Working out a BEC project, several questions so far.
Discussion
Hi there
I joined here via Google, searching about info on chassis setups, and various choices of Bike engines put into cars or kitcars.
I'll go straight to the point :
My Plan is to convert a Reliant Robin type car to Bike power.
Let's be clear, I'm not interested in biased views based on Clarkson and the Stigs inability to drive them in the Top Gear feature they did, and to the fact that they have bad handling characteristics.
That, is a given fact, in standard form, and, to be honest, give me a car with 4 wheels, and I'll easily be able to roll it if I drive it like a monkey.
I've owned all sorts of weird and powerful cars, but these are quite special, and not so ridiculous in stock shape actually, they are perfectly capable of keeping up with modern traffic today.
This was my last Reliant based 3 wheeler : A Bond Bug fitted with a 1000 cc R1 engine (4XV)
This was not built by me, but by a very talented guy, the car was truly a piece of art, quality was flawless.
Specs :
1974 Bond Bug
Weight : 395 kg
Engine : 1000 cc R1 4XV, around 150 HP give or take
Diff : 2,78:1 (Reliants own long eco ratio)
The Bond Bug chassis (pictured below), unlike the Reliant Robin/Rialto etc, has a very good rear suspension setup, no leaf springs and measly shock absorbers, it came standard with a 4 link rear axle and coilovers. Bags more cornering than a Reliant. No, really, I'm serious, haha. This car had Spax adjustables that were tuned in really nicely.
A few minutes of film of the car in action :
https://www.youtube.com/watch?v=ihFhSrS66Cg
Top speed around 130 mph, the original R1 Speedo was equipped with a Speedo healer that was calibrated with a GPS, so that what pretty accurate... :^D
Having sold that, and, majorly regretting it, I've decided to have a decent go at building my own.
But, wish to improve on the original concept I owned before.
Flaws of the Bond Bug that need addressing :
- the diff/Axle assembly :
The R1 is said to have 150 HP @ 10500 rpm or so, and 72.7 lb·ft @ 8250 rpm. that's what Yamaha claims, and thats not WHP, I seriously must have lost a few over the prop, diff and extra wheel to move...
But the main problem is, that to make use of the 150 whatever HP, (4 times original engine output, and at much higher revs) I'd be seriously abusing the diff, squeezing the revs out of it to hit the powerband.
It clearly was the fuse of the car, and hence I never really used that much of the HP available...
- Engine :
It was too revvy, output and torque are placed too high for it to be that comfortable to drive. It surely was bags of fun, but a better engine choice can be made. Main reason why he chose the R1, is because it is so compact, that he hardly had to mod the body to get it to fit, even the OE engine cover was useable...
- Suspension :
Frankly it was good, and as good as it could get on the OE setup. Not comfortable, very hard, wide cornering above 65 mph was totally doable, but there has to be room for improvement.
Here are the project ideas so far :
- Diff/Axle assembly/chassis :
In the 80s, an american company based in California went on a venture to produce a Reliant Rialto with hybrid or electric engines. They fitted an extra wide rear axle for improved cornering :
Now, a rear end this wide is ridiculous, but it is without a doubt a manner of improving cornering.
The problem with a RWD 3 wheeler like a Reliant, is that when in spirited driving, the rear end wants to kick out in corners, so the car will want to slide... add the factor that there is no front wheel to lean on, and obviously the car lifts the opposite rear wheel...
Add to the equation that it is a live narrow rear axle, and the ride height is quite massively high, and that's not going to help.
My first idea of improvement is to lower the ride height. that's "easy" enough.
Second idea, (related to the diff choice, also) is to adapt a rear subframe from an early BMW 2002, just like this :
This has about a 4 inches wider track than the Reliant, which can be aided by rim offset also if wider needs be, but I'm thinking, based on my experience with the 4 link "sports" setup of the car I had, that I might not need that much wider track ? Adding this IRS setup to the mix must surely help also, rather than the stiff tube axle that doesn't allow flexibility ?
Any ideas on that, theoretically (not 3 wheeler based experience, of course) ?
