100% Biker & Trike Magazine Forums

Go Back   100% Biker & Trike Magazine Forums > 100% Biker > Trike Magazine

Notices

Reply
 
Thread Tools Display Modes
  #31  
Old 10-11-2011, 09:37 AM
rob rob is offline
It's about time I shut the fuck up!
 
Join Date: May 2006
Posts: 1,809
Default

ok, perhaps they/you could explain to me how sticking a 5 foot lever into the back of a bike frame specifically designed NOT to have a 5 foot lever in the back of it is ok?

if you hit a brick, (for example), on a bike, even if it's with the side of the tyre, the leverage is only about 3" max. this amount of twisting stress, (with a saftey margin), is built into the design of the frame.

now fit an axle, and hit the same brick. the axle pivots about the other contact patch, about 5' away, twisting the swingarm pivot area of the frame with forces far in excess of it's design loading.

try undoing a stubborn nut with a 3" spanner, then put a 5' breaker bar on it and see how much more force you can apply....

3" x 4 = 1'.
1' x 5 = 5'.
4 x 5 = 20.

you're applying 20 times more leverage....

i'm damn sure bike manufacturers don't build in a redundancy factor of 20 into their frame designs.....

therefore it will fail at some point.

it might not be before the trike goes out of use, but it will happen..... would you take the risk?? or advise others to??

i have turned away literally dozens of potential customers who want 'bolt on' swing arm trike conversions. i won't do them because they will fail at some point.

Reply With Quote
  #32  
Old 10-11-2011, 11:21 AM
Nik Nik is offline
Banned
 
Join Date: Jan 2006
Location: Saarfuk
Posts: 6,072
Send a message via MSN to Nik
Default

Sorry, rob, I don't agree - as I said I know folk who've run swingarm trikes for donkeys and racked up good mileage on 'em and they've never broken.

If they're so dangerous, best you ring Hank and Haydn and tell them so - I think you'll find they'll just laugh.

Besides which, there's a risk like that involved with any modified vehicle. There's always a chance that anything can fail - be it a trike, a chop, a streetfighter, anything. I've heard of a lot of chops that have broken their frames too - are you going to tell people not to do them too?
Reply With Quote
  #33  
Old 10-11-2011, 11:43 AM
harry's Avatar
harry harry is offline
Techno Guru! He's Good! He Knows Everyfink!
 
Join Date: May 2005
Location: Taunton
Posts: 3,399
Default

The way I see it a swing arm conversion is not a good engineering solution.

If done by someone who understands that and builds it like a bridge and using the correct materials it will handle well, and not fail in a reasonable lifetime.

However because it's the easiest and cheapest way of building a trike it attracts those builders who may be well meaning, but don't understand the stress inherent in the design.

That's why I would always tell a newby to avoid them. If you don't know what to look for you could buy a death trap.

The fact that summat handles well don't mean it can't break. Just look at F1 cars, fantastic road holding but little reserve strength.
__________________
si is does non opportunus vos postulo a maior pango
Reply With Quote
  #34  
Old 10-11-2011, 02:25 PM
biggus mickus biggus mickus is offline
Chatter Box
 
Join Date: Sep 2008
Location: Ooop North where the black pudding roams free!
Posts: 213
Default

Rob, I see your reasoning but you haven't taken into account the fact that the front part of the frame will just lean over, way before it's subjected to 20 x the turning force.
If you don't want to build one, then fair enough. But show me several properly fabricated ones that have failed in use and I'll agree with you.

Cheers, Mick.
Reply With Quote
  #35  
Old 10-11-2011, 02:55 PM
rob rob is offline
It's about time I shut the fuck up!
 
Join Date: May 2006
Posts: 1,809
Default

Quote:
Originally Posted by Nik View Post
If they're so dangerous, best you ring Hank and Haydn and tell them so - I think you'll find they'll just laugh.
the trike shop build and sell swing arm trike conversions that bolt directly into an unmodified bike frame???

i'm suprised.
Reply With Quote
  #36  
Old 10-11-2011, 02:59 PM
rob rob is offline
It's about time I shut the fuck up!
 
Join Date: May 2006
Posts: 1,809
Default

Quote:
Originally Posted by biggus mickus View Post
Rob, I see your reasoning but you haven't taken into account the fact that the front part of the frame will just lean over, way before it's subjected to 20 x the turning force.
the initial forces, applied in fractions of a second before the frame starts to move, will be huge, and way beyond the design spec of the original bike frame.
hit enough bricks/pot-hole, and it will fail.
[edit]think about how much energy it will take to accelerate 1/4 of a ton of trike violently up and to the side almost instantly as it hits the obstruction, then think about where those forces are travelling...[end edit]
maybe not in a week, maybe not in a year, or 5 years, but it will....
and i don't want my name on something that i know will fail sooner or later, due to bad design. if others do, that's up to them.

Last edited by rob; 10-11-2011 at 05:23 PM.
Reply With Quote
  #37  
Old 10-11-2011, 03:03 PM
rob rob is offline
It's about time I shut the fuck up!
 
