Apax tilting trike

Discussion in 'Motorized Trikes' started by fredbert, Nov 16, 2007.

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  1. fredbert

    fredbert Guest

    I thinks this is a great innovation http://www.apax.ca/ check out the video.

    I have come up with a design to adapt this to a wheelchair but need some guidance with the type of suspension to use.

    I do not want the full tilting just the ability of the back wheels. If I could get this sorted it would be a gift to those in wheelchairs that lead a very active life and hopefully at a minimal cost. Too many are making money of the backs of the wheelchair users.

    The whole system is based on the calleja setup fig3.jpg this shows the the basic principle, Apax replaced the connecting bar with its hydraulic energy management system.

    This pic shows what happens when turning\tilting fig4.jpg note how the complete setup tilts, seat and all.

    I do not want this I want to keep the seat level which is obtained by some sort of suspension system like Apax uses, I need advice in choosing a simple version like springs of some type.

    The added advantage of what I have come up with is the ability for someone to still push the chair and it is still narrow enough to be pushed around shops if needed.

    Here is a system that tilts mipmip+3.jpg I think it can be described as tilting on a side way motion or is it lateral?. If you imagine the back end of the apax in place you will get the wheels going up and down on the vertical? Hopefully this gives an idea of what I am on about.

    Any advice will be welcome.


  2. JemmaUK

    JemmaUK Guest


    from what I can tell this system is basically two lighter duty versions of a rear motorbike suspension frame..

    Given that this is the case it shouldnt be a great problem to fabricate.. and from what little I know about wheelchairs there might be an added advantage..

    if you use a wheelchair frame as a base which has the wheel axle mountings that are straight in the vertical plane you might be able to set up some sort of torsion bar suspension which is then spring damped. This would use the mountings for the rear wheel axles for the fitting of the torsion bars. Damping could be achieved by a similar system as used on the trike. If you want to spend alot of money or produce a deluxe version shimano do a computer controlled air suspension system - two of the rear shocks from that and the control system/generator hub could be very useful.

    If you mount the wheels inboard to the suspension arms then you would indeed keep the narrow track of the traditional wheelchair. The only problem I can see is that of wheelbase. This might be solved with some clever engineering. if you pivot the suspension arm in the middle and link the dampers to the front end of the suspension arm - linking that to the outside of the armrest frames that would provide you with suspension movement and effective damping.

    Another method would be L frames with the torsion pivot at the bend and the damping on the top arm of the L mounted to the backrest frame via adjustable dampers and the end of the horizontal being the wheel mounting..

    And now my brain hurts - so I am going to go get something to eat :)

    Hope that helped

    Jemma xx
    Last edited by a moderator: Nov 16, 2007
  3. fredbert

    fredbert Guest

    Thanks very much for the advice it is appreciated, here is a crude drawing of the back end of the w'chair I hope you can see what I am trying to do. trike.jpg

  4. JemmaUK

    JemmaUK Guest

    Hi Ed,

    That is pretty much what I had guessed you were trying to do...

    The problem with that approach so far as I can see is one of the length of the machine in total. If its only intended for use cross country then that isnt a problem, but it might become a problem when you are trying to use the machine in an enclosed environment - you'd have a good 6-8 inches added to the wheel base.

    a different option would be as follows:-

    assuming the use of the same wheel size as is standard take a pivot point from the front upright with the wheel mounted to the pivot in the approximate location as it is presently (ie in a standard chair). If the tailframe is cut back it would allow you good ground clearance. This would allow another person to push the machine, allow use in enclosed spaces, and give good suspension travel. The combined damper/springer (AKA MTB rear suspension type) could be mounted between the mid part of the pivot and bracketed to the lower side of the armrest support arm.

    But I have another suggestion as well.

    You might have noticed that several bikes on here use the Schwinn-type open springer forks. These are available as retrofits in both 20" and 26" configurations - are adjustable for springing rates and the springs are strong enough as to be self damping.

    If one of these were to be fitted on each side (aka welded or clamped) and the relevant size wheel installed this would be a simple answer to your requirement.

    Assuming you had the donor chair & someone with expertise in welding that method would be quite cheap and still provide fair suspension travel (although the springers would have to be set quite 'loose' for this application). For example in the UK the springer fork of that type is available for £35 per unit approx - or for a more ruggedised version something akin to an MTB fork such as rock shox for £60 upwards...

