The Chopper Compendium

will it be structurally safe to weld the arms straight to the bottom of the yoke something like a 20mm OD tube, the wall of the bottom of this stem is about 5mm wall.
the bottom of the stem needs to remain hollow as i have this bolt going through as extra security to keeping the top nut secure with the extra forces that a girder set-up will put on the top yoke

aaaanybody at all?

Sorry, I don't have an answer for ya. Be patient, I think everyone is busy during the summer months.
I know I am!!!

Have you given any thought to using a solid Stem.

yea, but this stem is ready made,fits the head-stock,and the bearings drop straight in
i was thinking about this yesterday and i think it will be strong enough but if not i can always get hold of some 60mm diameter steel bar, chop it out to required height, have somebody bore two holes in the sides to hold the linkage arms and weld them in, then bore a 30mm hole in the centre for the steering stem. i can use a thicker yoke then if i dont bore the hole for the stem right the way through, i can drill and tap for the bolt that runs through the stem.

of course there is also no reason i couldnt weld the linkage arms directly to this stem and weld that washer to the underside of the stem too... this surely would add strength too. but i dont want to go ahead and trust my instinct when there's people here more knowledgable than me who will know for sure if that construction will fail and land me in a spot of bother later down the line

bobdit wrote:yea, but this stem is ready made,fits the head-stock,and the bearings drop straight in
i was thinking about this yesterday and i think it will be strong enough but if not.......

So how will you know?

I have no experience with girders, but there are a few who built them.

http://www.choppercompendium.com/ccforu ... f=34&t=152

I won't, and it will play on my mind.
what i meant was im looking for opinions from people here who have far more experience in engineering than myself and know better the strength a join like that would have as to whether it would be structurally safe .... however the first line of this post says it all which is why i decided ill order the steel and construct something im more comfortable with.

ill order a 60mm diameter by 25mm thick steel circle, bore a 30mm hole through the centre for the stem, and weld the stem in place
ill bore a 24mm hole through the sides, then taking some 24mm steel bar ill turn the ends down to 12mm for the linkages, cut them to length and insert each end into the hole bored in the side of the steel circle and weld the arms in place

the top yoke will be constructed the same as in the link you posted above, there is a 35mm difference between the linkage arms on the legs, so with the bottom linkages running parallel with the stem ill make the top one 35mm in front of the centre of the stem

from there i can mount the yokes to the bike and connect legs to fdetermine where the shock linkages for the suspension needs to be.
will post some pics later

this is the design i came up with, i think this should be more than sufficient, but always good to get some feedback

or not....

well, i did some more thinkin' and decided, that 2 arms welded off the side of that disc, is still going to play on my mind
ive ordered materials and once they arrive will asemble them in this kind of fashion, this should add more structural strength and give more area to get a weld on... i was also thinking that the tubes of a frame are butted up against the headstock and welded and carry the weight of the bike, but perhaps my way would be better in thisinstance

feel free to chip in

is there a reason you absolutely *must* have that bolt to help secure the top nut? i built mine without and have had no trouble with the top nut coming loose or anything. also, i think every girder i've ever seen has not had any additional security for the top nut.

i'm not trying to get you to abandon your design, but for me personally, having that bottom pivot in two pieces as opposed to one monolithic unit welded to the "puck," would make me much more uneasy than trying to add support to an area which has not traditionally been a problem (to my knowledge anyway).

take care,
-dan

the stem is from a standard gsxr which uses telescopic forks... the load is put on the bottom yoke, using it for girder forks where the load is more or less equal on the top and bottom yoke, that nut which origionally was designed for nothing more really, than to hold the top yoke in place, is now under pessure and trying to be levered off at every bump. you might well be right that it is sufficient enough to hold on its own,but for peace of mind it cant hurt to have the extra bolt there as an additional measure.

somebody else sudgested turning the ends of the arm down to 22mm and boring a hole for them to sit in, and welding.

the bolt isnt really a problem i can tap a thread into whatever gets in the way to bolt that in place.

you could weld a bung in the stem so you could use your jamb bolt. i would feel safer if the bottom yoke was one piece and then welded to the bottom of the stem.

agree with the above comment.... i will feel safer constructing it from 1 piece, this will do for now to wheel it around but i wouldnt feel safe riding it TBH
taa for the help...