Group C replica Mazda 787B
Discussion
pilbeam_mp62 said:
Very impressive Rob - you are making a lot of progress - I will follow this project with interest.
One question - and I am certainly no expert - can you comment on the sharp angle between the steering rack itself and the steering arms (shown in your first CAD picture)
I would have thought that this type of geometry could cause some problems with bump steer ?
Regards
It looks as if the TCA will maintain a parallel with the top wishbone - that'll be OK won't it?One question - and I am certainly no expert - can you comment on the sharp angle between the steering rack itself and the steering arms (shown in your first CAD picture)
I would have thought that this type of geometry could cause some problems with bump steer ?
Regards
(rushes off the read stuff up)
Hi Rob,
That is a very interesting project and will be following with interest your build.
I've always liked Group C prototypes and the late 80's and early 90's designs were great looking designs.
I've always liked the Mazda RX792P and I used it a few times to sketch my idea of a road going version.
Images of the car:
http://www.ultimatecarpage.com/car/4249/Mazda-RX-7...
I browsed your blog and saw a few Cad images I would like to work on a few rough sketches, do you mind if I do so ?
Thanks
Italo
That is a very interesting project and will be following with interest your build.
I've always liked Group C prototypes and the late 80's and early 90's designs were great looking designs.
I've always liked the Mazda RX792P and I used it a few times to sketch my idea of a road going version.
Images of the car:
http://www.ultimatecarpage.com/car/4249/Mazda-RX-7...
I browsed your blog and saw a few Cad images I would like to work on a few rough sketches, do you mind if I do so ?
Thanks
Italo
Cracking project 
Although I personally would have gone for a Jag then you could have put an "authentic" v12 in it!
Just taken a look at your blog and one observation would be how easy would it be to do anything to the engine once in (even just plugs etc) it looks tight and quite hard to get too even with just the chassis there let alone the body work, this is obviously more of a consideration if you are thinking of putting it into production.
Although I personally would have gone for a Jag then you could have put an "authentic" v12 in it!
Just taken a look at your blog and one observation would be how easy would it be to do anything to the engine once in (even just plugs etc) it looks tight and quite hard to get too even with just the chassis there let alone the body work, this is obviously more of a consideration if you are thinking of putting it into production.
fuoriserie said:
I've always liked the Mazda RX792P and I used it a few times to sketch my idea of a road going version.
Images of the car:
http://www.ultimatecarpage.com/car/4249/Mazda-RX-7...
Couldn't see anything on the link apart from a dieting advert, but would be more interested to see your sketches of the road version anywayImages of the car:
http://www.ultimatecarpage.com/car/4249/Mazda-RX-7...
Edited by singlecoil on Saturday 2nd January 10:57
singlecoil said:
fuoriserie said:
I've always liked the Mazda RX792P and I used it a few times to sketch my idea of a road going version.
Images of the car:
http://www.ultimatecarpage.com/car/4249/Mazda-RX-7...
Couldn't see anything on the link apart from a dieting advert, but would be more interested to see your sketches of the road version anywayImages of the car:
http://www.ultimatecarpage.com/car/4249/Mazda-RX-7...
Edited by singlecoil on Saturday 2nd January 10:57
Hello all, long-time reader, first time poster.
You may also want to look at the RCR SL-C for ideas as that is probably the most current Group C inspired street legal platform out there. It is unproven as of yet but on paper and "first-reports" of on track performance indicate it should come very close, if not match the Ultima. I know that is a bad car to bring up on this forum, particularly on this board, but I'm using it as my platform for my own version of the Mazda 787b. It will even be rotary powered with a single turbo 20b making ~800hp without breaking a sweat. In my opinion, they'd have to be rotary powered but assembling a 4 rotor isn't cheap either or for that matter, neither is a single turbo three rotor.
The 792 is a beautiful car and I've seen that in person many times as well as the 787b a few times. The sound from these cars is unforgettable.
You may also want to look at the RCR SL-C for ideas as that is probably the most current Group C inspired street legal platform out there. It is unproven as of yet but on paper and "first-reports" of on track performance indicate it should come very close, if not match the Ultima. I know that is a bad car to bring up on this forum, particularly on this board, but I'm using it as my platform for my own version of the Mazda 787b. It will even be rotary powered with a single turbo 20b making ~800hp without breaking a sweat. In my opinion, they'd have to be rotary powered but assembling a 4 rotor isn't cheap either or for that matter, neither is a single turbo three rotor.
The 792 is a beautiful car and I've seen that in person many times as well as the 787b a few times. The sound from these cars is unforgettable.
