Using the exam­ple of the elec­tric scoot­er illus­trat­ed in Fig­ure, the poten­tial of the new dri­ve con­cept has been illus­trat­ed in an artis­tic representation.

An elec­tric scoot­er equipped with Traction‑X would allow the motor to be rigid­ly mount­ed to the frame and with­in the rear wheel (see illus­tra­tion). The sig­nif­i­cant­ly enlarged rear wheel is also the rock­er arm for shock absorp­tion and damp­ing. The space gained facil­i­tates to accom­mo­date part of the bat­tery below the seat and in front of the rear wheel, so that the footwell is com­plete­ly avail­able to the dri­ver. Dri­ving sta­bil­i­ty, rolling com­fort and agili­ty of the vehi­cle are sig­nif­i­cant­ly improved, as described in sec­tion the inno­va­tion.

The over­all vehi­cle and its out­stand­ing tech­ni­cal improve­ments will rep­re­sent noth­ing less than a tech­ni­cal revolution!

I have been a pas­sion­ate motor­cy­clist for most of my life. In addi­tion to enjoy­ing the rid­ing expe­ri­ence, feel­ing close to nature and a feel­ing of free­dom, my enthu­si­asm is also based on a inquis­i­tive­ness for the inner­most tech­ni­cal con­nec­tions of motor­cy­cles, these mar­vels of mechan­ics, electrics and elec­tron­ics. Part of my pas­sion has always been the plea­sure of doing man­u­al work when I dis­man­tled my motor­cy­cles to restore or main­tain them and at the same time reveal their tech­ni­cal secrets. In lat­er years, when I asked for more com­fort, I found that many of the fea­tures of mod­ern scoot­ers suit­ed me, but that I was forced to accept some sig­nif­i­cant­ly poor­er rid­ing char­ac­ter­is­tics com­pared to the motor­cy­cle. As a tech­ni­cal­ly ambi­tious engi­neer, I soon began to think of a remedy.

The fol­low­ing is a brief analy­sis of the require­ments, cir­cum­stances and derived prop­er­ties of the com­pet­ing two-wheeled con­cepts: A motor scoot­er is char­ac­ter­ized in that there should be a splash-proof footwell behind the front wheel and in front of the driver’s seat, allow­ing the rid­er a nat­ur­al and relaxed sit­ting pos­ture. A motor­cy­cle, on the oth­er hand, is char­ac­ter­ized by the fact that the fuel tank and an engine are locat­ed between the legs of the seat­ed rid­er. Both assem­blies must there­fore be posi­tioned fur­ther back in a scoot­er. This would the­o­ret­i­cal­ly increase the scoot­er wheel­base. How­ev­er, since the wheel­base of a two-wheel­er must not become too large, all scoot­ers designed so far were forced to lim­it it by a com­bat­ion of essen­tial­ly two mea­sures. The first mea­sure to reduce the wheel­base is to instal­la­tion of small­er wheels com­pared to the motor­cy­cle. How­ev­er, this has three neg­a­tive effects

• The dri­ving sta­bil­i­ty of the scoot­er is low­er com­pared to a motor­cy­cle, because the sta­bi­liz­ing angu­lar momen­tum of the small­er wheels is low­er, and con­se­quent­ly the dri­ving behav­ior of scoot­ers is often per­ceived as “wob­bly” and “ner­vous”.
• The rolling com­fort of the small­er wheels is sig­nif­i­cant­ly worse, since due to their small­er diam­e­ter, even small pot­holes or uneven­ness­es on the road are ful­ly traversed.
• Dri­ving safe­ty is low­er because the small­er con­tact area or the small­er “tyre swath” means that there is less grip on the road.

The sec­ond pop­u­lar mea­sure to lim­it the wheel­base of any scoot­er is the instal­la­tion of so-called dri­ve train swingarms, which com­bine the motor-gear­box assem­bly with aux­il­iary com­po­nents includ­ing sec­ondary dri­ve as a large sus­pen­sion lever. The neg­a­tive effect of this tech­ni­cal mea­sure is the large unsprung mass, which must be coun­ter­act­ed by a hard spring coef­fi­cient and greater damp­ing of the rear wheel sus­pen­sion. As a result, the over­all sus­pen­sion ride com­fort is com­par­a­tive­ly poor.

The cus­tomer wish­es and require­ments for a relaxed seat­ing posi­tion, weath­er pro­tec­tion, com­fort and a maneu­ver­able vehi­cle, as shown in the fig­ure are there­fore bought with sev­er­al dis­ad­van­tages with con­ven­tion­al motor scooters.

This is exact­ly where the Traction‑X inven­tion comes in, com­bin­ing all the advan­tages of the scoot­er with all the advan­tages of the motor­cy­cle, “the best of both worlds”, so to speak..

