G/F class lakester in Wichita, Kansas

[ggl205]

Hi Rex:

Yeah, I had to bail this year. We were going to concentrate on getting Lyn into the 200 mph club but she crashed pretty hard at an SVRA Race of Champions held at the Indianapolis road course and fractured the T-22 vertebrae. She said everything was OK and that her doc had cleared her to drive but I was not going to risk it. Lyn is a true professional and she really wants into the 2-club (we want her there too) but in the event something should go dreadfully wrong on course, well, you know what I mean.

So, we will be back next year and really ready for some serious speed.

John

[ggl205]

We had a little time over 2018/19 to make changes and create a few updates. Attached are images of the completed Watts link, new battery placement (farther forward), wider front axle, new spindle arm, repositioned plate for all electronics and fire bottles (easy access) and a glimpse at what all new trailing links look like (much beefier). I think we now have better weight distribution. What remains is to build a three foot addition to the rear complete with rear stabilizer. This should give us a more favorable Cp/Cg relationship.

John 

[Lemming Motors]

John
How long (centre to centre) are your Watts linkage ?link arms??

I am trying to decide between Watts and a sliding block for the rear axle and was worried about short arms. (With deep pockets)

I guess the axle movement is quite slight in terms of bump and rebound so won?t find their limits?
Lemming John

[ggl205]

John, I will get those link lengths out to you tomorrow but it really doesn?t matter how long they are. Given the amount of vertical travel we see, even short arms work fine.

John

[ggl205]

John, horizontal links are 4.25 inches long end-to-end and 7.25 inches long center-to-center on rod ends. I can move the front axle up and down through a full range (before things begin to run into one another) and the vertical prop link hardly moves. When one end of the axle moves up, the prop link does move some but does so in concert with the other end. It is a great setup and should keep my axle in perfect alignment through bump. The old Panard bar caused the axle to shift laterally in bump.

I don?t see any problem with sliding block if it is aligned properly and kept greased. Things take a hard pounding on the salt so whatever you decide, make it sturdy, then go back and double that.

John

[Lemming Motors]

Thanks John

[ggl205]

Depending on how you go about it, I think a Watts link easier to build than a sliding block.

John

[Lemming Motors]

I am leaning that way. My rear design has subtly altered from my original concept sketches and may well be better suited to Watts. The rear axle rear cover with reinforcing and bracketry could go either way.

Recognising your Watts pic was a front end here,  I am still undecided on the front axle setup.

[ggl205]

I have been re thinking front suspension. I am uncomfortable with how close lower shock attachments are to the under tray. I have an axle droop stop but any compression of the rubber stop and shock mounts contact the tray. I was going to redo front shocks in favor of a rocker arrangement for 2021 but decided to do it this year instead. I think it better for a number of reasons so here is what it looks like so far. Just waiting for warmer weather to finish welding pivot posts and drop links.

John

[Lemming Motors]

I wish I could be at SW2020 and see it in the metal.

I have mocked up version 1 of my rear rockers but the load path isn't ideal so I am moving to version 2 and procrastinating by doing work in other areas hoping for a light bulb moment.

[ggl205]

John, I went through a similar process. Originally, I wanted to use as much existing utility on the car as possible. That meant making pivot post brackets bolting to top shock mounts. That didn?t pass muster with an aircraft structure engineer friend of mine so on to the next iteration. I must have gone through several designs in my head, hoping for that ?lightbulb moment?. Most ideas I was coming up with were 15W at best. Tom Burkland eventually bailed me out with the idea of simply welding directly into the top chassis crossmember, two pivot posts much like you would with threaded weld-in bungs. Perfect solution with an even lower profile. Only perceived downside is the rocker pivot is operating in tension rather than the more desirable compression. I think this acceptable because specs for these rod ends say they are safe to 17,000 psi. So, as it stands, other than having a beam front axle, everything has changed from the original front end.

John

[ggl205]

We are having unseasonably nice weather this week and it gave me opportunity to complete the front suspension. My version of a Watts link, rocker front axle.

John

[Lemming Motors]

That looks tidy. Is that a lot of preload on the springs or just in mock up at the moment?

[ggl205]

A mock up, for the most part, John. Once car is on the ground, spring perches will be adjusted for desired ride height. Any additional adjustments will be through vertical links from axle to rockers. If I got it right, springs will be in contact with both perches with axle in full droop. Counting on about .500? spring compression with tires on the ground.

John

[puppy]

Did you make the rockers for the front suspension more than 1:1 for a particular reason?
Also I noticed the front radius rods are ahead of the axle instead of behind like we usually see on roadsters, sprint cars ect... Any particular reason for this?
Also when one see's a G/F designation, does that mean you plan on running two different engine classes with the same car (I'm new to land speed racing)?