Porsche 911 with bespoke chassis

[manny 83]

As a 911 nut, I'm blown away by this project!  The best complement I can give you is that it looks like a finished production kit!

[IXLR8 1153]

1 hour ago, manny said:

As a 911 nut, I'm blown away by this project!  The best complement I can give you is that it looks like a finished production kit!

Oh Manny, thank you so much.     I've always tried very hard to make my scratch-built cars appear as refined as possible.

So, as a self-proclaimed "911 nut", what era/model is your favorite?  I tend to favor the older models but the 993 is really growing on me.

In fact, thanks in large part to @GermanTA03Guy and his incredible looking 993 GT2, I've decided to build that car next and put the RSR on hold for a while.  Today, the postman delivered the body, light buckets and a few other parts to begin the build.  The chassis for this one will be virtually identical to the 934.  This one shouldn't require 4 months to complete.  

 

 

 

[ChrisRx718 4470]

Oh wow - I didn't realise Tamico had stock again. Annoying about that minimum order value we need to place - I'm all spent out this month 

 

[IXLR8 1153]

1 hour ago, ChrisRx718 said:

Oh wow - I didn't realise Tamico had stock again. Annoying about that minimum order value we need to place - I'm all spent out this month 

 

Yeah, I happened to be at the right place at the right time and still had a few bucks on my pocket. 

I'm very disappointed that Tamiya has punched holes in this body - I won't be using body posts.  They even punched an antenna hole.  Why???  

[manny 83]

Any of the older air cooled models is fine with me. Noisy, hot, bad ergonomics...to this day my left clutch leg is way stronger than my right leg... A real car for sure!   I had one from the mid 70's and another from the mid 80's

 

I did a 911RSR  project a few years back.  It doesn't hold a candle to yours in complexity and I had to shelve it for a big move.  I am howerver quite proud of my Fuch wheels.  It's 2wd with a backwards one way in the front diff to provide four wheel braking. 

 

[IXLR8 1153]

3 hours ago, manny said:

Any of the older air cooled models is fine with me. Noisy, hot, bad ergonomics...to this day my left clutch leg is way stronger than my right leg... A real car for sure!   I had one from the mid 70's and another from the mid 80's

 

I did a 911RSR  project a few years back.  It doesn't hold a candle to yours in complexity and I had to shelve it for a big move.  I am howerver quite proud of my Fuch wheels.  It's 2wd with a backwards one way in the front diff to provide four wheel braking. 

 

You should be proud of those wheels, they look amazing!!  Adding a spacer to reduce the wheel diameter is very clever.  I may need to borrow that idea one day.  

[IXLR8 1153]

Well, the rain is over (finally) so I'm headed back to the tennis courts in the morning.

I'm going to try a different motor:

This is the stock motor for Kyosho's Fazer MkII (I have the Chevelle SS), it's powerful and fast. 

This motor is also VERY heavy so I'm certain it will change the car's balance.

Watch this space for a full report.  

[IXLR8 1153]

Hanging that heavy motor over the rear axle did indeed change the car's balance in the form of significant understeer during on-throttle corner exit.  I was able to counter much of the understeer by reducing rear toe angle from 2 to 1 degree.  The toe angle change freed the car a bit (bringing it closer to neutral) and should reduce tire scrub so perhaps it gained a little speed as well.  It was very windy today so that created another challenge.

I really didn't notice a change in the car's maximum speed after moving to the 14t, 550 class motor (the previous motor was 15t, 540).  After 30 minutes, I swapped batteries and checked the motor and it was only slightly warm so I think it's time to gear-up.  I've already fitted my largest pinion (20t) so I'll need to locate a smaller spur gear.

Although the new motor is heavy and changed the car's balance, I think I prefer how it handles now.   I'm ready for a little more speed.   

[IXLR8 1153]

After my previous post, I was able to locate a 22t pinion and I paired it with a 52t spur gear for a FDR of 6.15:1.  I ran the car again this morning and although it was faster with the new gears, at the end of a 30 - 35 minute run the motor was only slightly warm so I believe it would benefit from even more gear.

I'm certain now that 22t is the largest 32dp pinion gear I have so this afternoon I started rummaging through boxes and found a larger 38t 48dp pinion.  

The 38t pinion has been paired with a 78t spur for an FDR of 5.34:1.

I've been in the RC car hobby since the 1970's and that 38t is the largest motor pinion I've ever held in my hands. 

Anyway, I will return to the tennis courts in the morning.   I've increased rear camber by about 1 degree so I'm happy with handling now -- which tells me the car isn''t going fast enough. 

It was very windy again today but tomorrow's forecast is for sunny skies and calm. 

[IXLR8 1153]

The tennis courts were unusually dusty and slippy this time.  The car was faster but also much harder to control.  I think the high winds over the past few days are to blame for spreading the dust. 