    Just some more ideas :)

    Jemma xx
  5. fredbert

    fredbert Guest

    Thanks for the advice Jemma you really are putting some thought into this and I appreciate it.

    I have a spare w'chair to play about with I have a pdq power trike adapter which I am converting to run with an engine,with some help from this board.

    Basically I get the trike with out having to build from scratch which helps alot in developing this idea, this means I can concentrate on working out the back wheel issues.

    When you say pivot at the same location as the wheel is normally, that would mean the wheel will move up and down in line with the shoulder. Or have I misunderstood you?

    I just realised that my drawing has the suspension too long, a wheel travel of 8-10" or so would suffice.

    With regards to length I would not worry too much, the main issue is not to have the wheel raise so that it is near the user.

    I am not too sure how I am going to set the suspension up though so it moves independently like the Apax.

  6. JemmaUK

    JemmaUK Guest


    First off if you are thinking of a suspension travel (at the axle) of 8-10 inches thats a little ott ... you are building a off road bike effectively - not a full grown Tatra T813 military truck... there is also the fact that that amount of clearance would be more than enough to cause a risk of over turning in certain situations.

    As you surmise with the front mounted pivot the wheel would be at approximately its current location - with a degree of movement of maybe 2-3 inches which would provide enough suspension movement to deal with most issues that could be overcome without some sort of engine assist: either IC/Electric/Hybrid. With the smaller suspension travel there is also the possibility that with good design the machine might be able to be self propelled by the incumbant should that need to be the case. The trailing wheel designs dont allow that...

    Your point about the incumbent being at risk from the wheels is a fair one but then in that configuration its probably no more of a risk than would be usual.

    All of the configurations I have talked about and yours will provide independant wheel springing/damping. I am wondering if the Ajax system is more like a air damper with level assist - such as the electric Humber Selectaride system. If that is the case the machine could be made to be self leveling using this system. This would not be provided by a springer/damper system and would be a whole lot more complicated/expensive.

    Thinking of the trailing wheel design - I dont know if you have heard of something called the revowheel - a 26" wheel with a 21cc engine built into the hub with a single on/off start stop system limited to about 20mph which would make a wonderful IC assist system for such a project - I just dont know if its available yet..

    Jemma xx
  7. fredbert

    fredbert Guest

    "not a full grown Tatra T813 military truck. lol and ha ha good one, I'll be looking into tracks next.
  8. fredbert

    fredbert Guest

    I have for my main w'chair a JW11 which is the motor built into the wheel hubs, I was going to mention that to you but I did not want to get too far ahead.

    I take it you looked at the Apax video if you look at the rider he sits level going down the steps or along slopes, it is the level seat that I want.

    To be honest I thought the fixing of the suspension under the arm rest area is a good one,do you think we could get the movement as such to give the same as the apax, btw I do not want the tilt it has.
  9. fredbert

    fredbert Guest

    The revowheel is some job $400, I think an engine with a alternator to charge batteries would be an option though electric wheelchair motors on the back wheels would give another drive source.
  10. JemmaUK

    JemmaUK Guest

    ok.. that system is complex but it boils down to the fact that its two suspension moments..

    on is a lateral moment - which gives you the tilt - having the same effect as ailerons would have on an aircraft - except there is no control of yaw by the operator

    the other is the traditional medial moment which provides what is effectively a traditional car type suspension..

    herein we have our problem.

    in order to have the ability to go along a slope without the seat being tilted in the lateral (left/right) plane we need both moments (in this case provided by joints), ie running along the strike of the slope (I trained as a geologist)

    However going down the dip of the slope we have a different set of problems... it could be possible to make the seat sit level but then you would have no suspension action at all and would end up scraping along the floor most of the time... theres an apt Family Guy quote but I am so not gonna use it here...

    basically with all the systems discussed you will get some shock absorbing function... to get the same thing as in the video you would have to have a high deflection/short throw suspension which would likely make pushing a chair if required hard workif not impossible.. and unless you used small 16" - 20" wheels you'd end up looking like an inverted penny farthing... not to mention your doctor having 40 fits at my expense... lol


    further perusal shows me that their system uses one set of dampers/springs for control of both the lateral and medial movements... both of which are needed to provide that type of levelling because there is no way that just the suspension arm travel can go far enough to level the machine laterally and still be useful for general suspension.

