Rear under tray and diffuser attachment

[Swiss_Toni]

Does anyone have some good suggestion on how to attached a rear under tray and diffuser?

I don’t really fancy drilling a hole and putting a rivnut in, though I guess I could just weld a tab on.

For the diffuser I still want to be able to open the rear clam without a lot of pfaffing around.

Your suggest will be welcomed.

Greg

[V8Dom]

Swiss_Toni said:

Does anyone have some good suggestion on how to attached a rear under tray and diffuser?

I don’t really fancy drilling a hole and putting a rivnut in, though I guess I could just weld a tab on.

For the diffuser I still want to be able to open the rear clam without a lot of pfaffing around.

Your suggest will be welcomed.

Greg

for the undertray you can drill a hole and fit an insert and then bolt the undertray into position?

Dom

[k wright]

Don't drill into the chassis, weld locating tabs on the alloy sheet that you use for the tray. Across the top of the locating tabs bolt an alloy strap that holds the tray to the chassis. This will allow you to remove it from the top as well.

Make sure to have a provision at the front of the tray to prevent air from pulling the front down.

[Swiss_Toni]

k wright, interesting idea using your strap type arrangement. I need to explore this further.

The real tricky I think is the bit how to attach the diffuser. How do I get the right support though at the same time allow the rear clam to be open without having to unbolt the diffusers?

There is an older post from Wilder (Jonathan Kay) that looks like what I have in mind however, I can't see how he's attached it. Maybe Jonathan or someone who knows could enlighten me?

[k wright]

Not trying to be abrasive but a diffuser that intersects the bottom plane of the undertray at a sharp angle instead of a gradual curve up is likely to be unsuccesful. The chassis is not diffuser friendly at all. Not sure how you can make it so. Likely your best bet is to make a flat undertray for the car and limit the amount of air that is allowed to enter the front and sides on the bottom.

[Graham-P]

How about getting a strip of bristles (the sort around truck mudguards to stop spray) and attaching them to the undersides of the car to create a curtain and force the air out the back, like the 80's F1 cars?

Graham

[CJulian]

Guys, per Simon McBeath's book "Competition Car Aerodynamics" a proper rear diffuser angle should be somewhere around 8-12 degrees off the floor. There's no magic number as the entire car's areo setup needs to be considered but generally speaking it sounds like a good place to start. I've attached a couple of images of my rear diffuser and rear clip hinge system. I've also posted previously on this subject as I have a similar hinge system on the front of the car to allow for a full length splitter that is rigidly attached to the GTR chassis.

Thanks, Chris

[Rusti Evo]

This one is a development from the wind tunnel and race proven design off the Stealth race cars. Over a metre in length and the maximum width that will fit between the tyres. Fully integrated into the flat floor/splitters.

(Greg, Petes engine is fecking awesome isn't it!!!!)

[deadscoob]

How does the rear clip open? Hinged?

[Rusti Evo]

deadscoob said:

How does the rear clip open? Hinged?

Howdy deadscoob,

I seem to be having an "age" moment here, I thought it was your car that has been sitting along side mine at the SS workshops for a year or more?

Stuart

[deadscoob]

- it was next to yours for a while, but was moved in June this year. Not been down to see Steve since about April time.

[GTRCLIVE]

CJulian said:

Guys, per Simon McBeath's book "Competition Car Aerodynamics" a proper rear diffuser angle should be somewhere around 8-12 degrees off the floor. There's no magic number as the entire car's areo setup needs to be considered but generally speaking it sounds like a good place to start. I've attached a couple of images of my rear diffuser and rear clip hinge system. I've also posted previously on this subject as I have a similar hinge system on the front of the car to allow for a full length splitter that is rigidly attached to the GTR chassis.

Thanks, Chris

Nice piece of Engineering bud lovly hinge...

Any pics of the front hinge setup please always looking for great Ideas to incorporate on my car....;)

[CJulian]

Thanks!

Sure- here's the front hinge setup.

Believe it or not this was one of the most frustrating parts of the entire build. This is the third or four hinge iteration. Also- I failed to mention that the chassis had to be modified to allow the rear diffuser to properly meet up with the under tray.

Front Hinge system:





More rear hinge pics:







Interested parties can e-mail me and i'll send off the CADD files for the hinge setup but be aware that a lot of mods are needed for their use.

Thanks, Chris

[k wright]

Wow. Just wow.

Would instantly buy a hinge set up that allows use of that front splitter. If my car has enough wing for rear grip it gets light in the front at speed.

[V8Dom]

CJulian said:

Thanks!

Sure- here's the front hinge setup.

Believe it or not this was one of the most frustrating parts of the entire build. This is the third or four hinge iteration. Also- I failed to mention that the chassis had to be modified to allow the rear diffuser to properly meet up with the under tray.

Front Hinge system:





More rear hinge pics:







Interested parties can e-mail me and i'll send off the CADD files for the hinge setup but be aware that a lot of mods are needed for their use.

Thanks, Chris

I like that too..

looking at your exhausts are you running a cross over 180 system??

Dom

[CJulian]

Yes Dom,

Unfortunately the 1.75" primaries are a little undersized for a high HP LS motor but should be OK for the stock LS7.

Chris

[Swiss_Toni]

Some very interesting ideas.

Other than the beautifully engineer hinge from Chris, I’m still searching for methods of attaching things in place.

Stuart, I’m curious how is you diffuser attached and whether you needed to trim the rear clam to get it to fit?

As well after having a further look around the car I think the most straight forward thing to do, other than drilling holes and putting inserts in which I wish to avoid, is to attach brackets, either riveted where there are already ones or welding tabs on.

This is likely to work for the forward sections, however the actual diffuser itself is looking tricky. The only thing so far I’ve come up with is to have a slot in the preceding section which the forward edge of the diffuser slots into and then have some type of quick release pins arrangement that attaches it to the chassis.

This way the diffuser section can be removed easily for opening the rear clam or loading it on a trailer.

I’m not 100% sure it will work so I’m still open to suggestions.

[V8Dom]

CJulian said:

Yes Dom,

Unfortunately the 1.75" primaries are a little undersized for a high HP LS motor but should be OK for the stock LS7.

Chris

email sent as i dont want to take this off topic
Dom