# Mid-engine tube chassis build...



## Forty-six and 2 (Jan 21, 2007)

I have been wanting to design and build a lightweight tube chassis car for a while now. I ended up buying a MkI TT, so it didn't ever get the chance to leave the paper. It's been about a year since the TT came about, so now I decided to get back on track with the plan. 

Here is what I have done with the past weekend. 

Built a nice table. 










Then started jigging the tubes together. 










This is the incomplete base of the chassis. 










Next I started fitting the front and rear bulkheads and upper rails. 



















That's what I have for now. I will be building the uprights once I get this passenger compartment settled. As of right now the plan is to use plate steel, but I would really like billet aluminum. Nub has helped me out in the past, but I havebeen lagging on my end the past few months, so I will have to see if he still has any interest... 

I have been collecting parts, but am still waiting on back ordered items. 

These are the front brakes and hubs.


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

oooOOOooo! Watching... :thumbup:


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## Forty-six and 2 (Jan 21, 2007)

:beer: 


I got a little more done today. 

Finished the passenger side top rail and welded on the first triangle supports. 




























Next up will be the cross brace just in front of the dash.


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## BARELY LEGAL (Jul 2, 2009)

Following! 

Looking forward to more updates.


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

So whats going to be powering this beastie then?


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## Forty-six and 2 (Jan 21, 2007)

An aba/16vt. I don't know if you remember, but it's the same motor I built a few years ago for my old Corrado. I will get it up on the table as soon as I get the front end settled. 

The target weight is 1500lbs. or under. I would like to get 350-400 out of the motor with a smaller turbo. I need it to spool quickly. I still need the valve reliefs cut into the pistons, but the comp ratio at the moment is 9:1. Hopefully it doesn't drop down too far, as I would prefer higher to begin with. I will use MS for management.


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## carsluTT (Dec 31, 2004)

looks like a solid start, keep the photos coming!


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## Forty-six and 2 (Jan 21, 2007)

Tonight's progress... 





































:beer:


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## mldouthi (Jun 26, 2010)

Sub'd opcorn:opcorn: 

Looks like its going to be solid. Did you choose square tubing for a design reason or for ease of cutting and welding? I know there is much debate over the rigidity and flexibility of round vs square. 




I hope to be starting one of these some time soon also.


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## Forty-six and 2 (Jan 21, 2007)

I have read through the debates, and feel that their rigidity is fairly close to equal. I chose the square for the lower price and I hate notching round tubes. There is a major difference in the room for error with round notchs and it' harder to mount panels to it. I like the fast progress of square too. I will use more 1" dom for my secondary tubes though. I think it will look better, and may be a little lighter than the 1" square. I originally bought a bunch of it to builds my control arms, but decided to bump up a size, so I have plenty to spare.


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## mldouthi (Jun 26, 2010)

:thumbup::thumbup: 

Nice. Cant wait to see updates.


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## Forty-six and 2 (Jan 21, 2007)

A little more for today. I decided to use the 1" square, rather than the 1" dom. I will be making a set of carbon sheer panels, so the square is needed for the surface area to bond it to.

These were a nice tight fit, with a mallet...


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## Forty-six and 2 (Jan 21, 2007)

I wanted to see how much it weighs, and what it looks like at ride height, so I pulled it of the table...




























At a 3.5" ride height it's a wopping 23.5" to the top of the side rail.:laugh:


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## Brian.G (May 8, 2010)

This link is golden, and right up your alley, I keep it in my secret links folder, put on the kettle,:thumbup:

http://www.firearmz.com/user/SAE_983055.pdf

Brian,


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## jettred3 (Aug 5, 2005)

Brian.G said:


> This link is golden, and right up your alley, I keep it in my secret links folder, put on the kettle,:thumbup:
> 
> http://www.firearmz.com/user/SAE_983055.pdf
> 
> Brian,


stolen....:beer::beer::beer:


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## Forty-six and 2 (Jan 21, 2007)

Brian.G said:


> This link is golden, and right up your alley, I keep it in my secret links folder, put on the kettle,:thumbup:
> 
> http://www.firearmz.com/user/SAE_983055.pdf
> 
> Brian,


Thanks for sharing! That is exactly the kind of factual info I have been looking for.:beer: 

I am wondering if a panel bonded in, permenantly, with "panel bond" would yield similar or better results than test 5.?


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## Brian.G (May 8, 2010)

Forty-six and 2 said:


> Thanks for sharing! That is exactly the kind of factual info I have been looking for.:beer:
> 
> I am wondering if a panel bonded in, permanently, with "panel bond" would yield similar or better results than test 5.?


You are welcome guys - please share it about, had it for a long time and its not easy find. 

