Centre Section,
Engine / Tranny Mounts and Rear Crossmember |
By Frank Colgoni
We’ve reached a stage in the development of our
frame/chassis, that we can concentrate on the installation of our
main frame crossmember (centre section) and location and mounting
of the engine and transmission.
For our centre section, we’re using a Horton Hot Rod Parts WS13200
unit that we acquired in kit form (not assembled).
To begin, John at Dream Machines installed the upper crossmembers
and bracing. The lower crossmember, upper front portions and remaining
bracing will follow after the engine and transmission have been moved
into place and positioned at the correct height, laterally and fore/aft.
With the body on, the engine/tranny combo are swung into a “rough” position and supported. Our rad shell and radiator combo are then
mounted to check all critical dimensions at the front of the engine
(water pump) and at the bellhousing. This will establish the fore/aft
positioning. After that, height was established. Establishing the
correct height must be done as a function of driveline angle. That
is, back through the driveshaft and u-joints and, ultimately, at the
third-member pinion. The science of driveline angles is worth studying
up on. The are many sources and we recommend that you check it out
before committing to a setup. Avoiding this can bring on a world of
trouble resulting in vibration and component failure.
As it turns out, at our desired ride height, we can’t get as
much clearance as we’d like through the upper centre section
which necessitates Dream Machines notching the front-most tube.
With fore/aft and height/angle established, Dream Machines installed
a set of Welder Series’ motor mounts (#WS2050). John chose to
grab both the side and top of the rail for strength and at a height
in consideration of the route of the steering linkage which has to
pass below the mount. |
Our engine and transmission are very roughly positioned at this
point. |
Fore / aft clearances are looking pretty good.
The bell housing is a bit tight to the tunnel on the driver's side.
This will need relieving to achieve the correct height. |
The upper lateral tubes and braces of our Horton centre section
in place.
Note: The tranny tailpiece is NOT at its final height in this photo. |
The engine and tranny fore/aft position have been established.
You can see the Welder Series' motor mount plate bolted to the block. |
Motor mount in place waiting for final welding.
This will be strong and will allow for steering linkage below.
You can see the splined steering box input shaft below. |
With the motor mounts in, John moved on to mount the centre section
lower front tube (which was also notched for driveshaft clearance)
and the front upper tubes. To support the back end of our AOD tranny,
John fabbed a neat tubular cradle-type mount that terminates at urethane-bushed
ends.
To complete the centre section, John added the remaining bracing pieces. |
The lower centre section crossmember is ready to weld. |
John welds it up. Don't stare too long :-)
|
The chassis is coming together. |
The upper diagonals are in and that effective tranny mount noted
above. |
You can see the notched crossmembers in this shot.
Everything is done except the bracing. |
The completed centre section |
|
Back in article 5, we said “Unfortunately, our desired ride
height created another problem but we'll save that for another article.”
(revisit article 5 HERE) – time to explain.
In article 5, John and I had spent the day making decisions relative
to our rear track and the height of our chassis/body as it affects
the distance between the top of the tire and the wheel well. This
is primarily an aesthetic consideration but one that is important
to achieving the right stance. The diameter of the tire factors prominently
into the equation.
In a coilover spring/shock rear suspension like ours, the height at
the rear is a function of the operating length of the coilover (on
the optimum angle) combined with the upper and lower mounting positions.
That is, the upper being the rear frame crossmember and the lower
being the 4-bar axle bracket that doubles as the lower, multi-position,
attachment for the coilover. While the multi-positioning of the bracket
allows for some fine tuning of ride height, we feel it’s better
to place the lower mounting point in a neutral position and then dial
in ride height through coilover selection and upper crossmember placement.
Herein lies the rub so-to-speak.
Once we had decided on our ride height and operating length of our
coilover, we realized that the rear crossmember would have to be raised
to achieve that desired ride height (in effect lowering the ride height).
This would involve not only removing the straight crossmember and
replacing it with a raised version but also the trunk floor would
have to be altered to accept the raised crossmember. You can see where
this is going (er, went that is). As the following photo shows, we
lost the straight crossmember and Dream Machines replaced it with
a 2” raised version. What we do for the right look… |
|
|
Next Up - Introduction to some products / Our Performance World
chassis |
|