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Jon_Doe
03-29-2013, 06:23 AM
Hi guys

I've been thinking about suspension for the last half year or so.
I would like to build myself something that might resemble the flying dutchman cargobike.
And this beast needs full suspension as it must be able to take the curbs and bad pavement full steam ahead.
The rear is simpler especially since i already have the rear triangle from a full suspension bike.

The front is more complicated.
I have a suspension fork (cheap one) that is basically trash.
A good one costs more than my entire project.

So after lots of research (going from springer fork to girder to whatnot) i settled on the Hossack system.
(it is used on some BMW motorcycles by the name Duolever).

This looks simple to me and buildable/serviceable with the materials/tools i have around.
Basically i put the headtube + fork attached on the front of 2 swingarms and i add a shock on the parallelogram diagonal.
That makes a suspended headtube (suspension is independent of steering).
Pivots are regular sealed bearings.

I don't know if anybody has tried this before but input would be appreciated.

My biggest concern is the shock/damper.
The goon ones (from the biking industry) would cost me 3 projects.
However, i have found that ATV or Scooter parts are much more approachable.
I think i can even find some dirt cheap ones (from 15USD upwards, new, don't know about quality).
The good is that they have oil dampers and progressive coils which is a plus.
Depending on the coil hardness i can easily devise a way to change the ratio.

For the rear these shocks should work ok.
I have some doubts for the front tho.
I will need some soft ones for this spot.

Has anyone ever tried this ?

Ticktock
03-29-2013, 12:12 PM
Much easier to use a leading link swing arm, as used on BMW bikes, way back when I was a teenager!
Easier to make, only two bushes, and easy to make adjustable in all respects--height, trail and stiffness, all by different bolt holes.
Also as a bonus, elliminates front end dip under brakes--the front actually rises under brakes!
Steve G,
Beijing

macka
03-29-2013, 03:29 PM
Duolever is a very geometry oriented setup. If it's off just a wee bit, it acts completely different. They had used a few different angles in the Paris Dakar races, and found that they were very high maintenance. That is why if you look at the bikes they have bigger clamps on the triple tree. I'd go with the idea ticktock suggests.

Ibedayank
03-30-2013, 04:16 AM
the leading link was used for cycles with sidecars
BMW URAL Dnepr used them


Jon have you seen the springer designed by John Brain?
http://bikerodnkustom3.homestead.com/brainfork.html

Jon_Doe
03-30-2013, 06:22 AM
Thank you for the info.

Ticktock (http://forum.atomiczombie.com/member.php/3551-Ticktock)
Do you have any homemade examples of this design because that's what interests me, the homemade part.

Ibedayank (http://forum.atomiczombie.com/member.php/2899-Ibedayank)
I know of the Brainfork for some time. It was my first choice back then.
How does it behave if the headtube angle was similar to a regular bike and not like a chopper ?

What immediately comes to mind looking at the URAL-style or the springer (Brainfork or another) is that all that shock (and there are 2 of them) moves with the steering. Basically, the suspension is inside of the steering. (the springer seems a little better at this than the leading link URAL though).
And since i absolutely need a damper, not just simple springs (think the front without the cargo situation ... coil rebounding undamped -> front going all over the place) i thought of atv/motoscooter coilovershocks which are very cost effective for me.
Using the Duolever setup (i know the problems with it) there is only 1 shock and i can move that out of the way easily.
There can be only one shoch for the springer but i can't move it out of the way, it's there upfront.

This cargo bike needs to be very easy to handle at low speeds 10-25mph. I wuld extremely seldom go above that ...

