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Last Post 13 Mar 2017 09:33 AM by  loosecannon
EMod MGB-GT build thread
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loosecannon
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25 Sep 2010 04:24 AM
Thanks Dave, I was planning on making some changes to the pivot and will take a serious look at the way the tie rods are mounted. If I flip the ones by the spindle, I could get more triangulation,
loosecannon
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27 Sep 2010 09:18 PM

Notice anything different about the front suspension? That's right, it's all different. I solved a lot of issues by taking a complete Jag front crossmember, chopping 8" out of the middle and adapting the pushrod suspension and MGB steering rack to it.
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The car is sitting at it's ride height and everything fits under the hood:
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loosecannon
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28 Sep 2010 06:55 PM

Today I spent hours grinding off old brackets from the Jag crossmember and smoothing out the plasma cut holes, I turned a 5" grinding disc into a 2.5" grinding disc and my arm looks like I have poison ivy from all the hot sparks. I didn't take pics because it would be hard to see what I did.

loosecannon
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29 Sep 2010 11:39 AM

Decided to see how wide I could go with tires. Here it is with 15" wide tires in the back and 11" wide tires in front:
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loosecannon
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29 Sep 2010 04:49 PM

Update: I weighed the metal I have removed since weighing the whole car and I have shaved 74 lbs off it, including 43 lbs(!) of exhaust manifolds. I also tubbed the car in order to fit huge tires:

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loosecannon
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01 Oct 2010 10:35 AM

Both rear wheel tubs are done:
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And filled in some gaps between the floor and body. I made templates from paper then transfered to metal and plasma cut them:
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A picture of me with the car at it's ride height so you get a sense of scale:
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loosecannon
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04 Oct 2010 04:03 PM
Cut out the drivers side door inner structure and fabricated removeable door bars. The bars are not required for auto-x but are for road racing so I made them removeable.
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loosecannon
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05 Oct 2010 03:32 PM

Put in a passenger side door bar in and put a reinforcing piece of metal across the top of the door to stiffen it up a little.
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loosecannon
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06 Oct 2010 02:46 PM

Got the steering column and rack and pinion installed today. The stats are: 2.5 turns lock to lock, .9 degrees camber gain per inch of travel, no discernible bump steer and the 23.5X13-15 Hoosiers I just bought on EBay will fit on the front and the back.
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loosecannon
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12 Oct 2010 04:24 PM

Filled in some gaps between the new stuff and old stuff:
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Mounted the fuel cell low enough to keep CG down but high enough to put a diffuser below it:
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And have the rear pushrod suspension half done, I just have to make a mount for the top (back) of the shock:
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loosecannon
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13 Oct 2010 04:26 PM

My 13" wide Hoosier slicks arrived today, looks like they will fit so I ordered 13" wide wheels (with 8" backspacing!) to mount them on:

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I repositioned the front shocks to get a better angle for the pushrod and it all seems to work great. With the shocks on their medium spring position the car hardly moves when I jump on it and on the softest setting it moves up and down an inch or two.

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Proving that those fat tires will still turn and clear everything, although the front fenders will need some serious re-arching to make the turns. I will most likely run narrower tires but I wanted to build the car for the widest tire possible because it's then easy to get narrower tires on there:

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47CP
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13 Oct 2010 04:38 PM

Looks great.

A few observations, take them for what you paid...

1) I am not familiar with the 13" diameter slicks, but in general, you want to leave a lot of room for them to move around on the wheel on the inside. Our 27x14x16 rears, which will hold the car up without air (e.g. stiff sidewalls) move on the plus side of an inch. Various other versions of various tires have moved much more than that, the worst on 2 plus inches. I bring all this up because your rockers look kind of close to the tires.

2) You probably don't need that much steering angle, though it won't hurt anything. On the new car with the 10" backspace 12" wide wheel there is just over 20 degrees each way, barely enough to get a caster sweep. The CP car had a little more, but not more than 25. It is a little pit of a pain in grid, but overall this isn't a problem on course unless you run some really small lots at home.

IMO, YMMV, etc.,

DaveW

loosecannon
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13 Oct 2010 07:54 PM
47CP wrote:

Looks great.

A few observations, take them for what you paid...