Using an older BMW rear subframe, allows me to adapt a BMW diff, another big point of the rear end issues. Reliants 2,78:1 diff ratio was superbly long and plug and play, but too weak to make the most of the engine.
the 325 TDS E36 was supplied with a 2,56 diff, that will reduce revs at a same given speed, and improve top end if needed... I haven't found anything longer than that, and based on my experience with the Bond Bug (7000 rpm @ 80 MPH...) I sure could do with a bit of a quieter running machine...
And a BMW diff can no doubt handle 200hp and 13 kgm of torque all day, no ?
- Engine :
Torque, I want torque, obviously... But how much ? 1000cc Sportsbikes have improved in both HP and torque over the years, but it's always at High rpms, mainly...
FWIW, the car will hopefully weigh in UNDER 400kg.
Original engine :
Max Power
40 hp @ 5500 rpm
Max Torque
6,3 kg-m @ 3500 rpm
2 options have sprung to mind :
First Option (sane) :
955i Triumph triple :
Max Power
120 hp @ 9100 rpm
Max Torque
10.2 kg-m @ 5100 rpm
Thats 3 times the power, at only 3500 rpm higher, and 50% more torque only 1500 rpm higher.
I'm thinking that would be Lots of fun, very useable due to low RPM outputs, but I'm also wondering if it's not too little of a result for such work ?
Second option (less sane) :
ZZR 1400 :
Max Power
187 hp @ 9500 rpm
Max Torque
13.87 kg-m @ 7500 rpm
That's 5 times the OE power, at around the same RPM as the Triumph, and more than twice the torque at twice the RPM than the OE engine... That is going towards the revvy 1000s that I don't really want, but the supply is awesome. My concerns are getting that power down to the road...
Any info on dimensions of these engines ? And reliable OE Dyno charts ?
This car, if set up properly, would be quite excellent in corners if :
a - it has the chassis to "slide" without grabbing (and therefore rolling) in corners (lower ride, IRS, wider track, "bad" quality not too wide tyres)
b - it has the BHP at the right RPM to drift it in and out of said corners.
and any time lost in corners compared to a 4 wheeler would be caught up in the straights anyway :^)
Finally, this will be a road car/occasional track day car. And a proper build, too, not a Chavmobile built to crappy standards, and usually not finished before being ebayed.
I've almost written a book, congrats to those who've trawled through all my ranting crap.
Any serious advice on my chassis setup ideas more than welcome.
I joined here via Google, searching about info on chassis setups, and various choices of Bike engines put into cars or kitcars.
I'll go straight to the point :
My Plan is to convert a Reliant Robin type car to Bike power.
Let's be clear, I'm not interested in biased views based on Clarkson and the Stigs inability to drive them in the Top Gear feature they did, and to the fact that they have bad handling characteristics.
That, is a given fact, in standard form, and, to be honest, give me a car with 4 wheels, and I'll easily be able to roll it if I drive it like a monkey.
I've owned all sorts of weird and powerful cars, but these are quite special, and not so ridiculous in stock shape actually, they are perfectly capable of keeping up with modern traffic today.
This was my last Reliant based 3 wheeler : A Bond Bug fitted with a 1000 cc R1 engine (4XV)
This was not built by me, but by a very talented guy, the car was truly a piece of art, quality was flawless.
Specs :
1974 Bond Bug
Weight : 395 kg
Engine : 1000 cc R1 4XV, around 150 HP give or take
Diff : 2,78:1 (Reliants own long eco ratio)
The Bond Bug chassis (pictured below), unlike the Reliant Robin/Rialto etc, has a very good rear suspension setup, no leaf springs and measly shock absorbers, it came standard with a 4 link rear axle and coilovers. Bags more cornering than a Reliant. No, really, I'm serious, haha. This car had Spax adjustables that were tuned in really nicely.
A few minutes of film of the car in action :
https://www.youtube.com/watch?v=ihFhSrS66Cg
Top speed around 130 mph, the original R1 Speedo was equipped with a Speedo healer that was calibrated with a GPS, so that what pretty accurate... :^D
Having sold that, and, majorly regretting it, I've decided to have a decent go at building my own.
But, wish to improve on the original concept I owned before.
