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reversing bike boxes
m_rayfield - 22/2/02 at 01:33 AM

I've been tempted by talk elsewhere of a bike engined car - I reckon 12,000rpm will get me past any amount of 'helium fart' exhaust note!

Do I need a degree in mechanical wizardry to fit one, and is there a better way of reversing them than the 'Fred Flintstone Method'?

All ideas welcome but a student's budget doesn't stretch far at all!


Metal Hippy™ - 22/2/02 at 04:49 AM

I've got no particularly useful ideas for reversing one of those, I just wanted to say that it's nice to see other students in at the deep end and concentrating hard on studies....

How about dropping an anchor just before you know you have to reverse and pulling on the chain at the appropriate time?

Rich.


Dunc - 22/2/02 at 09:21 AM

How about a bike chain and starter motor attached to the propshaft via a freewheeling hub, a switch is all you need. Well you did want cheap.


macdave69 - 22/2/02 at 06:27 PM

how about a bike starter dogged into the exposed teeth on the driveshaft flange and a big button?


Jon Ison - 1/3/02 at 08:57 PM

use my method M8, get the bike engine in, enjoy the drive, plant right foot firmly to point said car in oposite direction, all you need. only 12000rpm, you must a lost 600rpm somewhere ? seriously just look for the odd incline, they help a lot failing that, right foot does work,


Zeuser - 6/3/02 at 01:38 AM

There's a company in British Columbia (Canada) that's going to fit a Suzuki GSX1300RR Hayabussa engine in a Caterham and they're having a reverse gearbox made by Nova Racing Transmissions ltd. (www.novaracing.com)

I need to get more info on it but here's a diagram of what it's supposed to be:


Jon Ison - 6/3/02 at 05:58 PM

reverse box's are ok ish, but the props go out of sync and vibrate the lot to death, this problem as not been solved by any one yet as if the car moves or you let the clutch out in gear with the reverse box in nutrual then the props like i said above can go out of sync, this only applys to the box mid mounted in the tunnel with a prop either side.


Dunc - 7/3/02 at 12:14 AM

'Scuse me for being stupid but how are the props going to vibrate the thing to death? It all should be properly balanced so it shouldn't matter if the props on either side of the box are out of synch, unless they all have a balls up in the design and have the natural frequency too close to the working frequency without being effectively damped.


Jon Ison - 8/3/02 at 06:18 PM

Q:- what happens to your prop if you cut n shut it, and when welding the uj back on you don't get them in line ?
A:- the same as wot happens when either prop moves slightly when the reverse box is in nutrual, check out the BEC group website, you will find they are all, either A) taking the box's out, or B), allready took them out, they do crsate severe vibration once out of "phase" which is the posh word there all using on there.


Jon Ison - 8/3/02 at 06:24 PM

oh, the add


http://groups.yahoo.com/group/bike-engined-cars/

take a look, the group is full of racers, track day and road car owners, with 1,000's of miles under there belts, oh and a few dented transmission tunnels and the odd loose bolt, take it from me once out of sync they vibrate.


Zeuser - 8/3/02 at 10:55 PM

Well... just make sure you do it right!

If the driveshafts of an AWD don't vibrate "the thing to hell" then I don't see why it would be any different for a reverse gearbox.

Seems to me like it's more of a problem with poor worksmanship than a design flaw.


Dunc - 9/3/02 at 12:34 AM

I agree with you Zeuser, if your theory was correct Jon then why don't you get the same effect with drive shafts going out of 'phase'. It just seems to me that they haven't been balanced well enough for the speed they operate.


Dunc - 9/3/02 at 12:36 AM

Bikers eh! give them four wheels an they don't know what to do. Hehehehe.


Metal Hippy™ - 9/3/02 at 12:45 AM

As an engineering student and general with 3 stars I agree with Dunc and Zeuser in that I reckon for it to bugger up.. surely it's either:

a. Poorly set up or
b. Not made well enough and so comes loose or something....

That's my penny's worth.


macdave69 - 9/3/02 at 01:50 AM

Dear oh dear oh dear

Driveshafts are powered through the diff, they can't go out of phase because they aren't joined to each other directly...

I'm not clever enough to explain plus there are plenty of other boring lists where over opinionated people could spout on about it before dismissing it as trivial because bike engines aren't provided by Toyota if you must persue this tedious line.

as I say to my kids, sometimes poo happens and it's the same for phasing of props

If you still haven't worked it out by Wednesday, I'll draw you a picture on the back of a beermat at the beverly arms


Metal Hippy™ - 9/3/02 at 01:56 AM

Take a deep breath Dave, not everyone is as smart as you.

Oh, btw....

Is the baldness a cooling aid for your extensive brain?

Just wondering, cause I've been getting severe overheating problems when I've been thinking.....

That's why I normally talk crap, cause it involves no thinking.

Rich.


macdave69 - 9/3/02 at 02:04 AM

indeedy and my expansive gut is merely the petrol tank for my overheating brain


Metal Hippy™ - 9/3/02 at 02:06 AM

So you're in full preparation for a marathon thinking session then.


Dunc - 9/3/02 at 10:22 AM

I agree with you Dave that the driveshafts are driven by the diff but the whole point of the diff is allow the driveshafts to go out of synch. Otherwise the inner wheel would turn at the same rate as the outer wheel when turning round a corner. And I don't know what kind of magic diff you have on your car Dave but mine are connected but a couple of coggy thinys. The whole point that the driveshafts aren't joined means they can go out of synch, it they were joined directly then they couldn't go out of synch. Look forward to your beer mat sketch, could be a patent in if for you.


Marcus - 9/3/02 at 01:54 PM

I don't think there's a problem with reversing boxes as they've effectively got 2 propshafts. The problems arise with one prop and having the yokes out of phase (there's that word again). ie having the wrong part of the yoke accelerating at the wrong time, giving rise to vibration and eventual destruction. This is why they're also known as constant velocity joints - the angular velocity changes constantly which can lead to the aforementioned vibration if out of phase. Of course you could have twice the problems with 2 props and a reversing 'box, maybe that's the issue.
Does that make sense?
Marcus (prepared to be shot down in flames)


Jon Ison - 9/3/02 at 05:35 PM

last word from me on this one, reverse box's fitted with a prop either side vibrate, once the props are out of phase, theroy may say it won't happen, practice says it does check out the general opinions on the site i posted above, most of the cars used by the guys on there don't use home made props as there the load'ed racer type. full stop.