UK mobility scooter is well made

I was asked to change a control on the handlebars of a mobility scooter.

Tramper TWS right hand control

It is a ‘TWS‘ model from UK scooter firm Tramper.

Both designed and made in the UK, it has two-wheel drive through twin motors and a microcontroller system.

Having taken apart motorcycle handlebar controls before, a long time ago, I was expecting the worst – wires tightly crammed together and poorly-made switches with burned contacts (that’s right, I used to work on old Italian bikes :-).

Anyway, the control came apart easily, and I was pleasantly surprised to see connections to the rest of the bike were through an Ethernet-style connector – which meant I could disconnect it and work on the thing in the warmth of the living room, and most of the connections were made though a neat pcb which also held most of the switches.

Tramper TWSAll very tidy and professional – although, fair’s fair, it does take up more room than is available on many motorcycles.

I needed to change the rotary control, which is wired because it fits from the outside. Tramper had not soldered it, but thoughtfully provided a screw terminal block – apparently this control can get wacked when users drive their scooters through hedges. A spare was about Β£20 straight from the maker.

As it happens, the potentiometer was in perfect condition and changing it did not cure the slight juddering sometimes experienced on this particular scooter, so more investigation is required.

Tramper 6x6But what a delight to work on.

All the welding and mechanical design looks exemplary too.

I particularly like the robust parallelogram front forks, which are actually rose-jointed – Shades of Norman Hossack’s amazing motorcycle front suspension – ‘Hossack 1’ (google it) was entertainingly campaigned at Brands Hatch by Vernon Glasier, also years ago.

BTW, Tramper also makes a remote-controlled military vehicle – the 6×6.


Comments

4 comments

  1. In this case, the Ethernet connector is thankfully in a shower-proof enclosure. There is actually an additional issue. The cable goes on to be zip-tied to the handlebars, which have a near vertical section, which does end-up putting tension on the cable as the zip-ties creep downwards.

    On the steering front – My feeling it that the weak point is where the threaded rod enters the rose joint. Some bad thread-forming could make it break suddenly. I will advise the rider to stay away from cliffs! I used have such joints on my recumbent bike – glad I was ignorant of sudden failure at the time.

  2. My comments probably just reflect personal traumatic experiences. πŸ™‚
    Ethernet is becoming popular on vehicles, so finding suitable connectors is a challenge. The RJ45 has the virtue that it doesn’t change the conductor geometry used in the cable, so the impact on characteristic impedance is minimal. I’ve seen a shell/boot used with the RJ45 to allow it to survive a moderately rough environment. It provides strain relief and some protection from moisture. Not a bad way to get a bit of improvement at low cost.

    Steering controls or linkages are critical to safety, although if the vehicle is only going 4mph, then it’s unlikely that you’ll go flying off of a cliff or into the path of a huge truck/lorry when the linkage breaks. I’ve seen similar linkages on bicycles that will travel 4 or 5 times faster, and it’s caused me some concern. All mechanical parts will fail eventually… hopefully the failure mode will be gradual and provide some indication of what is happening. The same problem exists for bicycle forks, stems, and handlebars, so it is probably an acceptable risk for the steering linkage.

    (is it acceptable for engineers to worry this much? πŸ™‚ )

  3. Hi Mr Kurt.

    I had not thought about the Ethernet connector under vibration, and I take your point. Actually, I hadn’t got much beyond being pleased it had a connector of any kind. Hopefully it is not stressed much as the machine only does 4mph and its electric motors are smooth-running. I am now starting to wonder if it is solid or stranded cable….
    In a past life, we tested ordinary ribbon cable connectors on a shaker table and found they were remarkably vibration resistant as long as the strain reliefs were used – the type that the cable doubles back behind.

    On the subject of front suspension, I really like the arrangement as handlebar position becomes independent of fork position. And I don’t think hands would last long being vibration tested on top of un-sprung forks…
    Also the steering works though rose-joints – which seem wonderfully reliable – although with your vehicle experience you may know better here!

  4. My experience is with vehicles operating in more severe environments than this scooter, which is why I’m surprised that the RJ45 ethernet connector is used. The connector is designed for stationary applications, where there isn’t any vibration or fretting of contacts.
    The scooter is unlikely to see the awful conditions that I’m accustomed to, so perhaps it is suitable. There must be some inexpensive Molex connector available that is actually designed for a bit of vibration??

    The steering/shock arrangement is new to me. I’ve seen linkages like that on the fork itself, so why put the steering mechanism on the other side from the handlebars? i.e. why require the steering linkage going across the suspension linkage?
    Safety is always a concern with vehicles, so adding to the complexity of the steering mechanism is just adding more parts to fail and reduce reliability.

    Steve K.

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