Flaws of the Bond Bug that need addressing :
- the diff/Axle assembly :
The R1 is said to have 150 HP @ 10500 rpm or so, and 72.7 lb·ft @ 8250 rpm. that's what Yamaha claims, and thats not WHP, I seriously must have lost a few over the prop, diff and extra wheel to move...
But the main problem is, that to make use of the 150 whatever HP, (4 times original engine output, and at much higher revs) I'd be seriously abusing the diff, squeezing the revs out of it to hit the powerband.
It clearly was the fuse of the car, and hence I never really used that much of the HP available...
- Engine :
It was too revvy, output and torque are placed too high for it to be that comfortable to drive. It surely was bags of fun, but a better engine choice can be made. Main reason why he chose the R1, is because it is so compact, that he hardly had to mod the body to get it to fit, even the OE engine cover was useable...
- Suspension :
Frankly it was good, and as good as it could get on the OE setup. Not comfortable, very hard, wide cornering above 65 mph was totally doable, but there has to be room for improvement.
Here are the project ideas so far :
- Diff/Axle assembly/chassis :
In the 80s, an american company based in California went on a venture to produce a Reliant Rialto with hybrid or electric engines. They fitted an extra wide rear axle for improved cornering :
Now, a rear end this wide is ridiculous, but it is without a doubt a manner of improving cornering.
The problem with a RWD 3 wheeler like a Reliant, is that when in spirited driving, the rear end wants to kick out in corners, so the car will want to slide... add the factor that there is no front wheel to lean on, and obviously the car lifts the opposite rear wheel...
Add to the equation that it is a live narrow rear axle, and the ride height is quite massively high, and that's not going to help.
My first idea of improvement is to lower the ride height. that's "easy" enough.
Second idea, (related to the diff choice, also) is to adapt a rear subframe from an early BMW 2002, just like this :
This has about a 4 inches wider track than the Reliant, which can be aided by rim offset also if wider needs be, but I'm thinking, based on my experience with the 4 link "sports" setup of the car I had, that I might not need that much wider track ? Adding this IRS setup to the mix must surely help also, rather than the stiff tube axle that doesn't allow flexibility ?
Any ideas on that, theoretically (not 3 wheeler based experience, of course) ?
Using an older BMW rear subframe, allows me to adapt a BMW diff, another big point of the rear end issues. Reliants 2,78:1 diff ratio was superbly long and plug and play, but too weak to make the most of the engine.
the 325 TDS E36 was supplied with a 2,56 diff, that will reduce revs at a same given speed, and improve top end if needed... I haven't found anything longer than that, and based on my experience with the Bond Bug (7000 rpm @ 80 MPH...) I sure could do with a bit of a quieter running machine...
And a BMW diff can no doubt handle 200hp and 13 kgm of torque all day, no ?
- Engine :
Torque, I want torque, obviously... But how much ? 1000cc Sportsbikes have improved in both HP and torque over the years, but it's always at High rpms, mainly...
FWIW, the car will hopefully weigh in UNDER 400kg.
Original engine :
Max Power
40 hp @ 5500 rpm
Max Torque
6,3 kg-m @ 3500 rpm
2 options have sprung to mind :
First Option (sane) :
955i Triumph triple :
Max Power
120 hp @ 9100 rpm
Max Torque
10.2 kg-m @ 5100 rpm
Thats 3 times the power, at only 3500 rpm higher, and 50% more torque only 1500 rpm higher.
I'm thinking that would be Lots of fun, very useable due to low RPM outputs, but I'm also wondering if it's not too little of a result for such work ?
Second option (less sane) :
ZZR 1400 :
Max Power
187 hp @ 9500 rpm
Max Torque
13.87 kg-m @ 7500 rpm
That's 5 times the OE power, at around the same RPM as the Triumph, and more than twice the torque at twice the RPM than the OE engine... That is going towards the revvy 1000s that I don't really want, but the supply is awesome. My concerns are getting that power down to the road...
Any info on dimensions of these engines ? And reliable OE Dyno charts ?