I would think it could be ok, keep the epoxy bond thin as possible, and perhaps a semi flexible bonding agent could be used. A uniform bond film thickness can be achieved by adding hollow glass micro spheres. These can be had in all diameters and ensure that your film thickness can never reach zero if clamped too tight.

It has been a while since I read the full pdf, so Ill read it again and add another reply.
The reason he used hard point ferrules and rivets/bolts is because he was using cored panels. 
The only way to introduce loads equally when fitting a panel to one surface is to use these bonded hardpoints. These make sure that loads are introduced into both skins either side of core equally. 
If you are not using cored panels it could turn into a nightmare for you in terms of mounting stuff to them. Although a single skin will be fine for torsional rigidity of the frame(panel should NEVER see bending loads), it will be no good for taking loads on the face for mounting other stuff.
You can easily lose a load of stays and braces if you use a core panel in the odd area. 
For example, a 1'' thick or even 3/4'' thick cored panel will easily take the load for the seats/dash/other stuff that I cant think of right now.

If I was you, Id go with aluminium skinned cored panels instead of CF. Its not as bling but far cheaper and can be machined with a hobby router and a flush trim bit directly off your 1/4 mdf panel templates. 

You will need ferrules as I mentioned for load introduction but these can be bought for a few cent each premade. 
The bolts/rivets also gives you the option of removing a panel should you need to carry out repairs. They will also give you better intrusion protection than CF I would Imagine. 

To give you an Idea of cost, an 8x4 sheet of 15mm al hcomb panel is about 300euro - one panel goes a long way if you plan cuts + all offcuts can be used for brackets(using cut and fold method)and bonded to panels for attaching other stuff. 

Lastly, core panels will be less boom'yer than single skin CF as they will have are more dampened makeup and will resonate less by nature of design.

Im just typing as I think of it really, so if you want to know about anything else ask.

Brian,

ps, if you want to know correct adhesives to use during construction let me know, I have a list all used in F1 that you can buy easily. For the next build you will then be able to lose the spaceframe and just use cored panels for construction.


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## Forty-six and 2 (Jan 21, 2007)

I considered a monocoque design before going with the space frame, but after adding up the cost of the of core material, I decided against it.

I think aluminum panels on the inner side of the tubes, with a coreless carbon outer skin will be what I settle on for this one.


Again, thanks for sharing your thoughts.:beer:


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## EasyTarget (Sep 11, 2007)

I've been following this build on the lowcostusa.com forums. :thumbup:

Pretty stoked to see this thing finished, I've been contemplating a similar build, but using a longitudinal transaxle from an Audi/Porsche powered by either a 1.8t or 16vABAt. What are your plans for suspension?


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## Forty-six and 2 (Jan 21, 2007)

A longitudinal setup would be awesome! I wish I were able to afford a different transmission. Longitudinal makes the rear suspension simple to design. With the transverse, you have to work around the motor/trans for the forward lower control arm pickups.

I will end up with a pushrod setup, using QA1 coilovers.


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

A4 / Passat transmissions are dirt cheap though...?


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## Forty-six and 2 (Jan 21, 2007)

How are they for strength? I will have to look around for one.


edit: I just made an offer one.


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

For something that light I don't think you'll trouble it  They'll happily take 300hp in a 3000lb Quattro B5.

Assuming the trans is from a 1.8T then if you can grab clutch, flywheel, starter and the plate that sits between the engine and trans you should be set  You can use the same parts from a B4 80 as well. The B5 will be a dual-mass fw of course, but there are smf options. The B4 will be smf stock. 

The longitudinal setup uses a pilot bearing in the end of the crank. I'm not sure if the ABA crank will already be sized for the bearing or not - you might need to turn up an adapter for it. 

The V6 trans will bolt up as well, but obviously flywheel, starter etc will be different.


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## Forty-six and 2 (Jan 21, 2007)

I believe you have convinced me Mikki. It makes sense for a good handful of reasons. I can come up with only two downsides...

#1. Weight distribution might be slightly more rearward. That is just a guess at the moment. If it does, I doubt it will be noticed.

#2. It will extend the wheelbase to 100" or a few over. I don't know if I can really consider this a bad thing or not, it will just differ from my original plan of 95". I can compensate for the rearward extension by changing the design of the front control arms. If I make the rear tube of the "A" straight, and use the front tube to compensate the lack of angle, I may be able to reduce the wheelbase by moving the front hub closer to the rear. I don't know if I like the idea of that control arm design. I know Porsche 914's use a similar design, but combating dynamic loads suggest it is not optimal. Any thoughts on this whole control arm/extended wheelbase subject would be appreciated.:beer:


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

Agreed on the weight distribution - it is a fairly heavy transmission. I think about 80lbs last time I weighed one. Heavier than an 02A, but I think about the same as an 02M. It extends past the rear axle line quite a bit, so would make the car more of a long-tail design than say, an Ariel Atom or Elise, although no more so than a Corrado.

