Kiwi 26/27 RPU build

[gudgyz]

Had a busy day on the car today. Got the frame horns all tidied up, drove the neighbours nuts, about 3-4 hours of grinding to get them looking nice. Then took the front axle & everything out, cut off the front of the frame and set up the new front. Lots more cutting to get everything sitting just right. It's just clamped on at the moment but looks sweet.
Will post some pic's tonight after i've cleaned up and had a feed.

 

[gudgyz]

OK heres what i got up to today, maybe its just me but what i expect to be simple tasks take a lot longer than planned, anyway i started grinding up the front frame horns, a couple hours, a couple of discs and and they were starting to look OK.

 

[gudgyz]

A few hours later, a bit more grinding followed by some sanding and they were both looking respectable.

 

[gudgyz]

Then the fun started. The temp mount were perfect for seeing how the leaf springs would behave BUT they were also welded on while the body was off which enabled me to ensure everything was perfectly square, wheelbase was perfect side to side, something i needed to maintain. Unfortunately the body is currently tack weld to the chassis to hold it square while i weld the bits in to lengthen it etc. My solution was lots of careful measuring, keeping everything level & square and it all should be OK. This involved stripping off the spings axle etc then levelling up the front of the chassis and getting some reference points i could use after front end was cut off.

A bit crude but i laid two peices of timber under the existing rails with the sides parallel to the rails. Using a square off the timber i marked where the centre of the bolts holding the springs in were. I check both sides of each rail and marked the timber. I then ran a line across using the square and the marks line up perfectly confirming it was all square to start with. I now had a refernce point ot work to. The bolt centres were both 175mm above the timber, the new horn are designed to reduce this by 25mm.

http://www.nz-hotrod.com/vbulletin/attachment.php?attachmentid=5222

 

[gudgyz]

I then had to measure back from the spring bolt pilot holes on the new frame horns to where the end of the boxing at the bottom was, 215mm. I then measured back on the timber 215mm from the refernce line and marked the chassis rails, this was where they would be cut off.

 

[gudgyz]

Then it was a case of trim the new horns to fit the chassis. The inside of the chassis was alway going to be shorter due to the radiator support so the insides were cut back about 100mm or so, the outsides looked odd witha square end so i cut the corners back, still looked odd, radiused them not much better so used my 3" hole saw to mark a half circle, still not sure but i think its OK, runnning out of ideas & steel to do much else now!

http://www.nz-hotrod.com/vbulletin/attachment.php?attachmentid=5224

 

[gudgyz]

With them both clamped in place it was time for a quick measure. The centre of the pilot holes lined up perfect with the reference lines, and a level across the two horns showed it to be nice and level side to side as well, so i was pretty happy with it all. Just need to weld it all now.

The new frame horns had the pilot hole 25mm or 1" lower than before which is exactly what i was after to lift the car an 1" for a bit more clearance.

http://www.nz-hotrod.com/vbulletin/attachment.php?attachmentid=5226

 

[gudgyz]

All in all a good productive day and i'm quite happy with the finished result, looks nice and clean and once welded will be very strong.

Onces its all been welded and been through the next phase of inspection i will box up the top of the rails to tidy it all up.

 

[gudgyz]

Got the front tacked in place then tried to fit the springs, only to find i had not allowed enough room for the welds inside which fouled them by a few mm. Fortunately the pilot holes i had drilled were only 8mm so it was a case of slot them across with a file, then open them up a bit and drill to the correct size. Just another case of best laid plans not quite working out resulting in a 10 minute job taking a couple of hours.

Now everything is sitting in the final place i can drill the chassis for the rear spring hanger mounts.

 

[gudgyz]

I'm pretty happy with the way it has all come out, nice clean lines, looks good and is functional

 

[gudgyz]

The new frame horns have also lifted the front of the chassis by about what i hoped, now have 130mm under the chassis at the front axle, just need to change the rear leaf mounts to lift it a bit to level things up, only 110mm clearance at the bottom of the kickup so will lift it to 150mm to allow for fuel etc and a fat bastard in the driver seat.

 

[gudgyz]

Got a bit more done during the week, got my HT/G steering box which will be a lot easier to use. Cut the hole in the body and tied it up with wire for now, will start on mounts for it over the weekend.

 

[PeteT]

That's some great work you doing there, well done.