Join Date: May 2006
Posts: 1,809
Default

Quote:
Originally Posted by Nik View Post
There's always a chance that anything can fail - be it a trike, a chop, a streetfighter, anything. I've heard of a lot of chops that have broken their frames too - are you going to tell people not to do them too?
you're missing the point, nik. anything of a mechanical nature can/will fail, chop frames included.
the fitting of an axle on a swingarm into an unmodified bike frame, as in my sketch above, is a badly engineered, badly thought out solution to a loophole in the MSVA regs, and nothing more.
Reply With Quote
  #38  
Old 10-11-2011, 03:48 PM
Nik Nik is offline
Banned
 
Join Date: Jan 2006
Location: Saarfuk
Posts: 6,072
Send a message via MSN to Nik
Default

Quote:
Originally Posted by rob View Post
the trike shop build and sell swing arm trike conversions that bolt directly into an unmodified bike frame???

i'm suprised.
No, they don't, rob, nobody does that. They all take the swingarm out and replace it with a fabricated system that converts the swingarm back end into a trike and you said:

Quote:
Originally Posted by rob View Post
for god's sake DO NOT go for a swingarm conversion!!!

the original frame was NOT designed to take the stresses imposed by bunging a fekkin' gert axle in the back of it!!!!!

it's a fatal accident waiting to happen.

yes, i know there are some out there that seem ok, but don't do it!! it's not safe.
You can't start changing the definition of the terms now.
Reply With Quote
  #39  
Old 10-11-2011, 05:14 PM
rob rob is offline
It's about time I shut the fuck up!
 
Join Date: May 2006
Posts: 1,809
Default

Quote:
Originally Posted by Nik View Post
No, they don't, rob, nobody does that. They all take the swingarm out and replace it with a fabricated system that converts the swingarm back end into a trike and you said:



You can't start changing the definition of the terms now.

i'm not m8, perhaps you should re-read it.....

i said;
the trike shop build and sell swing arm trike conversions that bolt directly into an unmodified bike frame???

i'm suprised.


you said;
No, they don't, rob, nobody does that. They all take the swingarm out and replace it with a fabricated system that converts the swingarm back end into a trike.


which is exactly what i said. *facepalm smilie*

the issue is the swingarm pivot area of the original, standard frame not being designed to take the hugely increased stresses imposed by a swingarm trike conversion. the design of the replacement swing arm is not the point, though i have seen some where an axle has just been welded onto a standard swingarm.....



[edit]
and i stand by my original statement, any trike with a rear suspension system based on the design in my sketch above, (i.e. a swingarm conversion), that bolts directly into an unmodifed, standard bike frame is inherently unsafe. i would not ride one or build one, and i would not reccomend anyone else does either.
you can argue on behalf of third parties all you like nik, i know i'm right.

Last edited by rob; 10-11-2011 at 05:21 PM.
Reply With Quote
  #40  
Old 10-11-2011, 05:24 PM
Nik Nik is offline
Banned
 
Join Date: Jan 2006
Location: Saarfuk
Posts: 6,072
Send a message via MSN to Nik
Default

Quote:
Originally Posted by rob View Post
i'm not m8, perhaps you should re-read it.....

i said;
the trike shop build and sell swing arm trike conversions that bolt directly into an unmodified bike frame???

i'm suprised.


you said;
No, they don't, rob, nobody does that. They all take the swingarm out and replace it with a fabricated system that converts the swingarm back end into a trike.


which is exactly what i said. *facepalm smilie*

the issue is the swingarm pivot area of the original, standard frame not being designed to take the hugely increased stresses imposed by a swingarm trike conversion. the design of the replacement swing arm is not the point, though i have seen some where an axle has just been welded onto a standard swingarm.....



[edit]
and i stand by my original statement, any trike with a rear suspension system based on the design in my sketch above, (i.e. a swingarm conversion), that bolts directly into an unmodifed, standard bike frame is inherently unsafe. i would not ride one or build one, and i would not reccomend anyone else does either.
you can argue on behalf of third parties all you like nik, i know i'm right.
We'll agree to disagree on that point then, won't we?
Reply With Quote
  #41  
Old 10-11-2011, 07:06 PM
devon-tony devon-tony is offline
Lucky Wombling Bastard except when he's not Wombling, when he's just a Lucky Bastard
 
Join Date: May 2004
Location: Devonshire
Posts: 4,371
Send a message via AIM to devon-tony
Default

ah good, now we can all play nicely
__________________
nowt of much use here
Reply With Quote
  #42  
Old 11-11-2011, 10:03 AM
Nik Nik is offline
Banned
 
Join Date: Jan 2006
Location: Saarfuk
Posts: 6,072
Send a message via MSN to Nik
Default

Hippy ...
Reply With Quote
  #43  
Old 11-11-2011, 07:55 PM
themanfromporlock themanfromporlock is offline
Chat Slut
 
Join Date: Jul 2011
Location: guess
Posts: 116
Default

I see Peter with his new business is flogging mystery trikes sorry, Mystery Trikes and, as I know nothing about trikes (or much else) I looked at the technical page for them.
The heart of the conversion seems to be two of these plates, bolted or welded to your swingarm



and then you bolt X000 quids worth of this to the bracket



Simples.
Want one for Christmas, Rob?
Reply With Quote
  #44  
Old 11-11-2011, 10:10 PM
harry's Avatar
harry harry is offline
Techno Guru! He's Good! He Knows Everyfink!
 
