty much all of the major German scooter shops including: Worb5, SIP, Scooter Center (BGM), LTH and Jockey’s Boxenstop. Harald draws the majority of parts in Computer Aided Design (CAD) software – very few designs are supplied from outside.

Some of these then make it onto the market as MMW parts through a range of dealers, or alternatively the shops ask for parts to be produced exclusively for them; such as the BGM clutch in the video.

For LTH the range includes a massive selection of Lambretta light switch and hydraulic brake master cylinder units with variations to suit all the different Lambretta and even Serveta models. One advantage of CNC production is that you don’t need to re-tool for a variation (like you would with castings), you simply re-programme the CNC machine to modify the tool paths.

First operation machining on the BGM Superstrong Vespa clutches
First operation machining on the BGM Superstrong Vespa clutches

Latest Developments

The product range continues to expand from engine parts to brakes, clutches and suspension.

Latest products include some strong lower damper brackets to adapt 125 and 150 Lambretta fork links. These are a much sturdier solution to the bendy pressed-steel brackets produced now in India.

Prototype MMW RS2000 mechanical muffler
Prototype MMW RS2000 mechanical muffler

Shhhhhhhhhhhhhhh

Harald is also working on a mixed mechanical and absorption exhaust muffler to keep the noise down on engines with expansion chambers. A version for the popular TSR Evo exhaust was one of his first solutions.

The issue of motorcycle and scooter engine noise is currently a very hot topic, with the Tirol area of nearby Austria recently introducing a ban on any motorcycle producing over 95dB; according to the registration process. Bear in mind that this is a lower figure than many production bikes leave the factory with, let alone before they are fitted with any tuning parts.

You can read more about the ban here.

Components for the excellent 7-plate Liedolsheim clutch from LTH
Components for the excellent 7-plate Liedolsheim clutch from LTH
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Lambretta KillerCase

Easily the most complex scooter part project has been the KillerCase; a new Lambretta engine casing designed to take an air-cooled Simonini paraglider cylinder. We’ve covered the KillerCase project before on Scooterlab, but I finally got a chance to ride one the previous day at Kevin Becker’s place as part of my work on the forthcoming (but Covid-delayed) Complete Spanner’s Lambretta kit Book.

On the KillerCase the drive bearing is fitted from the outside
On the KillerCase the drive bearing is fitted from the outside

The engine is essentially a complete CNC Lambretta casing that takes all the standard transmission, crankshaft and mag-side components, with the exception of having a crankcase mouth pre-machined for the Simonini barrel and a crankcase reed-valve feeding in behind the kickstart-side engine mount.

The concept is to create a simple performance motor aimed at touring. Several notable figures from the German scooter scene are now making parts for this project and it’s safe to say that the results are quite impressive for what is essentially a bolt-together ‘kit’ of parts.

2% oil mix

The great advantage of a crankcase reed feeding directly over the crankshaft is improved lubrication as the incoming fuel/oil mix aims straight over the big-end bearing. As such it is possible to run 2% oil mix ratio on these motors; which offers both cost and weight advantages when touring, compared to a 4% oil ratio engine.

A typical 'kit' of parts to assemble a KillerCase Simonini engine
A typical ‘kit’ of parts to assemble a KillerCase Simonini engine

Hefty lump

The only detrimental thing I could say about the KillerCase is that it is heavy compared to a cast crankcase; weighing around 8kg when empty compared to 6kg for a standard engine.

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Fuel Injected Lambretta

One of Harald’s other pet projects has been to convert not one, but two of his Lambrettas to run electronic fuel injection instead of a carburettor.

To the left is the air-box with MAP sensor and below it is the fuel pump.
To the left is the air-box with MAP sensor and below it is the fuel pump.

The advantages of this system are more accurate fuelling across not only a range of rpm and temperatures, but also over a range of different altitudes. The system uses a lambda sensor in the exhaust to adjust fuel injection ratio ‘live’ according to a predefined map.

The disadvantages of the system stem chiefly from its complexity. For a start, it needs a flywheel and stator with a high electrical output in order to run both the injection system and the high-pressure electric fuel pump.