I'm very interested in your steering as it's right hand drive. I see you drive on the wrong side just like we do in England :rofl:... I wondered what vehicle did the steering box came from?

 

[gudgyz]

I wondered what vehicle did the steering box came from?

The steering box is from a 1969-71 Holden, which were sold in Australia, NZ and i believe South Africa. They were a large(ish) car, about the same sort of size as a Zephyr with engines between 3 and 5.7 litre. The steering boxes and parts are still readily available, it took a week to find this one and cost the equivalent of 40 quid.

Below are a couple of photos of my old 1969 HT Kingswood. Rego plate is "I SKID" which it certainly did.

 

[gudgyz]

Having a bit of a rethink on the bellcrank postion now that the steering box & pitman arm are sitting there, I HATE the angle of the steering rod from the pitman arm down to the bellcrank under the beam axle, just looked all wrong. I will have to move the bellcrank up above the beam to get everything looking right, so the steering shaft will look right, i just have the bell crank sitting up high on its own, which also looks odd, but not as bad.

 

[LumenAl]

Question... why not just use an upper steering arm that attaches by two upper bolts through the upper 2 backing-plate-mounting holes on right side spindle... you could build something like this...

perhaps (very possible) I just don't get it...

 

[gudgyz]

Question... why not just use an upper steering arm that attaches by two upper bolts through the upper 2 backing-plate-mounting holes on right side spindle... you could build something like this...

I had looked at that originally BUT it would create shocking bumpsteer. With the axle pivoting at the front of the chassis and the steering arm pivoting back on the cowl, any suspension movement would have a profound reaction on the steering. Having the bell crank set up simulates having a steering box in cross steer configuration, which should drive nicely, just a bit more work.

 

[PeteT]

Thanks for the info on the Holden, don't think I'll find one of them in England :lol: but I may be able to find somethink similar.

I can't get my head round the bumpsteer problem. I have got an upper steering arm exactly like LumenAl suggested. I was going for convential sidesteer but don't have room for the steering box. Doesn't cowl steering follow the same rules as side steering? I know you need to get the steering link in parrallel with the four bars and the pitman arm will be slightly further back but is there some other problem I've missed. I'll have to draw it on CAD and see how it works out.

 

[gudgyz]

Re: Bumpsteer 101 -sorry if its a bit long winded

I hope this makes sense...

Bumpsteer occurs when the arc of the steering travel and the arc of axle travel are different, something that can be designed out with care. If you only drive dead flat freeways with no bumps or undulations its probably not a problem, but crap roads we have in NZ and parts of the UK you need to avoid it. With your case of fourbars (although your wheelbase does change slightly with travel) it should not be so bad as mine but it is worth drawing it up first and seeing what happens, as i feel its better to design it out first than try and modify the problem out later.

Basically if you draw the arc the axle travels in, say 2" up & down, 4" in total you will get an arc that in my case pivots at the front of the chassis. For the same 4" of travel the steering shaft from the steering box will travel in an arc that pivots in the opposite direction. At rest the two arcs touch/intersect. As axle travels up or down when you hit a bump the arcs try move away from each other, but because the steering arm from the steering box is joined to the steering arm pivoting on the stub axle, the result is something will move, typically the steering arm on the stub axle will rotate, which turns the car unexpectedly. Hence the term bumpsteer, you hit a bump and the car steers.

http://i372.photobucket.com/albums/oo167/gudgyz/Early days/Bumpsteer.jpg?t=1232859525

The same thing happens when your steering box is mounted so the pivot point is a lot different to where the split bones pivots or when the steering arm is not parrallel to the fourbars, you have arcs that are working on different pivot points, that only intersect briefly and for some of the sspension travel will trun your car when you least expect it.

My last T had a vertical column with a rack and pinion mounted under the floor. With the wheels in the straight ahead position the end of the rack that the steering shaft came off was exactly on the same line as the pivots for the split wishbones, hence no bumpsteer. I have driven some that did not have the same attention during construction that were very twitchy on bumpy roads as the car steered itself with every bump.

What i am trying to do is avoid these problems now, rather than trying to get it on the road, failing inspection and then trying to fix it all. Better to get it right first time.

 

[gudgyz]

OK i had a bit of a play today and this is what i came up with, not the finished article obviously but something roughed up to see if it would work, which it does. Have drawn up what i want the final piece to look like and will be getting a mate with a better home workshop than me to machine it all up. Anyway heres the rough version!