Ticktock
03-30-2013, 09:58 AM
Not just with sidecars, BMW was using leading link on a solo, as was Vincent. Advantage for the side car was that it was easy to reduce trail for Steve G

Ticktock
03-30-2013, 10:24 AM
Hi Jon,
Nothing to hand unfortunately . Its about 30 years since I built the last one! But just run Leading link suspension past Google and you will gets heaps of info. Don't be put off by the fact that it all seems to refer to sidecars---it works just as well on solos--just get the trail right. Building a leading link set up is no harder than building the rest of the bike, and it can be easily adjusted or even altered after building. Basic steering and handling will be the same, but probably smoother suspension action, with the only noticable change being that the front tends to rise under brakes (front brake )
Its much simpler than what you had in mind, and almost mainainance free once set up properly.
Let me know if you can't find enough info.
Steve G.
Beijing

Ibedayank
03-31-2013, 03:44 AM
the other option is a girder fork
http://www.spartanframeworks.com/Forks/Girder4.jpg

drawback COMPLEX to build

yes stock length springers work well
factory built bicycle springers Monarch brand comes to mind

remember before 1960 on motorcycles you had springers girders and sprung teloscoping forks

Jon_Doe
04-01-2013, 05:12 AM
Hi all,

I've been looking at the details of the leading link fork.
Also, a good option might be Earles or a hybrid towards what Birdy bikes had.
According to this:
http://blog.autospeed.com/2010/06/21/absorbing-bumps/
some backwards motion is desirable.
Basically an Earles with the Birdy angles might work better ?

My remaining issues are:
1. I need large travel (4in is absolute minimum, i was thinking double that)

2. It seems that there are 2 springs needed and the ones i have access to are too high of a ratio (think 450lbs/in rear mountain bike springs) for this use and lack a damper.
I could use rear ATV/motoscooter spring/damper combo since they are readily available and cheap but they're ratio is also high.

I could use a setup like the Birdy one to use just one spring but members would have to be much stiffer and heavier.
I still haven' managed to do an analysis on wheel/spring motion ratio for this system.
I guess i could manage to increase the ratio by choosing a different location for the spring mounts but this has the immediate consequence of increased member strength and thus weight.

Ticktock
04-01-2013, 09:11 AM
Thats one of the main attractions of a leading link system! You only need a row of strategically placed holes on the top of the swing arm, and the shocks can be moved just by removing and replacing two bolts. Takes about two minutes ifnyounhave the tools in your hand.
So you make a good guess where it should be, then provide a few holes on each side for later adjustment.
And 8inch travel is easy if the shocks will cater for it, and stiffer shocks do help there, as the mounting would have to be loser to the fork tube to give the softer ride, and this in turn gives longer travel. Win both ways.
Cannot think of a simpler home build suspension, only two bushes, simple swing arm, anti dive braking, adjustable (and simple) geometry.
and, apart from the shocks, can be entirely home built.

Steve G,
Beijing

Jon_Doe
04-01-2013, 09:28 AM
I don't know why i haven't looked at this system more in depth before ...

I still have 2 more questions:
1. What if i want to use only 1 shock ?
2. What kind of bushes are needed (flanged bronze or rubber, car swingarm, types)?

Ticktock
04-01-2013, 09:55 AM
Second question first!
Try motorcycle swingarm bushes. The older, smaller Honda bikes use two small bearings which swing between trwo flanges each side, and the swing arm is extended on the front for these short bushes. You don;t need the swing arm--its too heavy, just the bushes.
A bronze bush on a smooth steel shaft is all that is needed, along with a grease nipple if possible.
You could use the entire front tube part of a swingarm from a M/Cycle, and add you fork tubes, but this would limit the hinge position to being behind the back tyre, which is a pretty good place anyway, for general use machines, and gives a good range of adjustment.

First question---it would be difficult, and probably heavier than then simple two shock system. And you will need somer form of damping on the front end. I would be looking at electric bike and scooter units, with spring and shock combined. Much easier that way.
The single shock is probably off the back of an MTB, and would be far too stiff to use in a front end, unless it was made strong enough to take the stresses from the singlr shock, and that meands more weight.
The Birdy bike concept may be tecnically good, but you won't get much true vertical suspension travel, as the wheel starts to move backwards more than it moves upwards!
Steve G

Jon_Doe
04-01-2013, 10:11 AM
2 of these on each swingarm ?
6728

Regarding the combined spring/shock, i do have access both physically and financially to ATV/scooter types.
Basically, it's the only thing with a damper that i can touch moneywise.
My concern is that these would be too stiff since they are designed for the rear.
As for a "simple" single shock/spring system i was thinking of something like the following:
6727