What’s odd is that it the handled fine through the curves but the tires would suddenly break loose in the middle of a straight section. The tire spin was completely random and, of course, created a loss of control.  I had been lucky so far -- not hitting anything -- but eventually the car spun and I was unable to stop before it backed into one of the support posts for the nets.  A wheel is broken, the motor plate is bent and even the chassis plate is bent.  I think the axle might be bent as well.    I’ll order another set of wheels and axles and straighten the bent plates.

Fortunately, the printed trailing arm has survived the impact. 

The bunnies are okay as well.  

 

[IXLR8 1153]

Fortunately, the axle wasn't bent so I was able to complete repairs. 

Anyway, the bent plates have been straightened, the rear wheels re-aligned and we're ready to go again.

I can run the heavier aluminum wheels until the replacement plastic Tamiya wheels arrive.

 

Bugs is happy.  

 

[Keracticus Pots 187]

On 5/6/2023 at 5:17 PM, IXLR8 said:

The tennis courts were unusually dusty and slippy this time.  The car was faster but also much harder to control.  I think the high winds over the past few days are to blame for spreading the dust. 

What’s odd is that it the handled fine through the curves but the tires would suddenly break loose in the middle of a straight section. The tire spin was completely random and, of course, created a loss of control.  I had been lucky so far -- not hitting anything -- but eventually the car spun and I was unable to stop before it backed into one of the support posts for the nets.  A wheel is broken, the motor plate is bent and even the chassis plate is bent.  I think the axle might be bent as well.    I’ll order another set of wheels and axles and straighten the bent plates.

Backing into the scenery sounds like a proper 911 accident! 

Glad you got it fixed.

KP

[IXLR8 1153]

3 hours ago, Keracticus Pots said:

Backing into the scenery sounds like a proper 911 accident! 

Glad you got it fixed.

KP

 So I've been told.

I've never driven an actual Porsche but I can imagine how much fun that would be.

I live about an hour from Barber Motorsports Park near Birmingham Alabama.  By the way, if you're ever in the area, you owe it to yourself to visit the park and its world class vintage motorcycle and racing museum --  you won't be disappointed.

Anyway, Barber hosts the Porsche Track Experience driving school.  It's not cheap (2-day courses start at $3.900) but the experience of driving a fast Porsche around that epic track is something I'd never forget.    Maybe someday.

https://www.porschedriving.com/track-experience

 

 

By the way, your screen name made me chuckle.    

[IXLR8 1153]

More rain fell last night but it came and went quickly and washed the dust from the tennis courts.  Overall, traction on the clean surface was fantastic but it did unbalance the 934 a bit giving it some understeer.

Anyway, I’ve been giving the GT2 build more thought and I’m going AWD with that one.  I have a TT-02 chassis on the shelf that could be used as a start (it’s very inexpensive) but reducing its wheelbase from 251mm to 236 (or 232?) could be a challenge -- not impossible but very difficult.  This will likely require removing a section from the chassis tub then reattaching the two parts with plates, glue and screws – like Frankenstein’s monster.  Is there another way?

As an alternative, I happened upon this blingy TT-01 clone chassis on ebay (also very inexpensive):

 

The main chassis parts are simple flat plates so I think I could easily re-make them from materials on-hand and shorten the prop shaft to achieve the desired wheelbase.

There are other versions with plastic arms that are even cheaper.  I have no experience with these TT-0x clones.  This one appears to be mostly aluminum and cf and at the listed price point, it’s probably not the best quality (brittle materials, sloppy fit, etc).  What do you think?  Are these cheap ebay chassis’ to be avoided or can they be made to run with some work?? 

[ThunderDragonCy 7878]

@IXLR8 I don't have any experience with those carbon TT01 chassis, but if you are modifying it anyway you could make it work. The TT02 diffs fit too so you can use the latest oil filled versions. If there is a TT02 variant you could add the Type S conversion so you can use TRF style arms. You might be able to do that with the TT01 version there if you are making your own deck, because you could include the mounting points for the aluminium suspension blocks from the modern TA/TB/TRF cars.

Alternatively, the porsche bodies with 4wd traditionally come in the TA02 chassis from tamiya. Apparently the wheelbase is a bit off, but I easily designed and printed different geometry arms for my TA02 and (closely related) FF01 so I am sure you could do the same. Would be easier than trying to make a shorter prop shaft for the TT01 chassis. 

[middleagedgrup 218]

As @ThunderDragonCy says, getting hold of a TA02 SW chassis is the way to get a 4WD GT2. The wheelbase is 6mm too long for the body, but can be shortened as per the below guide: https://www.tamiyaclub.com/showroom_model.asp?cid=129718&id=9813

The Lancia 037 kit is your best starting point, as it has the correct rear arms to fit the GT2 body.