This car, if set up properly, would be quite excellent in corners if :
a - it has the chassis to "slide" without grabbing (and therefore rolling) in corners (lower ride, IRS, wider track, "bad" quality not too wide tyres)
b - it has the BHP at the right RPM to drift it in and out of said corners.
and any time lost in corners compared to a 4 wheeler would be caught up in the straights anyway :^)
Finally, this will be a road car/occasional track day car. And a proper build, too, not a Chavmobile built to crappy standards, and usually not finished before being ebayed.
I've almost written a book, congrats to those who've trawled through all my ranting crap.
Any serious advice on my chassis setup ideas more than welcome.
Edited by Reliant on Wednesday 5th April 18:04
Really quite different in many ways, but identical in some others, I converted our old Marcos Mantula from live axle to IRS. It made a huge improvement to the ride quality of the thing for quite a few reasons but one for sure was the big reduction in un-sprung weight. That will make a big difference to your project I think and all the other benefits aside, worth doing just for that aspect I reckon. A live axle is fine on smooth roads, but where do you find those other than a circuit?
Interesting project, keep us posted.
Interesting project, keep us posted.
Indeed, it's a bit of just because i can.
But honestly they're fun cars in stock form, and with a bike engine even more so. Not to mention the look on peoples faces. I actually outran a mk5 golf gti on a moderately curvy road in my r1 bug, and judging by the view in the mirror the guy was clearly trying :^D
Reliant Kitten 4 wheeler would indeed have been a better start (double wishbone coilover front axle as standard equipment), but i prefer the tripods and like the challenge of making the illogical a bit more logical
But honestly they're fun cars in stock form, and with a bike engine even more so. Not to mention the look on peoples faces. I actually outran a mk5 golf gti on a moderately curvy road in my r1 bug, and judging by the view in the mirror the guy was clearly trying :^D
Reliant Kitten 4 wheeler would indeed have been a better start (double wishbone coilover front axle as standard equipment), but i prefer the tripods and like the challenge of making the illogical a bit more logical
Edited by Reliant on Wednesday 22 April 22:54
Thanks for your input Chris. I do believe it will change the driving experience substantially, although in the case of the Reliant it will add a bit of weight overall.
More research is being done before anything gets started yet but i'm on the right track i think.
After all, Nissan did very well at the 24hrs with theirs, so I'm sure I'll be OK with my minor attempt
More research is being done before anything gets started yet but i'm on the right track i think.
After all, Nissan did very well at the 24hrs with theirs, so I'm sure I'll be OK with my minor attempt
Edited by Reliant on Wednesday 22 April 22:55
fantastic project :-)
How about a fully bespoke rear suspension set up?
If budget is not a major concern you could have something designed specifically for the job.
have a look here:- http://www.walker-partnership.com/ (most of the images show only the set up on the front end, but it is also available for the rear).
On a side note..... You do not need to use the word "rear" when referring to your diff as your car is not All Wheel Drive. It's just "The Diff"........ Sorry, a pet hate of mine ;-)
How about a fully bespoke rear suspension set up?
If budget is not a major concern you could have something designed specifically for the job.
have a look here:- http://www.walker-partnership.com/ (most of the images show only the set up on the front end, but it is also available for the rear).
On a side note..... You do not need to use the word "rear" when referring to your diff as your car is not All Wheel Drive. It's just "The Diff"........ Sorry, a pet hate of mine ;-)
Reliant said:
Thanks for your input Chris. I do believe it will change the driving experience substantially, although in the case of the Reliant it will add a bit of weight overall.
More research is being done before anything gets started yet but i'm on the right track i think.
After all, Nissan did very well at the 24hrs with theirs, so I'm sure I'll be OK with my minor attempt
For sure it'll be heavier than the OEM setup, but hopefully not too bad. I think shifting the balance a bit further back wouldn't be all bad either. It'll help it to feel (and actually be) better planted at the back, less of that feeling that the tail is wagging the dog.More research is being done before anything gets started yet but i'm on the right track i think.
After all, Nissan did very well at the 24hrs with theirs, so I'm sure I'll be OK with my minor attempt
Edited by Reliant on Wednesday 22 April 22:55
rhinochopig said:
@ Dave Brookes :
I'm not planning on skimping on the job, but I'd rather not go too overboard on the final budget. Of course, the car finished and done will probably still be cheaper than just a set of cams for a Testarossa engine
, but I reckon the home grafted IRS will be good enough for the project (and yes indeed, the rear diff... haha)@ Chris :
Indeed more weight on the back should also mean some gain in traction if I'm not mistaken ?