In terms of wheelbase you're actually only talking 4 inches. I just measured the Corrado from driveshaft to the front of the oil filter and its about 20", compared to the A4 which is 24" from axle to front pulley. One thing you could do is move the rear hubs forward to compensate - Audi axles point forward an inch or so already, and its feasible to push that a bit more if you need to. That would move the weight distribution even further back though.

A longer wheelbase will be less responsive but more stable. Depends what you're doing with the car I guess, and your skill level. For autocross shorter is probably better, but I'd prefer longer at the limit since its easier to control. There's probably nothing in it with only 4" difference though.

Beetle Fun Cup cars use this layout, with an I4 VW motor attached to an A4 transmission. Most of them are 1.8s, but there are a few TDIs about too. Tricky to find any good photos of the drivetrain on Google tho.


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## Forty-six and 2 (Jan 21, 2007)

I'm sure I will autox, but I am building it for track day use. The longer wb may turn out for the better. I just measured it out, and if I place the motor as close to the rear bulkhead as possible, angle the axles forward a few degrees, and plan the front control arms well, I may be able to get it within the 97-100" range. Of course when the time comes it will be a precise length. 

The weight distribution may be the bigger concern now. 40/60 is the goal. At the moment the raise floor pan and cowl bracing are out weighing the rear of the chassis. I suppose I will have to pay close attention to component weight and placement as I progress. I had already planned to, inorder to keep the cog height as low as possible, but now I will need to figure how to offset the higher rearward weight. I may end up switching over to round tubing for the rear. It will save me a couple pounds.

You are right about the Beetle's drivetrain pictures. I found a clear shot of the trans, but it wasn't in the car.

I'm still waiting to hear if they will accept my offer. If they don't, I am looking at a couple others in the same price range.


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## Forty-six and 2 (Jan 21, 2007)

The transmission finally showed up....










and a few shots of the motor.



















the exhaust ports still need a little more work.




















I am going to pick up a drill press after work tomorrow, so fun progress will be coming soon.


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

Sweet


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## Forty-six and 2 (Jan 21, 2007)

I settled the suspension geometry, and started assembling the back end.


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

Great stuff :thumbup: 

If you look around for a driver's side trans mount from a V6 A4 or Passat you'll find it uses the same sort of mount as on the other side, which might be easier to accommodate. Unless you're making new ones of course


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## PapioGXL (Jun 3, 2008)

Looks awesome. I'd love to build one of these someday... when the budget allows.


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## Forty-six and 2 (Jan 21, 2007)

MikkiJayne said:


> Great stuff :thumbup:
> 
> If you look around for a driver's side trans mount from a V6 A4 or Passat you'll find it uses the same sort of mount as on the other side, which might be easier to accommodate. Unless you're making new ones of course


 I am still undecided on engine mounts. I actually like the design of the driver's mount. Maybe not the factory mount itself, but I did cone across a really nice aftermarket one. The engine wants to rotate to the passenger side, so the factory style mount seems like a good method to keep the forces off of the bolt head and bracket itself. Remembering back to my 4 cylinder Corrado and GTI days having to deal with broken motor mount brackets. 

I may end up with something completely custom though. I will figure it out in the next couple of weeks. Thanks for the suggestion though.


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## sdezego (Apr 23, 2004)

Looking good Matt. Hope all is well!


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## AceWaters (Sep 2, 2008)

Quite jealous of this. Looking forward to more updates!opcorn:


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## Forty-six and 2 (Jan 21, 2007)

sdezego said:


> Looking good Matt. Hope all is well!


Thanks Shawn!:beer: I have been doing pretty good.

I had some plate waterjet cut for my rear uprights. I am still waiting on the interior bracing pieces. I wanted to assemble the 3/16" pieces before cutting the 1/8" parts.

Here is what I have as of now.





































I still need to assemble the other side. Then design the fronts.


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## mldouthi (Jun 26, 2010)

Looking awesome. :beer:

opcorn:


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## Daskoupe (Oct 9, 2006)

once I get my own shop I'll be copying the **** outta this :thumbup:


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## s4mt3k (Dec 18, 2008)

wow sub'd


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## Forty-six and 2 (Jan 21, 2007)

The car will be sponsored by Nutek wheels! After asking them if they could make an existing wheel in their line as an 18", they decided to design a wheel specifically for me. I will post the rendering once I'm allowed to.


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

Wow nice deal! :thumbup:


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## Afazz (Feb 10, 2002)

What spindle/hub/wheel bearing setup is that? 