    If all you are interested in is the medial (fore/aft) leveling then there is another option. That is to remove the seat from the chair and make up a frame mounted on bearing races to hold the seat and by extension the occupant - which with one of the discussed suspension set-ups should allow both springing/damping and keep the occupant horizontal in the fore/aft plane...

    does that help any?

    Jemma xx
  11. fredbert

    fredbert Guest

    I have found another site that explains the basic principle that Apax uses http://www.moebius.es/ccalleja/index3.htm

    Fig 6 shows the complete system the front half controls the tilting which is not required.The back end with 2 ram rods gives a push pull,so I am told, which controls the up down movement of wheels.

    Apax has really complicated the issue if you go here http://jetrike.com/plans.html a more basic system is shown for recumbents, I can build this but it is too low down.

    btw I meant 8-10cm and I am sticking to it.
  12. JemmaUK

    JemmaUK Guest


    sorry was thinking in inches. 8-10cms is equal to the 3-4 inches travel I mentioned.
    I think I understand better what your aiming at so how does this sound?

    L shape suspension arm with MTB rear shocks mounted at the top in extension. pivot mounted halfway down the upright using wheel axle mounts with inboard 16" wheels - should give you the travel you want.

    what, if any brake will you fit?
  13. Alaskavan

    Alaskavan Guest

  14. fredbert

    fredbert Guest

    Sorry for not replying I am knocked off me feet with a silly bug my daughter brought home, she fine though! huh!

    Thanks for the link Alaskavan I would really love a fully tilting three wheeler but they are too low down.

    Jemma I found out that the two swing arms need to be connected to balance their movement so one goes up the other down or else it tips, I am sure you know that. I saw these site's http://jetrike.com/ or http://www.fastfwd.nl/eng/index.php I will try to adapt.

  15. mnbiker

    mnbiker Guest

  16. Alaskavan

    Alaskavan Guest

    How about taking the plans for the Jetrike and altering them so it has a platform that you could roll your chair onto and fasten it down?
    Last edited by a moderator: Nov 23, 2007
  17. fredbert

    fredbert Guest

    Hi mnbiker thanks for the help Jemma and I was talking about that sort of arrangement but with me getting this bug I have'nt followed it up yet.

    I was thinking about how to set the springs/shock so they are strong enough to hold up the back end and still allow the wheel move up when it goes over uneven ground. As I am not too sure about spring/shocks this is where I get lost.

    Alaskavan I would need some sort of driving unit I am unable to peddle, saying that the Jetrike is a full tilter I would not feel safe. Is there a special reason why tilters are so low down?
  18. Alaskavan

    Alaskavan Guest

    The tilting trikes are so low for 2 reasons. 1) Being low keeps the center of gravity inside the triangle of the wheels when cornering; and 2) Aerodynamics. Both related to high speed cornering.
    I guess you are more interested in being able to operate on uneven terrain, and that poses different requirements. So I have to agree that the trikes on that site probably wouldn't have much relevance to your needs.
    IMO, the question of power is relatively simple compared to the suspension issue. Something like the Staton setup shown in your first posts should be adaptable to most any wheeled vehicle.
  19. JemmaUK

    JemmaUK Guest

    ...What alaskavan said lol ...

    The higher the centre of gravity the less stable the what-ever-it-is will be... which is why you find things like the new Discovery have computer controlled suspension so they dont end up doing the wingless equivalent of a ground loop ala the old Suzuki 4x4s and the Merc A class...

    As to the interlink on the suspension it depends what you want ... if you want a non indepandant system two swing arms linked in a H frame shape with the damper on the crossbar of the H would be fine... but that wont do what you want..

    the best way is a linked fluid/gas damper system such as that known as hydralastic/hydragas in the BL cars (princess & 1100/Mini) - problem there is complexity... and it can be a pain to get set up right (there was a reason the former was referred to as 'hydraspastic' in a less PC age - although that was, to be fair, more to do with BL's quality control rather than inherant faults with the system itself).

    Oh and dont do what Rover did with the 213/216 - they managed to engineer in a 17% difference between the left and right rear springing rates... must have been the kid on work experience lol..

    good luck with it

    Jemma xx