There's a good video on youtube about the Nissan Deltawing, Chris Harris has a chat with the guy who designed the thing, he explains chassis theory, of course hardly any is relevant but some of it sounds OK as far as this 3 wheeler is concerned.
There's a guy who built a 350HP hayabusa engined Bond Bug, Z-Cars took care of the chassis, lowered height, with IRS and a Sierra diff. Never seen it perform on the road, but the builder who I met said it was nicely setup for cornering. As for performance : 0-60 in 3 sec, top speed 120 or so, 1/4m in 10,4, and 0-120 in 8 sec
You need to read and understand this if you want to design a trike that handles:
http://www.rqriley.com/3-wheel.htm
Hope it helps.
http://www.rqriley.com/3-wheel.htm
Hope it helps.
My plan was to adapt the e36 diff to fit the 02 rear subframe ? I need the rear arms setup, then i jyst need to support the e36 diff and work out drive shafts
I do need the highest diff ratio possible in order to keep revs down in a comfortable region. Hence the 2,56:1 TDS diff
No idea what is available on mx5, i'll go look into that, but i'm guessing it's a bulky/heavy unit ? I do need to keep weight down
Thanks
I do need the highest diff ratio possible in order to keep revs down in a comfortable region. Hence the 2,56:1 TDS diff
No idea what is available on mx5, i'll go look into that, but i'm guessing it's a bulky/heavy unit ? I do need to keep weight down
Thanks
Edited by Reliant on Thursday 4th June 14:44
Hey
I'm digging this up, the project is slowly evolving.
Turns out I wasn't able to find a good Mk1 Reliant Robin saloon before I managed to cross paths with an unfinished resto project of a Bond Bug.
So, seeing that it is sold without a motor, I'm happy to announce that it's going to be the racier sportier looking Bug being converted to bike power.
I've been looking at diffs available, i was thinking of using the BMW 2,56:1 easily available.
Trawling through ebay listings on german ebay, in the hope of finding dimension infos, i actually found out that more recent diesel beemers were supplied with :
- 2,47
And even
- 2,35
Damn thats tall !
So, i was wondering what BEC that are diff driven usually use in terms of diff gearing ?
Seeing that bikes have a gearbox output usually around 1,5 (I read somewhere that the ZZR1400, which i'll probably be using is 1,556:1)
That means a real final drive of 3,65:1 if i'm not mistaken, once bolted to the tallest BMW diff ?
Thanks for your insight
I'm digging this up, the project is slowly evolving.
Turns out I wasn't able to find a good Mk1 Reliant Robin saloon before I managed to cross paths with an unfinished resto project of a Bond Bug.
So, seeing that it is sold without a motor, I'm happy to announce that it's going to be the racier sportier looking Bug being converted to bike power.
I've been looking at diffs available, i was thinking of using the BMW 2,56:1 easily available.
Trawling through ebay listings on german ebay, in the hope of finding dimension infos, i actually found out that more recent diesel beemers were supplied with :
- 2,47
And even
- 2,35
Damn thats tall !
So, i was wondering what BEC that are diff driven usually use in terms of diff gearing ?
Seeing that bikes have a gearbox output usually around 1,5 (I read somewhere that the ZZR1400, which i'll probably be using is 1,556:1)
That means a real final drive of 3,65:1 if i'm not mistaken, once bolted to the tallest BMW diff ?
Thanks for your insight
Edited by Reliant on Friday 5th February 20:12
MK1 MX5 is out, they are around 4-1, Some use a Freelander and others BMW. With around 3.5-1 you should be in the right ball park depending on wheel/tyres. Assuming you are going direct with a prop and a sprocket/prop-shaft adapter. Best to go easy on the clutch when choosing ratio's and sacrifice the top end speed.