1) I am not familiar with the 13" diameter slicks, but in general, you want to leave a lot of room for them to move around on the wheel on the inside. Our 27x14x16 rears, which will hold the car up without air (e.g. stiff sidewalls) move on the plus side of an inch. Various other versions of various tires have moved much more than that, the worst on 2 plus inches. I bring all this up because your rockers look kind of close to the tires.

2) You probably don't need that much steering angle, though it won't hurt anything. On the new car with the 10" backspace 12" wide wheel there is just over 20 degrees each way, barely enough to get a caster sweep. The CP car had a little more, but not more than 25. It is a little pit of a pain in grid, but overall this isn't a problem on course unless you run some really small lots at home.

IMO, YMMV, etc.,

DaveW

Your observations are spot on. I didn't realize that slicks move around so much so I drove back to the shop to double check. Pulling the tire out a little gets me the clearance to the pivot plus I get more steering angle. The tires are 23.5x13x15 and I suspect I will be running them only on the back and getting the 23x9.5x15 for the front.

amaff
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14 Oct 2010 07:06 AM
loosecannon wrote:

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And I need a new pair of shorts... holy crap those 13" slicks look huge on a car that small [:O]

JBrettHowell
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14 Oct 2010 09:31 AM

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Hawt!

cmt52663
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14 Oct 2010 09:33 AM

impressive paws.

I wonder what the factor is that gets one from the original designer's load assumptions, to the capabilities of this version?

At least 2x, perhaps a bit more?

Less mass, but way way more traction.

loosecannon
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14 Oct 2010 10:27 AM
Thanks guys :) I changed my wheel order so they will have 7" of backspacing and with that I will have 26 degrees of turning. If I find that is not enough on our landing strip courses, I can add a wheel spacer and get 31 degrees of turn. Working on rear shock mounts and pushrods now, pics up later.
loosecannon
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Advanced Member
Posts:872


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14 Oct 2010 04:40 PM
Had a little drama with the back suspension today. At first I used a simple tube going from the front fuel cell mount to the back one and attached the shock to that. This was fine on the drivers side but the passenger side shock had to have the resevoir on the bottom, which then interfered with the tube. I cut all that work out and built the U-shaped pieces you see in the picture. They worked fine until I put the weight of the car on the suspension, which promptly bent the pieces down and twisted the rear fuel cell mount as well. I straightened all that out and welded in gussets and when I put the car on the suspension, it nearly bottomed out the shocks. This is strange considering that the same shocks when mounted on the front of the car (the heavier end) were perfect. I flipped the triangle shaped pivot around to reduce the mechanical advantage of the pushrod and now the rear suspension bounces exactly as much as the front suspension, which I think means I'm on the right track.
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47CP
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14 Oct 2010 05:27 PM

More unsolicited opinions....

I am not real comfortable with that rearr shock mount on the frame side. The forced is going straight back into the U shaped pieces which goes into the cell mount, but there is nothing triangulated in that direction whatsoever (that I can see). Basically, the force is going into the plane at the level of the top of the cell, straight forward and back and there is nothing but a couple of shirt 1x1 down tubes resisting that.

I am not sure how to fix it, but I think some triangulation needs to be done. Also, if you strengthen it in that plane, that back crossmember for the cell may not be strong enough, depending on the wall thckness of that tube.

All IMO, trying to be helpful, etc. :)

DaveW

loosecannon
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Posts:872


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14 Oct 2010 06:41 PM
47CP wrote:

More unsolicited opinions....

I am not real comfortable with that rearr shock mount on the frame side. The forced is going straight back into the U shaped pieces which goes into the cell mount, but there is nothing triangulated in that direction whatsoever (that I can see). Basically, the force is going into the plane at the level of the top of the cell, straight forward and back and there is nothing but a couple of shirt 1x1 down tubes resisting that.

I am not sure how to fix it, but I think some triangulation needs to be done. Also, if you strengthen it in that plane, that back crossmember for the cell may not be strong enough, depending on the wall thckness of that tube.

All IMO, trying to be helpful, etc. :)

DaveW

You are being helpful :) I was not finished with the bracing. After the earlier fiasco with the bent shock mounts, I had decided to better brace the front and rear mounts, I'll be beefing those areas up significantly. What size bolts do you think I need to fasten the pushrods? M10? M12?

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