This KillerCase motor runs a TSR Evo exhaust with a special downpipe and MMW RS2000 muffler
This KillerCase motor runs a TSR Evo exhaust with a special downpipe and MMW RS2000 muffler

He used this system on his KillerCase-powered LI Series 2 for the EuroLambretta in Poland in 2019, and has subsequently fitted another to his Serveta.

The system uses an MMW-produced throttle body, but all the other injection components are off-the-shelf from various production vehicles to ensure maximum reliability. Only the Microsquirt injection controller is proprietary.

The injection system can be reprogrammed via Windows tablet or even from a phone app.
The injection system can be reprogrammed via Windows tablet or even from a phone app.

German humour

 

The boring stereotype is that ‘funny’ is not a strong-point among the Germans, but that’s clearly not the case with Harald. Despite his laid-back manner there’s an undercurrent of subversive humour that is apparent in his use of English phrases for product names.

Originally the control system was an ‘Alpha-N’ system; using Lambda and throttle position inputs to set the fuelling. This latest set-up instead uses ‘Speed Density’ control; using Lambda input and a Mass Air Pressure (MAP) sensor in the inlet to assess engine load.

“The problem with a 2-stroke injection is always the Lambda sensor”, explains Harald. The oil residue and carbon build-up inside a 2-stroke exhaust is a hostile environment for a delicate gas sensor.

So, does the fuel injection offer enough advantages to be worthwhile?

“When you ride up a mountain it works perfectly, but it is so complex that you can’t sell this to the public. It’s just for fun.”

Elements of the 'Dirty Sanchez' front brake conversion for Lambretta.
Elements of the ‘Dirty Sanchez’ front brake conversion for Lambretta.

Dirty Sanchez

A good example is the MMW-produced anti-dive disc brake conversion which he called ‘Dirty Sanchez’ after the same unsavoury sexual practice that inspired the Welsh self-abusers of the same name. You’ll have to look it up on Urban Dictionary if you don’t know what it means.

Harald's long-fin CNC fan for the SIP Vape Lambretta ignition which he has nicknamed 'Blow Job'.
Harald’s long-fin CNC fan for the SIP Vape Lambretta ignition which he has nicknamed ‘Blow Job’.
Golden Shower injection, in the documents for Harald's scooter.
Golden Shower injection, in the documents for Harald’s scooter.

Golden Shower

Perhaps my favourite though is the name he gave to his fuel injection conversion. With the German TuV inspection system all modifications must be technically assessed, homologated and recorded. As a result the vehicle documents for his Serveta now proudly state that it is fitted with a ‘Golden Shower’ injection system. If you don’t know what that is then you haven’t watched enough German porn.

VIDEO | Harald’s fuel-injected Serveta

Luxury For Your Scooter

 

Increasingly Harald is finding that his own customers are also some of his biggest rivals. The German shops are increasing their product ranges by producing their own ranges of CNC parts, often in countries where manufacturing is cheaper. This means that they have no incentive to stock Harald’s more expensive German-made equivalent.

CNC carb top adapters including a wheel and 90-degree cable entry for various carburettors
CNC carb top adapters including a wheel and 90-degree cable entry for various carburettors
MMW Lambretta fork link damper brackets
MMW Lambretta fork link damper brackets

In response, Harald set up his own website called www.luxury-for-your-scooter.de/ to ensure that all his CNC products still have a route to market.

Everyone’s got to make a living. When the reality of running this company is that he’s in work on many Sunday mornings feeding the hungry CNC machines with fresh billets of metal, it’s difficult to say he doesn’t deserve it.

At least he has Saturday’s off; which he spends at work, messing on the dyno with friends and talking scooters over a beer and a Bavarian sausage. Occasionally he has time to ride a scooter and then he thinks about the next parts that he is going to make.

There’s no rest for the wicked. Nor the inventive Scooterist.

Text, photos and video: Sticky

 

Thanks to Harald, Boris and Kevin for help with this article.

Do you like German engineering? We’ll soon be supplying selected BGM & LTH products

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