For sure, all that extra metal weights but it displaces the other shock so not that much different.
If springs are too stiff, this might be a solution.
Only downside is that you can't easily adjust compression ratio.

sandman
04-01-2013, 05:51 PM
Hi Steve, dont forget to mention the douglas dragonfly or the greeves machines ( Greeves Scottish)which I still lhave in bits or that gem of russian engineering the Ural

regards
John

Ticktock
04-02-2013, 10:04 AM
As I said before, thats the beauty of the simple leading link--it'
s so adaptable to different spring frates. If your springs are stiff, just move the lower attachment point back closer tomthe nswing arm pivot. There arte no rules as to how far you can go---if it works, do it.!
If your single spring is stiff, it wont work used as in the photo---be like an iron bar!

Yes two of "them" in each side will work fine. Best on the end of the fork tube, then you can have a row of fixing points on top of the swing arm.
Steve G

There's also a Chinese near copy of the Ural seen here ocasionaly with a side car, and leading link front end.

Ticktock
04-02-2013, 10:17 AM
Hi Sandman,
I was not trying to name bikes or start a history lesson!! Just trying to promote the best solution to the problem.
So why is the Greeves still in bits? you make it sound like its been that way for a while. It's a nice bit of bike history to have in the shed.
It seems that the three things that cause design problems with bicycles is gears, steering geometry, and suspension!
And half the suspension problems come from trying tomapply car rules to our creations. (it's even got books on it, so then age is showing)
or maybe even Google.
Have fun,
Steve G,
Beijing

Jon_Doe
04-02-2013, 10:23 AM
I did some calculation and for the above image the wheel/spring ratio is at best unity ... not very helpful except i only need to buy one shock.

PS
As a somewhat unrelated question, what wheel sizes do these leading link bikes use ?
For my cargobike, my first choice would have been 24" wheels (not too small and not to large).
However i have found some sweet prices for some 20" tough BMX wheels and it got me thinking.
Whichever wheel size i will use will have to go head to head with 15cm/6in curbs on a regular basis.

bambuko
04-02-2013, 12:24 PM
...or that gem of Russian engineering the Ural...
actually German engineering - Soviets "acquired" the design from BMW in around 1940 :rolleyes4:

Ticktock
04-02-2013, 02:07 PM
Can use any size you like--wheel size dictates swing arm size, and the rest of the layout dictates fork length.
20 inch BMX will be stronger, usually, than any other wheel. But if you have a dead load, and cannot "help" by lifting the front wheel, you are playing with fire regards wheel damage, whatever you use!
I do not understand the first part of your post! No image to refer to.
You keep refering to one shock. The only way I see you can use one shock is as on the Birdy bike thing, above the front wheel.
Here you need a softer shock, not a stiffer one. Any MTB rear shock here would be as good as solid suspension!
I cannot see how you can use one rear shock and spring on a leading link, using ordinary bike type parts , and get a working suspension to do what you want.
Steve G

Jon_Doe
04-03-2013, 03:20 AM
Can use any size you like--wheel size dictates swing arm size, and the rest of the layout dictates fork length.
20 inch BMX will be stronger, usually, than any other wheel. But if you have a dead load, and cannot "help" by lifting the front wheel, you are playing with fire regards wheel damage, whatever you use!

I know. There will be suspension available.
I was asking since bigger wheels "walk" easier over obstacles than smaller ones.
So my question was if there would be such a great difference in riding by going from 20" to 24"-26".



I do not understand the first part of your post! No image to refer to.


I was refering to the horizontal single shock.
6773
The ratio is close to unity, therefore requiring a soft spring.
The only advantage is that it needs only 1, not 2 (these need to be bought).



