Author Topic: Mid- Engine Modified Sports  (Read 784810 times)

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Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1095 on: April 17, 2016, 01:23:26 PM »
I had the inner CV joints unbolted from the transaxle and wired up out of the way but when I rolled the car on & off a trailer to take it to a car show, the wire tore both rubber CV boots. A pair of new boots arrived the other day so I pulled the right rear upright off and removed the axle. Removing and replacing the inner CV boot was a messy job- that black molybdenum sulfide grease gets on everything.  :x
Now I have to do the left rear boot, a job that I'm not looking forward to.

The CV bearings seemed to be in good shape so that's a relief. The axles & rear uprights are from a 996 Porsche.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1096 on: April 20, 2016, 03:43:06 PM »
When I pulled off the left rear inner CV boot the grease looked a bit dry and chalky so I pulled the CV off the axle and cleaned out the old black molybdenum sulfide grease with paint thinner. This morning I greased it with Red Line CV-2 and reinstalled it on the axle after replacing the torn rubber CV boot. Now I'm bolting everything back into place in the rear suspension.

Red Line CV-2 seems to be good stuff for a variety of heavy-duty applications.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline salt27

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Re: Mid- Engine Modified Sports
« Reply #1097 on: April 20, 2016, 07:05:41 PM »
Sometimes what seems to be a mistake (wire tearing boot) can save us (dry joint).
I like it when things work out like that.   :cheers:

Nice work Neil.

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1098 on: May 01, 2016, 12:27:15 PM »
Both axles are bolted back in place now as are the rear uprights and the suspension arms. I've added the required safety washers that prevent the rod end from coming off in case the ball separates from its housing. The cone spacers give the rod end more angular motion before bottoming out.

The alignment is close but I'll need to fine tune it at the proper ride height. One suspension arm is a bit short (see photo) and I'll replace it later with a longer one to give me more thread engagement.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1099 on: May 01, 2016, 12:30:14 PM »
One more- an outer suspension arm connection to the left rear upright.

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1100 on: May 02, 2016, 09:54:02 AM »
You are right of course, Mark, but in some cases, it was unavoidable. The car weighs 1950 lbs dry and the bolts are 1/2" & 5/8" diameter and, with a couple of exceptions are NAS & MS titanium or A256 so the shear stress should not be a problem.

I used double shear attachment brackets where possible but in some places it wasn't practical.

See: http://ntrs.nasa.gov/archive/nasa/casi.ntrs.nasa.gov/20120003667.pdf

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline ggl205

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Re: Mid- Engine Modified Sports
« Reply #1101 on: May 02, 2016, 10:33:19 AM »
One more- an outer suspension arm connection to the left rear upright.

Regards, Neil  Tucson, AZ

Neil, I gave careful consideration to using swedged tie rods like ones you show in your suspension picture. They are economical and can be had in inch long increments. What I was not sure of is strength in tension. My front axle trailing links (four of them) will mostly be in tension. I could find no spec data for these links. Were you able to source any?

John

Offline wobblywalrus

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Re: Mid- Engine Modified Sports
« Reply #1102 on: May 02, 2016, 08:37:24 PM »
Neil, one issue with titanium is its low modulus of elasticity.  It takes bigger dia bolts to get the same clamping force as with steel bolts.

Another issue is thread galling.  It can be like stainless steel in this respect.  Use of ti bolts with stainless nuts is what I did to prevent this.  The frictional coefficient needs to be derived empirically to figure out the torque wrench settings.  This was no big deal.  I torqued a ti bolt with a stainless nut that was in a hole in an old pair of cylinders.  A curve was made relating the toque wrench reading vs the bolt elongation.  Then I back calculated the clamping force vs elongation and clamping force vs torque wrench reading.

That is when I learned that ti loves to stretch and it does not do a good job in the clamping department.  The old style carbon steel or stainless steel bolts went back onto the bike.  The Triumph will be retired some day and I will put the ti bolts back on.  They look sorta trick and cool.

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1103 on: May 02, 2016, 09:35:56 PM »
John;

I haven't found any data on that either. The fact that they are almost universally used on sprint cars, etc. gives me a feeling of confidence, though.

WW;

Yes, I'm aware of the galling problem with Ti; these NAS locknuts have a MoS2 dry film lubricant baked on to minimize galling. I also used Never-Seez as an extra measure. The modulus may be lower than alloy steel but these bolts are 1/2" & 5/8" and my car is light so the stress will be pretty far below where stretch or bending of the bolts would be a problem. One other consideration was that Ti & A256 bolts won't rust.

This presentation has useful info about bolted joints: www.instarengineering.com/pdf/Instar_DABJ_Course_Sampler.pdf

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline Rex Schimmer

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Re: Mid- Engine Modified Sports
« Reply #1104 on: May 03, 2016, 12:21:56 PM »
Neil,
Thanks for the great link to the bolt design and analysis info. Great stuff!!

Rex
Rex

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Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1105 on: May 03, 2016, 10:15:09 PM »
You're welcome, Rex. There is a lot of useful stuff on the internet but finding it is not always easy. Finding totally useless crap is, however.  :-)

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline Finallygotit

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Re: Mid- Engine Modified Sports
« Reply #1106 on: May 05, 2016, 09:49:12 AM »
You're welcome, Rex. There is a lot of useful stuff on the internet but finding it is not always easy. Finding totally useless crap is, however.  :-)

Regards, Neil  Tucson, AZ

Amen to that!  :cheers:
Dan
Tucson, AZ

Offline DaveB

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Re: Mid- Engine Modified Sports
« Reply #1107 on: May 10, 2016, 04:44:35 PM »
Neil, I just perused your build thread. That car seams more like a Can Am car (yea I know its a Manta therefor shaped like a McLaren) than a land speed racer. What with a Porsche transaxle, Chevy V8, what looks like road race suspension, those big meat tires etc. I bet that thing would go like stink on a coarse.

I maybe read there were enough made to get you in a production LSR class, or something like that. I'm sure it will go great in LSR but I am wondering are you going to road race this car? Is there any way it can fit in a vintage road race class or are to many of the components too modern?
Everything I know about opera, I learned from Bugs Bunny.

Offline manta22

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Re: Mid- Engine Modified Sports
« Reply #1108 on: May 10, 2016, 11:20:02 PM »
Dave;

Yeah, the Manta Mirage body was copied from a McLaren M8 Can-Am car (Brad LoVette, the founder of Manta Cars, was crew chief on a Lola) but he made it into a closed-cockpit coupe instead of the original open-cockpit M8. I used the Mirage fiberglass body because of its aerodynamics. There were definitely more than enough produced (noted by Stainless a long time ago) to qualify for Modified Sports.

I built my car to meet the SCTA requirements but also to my view of what a "Sports" is. Yes, I plan to do some laps on an independent road course outside of Willcox, AZ. Due to the SCTA requirements, it will be a bit heavy to be competitive but it should be fun. It isn't really "vintage" since it isn't even a "replica" of an existing car so I'd probably be invited to leave any vintage event.  :-P

Regards, Neil  Tucson, AZ
Regards, Neil  Tucson, AZ

Offline DaveB

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Re: Mid- Engine Modified Sports
« Reply #1109 on: May 11, 2016, 09:28:52 AM »
Thanks Neil. It's a beautiful car. McLaren, Chaparral, Lola were the pinnacle in my opinion.
« Last Edit: May 11, 2016, 09:39:59 AM by DaveB »
Everything I know about opera, I learned from Bugs Bunny.