power assist is definately a reasonable subclass

[John Tolhurst]

buyagain wrote: There is nothing going on back there that is any different than the original peddle power configuration.

I'm not convinced that's true. Have you done a static analysis?

Look at it this way, the motor is trying to pull it self backwards, just as well it has a tension strap connected to the top of the seat stays, but wait, the seat stays are not solid, they are a suspension element. The internal nature of the suspension element between seat stays and seat post is unknown to me.

 

[buyagain]

John Tolhurst wrote: just as well it has a tension strap connected to the top of the seat stays, but wait, the seat stays are not solid, they are a suspension element. The internal nature of the suspension element between seat stays and seat post is unknown to me

Hi John Tolhurst;

I walkaround Dinnis's web site might save me a diagram or 2. None the less I'm impressed with the detail you've observed from just these photos. I can see the side pulling stress on that shock absorber from the tension strap just as you say. I like to follow the stress and loads on a frame too. The most stress, as I see it, piles up where the whole rear unit hinges right behind the old BB seats. None the less I can concur that that piston or shock is not designed to take a high degree of side pull. There is some relief born by the stay weld points at it's axle juncture.

All this said That web site for Golden Eagle Engines has an many many examples and testimonies of satisfied customers with similar configurations. As a matter of fact I've never seen so many authentic testimonies at one site. I know that's not the really a good engineering answer, John, but please. You're starting to stress me out over all this stress. I'm just an amateur engineer and I'm not about to go out and buy a dinometer. LOL

 

[John Tolhurst]

The locating strap should bypass the shock and fix to the seat post, then it will be fine. Is there room for it under the crown of the seat stays or would it clash the tire there?

 

[WhiteSilvio]

John Tolhurst wrote: The locating strap should bypass the shock and fix to the seat post, then it will be fine. Is there room for it under the crown of the seat stays or would it clash the tire there?

Hi John,
Going by IMG-1248a, it looks just fine the way it is.
Changing the curved "strap", that resists the motor trying to go backwards as the wheel goes "forward", will only mean that there is then a problem with the rear suspension working properly. The suspension movement will be effectively clamped with a "link" to the seat post, or any other part of the main frame that is not part of the suspension.

At the moment all the forces are contained "within" the rear suspension frame and motor mounts, and that is fine.
Unless there's something I've totally missed in the picture, buyagain, should leave it as is.
Regards,
John R.

 

[John Tolhurst]

Hi John,
We need a static analysis diagram of forces. A side load on the suspension unit might satisfy this particular user in this particular case, but are we satisfied it is a model we'd have others follow. I think the subtext of this thread is the proposition that the configuration is a good model. I am not satisfied on that point and given the litigious propensities in the US, I may never claim satisfaction!

On a sofrider it would be fine as the rear triangle retains the 'seat post' element. This element serves only to keep the shock aligned with the seat stays, so with this different style shock on the avalon frame, they have omitted this seat post element of the structure. On Silvio, this element is represented by the Ti link.
John

 

[rearengine]

Tiara E- Cruzbike

Really a poor mans quest

John T , Doug ! I have a question .. If I put a short chainstay on , could I expect a 22" B/B or lower ? It is now at 25".. I guess what I am asking is , how much shorter is the short chainstay than the original Kit stay.. I'm also thinking of using a 20" fork , but might have to little trail .. only reason It would take care of the front brake problem ... Thanks.. Bill

PS Can I get the short stay in black

500-600 watt front hub motor on rear, 50 amp controller 36 volt sla battery..

 

[John Tolhurst]

Hi there rearengine,

The quest 451 chainstay is colour coded to Quest. No doubt you are handy with a rattle can.

It measures 85mm less. My guess is it would drop the bb height around 3" maybe more, but you can test just with a pair of strings and find the meeting point.

 

[rearengine]

Hey Fohn T ... That was fast... YA i can rattle the can or kick it :lol: Thanks for the reply .. I will check it out in the morn... Bill

 

[rearengine]

Hi ! Just orderd a short chainstay from Maria for my 20" wheel electric Tiara cruz..Should have it end of wk ,or first of next ..I'll post a pic to compare with the above pix, and let you know how this works out...Bill

 

[Doug Burton]

Hey Bill,

Is that a "Cruzvair"? After all, it is "rear engined"...

Good stuff.

Best,

Doug

 

[rearengine]

Doug ! Cruzvair it is ... I like that.. Yup It's rear engined, and also air cooled ... Say could you tell me what that riser is that is on your Son's TIARA ? The one mounted on the tellie tube ... It's kind of like mine, but yours comes up strait.. I'm Posting a pic of the SHORT chainstays.. I had the Big Apple 2.35 tires , so used them, but had to do a little modifying to the dropouts for tire clearance ... 2.25 or smaller would be best.. The bike handles really good, It seems like it could be ridden hands off easer now..( I don't though )...18" BB - 22" seat .. Not very airo, but neither am I... Take care all... Bill