You keep refering to one shock. The only way I see you can use one shock is as on the Birdy bike thing, above the front wheel.
Here you need a softer shock, not a stiffer one. Any MTB rear shock here would be as good as solid suspension!
I cannot see how you can use one rear shock and spring on a leading link, using ordinary bike type parts , and get a working suspension to do what you want.
Steve G

There is a way.
I call it leading link springer hybrid.
6774
Basically it is a leading link but the springs/shocks are not mounted directly but upfront with a springer-like front legs.
The type of shock i am referring to is something like this one:
6775
It's a scooter/atv type and has a progressive spring coiled over a a damper.
It's the only thing i can buy rather cheaply around here.
There are rear mtb springs, dirt cheap, butt they are just that, springs, no damper, and they are too stiff.

Ticktock
04-03-2013, 04:36 AM
What you have in the picture is exactly what I would buy if I was doing the same thing---two of them.

Your maths is a bit off line!! Distances must be measured from the swingarm pivot each time, so in this the load on the shock is approx HALF the load on the axle--not equeal to it! Hence the need for a softer spring.

The hybrid idea is a good one provided the strut can be kept straight. If it is used with a stiff spring, I doubt it would work too well.
With the correct spring--it's OK, but would lack the adjustment range of two springs ,mounted lower down.
Those scooter shocks you can buy will do the job if placed correctly, and probably better than anything else.
As to bouncing up gutters--I tried to hint its not a good idea!!! but if you must do this, a well built 24inch is probably better than a 20inch.
Strongest rim you can find, with the highest number of spokes, 48 is good, but you may have to settle for 32. Never had a 24 inch wheel on my trikes, so I can't tell you. Can tell you that 20 inch does not really like gutters!
Steve G,
Beijing

Jon_Doe
04-03-2013, 09:08 AM
Your maths is a bit off line!! Distances must be measured from the swingarm pivot each time, so in this the load on the shock is approx HALF the load on the axle--not equeal to it! Hence the need for a softer spring.

Actually, it's a little bit more complex.
I have done some simulations in a CAD program and this is what i found:
1. 5cm wheel travel => 8.6cm spring travel; RATIO = 1.72
6777

2. 10cm wheel travel => 14.5 cm spring travel; RATTIO = 1.45
6778

So it's not 1, but the main problem is that it is not constant.
And worse, it decreases as you increase the wheel travel which is exactly the opposite of what is needed.


The hybrid idea is a good one provided the strut can be kept straight. If it is used with a stiff spring, I doubt it would work too well.
With the correct spring--it's OK, but would lack the adjustment range of two springs ,mounted lower down.
Those scooter shocks you can buy will do the job if placed correctly, and probably better than anything else.

The strut can be set straight (rectangular hollow section) and firmly fixed to the spring.
Basically it's an elongated horseshoe, the bottoms go to the leading link and the top has a spring to the top of the headtube.
It is basically used as a means to extend the springs from the leading arms to the top of the headtube.
Plus there is a link above the wheel and there a single spring is to be mounted.

Depending on the price of these scooter damper shocks i will try either variant.


As to bouncing up gutters--I tried to hint its not a good idea!!! but if you must do this, a well built 24inch is probably better than a 20inch.
Strongest rim you can find, with the highest number of spokes, 48 is good, but you may have to settle for 32. Never had a 24 inch wheel on my trikes, so I can't tell you. Can tell you that 20 inch does not really like gutters!
Steve G,
Beijing

It's a must.
This is an old European city, plenty of intersections close by with high, straight edge curbs.
There is no way i will get off the cargobike (with my kid and all sorts of stuff in it) just so that i go over the 50 odd curbs that i encounter each way, 4 times a day, everyday.

Standard spoke count is 36. 48 only for 20" BMX.
Problem with 24" an upper rims is that good ones are expensive ...

darnthedog
04-03-2013, 10:54 AM
Joe_Doe
I have been following this thread for a bit now. And in all honesty I am not sure the dutch cargo is going to work to your desire with the 10 to 11 cm climb up on a curb. That is a pretty heffty climb even for a high end Mountain bike at 10 to 25 mph. The drop would be ok except you might scrap bottom as your going over the curb. Dutch cargo bike are fairly long and low to the ground. So they are only really good for level roads and not going up and down the curbs as you describe. Another Zombie is having issue with stressed tubes just doing normal travel. So even with suspension I don't know how well it will do in mountain climbing the curbs. Just an opinion.