Edited by Stuart Mills on Friday 5th February 18:48
We use the ZZR1400 in the Furore, all up weight of around 565kg (plus driver & passenger), running 245/45/17 tyres, we run 3.28:1, this gives 70mph at 4750rpm or thereabouts, which is pretty relaxed for a bike engine. The ZZR1400 really is a fantastic engine, it will pootle round at 25mph in 6th gear without complaint, but drop it a few gears & boot it & it's a bit like hitting the hyperspace button!The car will happily pull away in 2nd, & I have yet to trash a clutch - one of my customers did, but he did admit he'd been doing donuts with it!
If you are running similar weight & tyre size then anything around 3.1 - 3.4 should be fine, if your tyre diameter is smaller (which I suspect it will be) then you'll probably want to go a bit lower, it's worth sacrificing a fraction of acceleration for a more relaxed cruise in my opinion
If you are running similar weight & tyre size then anything around 3.1 - 3.4 should be fine, if your tyre diameter is smaller (which I suspect it will be) then you'll probably want to go a bit lower, it's worth sacrificing a fraction of acceleration for a more relaxed cruise in my opinion
Ok.
is my theory correct as far as multiplying the bike gearbox output ratio by the diff ratio to get the final ratio ?
I had a 2,78 on my first bond bug, so times the 1,5 approx ratio of the bug, that meant 4,17:1 ?
It was fitted with 175/65/13, not really possible to put bigger on it.
I seem to remember it was hitting 7000 rpm at 80 mph.....
I agree that i won't be driving at 120 mph all the time, and a bit of a smoother ride would be good. 200hp and so much torque is heaps more than enough to pull the thing.
Weight will probably be around 400-420 kilos, what with extra bracing and heavier rear axle/end
is my theory correct as far as multiplying the bike gearbox output ratio by the diff ratio to get the final ratio ?
I had a 2,78 on my first bond bug, so times the 1,5 approx ratio of the bug, that meant 4,17:1 ?
It was fitted with 175/65/13, not really possible to put bigger on it.
I seem to remember it was hitting 7000 rpm at 80 mph.....
I agree that i won't be driving at 120 mph all the time, and a bit of a smoother ride would be good. 200hp and so much torque is heaps more than enough to pull the thing.
Weight will probably be around 400-420 kilos, what with extra bracing and heavier rear axle/end
Edited by Reliant on Friday 5th February 21:05
Most BECs (7's, Fury's, etc) are running Sierra diffs. Anything from 3.12:1 (works well with BUSA's) to 3.65 is some of the older lower powered motors. Injection R1's go well with the Freelander diff which is 3.21:1. Thats what I have in my Fury and with 205/60/13 tyres it hits 70+ in first and tops out just shy of 150... probably a bit long in your Bug. Probably better with the Sierra 3.35 or 3.65.
Russ-l1hze said:
We use the ZZR1400 in the Furore, all up weight of around 565kg (plus driver & passenger), running 245/45/17 tyres, we run 3.28:1, this gives 70mph at 4750rpm or thereabouts, which is pretty relaxed for a bike engine.
If you are running similar weight & tyre size then anything around 3.1 - 3.4 should be fine, if your tyre diameter is smaller (which I suspect it will be) then you'll probably want to go a bit lower, it's worth sacrificing a fraction of acceleration for a more relaxed cruise in my opinion
In theory your tyres are 10cm taller in diameter than those i had on my R1 Bug.If you are running similar weight & tyre size then anything around 3.1 - 3.4 should be fine, if your tyre diameter is smaller (which I suspect it will be) then you'll probably want to go a bit lower, it's worth sacrificing a fraction of acceleration for a more relaxed cruise in my opinion
Motorway speed in France is 80mph, as i said, with the 2,78 rear end, the R1 was doing 7000 rpm pulling a 400 kilo car...
I guess that is due to :
- less HP
- less torque (much less)
To pull the extra weight and work against the extra drag, to achieve a similar speed.
If i understand correctly, the superior engine characteristics of the ZZR means that a shorter diff ratio could be used ?
This car will be built for the road, and occasional track day, i would really appreciate the kind of speed/rpm ratio you have on your car, it was earbleeding hell crusing on the motorway with my R1...
Edited by Reliant on Saturday 6th February 09:17
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