I started quite a lengthy thread on Locostbuilders about doing my own Group C car...
It is a big dream for me, but we bought a flat in town (instead of a house with a garage) and we are working too hard for me to get the time to dedicate to the project, I am sorry to say...
So, if you are looking to sell a car that looked like the Mazda, I would be very interested indeed!
It is a big dream for me, but we bought a flat in town (instead of a house with a garage) and we are working too hard for me to get the time to dedicate to the project, I am sorry to say...
So, if you are looking to sell a car that looked like the Mazda, I would be very interested indeed!
singlecoil said:
Sam_68 said:
Paul Drawmer said:
Minimum headlamp height for IVA will be a challenge.
...but it's quite easy to cheat on that particular test, unless they've tightened up the rules on blatant piss-taking recently. 
Edited by singlecoil on Thursday 31st December 10:09
Hi Everyone,
Sorry for the delay in replying. I have had a very busy beginning to the year. Had to swap my Merc Cosworth for something a little more practical/economical amongst other things. Never seemed to get any better than 25mpg no matter how i drove it! Now driving a Pug 306 TD. Not especially quick but handles nicely.
Ive just been going over some of the posts on this thread..
Pilbeam mp62 - As Paul correctly stated, althought the steering arms in my design to run at an angle, they are the same length as and do run paralell to the upper control arms meaning there will be no bump steer. The basic theory behind setting up a geometry for zero bump steer is that the upper and lower control arms and the steering link all converge and intersect about a common instant centre. I am using this design so that i can adjust static geometry such as camber by adding or removing shims from behind the common mount for the top link and steering link without affecting bump steer at all.
Fuoriserie - Im not sure what exactly you are asking. Im more than happy for you to make some sketches. Im sure everyone would be interested to see your work but do you just want to work from the pictures on my blog or do you need me to send you some more useful ones? Let me know and i'll see what i can do.
n3il123 - Yes the structure over the engine is in places very close to the engine. That section of the spaceframe is however quick and easy to remove for installation, removal and if necessary working on the engine and ancilliaries. Even with this piece removed the spaceframe is more than adequate in terms of torsional and beaming stiffness. I did even contemplate not having it at all but in the end decided the 50% increase in overall stiffness was worth the extra 20-25kg. As i mentioned before, i intend ultimately to install a mazda rotary engine in place of the audi v8 as it seems far more apprpriate seeing as it is a mazda afterall and then space should be far less of an issue.
Browser07 - Yes i think making a more universal underpinnings to the car so that different bodies could be fitted would be a very good idea. Overall height and width are very similar between models although wheelbase i found from my research seems to be very varied. For example, the mazda 787 measures 2640mm and at the other end of the scale we have the Aston AMR1 at 2896mm. There is also the added issue of placement of cooling rads and fans which are sometimes up in the nose of the vehicle or in the side pods or even in the rear engine compartment - see Aston AMR1 again! I think i remember reading somewhere that some of the Porsch 917s had adjustable wheelbases. Any ideas anyone?
Dom9 - thankyou for your interest in my project. I will obviously get in contact when the time comes!
Anyways, back to the project as it stands...
I've been working on designs for the front uprights for the last couple weeks. As for wheel bearings, im going the same route as are F1 teams, BTCC and WRC (i think) where the wheel loads are taken through two large, low profile bearings found in the upright itself. The bearings are spaced apart as wide as is sensibly possible to reduce loadings that result from cornering. In my design, the hub is then a large hollowed-out part that sits inside these bearings, wheel mount flange one end and a split nut and thread to secure it at the other. Once again i have tried not to commit to a specific brake package but at this stage i am working around using the Wilwood W6A caliper and a matching disc that just fits within my 17" wheels. Im happy with my current design but am just doing some calcs and running some final FEA Simulations to check ive not taken too much meat out of the structure in my efforts to keep things lightweight! I should have some more images posted during this week and then i'll be starting manufacture.
Interstingly, if anyone else has had to replace wheel bearings on a more modern car they'll notive how small a unit the sealed pair of bearings is (eg skoda octavia, pug 206...). To me it is no surpise that they can fail, especially when driven hard or the tyres are replaced to improve grip.
Sorry for the delay in replying. I have had a very busy beginning to the year. Had to swap my Merc Cosworth for something a little more practical/economical amongst other things. Never seemed to get any better than 25mpg no matter how i drove it! Now driving a Pug 306 TD. Not especially quick but handles nicely.
Ive just been going over some of the posts on this thread..