[TurboRSR 356]

1 minute ago, middleagedgrup said:

As @ThunderDragonCy says, getting hold of a TA02 SW chassis is the way to get a 4WD GT2. The wheelbase is 6mm too long for the body, but can be shortened as per the below guide: https://www.tamiyaclub.com/showroom_model.asp?cid=129718&id=9813

The Lancia 037 kit is your best starting point, as it has the correct rear arms to fit the GT2 body.

The TA02SW wheelbase (236mm) is correct for the GT2, it's only the 934 that has a smaller wheelbase (230mm). 

[middleagedgrup 218]

Sorry, you are completely correct. My mistake and I should know better really! 🫣

 

[IXLR8 1153]

@ThunderDragonCy Indeed, there is a TT-02 variant but it uses a molded tub with integrated gear cases so it would be difficult to shorten.

My knowledge of the various Tamiya models is very limited so I wasn’t aware that TT02 diffs also fit the TT01.  That’s something to consider.

You’ve mentioned the possibility to fit (plastic?) arms from other Tamiya models.  That reminds me that I’m really not fond of metal arms on a runner car for reasons we’re already familiar with.  However, there are TT01 clones available with plastic arms so I could go that route.  Apparently, parts will interchange between the genuine Tamiya and the clone so a broken arm could be replaced.

I also have other projects, either planned or currently underway, so I’m working with a very limited budget here.  I have some of the parts needed to scratch-build a belt or chain drive AWD chassis but I’d probably invest well over $100 once completed.  Honestly, that’s more than I wanted to spend for a chassis for this project.

My budget limitations also rule out a TA02 from Tamiya unless I could find a relatively inexpensive (used) set of front and rear subassemblies.  I can make the parts needed to bridge the gap using materials on hand.

It would be great to keep this build closer to the original TA02SW but I’d need to source chassis parts that don’t break the budget.  As mentioned, I have chassis plate materials on-hand as well as a set of Absima shocks.

Anyway, I can take a couple weeks to decide so I’ll keep looking for a bargain and listening to everyone's comments and suggestions.

 

[ThunderDragonCy 7878]

@IXLR8 Is there any way you can make a longer shaft and punch a hole in the side of the transmission you have on the 2wd car? If you can, could you do something like an XV01 in reverse with a belt running to another one of those transmissions at the front with belt drive and pulleys between the two? Basically do a 4wd version of the chassis you have? That would be really cool. 

[IXLR8 1153]

3 minutes ago, ThunderDragonCy said:

@IXLR8 Is there any way you can make a longer shaft and punch a hole in the side of the transmission you have on the 2wd car? If you can, could you do something like an XV01 in reverse with a belt running to another one of those transmissions at the front with belt drive and pulleys between the two? Basically do a 4wd version of the chassis you have? That would be really cool. 

Thank you .  Actually, that's precisely what I had in mind.  So yes, I can do exactly what you've outlined.  Except, maybe reverse the rear transmission so it's mid motor to add more weight over the front wheels.

Anyway, when I total the cost of the parts and add a bit of margin, I can purchase a TT01 clone for about the same money.

Not sure what to do at the moment but I really appreciate everyone's advice.   

 

[ThunderDragonCy 7878]

Doing a 4wd version of your design would be way cooler, even if it takes a little while for you to save up. 

[ThunderDragonCy 7878]

@IXLR8 Another thought. How about an mf01x with conversion to 190 width with TL01 arms and driveshafts? 

[manny 83]

3 hours ago, ThunderDragonCy said:

@IXLR8 Another thought. How about an mf01x with conversion to 190 width with TL01 arms and driveshafts? 

That makes the most sense to me since the motor is in the right place and compatible TL01 parts are still in production.

[IXLR8 1153]

4 hours ago, ThunderDragonCy said:

@IXLR8 Another thought. How about an mf01x with conversion to 190 width with TL01 arms and driveshafts? 

Okay, hmmm, I know nothing about that chassis so I'll need to price it out and see if it fits the budget.

Meanwhile, I'm taking a hard second look at the scratch build approach using my 2wd chassis as a template.

I'll definitely want to keep the trailing arms and use the same transmission but simply spinning the motor and trans around 180 degrees (making it mid-motor) causes interference with the spur gear and the upper radius rod and shock.  There's simply no way that will work without major suspension design changes so I'm thinking about keeping rear motor but moving the servo to the side so I can slide the battery forward for more front weight.

Also, I found some timing belt pulleys on ebay for cheap - less than $3 each - but they are MXL 2mm.  If I go forward with this , at some point I'll need to decide between MXL (trapezoidal, 2mm pitch) or HTD (curvilinear, 3mm pitch)?  I'm used to designing with gears not belts so this is new to me.