The state of the art in scoot­er dri­ve trains is the com­bi­na­tion of a so-called swing arm dri­ve train with a con­ven­tion­al rear wheel that has a cen­tral mount­ing. A swing arm dri­ve train is an inte­gral design of engine, trans­mis­sion and rear wheel swing arm. The motor and dri­ve hous­ing is swiv­el-mount­ed in the motor­cy­cle frame and fol­lows the move­ments dur­ing the com­pres­sion and rebound. The dri­ve shaft and swing arm are also func­tion­al­ly and spa­tial­ly sep­a­rat­ed. The dis­ad­van­tage of this design is the large unsprung mass, i.e. the large moment of iner­tia, which results in a mod­er­ate response and com­fort of the rear wheel sus­pen­sion. The advan­tage of this design is the con­stant dis­tance between the chain sprock­et and the rear wheel sprock­et in the chain dri­ve or between the front and rear pul­ley in the belt drive.

The inven­tion of the Traction‑X was moti­vat­ed by the task to devel­op a com­pact unit for pow­er-trans­mis­sion and wheel sus­pen­sion for a motor scoot­er, which meets the fol­low­ing requirements

• A short wheel­base of the two-wheel­er in com­bi­na­tion with a small turn­ing cir­cle and a low moment of iner­tia around its ver­ti­cal axis were sought to real­ize, with the aim to achieve good agili­ty and mobil­i­ty of the scooter.
• A large wheel diam­e­ter was sought to facil­i­tate, so that dri­ving sta­bil­i­ty, road-hold­ing, and ride com­fort are sig­nif­i­cant­ly improved com­pared to con­ven­tion­al scooters.
• The mass of the motor-gear unit should have no influ­ence on the shock-absorb­ing and spring-loaded wheel sus­pen­sion, i.e. the unsprung mass of the entire wheel sus­pen­sion should be small, regard­less of how large the motor-trans­mis­sion unit is.

Tech­ni­cal­ly, the Traction‑X inven­tion could be referred to as a “dri­ve arm wheel sus­pen­sion”. It com­bines the func­tion­al­i­ty of three tech­ni­cal components

1. the sec­ondary dri­ve from the motor or trans­mis­sion out­put to the dri­ve wheel, depend­ing on whether it is an inter­nal com­bus­tion engine or an elec­tric motor drive
2. the swing arm or the rock­er arm of the resilient sus­pen­sion, and
3. the dri­ve wheel itself.

For this pur­pose, Traction‑X fea­tures a very large wheel bear­ing, which has the same dimen­sions as the wheel rim itself, so that there is an inner ring inside the wheel, which is not rotat­ing w.r.t. wheel rim and tire. The wheel is sup­port­ed like a rock­er arm by means of a spring strut and an axle. This axle or wheel lever shaft at the same time is the dri­ve shaft for the wheel itself. For this pur­pose, it has a dri­ve gear­wheel with exter­nal teeth, which is in engage­ment with an inter­nal tooth­ing con­nect­ed to the out­er wheel rim. The dri­ve shaft is dri­ven at an out­er end by a motor gear unit, for exam­ple via a chain, belt or spur gear dri­ve. For its sec­ond func­tion as a swing arm, the dri­ve shaft is mount­ed at its out­er ends via plain or roller bear­ings into the frame of the two-wheel­er. The inner com­po­nent of Traction‑X, which is non-rota­tion­al w.r.t. the wheel rim, is mount­ed sta­t­i­cal­ly deter­mined onto the com­bined dri­ve and wheel lever shaft by means of a ball bear­ing and a nee­dle bear­ing. The heli­cal gear unit and the bear­ings inside the hous­ing made of the inner wheel ring and wheel rim can be sealed to the out­side by means of radi­al shaft seals. Thus, the entire Traction‑X dri­ve arm wheel sus­pen­sion can be ful­ly oil-lubricated.

In a sec­ond vari­ant of the inven­tion the wheel is sup­port­ed by means of three rollers, which engage and roll in a ring groove. This replaces the very large ball bear­ing. Again, this arrange­ment results in an inner com­po­nent that is not rotat­ing w.r.t. wheel rim and tire. The roller cas­ings pro­trud­ing into the inside of the wheel slight­ly reduce the inte­ri­or clear­ance, but yield some coun­ter­ing advan­tages. They can be used in a sealed vari­ant that is lubri­cat­ed for life. With­in a scoot­er of mod­er­ate dri­ve pow­er, oil bath lubri­ca­tion can be dis­pensed with, so that the two large radi­al shaft seals can be omit­ted. This in turn reduces the fric­tion­al moment in the system.

The use case of Traction‑X with­in a scoot­er was the moti­va­tion of the inven­tor. There­fore, the advan­tages of the inven­tion for this appli­ca­tion will be worked out in the sec­tion Inno­va­tion.