Join Date: May 2005
Location: Taunton
Posts: 3,399
Default

I haven't done MSVA testing for some time now.

But I wouldn't pass that.

However Chris's opinion is what counts.
__________________
si is does non opportunus vos postulo a maior pango
Reply With Quote
  #45  
Old 11-11-2011, 10:36 PM
rob rob is offline
It's about time I shut the fuck up!
 
Join Date: May 2006
Posts: 1,809
Default

that, IMHO, is dangerous, but hey, what do i know.....
Reply With Quote
  #46  
Old 12-11-2011, 12:35 AM
themanfromporlock themanfromporlock is offline
Chat Slut
 
Join Date: Jul 2011
Location: guess
Posts: 116
Default

Look at it from the point of view of the swingarm and its bearings.
There you are, happily bobbing up or down, designed by a Japanese committee to hold one wheel in place and a chain or driveshaft to it. Go round a corner and the forces acting on you stay roughly in the same plane as the bike leans over. Only if the twat riding you clips a kerb do you feel major sideways pressure.

Get rid of the central wheel, stick two fucking great car tyres 5 foot apart, join them up with a big chunk of solid metal and go round a fast corner.
The forces acting on the bearings and swingarm are coming from a new direction and if i could do the sums, I bet they'd be huge on a big trike.
Fuck that for a game of soldiers.
Reply With Quote
  #47  
Old 13-11-2011, 09:55 AM
addjunkie's Avatar
addjunkie addjunkie is offline
It's about time I shut the fuck up!
 
Join Date: Nov 2004
Location: Below the Dam, Northumberland
Posts: 1,857
Default

That axle is kind of sexy in a shiney billet sort to of way. would look great in a hard tail on off frame.

But the swing arm.......nah as an engineer it just dont look right, its like a hooker in a chastity belt. legs closed, too close together etc. no triangulation.

Then take a close look at the bearings they look like speherical bearings to me, or is it my eyes.

I'm with Rob on this one espescially when an axle is lobbed on the end of a 25year old jap frame. Im actually looking at doing a harley trike at the moment, and have looked at a few of these back ends, looking for ideas to copy, but for me a triangulated IRS set up, is the only way to go.
__________________
Live fast, die young, save on pension contributions!!!!!!!!!!!
Reply With Quote
  #48  
Old 13-11-2011, 12:51 PM
droid's Avatar
droid droid is offline
Been out, but rather stay in!
 
Join Date: Mar 2008
Location: Tamworth
Posts: 1,338
Default

Anyone that doubts what rob is on about needs to revise the Law of Moments.
Reply With Quote
  #49  
Old 13-11-2011, 02:59 PM
harry's Avatar
harry harry is offline
Techno Guru! He's Good! He Knows Everyfink!
 
Join Date: May 2005
Location: Taunton
Posts: 3,399
Default

Yup that axle sure looks pretty. Nice machining.

There is another problem as well as the strength of the swing arm.

The MSVA manual in line with the euro regs says:-

Note. The braking devices must act on brake surfaces permanently connected to the
wheels either rigidly or through components unlikely to fail. A chain is considered to be
a component likely to fail, as are sprockets.


Looks like the brake disc operates on the diff. and therefore shouldn't pass the test.

If you're gonna make summat similar best check with Chris first.
__________________
si is does non opportunus vos postulo a maior pango
Reply With Quote
  #50  
Old 14-11-2011, 08:55 AM
addjunkie's Avatar
addjunkie addjunkie is offline
It's about time I shut the fuck up!
 
Join Date: Nov 2004
Location: Below the Dam, Northumberland
Posts: 1,857
Default

Quote:
Originally Posted by harry View Post
Note. The braking devices must act on brake surfaces permanently connected to the
wheels either rigidly or through components unlikely to fail. A chain is considered to be
a component likely to fail, as are sprockets.


Looks like the brake disc operates on the diff. and therefore shouldn't pass the test.

If you're gonna make summat similar best check with Chris first.
I asked a queston on the thread in the workshop section, but Chris hasnt answered it, is there another way to easily contact him.
__________________
Live fast, die young, save on pension contributions!!!!!!!!!!!
Reply With Quote
Reply

Thread Tools
Display Modes

Posting Rules
You may not post new threads
You may not post replies
You may not post attachments
You may not edit your posts

BB code is On
Smilies are On
[IMG] code is On
HTML code is Off

Forum Jump


All times are GMT. The time now is 04:20 PM.


Powered by vBulletin® Version 3.8.8
Copyright ©2000 - 2017, vBulletin Solutions, Inc.