Jon_Doe
04-03-2013, 12:45 PM
Joe_Doe
I have been following this thread for a bit now. And in all honesty I am not sure the dutch cargo is going to work to your desire with the 10 to 11 cm climb up on a curb. That is a pretty heffty climb even for a high end Mountain bike at 10 to 25 mph. The drop would be ok except you might scrap bottom as your going over the curb. Dutch cargo bike are fairly long and low to the ground. So they are only really good for level roads and not going up and down the curbs as you describe. Another Zombie is having issue with stressed tubes just doing normal travel. So even with suspension I don't know how well it will do in mountain climbing the curbs. Just an opinion.

I have stated from the begining that it will be dutchman like, not an exact replica.
Main points is that it will be full suspension.
The speed for climbing a curb will be small, enough to get going and not stall.
The bottom scraping will be limited because i want the main body to be somewhere around 30cm from the ground especially for these reasons.
The metal stresses will be addressed at all times.

The main point is that i don't really have a choice.
I need a transport and a car is out of the question for too many reasons.
I already am doing this with a regular bike and a kid on the back plus whatever i can take on my backpack (10-15Kg) an this is no fun.
Regular bikes were not meant for this ... and i tried some on all weather (i'm the crazy guy biking around with a kid and .... if you ask around).

So, either i do it or go bust, period.
It's simple now, ain't it ?

Tradetek
04-03-2013, 05:17 PM
Are you planning to build with the Dutchman style of rider in back and cargo in front?

And are you planning on a 2 wheel bike, or a 3 wheel trike?

If a trike, which configuration: Delta or Tadpole?

I ask all this, because during my mountain bike days, crawling over rocks, roots and fallen branches in the size range you are talking about at low speeds took a coordinated effort to unload the front wheel, shift body weight back to rear, and have one foot at the top of the pedal stroke to give a good drive push at the moment of contact and this was with an expensive dual suspension bike.

I don't see this being possible on the traditional dutchman design and would be concerned that the only thing you are going to accomplish is to either bend the front wheel, or deflect it from the curve and fall over, especially given the amount of ground clearance you just said you are planning to design into the cargo area which is going to lead to a very high COG.

Since you are doing this on a DF right now with smaller loads, the next time you ride pay really close attention to everything you do to make it easy to get up the curbs, and then try it while focusing on trying to keep your body still and only keep your wheel straight at the speed you expect to ride at with the cargo bike...

Bill

trikedoc
04-03-2013, 05:24 PM
Anyone remember the post with the video of the French(Ithink) delta leaning trike. It was going up and down curbs with hardly a bounce. Can't even remember what it had for a front wheel or suspension?
Al

bambuko
04-03-2013, 05:29 PM
Anyone remember the post with the video of the French(Ithink) delta leaning trike...
yes, I got excited about it for a minute or two: I want one! (http://forum.atomiczombie.com/showthread.php/7523-I-want-one!)
I don't think it had any suspension on the front - at least I can't see it?

trikedoc
04-03-2013, 06:38 PM
yes, I got excited about it for a minute or two: I want one! (http://forum.atomiczombie.com/showthread.php/7523-I-want-one!)
I don't think it had any suspension on the front - at least I can't see it?

That is cool. The one I was looking for was a pedal powered delta with long suspension arm on the rear. with a great deal of suspension travel.
Al

Ticktock
04-03-2013, 09:54 PM
Hi Bill,
You have expressed my concerns with jumping over giutters very well! I remember back in the younger days riding a Post Office mail bike, heavey load on the front, and it really was an aquired art to get up a gutter without stopping, or to ride off one and not go over the bars!!
I have only once pushed my 20 inch trike over a 6inch gutter, and push is the right word--I had to peddle it up, as I could not shift weight. Only way the back came up was at an angle, one wheel at a time. Here I could throw a bit of weight side ways at the right time. Good that I could not see the tyres!
When riding in MC trials, we could ride up a 4ft wall easily because we could shift weight around the bike--sitting still in the seat would have meant a dead stop! And going down, we would have landed before the bike!