Pilbeam mp62 - As Paul correctly stated, althought the steering arms in my design to run at an angle, they are the same length as and do run paralell to the upper control arms meaning there will be no bump steer. The basic theory behind setting up a geometry for zero bump steer is that the upper and lower control arms and the steering link all converge and intersect about a common instant centre. I am using this design so that i can adjust static geometry such as camber by adding or removing shims from behind the common mount for the top link and steering link without affecting bump steer at all.
Fuoriserie - Im not sure what exactly you are asking. Im more than happy for you to make some sketches. Im sure everyone would be interested to see your work but do you just want to work from the pictures on my blog or do you need me to send you some more useful ones? Let me know and i'll see what i can do.
n3il123 - Yes the structure over the engine is in places very close to the engine. That section of the spaceframe is however quick and easy to remove for installation, removal and if necessary working on the engine and ancilliaries. Even with this piece removed the spaceframe is more than adequate in terms of torsional and beaming stiffness. I did even contemplate not having it at all but in the end decided the 50% increase in overall stiffness was worth the extra 20-25kg. As i mentioned before, i intend ultimately to install a mazda rotary engine in place of the audi v8 as it seems far more apprpriate seeing as it is a mazda afterall and then space should be far less of an issue.
Browser07 - Yes i think making a more universal underpinnings to the car so that different bodies could be fitted would be a very good idea. Overall height and width are very similar between models although wheelbase i found from my research seems to be very varied. For example, the mazda 787 measures 2640mm and at the other end of the scale we have the Aston AMR1 at 2896mm. There is also the added issue of placement of cooling rads and fans which are sometimes up in the nose of the vehicle or in the side pods or even in the rear engine compartment - see Aston AMR1 again! I think i remember reading somewhere that some of the Porsch 917s had adjustable wheelbases. Any ideas anyone?
Dom9 - thankyou for your interest in my project. I will obviously get in contact when the time comes!
Anyways, back to the project as it stands...
I've been working on designs for the front uprights for the last couple weeks. As for wheel bearings, im going the same route as are F1 teams, BTCC and WRC (i think) where the wheel loads are taken through two large, low profile bearings found in the upright itself. The bearings are spaced apart as wide as is sensibly possible to reduce loadings that result from cornering. In my design, the hub is then a large hollowed-out part that sits inside these bearings, wheel mount flange one end and a split nut and thread to secure it at the other. Once again i have tried not to commit to a specific brake package but at this stage i am working around using the Wilwood W6A caliper and a matching disc that just fits within my 17" wheels. Im happy with my current design but am just doing some calcs and running some final FEA Simulations to check ive not taken too much meat out of the structure in my efforts to keep things lightweight! I should have some more images posted during this week and then i'll be starting manufacture.
Interstingly, if anyone else has had to replace wheel bearings on a more modern car they'll notive how small a unit the sealed pair of bearings is (eg skoda octavia, pug 206...). To me it is no surpise that they can fail, especially when driven hard or the tyres are replaced to improve grip.
RobBiggs said:
H
Fuoriserie - Im not sure what exactly you are asking. Im more than happy for you to make some sketches. Im sure everyone would be interested to see your work but do you just want to work from the pictures on my blog or do you need me to send you some more useful ones? Let me know and i'll see what i can do.
.
Hi Rob, yes I would like to work with more renderings and use your CAD images just like the ones you have in your blog.Fuoriserie - Im not sure what exactly you are asking. Im more than happy for you to make some sketches. Im sure everyone would be interested to see your work but do you just want to work from the pictures on my blog or do you need me to send you some more useful ones? Let me know and i'll see what i can do.
.
You have a PM
Thanks
Italo
Edited by fuoriserie on Tuesday 19th January 08:52
RobBiggs,
From the CAD drawings you did it looks like you designed the chassis to fit a SBC? Is that still the case? Just thinking its a cheap, plentyfull and can be made very powerfull power plant.
Also what did you make the sapceframe out of? and how much dose it weigh?
Cheers
Chris.
From the CAD drawings you did it looks like you designed the chassis to fit a SBC? Is that still the case? Just thinking its a cheap, plentyfull and can be made very powerfull power plant.
Also what did you make the sapceframe out of? and how much dose it weigh?
Cheers
Chris.
AtomicRex said:
.... I have access to body moulds of a 962 which I was looking to modify...
Planning to produce any bodies Rex?What I really want is the body and then have a bespoke chassis designed for it for a particular engine I have in mind! However, if this project goes commercial then I have definite interest!
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