Looks good so far! :thumbup:


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## Forty-six and 2 (Jan 21, 2007)

The wheel bearing is from an A3, and the spindle is my design. I had to make done revisions to it today. Clearances are tight now...:facepalm:


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## federikg (Mar 13, 2011)

Great job, congratulations !


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## Forty-six and 2 (Jan 21, 2007)

Today's work. Still need to make the toe adjustment arm.


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## mldouthi (Jun 26, 2010)

What did you use to come up with your suspension geometry?


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## Forty-six and 2 (Jan 21, 2007)

I used a program that allows you to input all of your data, and then move it through bump/droop and roll. It doesn't have an option for CoG height, so the actual amount of roll is hard to determine. I just tried to maximize the amount it can possibly roll without going into positive cambe, while maintaining a stable RC. The rear can roll just under 4° without crossing over. That is with zero bump, so that is really an unlikely situation, but can be considered "most extreme". Introduce any bump and the negative camber gain starts canceling any positive gain, due to roll, out. Once the corners can be weighed, the appropriate springs will be chosen to hopefully remove most of the roll from the start.


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## MikkiJayne (Jan 1, 2007)

*FV-QR*

Thats pretty cool


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## mldouthi (Jun 26, 2010)

Forty-six and 2 said:


> I used a program that allows you to input all of your data, and then move it through bump/droop and roll. It doesn't have an option for CoG height, so the actual amount of roll is hard to determine. I just tried to maximize the amount it can possibly roll without going into positive cambe, while maintaining a stable RC. The rear can roll just under 4° without crossing over. That is with zero bump, so that is really an unlikely situation, but can be considered "most extreme". Introduce any bump and the negative camber gain starts canceling any positive gain, due to roll, out. Once the corners can be weighed, the appropriate springs will be chosen to hopefully remove most of the roll from the start.
> 
> /IMG][/QUOTE]
> 
> ...


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## Forty-six and 2 (Jan 21, 2007)

mldouthi said:


> What program is it?




http://www.vsusp.com/:beer:


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## mldouthi (Jun 26, 2010)

:thumbup:


Forty-six and 2 said:


> http://www.vsusp.com/:beer:


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## _Growler (Apr 28, 2007)

Are you going to use any castle nuts and cotter pins on those suspension bolts? or are they designed such that the torque of the nut will keep them from backing off?

Enjoying the thread so far. keep us updated.


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## AntiMatterMaus (Jan 15, 2013)

Excellent work on putting those sphericals in double shear - A+. The rest is looking kinda scary; I wouldn't drive it more than 20mph


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## AntiMatterMaus (Jan 15, 2013)

Talking about uprights. frame looks good


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## Forty-six and 2 (Jan 21, 2007)

AntiMatterMaus said:


> Talking about uprights. frame looks good



:laugh: What about them scares you?


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## JsTT225 (Nov 23, 2012)

Please tell me you've completely documented the plans for the frame and would be willing to sell a copy? I was just talking that I'd love to build something like this but with a B5 S4 powertrain.


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## Brute71 (Sep 24, 2012)

Any more updates? Rather inspiring thread you have here!


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## TheDeckMan (Sep 26, 2004)

Nice work Matt :thumbup:


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## boner (May 19, 2002)

just saw this thread. you are feeding my very bad longterm ideas for my golf 

could you please help me out though? is that a 6-speed box? how long is it? how far are the axle centerlines from the front face? REALLY wanna find a 3d CAD model of it but so far no luck....


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## mad haggis (Nov 21, 2011)

:thumbup: on the build, can't wait to see the final product
:beer: for a fellow Tool fan


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## B5Bombers (Aug 20, 2008)

Which rod ends did you go with?


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## boraspecvr6 (Jun 17, 2005)

Nice build, keep posting. PM Sent


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## weiRtech (Jan 17, 2006)

awesome stuff. I've always wanted to build a car from scratch, but i'm no engineer. love seeing stuff like this develop. thank you for sharing so everyone has an opportunity to learn something.

aaron


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## VWDugan (Mar 22, 2001)

in for updates


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## groundupjetta (Feb 1, 2010)

sbscribed, any updates?


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## Forty-six and 2 (Jan 21, 2007)

weiRtech said:


> awesome stuff. I've always wanted to build a car from scratch, but i'm no engineer. love seeing stuff like this develop. thank you for sharing so everyone has an opportunity to learn something.
> 
> aaron




:beer: Thanks Aaron. I have always admired your work.

I had to take a beak from this build for now. My TT needed/needs some work. I have been making good progress on it, and needs to swap a motor into it soon. Once I wrap that up, my focus will turn back to this build. I definitely haven't given up on it. Thanks for following along. :beer:

A shot of the TT. Just so you don't think I'm just screwing around. :laugh:


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