Steve G,
Beijing

Ticktock
04-03-2013, 10:03 PM
The thread was , as you say, " I want one" and the bike was " Longa bike"
Steve G

trikedoc
04-03-2013, 10:17 PM
The thread was , as you say, " I want one" and the bike was " Longa bike"
Steve G

Thanks. Ticktock. My bad I didn't go to the start of the thread
Al

Tradetek
04-03-2013, 11:31 PM
Right TickTock, here in the US we call that "Body English" but didn't use that term since it is typically slang that causes confusion with people who don't speak the same native language :)

Bill

Jon_Doe
04-04-2013, 04:01 AM
Dear all,

Thank you for your concern regarding the bike and my own integrity.
Case in point is that you should not be so concerned.
You mentioned the Longabike.
Well, what you see in the video, except the stairs, is what i do everyday.
Same type of curbs/gutters, roughly 8-10cm/3-4in with some that i can't avoid at 15cm/6in.
As you have seen, the Longabike has no problem with them and that is with a 20" no suspension front wheel.

My current bike that i take my kid to kindergarden and other stuff is a 28" ladies bike (don't laugh).
Your back is straight on it.
I have tried with kid on the back to just sit stiil and titanic style hit the curbs.
Well, the single wall 23mm rims did not care and of course at that time the spokes were badly out of tension.
I remedied that afterwards.
Only thing is that due to the 1.5" tires i could hear the rear, not the front, rim hitting the curb.
That has not happened very often and this flimsy rim still keeps on going and doesn't seem to care.
This bike was the cheapo bike back in the days so there are only low quality parts in it (well, except the Sachs IGH).

So, extrapolating from this, if i get a 26" downhill rim with 2.25 - 2.5" balloon tires plus suspension i would be set and ready.

The cargobike will be bakfiets/flying dutchman like and have 2 wheels.
That means cargo/kids between me and front wheel.

Ticktock
04-04-2013, 05:50 AM
Hi Bill,
Same slang in Australia, and I assume in England. Don't know what fancy name they would give it here in China!
But without Body English, you fell off pretty quick!
Steve G

bambuko
04-04-2013, 07:27 AM
BTW... I take it, you have been to WISIL (fwd suspension) (http://www.recumbents.com/wisil/fwdsusp/fwd_suspension.htm) to check for ideas?

Tradetek
04-04-2013, 10:35 PM
I'd actually recommend against a balloon tire in this situation and go for one that can handle a decent pressure rating or you risk pinch flats.

macka
04-08-2013, 01:28 PM
I'd go with a wishbone suspension with HDPE bushes,http:// www. autospeed. com/ c ms/A _2 93 6 / article.html

Jon_Doe
04-09-2013, 03:40 AM
I'd go with a wishbone suspension with HDPE bushes,http:// www. autospeed. com/ c ms/A _2 93 6 / article.html

The Hossack/Fior is such a double wishbone configuration which has advantages and drawbacks.
As it seems, the Hossack is not a very good candidate for a garage/backyard builder like myself.
That's why Steve recommended the LL which is tons easier to setup and adjust and is pretty much set and forget.
This article is just the first in a series.
The author then builds Another HPV and then, finally, after the experience gained, builds Chalky, which is pretty unique (water/air suspension).
He admits that the wishbone style is not necessarily the greatest for a HPV.
And he did have access to CrMo tubing which most don't.

I know of the HDPE bushes but i'm not sure how to get them.
Motorbike, ATV and scooter shops might have them.
For this i will also need the pivot axle.
I'm not sure if the money for these might not be better spent on getting bronze bushings.

Now regarding the pivot bushings, i have done some research.
In my situation i would need any bushing to resist the fierce spraying of water/dirt/salt/etc from the roads during the winter.
That means very good seals.
I have found that the Ural uses automotive style steel-rubber torsion bushes for it's pivots.
That definitely solves all the sealing problems since there's nothing to seal.
However, for any decent vertical travel, these bushes would need to rotate in excess of 45 degrees ...

