a frame questions

[Bartso]

im going a rear a frame on my GQ here it is it is set up for a standard GQ



as mine is not standard it has been extended to a mid wheel base i want to know how i should modify the a frame to suit i have a couple of thoughts but i want to know my best option
here is one


or here is another option on an 80's cruiser


also while im at it will there be any benifit in moving my lower arms to the inside of the chassis and trianglate them or just leaving in the oe spot

[bru21]

mate if its more than 100mm i would re do the triangle or sheet it in with 4mm sheet.

moving the links in reduces the linkages binding in the scenario that 80series in in and will reduce the rear steer effect too.

Edit
fixed as i had it the wrong way round
i explained it later once i notced the mistake thanks bushy. I was thinking one thing and saying another. must be the 5 glasses of red last night when i typed it.increase the rear steer effect. 80s have them under the rail and that would be one reason he has moved them. also tyres may hit the arms at full flex without gu diffs, are they 10" rims with 4"backspace or what, so moving them in might be an advantage

[bru21]

2 posts

[Bartso]

mate if its more than 100mm i would re do the triangle or sheet it in with 4mm sheet.

it needs to be extended by around 350 - 400 mm

moving the links in reduces the linkages binding in the scenario that 80series in in but will increase the rear steer effect. 80s have them under the rail and that would be one reason he has moved them. also tyres may hit the arms at full flex without gu diffs, are they 10" rims with 4"backspace or what, so moving them in might be an advantage

i will be using 10 inch rims with 4 inch backspace also the rear arms should they be triaglated as in / \ or straight,

so the difference may be that by moving them on the inside i get less binding but more rear steer

and on the outside i will get binding but less rear steer

[Bush65]

mate if its more than 100mm i would re do the triangle or sheet it in with 4mm sheet.

it needs to be extended by around 350 - 400 mm

moving the links in reduces the linkages binding in the scenario that 80series in in but will increase the rear steer effect. 80s have them under the rail and that would be one reason he has moved them. also tyres may hit the arms at full flex without gu diffs, are they 10" rims with 4"backspace or what, so moving them in might be an advantage

i will be using 10 inch rims with 4 inch backspace also the rear arms should they be triaglated as in / \ or straight,

so the difference may be that by moving them on the inside i get less binding but more rear steer

and on the outside i will get binding but less rear steer

Don't extend the a frame like that 80s.

If you triangulate the lower links so they are closer together at the chassis end (than at the axle end), it will reduce rear steer not increase it. But you have more chance of catching on rocks.

[bru21]

they are like / \ to encorage the std setup to drive towards the centre when acclerating. i guess with an a frame this is less important, but i would still want some / \.

yes about the inside etc, as you said.


to work out the difference just think what would happed if the links were 20m apart and what would happen if they were 20mm apart.

as the distance apart at the diff is the same the difference between in and out (of the chassis)
is the height.

assuming the links sit at 45 degrees to the ground at resting height. when on rear wheel is on a drum the raised wheel compresses to be parallel to the ground, whilst the other extends and becomes say60 degrees.

now assuming the bottom lings were 20mm apart one would be 10mm higher than the other so one is still at 180 and one is still at 60. they would form an a and their lenghts reletive to each other would be very close.

now assume the opposite. the links are mounted 5m apart. the one link would be at 180 still the other at 60. at 180 it is at its longest and at 60 its shortest. as they are now seperated vertically by say 3m they are vastly different in length and have rear steer of say 1m on the short side.

now you see the difference is proportional to their mounted width due to the affect of the height change has. the further from the centre the bigger the length chenge hence the greater the rear steer.

hope that helps.


400 longer i would make new arms from scratch with a bar running left to right at 1/3 and near the 2 eyes, trussed with 4mm plate in between the two bars. this gets a push pull as well as a lateral loading so strengthen for both

cheers bru

[Wendle]

moving the lower link in at the chassis will flatten out your roll axis, you definitely want to do this, especially if you are running tall springs, and especially because it is a GQ, because the chassis already tapers out into a painful rock catching wedge there even without the links hanging onto the sides of it. i lost count of the amount of times i got stuck trying to pivot around a rock on a sideslope or something just because of the link mount hanging out there. then i moved the links to the inside and it was much better, although would still get stuck on really tight stuff occasionally because of the wedge shape of the chassis.

[Bartso]

cheers guys