Hello all,
Happy New Year!
Well here is the next update at long last; I had a bit of time over the holiday season to get some work done between family stuff so here it goes.
The front suspension building process is similar to the rear with the exception of needing to add caster angle to the set up. I did it the same way it was done in the MG’s and others like the Lister Jaguar back in the day. This is due to the fact that the uprights have no ball joints. MG did it by building the suspension as a sub assembly and mounted it at an angle to the uni-body,I did it more like the Jaguar with the arm mounts mounted at an angle with the upper and lower pivots parallel .
I waffled a bit on what this angle should be factoring in old bias ply tires verses radials and what folks on MGB sites were saying. It’s a bit of a debate, some folk swore buy adding shims to reduce the caster angle from 6.5 or 7ish degrees to 3.5 or 4ish degrees to reduce the steering force at low speeds especially if you use a small sport steering wheel and some folks say the old cars handle just fine in stock form and people have just gotten soft because even the smallest cars today seem to have power steering. You can also factor wide tires into this equation too.
I have settled on 5 degrees, a little bit less than stock MGB and I have driven a few over the years and found yes, I think they drive just fine.
I am using the Moto-Lita 16 inch wheel with narrow (ish) radial tires and wearing a flat cap so I think it is a fair compromise. I have also noted in the chassis manual that the 427’s ran 6 degrees as well so I hope I am right as it would be extremely difficult to change later.
I think if anything the steering might feel a tad heavy at low speeds but I do prefer a car that wants to keep going straight when it’s rolling at speed so we will see how it works out. Back in the day I drove a slightly hotted up 70 VW Beetle for several years, no power steering and I added shims to the front suspension to INCREASE the caster to help keep it straight!
It also featured one of those classic small 3 spoke Grant sport steering wheels, I thought it drove fine so I guess I can adapt to anything.
I am sure my current stock Suzuki SX4 would drive rings around the old bug but honestly nobody has ever slowed down to give me the “thumbs up” on the hi-way driving the SX4, so I still miss the Beetle sometimes………..
The basic trick as I said is the same as the back, I built up the arms from my drawings.
Then I fitted up the lower mount at the 5 degree angle and then made another spacer jig to help set the point in space for the upper arm mount and keep it parallel to the lower mount.
Based on my drawings I needed to extend that mount point inboard as the spring also needs to pass through the exact same location.
Sometimes I think this might also be some sort of art project going on, Hmmmm,
Beauty is in the eye of the beholder I guess.
I then added tubes down to the main chassis tube similar to the 427 chassis and figured out a top mounting plate based on the 289 upper shock mount from Chuck’s drawings as the rad hose and steering shaft need to pass through these areas later and I am also trying to keep things looking a “bit correct” under the hood.
The coil over upper mounts of course need to be in the correct place for full travel, and very strong. So again using CAD I came up with a nice reinforced box structure that I will try and mask with a faux leaf spring assembly in the end….well at least that is the plan. I wish they did not stick up so much but those points need to be where they need to be so that is what you get. As I said at the beginning I am really trying to use the parts I have easily available to me in the best way I know how.
Just had to try the rims
Lots of room!
That brings us to the steering rack! I have known for a while this was going to be a bit of a trial and error type affair. The inner arm mounts center line does sort of work out nicely with the MGB rack but due to the design of the uprights and steering arms a conventional layout drawing is not going to really work. It gets you in the ball park but there will be some tweaking required. This rack worked well on the MGB and AC figured out how to make it work on the old transverse leaf spring suspension so I am sure I can come up with a placement that can work. The goal would be zero bump steer in a perfect world but I will settle for slight toe out on bump so it feels better in a corner. The world is not a perfect place and the roads are not always smooth, there will be bumps but I would prefer that the car not try and change lanes when we hit one.
So that is where it’s at kids.
The rack is now attached to a frame that lets me move it up and down and forwards and back fairly easy. This will allow me to fine tune the location of the steering rack and then I will do some more CAD to make the mounting brackets in a similar shape to the original style. Then on to a final check of angles and such before another bunch of welding…….
!
I think my next major phase will involve mounting the engine, transmission and differential so I wanted to ask a couple of questions to the group………
What kind of angle is the engine mounted on relative to the chassis tubes? I am guessing it would be kind of parallel?
Most RWD cars have the engine mounted at an angle to the rear. I guess it looks nice when you slam the front of the car way down( yes I know, driveline angles
) but the intake manifold has the angle included in it to keep the carb somewhat level, how about in a Cobra?
There is no need to angle it down, the driveshaft is very short and the differential is fixed in place. I currently have a nice old Edelbrock F4B that I was planning on using and it has a very noticeable angle but that can be changed.
I am using the correct engine mounts in the front but it is the transmission end of things that is the big question. I am using a T5 with an S-10 style tail shaft conversion to fix the shifter location issue. I am sure the mounting point will be completely custom, but where is the question.
I guess the real question is does anybody know how high the centerline of the driveshaft needs to be above the chassis tubes? I don’t need it to the thousands but close would be good; it will also help with locating the differential too.
The other thing and I am thinking way ahead again, is about the turn signal lever.
I know the column is from the MG but the signal assembly is from a VW with a spacer made to fit it up. Most of the good replicas I see have the VW switch with the extra button on the lever and I know VW used it for the headlight dip switch but Cobra folks seem to use it for the horn. That’s good except I know that particular type of lever is a later 60’s part 1966 / 67 and the earlier one did not have the extra button.
I am curious as to what is really correct?
To be honest I kind of like the idea of the horn being there correct or not but I just can’t seem to find the answer in any of my reference books. Any pictures I see of an early dash there is a white push button that I assume is the horn? My copy of the 289 chassis manual is a bit hazy there so any help is appreciated.
So that about wraps it up, questions and comments are always welcome, if you want more details about something just ask and I will do my best to answer. And of course if you can help answer my questions I am always grateful for the knowledge found here
So I am back out in the shop this weekend and hopefully getting the rack location sorted and mounts made then………..everything else
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