Steve G. has recommended bronze bushes. How do i seal these ?
And if there are other alternatives please tell.

Ticktock
04-09-2013, 08:58 AM
Try a custom made vynyl boot, can be joined at the back and bottom with velcro. Then adda grease nipple. Then remember to use the grease gun!
I would have suggested rubber bushes, except for thenfact that you will need such a large movement!!
You may be able to find something in the MC shops, as most bikes have a cover type seal to the swingarm pivots.
Steve G

darnthedog
04-09-2013, 11:18 AM
First off most bushings in automotive are NOT sealed. They just get grease to prevent water from doing any damage. Secondly many inexpensive mountain bike have plastic bushing for their pivots. Some have lead. Using a brass bushing it should last a long time provided as Ticktock mentioned you keep up with the grease. Re-greasing pushes dirt and moisture out of the joint that may have worked its way in from the pivoting motion. If your really worried about motion and movement you could mount sealed pilot bearing as are used in our axles on our delta trikes. That way you have full rotational ability and the seal your looking for. Just some thoughts

Jon_Doe
04-10-2013, 03:29 AM
Steve G, i have a hard time visualizing the vinyl boot. Can you give me some clues ?

Regarding the motorbike cover type seal, the bronze bush flange is only 2mm thick and the seals on these covers are way larger (this is from the pictures).
So, either i am doing this all wrong or i am missing something.

This is how i imagined the pivot:
6865

And this is how a motorbike cover seal looks like:
6866

Whatever seal i end using, the flange width is small so it will have to fit (pressed).

Ibedayank
04-10-2013, 05:54 AM
why not just use a sealed bearing to begin with?
6867
sealed flanged bearing... no need for extra seals

Ticktock
04-10-2013, 10:28 AM
Hi,
What you have drawn is nearly spot---just a rubber O ring over the flange of the bush, but sandwiched between the fork leg and the mounting lugs on the swing arm will work fine. Using a water resitant grease will help--its used in the food industry. You can eat it---but it tastes like xxxxx!
Dont get too carried away with sealing here--a regular squirt with a grease gun, and a water resistant grease is all you really need.
I would not worry about a seal at all! Even water reistant grease is overkill, except I know it exists. Just regular greasing, and cover the whole thing with a flexible "boot".
Don't know ant other word! Bit of vynyl cloth, cut to make a cover around the forks and swing arm, with (suggestion) Velcro to join bottom and rear edges. easy to remove to clean off excess grease , will keep out most water and 99.9% of road dirt. Thats better than most bike seals can do.

Jon_Doe
04-10-2013, 10:54 AM
Oh, i see now.

Once upon a time i thought of just putting a piece of inner wheel tube over the whole thing and clamp it at both sides with plastic collars.
But this is a T junction so it's not that easy.
I could of course put a spacer on the swingarm, underneath the pivot, just enough to be able to clamp to.
But then i would lose the ability to move the pivot point on the swingarm ...
Or i could make this spacer mobile on the swingarm ....

Oooooh
Decisions, decisions.

Thanks for the input.
It's been mostly valuable.

Jon_Doe
04-15-2013, 03:34 AM
I'd actually recommend against a balloon tire in this situation and go for one that can handle a decent pressure rating or you risk pinch flats.

Thinking about what you said, i went and got myself this saturday a pair of 28x1.75 (47-622) cheap chinese tires for some tests.
They are wider and "taller" than my actual 28x1.5 (35-622) so i actually don't hit the curbs with the rim (within reason) and dampen a lot more irregularities in the road.
I did feel an increase in rolling resistance though.
These are rated 2-3.5 bar and i inflated them to the max.
However i do "feel" the need for some extra pressure just to be safe.

Now my question is, what would a "decent pressure rating" be ?
I can get at a reasonable price the SCHWALBE Road Cruiser 47-622 that is rated at 4.5 bar max.
Is this enough or more is needed ?

Thanks