JoelP
|
| posted on 16/8/04 at 08:33 PM |
|
|
middy dimensions dilema
hi all. Im doing a few sketches of a middy project i have lined up. Base on a sierra track of 54 inches, i work out from the 1.6 rule that the car
wants to be around 86 inches wheelbase. Unfortunately, my sketches come out at 114 inches long, about 2 and a half feet over. this allows 12 inches
for the front bones, 72 for the cockpit, 30 inches for the longtitudinal bike engine and another 12 for the back wishbones. The cockpit is this long
due to the reclined driving position, as a result the car is only 30 inches tall, from floor to rollbar/roof (it has a full roof built in).
so, as i need to reduce the length a bit, am i best off shortening the cockpit area, or just moving the front wishbone back so that the pedals are
infront of the springs? the cockpit might go down to 60 inches, infact ive just measured it on the floor and i think i would manage, with tidy
pedals.
so that takes me to 102 inches, from the centers of teh wheels. Still 18 inches over the target, or if left, a length-width ratio of 1.9.
any thoughts anyone?
ps the bike engine has to be longtitudinal cos there will be two, side by side. chain driven to the diff.
|
|
|
|
|
kb58
|
| posted on 16/8/04 at 08:47 PM |
|
|
It's a bad idea having your feet ahead of the front axle line. In a frontal collision you won't be walking away from it... This is bad
on the track, and worse on the street. If this is for the street, I'd say 30" is bad since you'll be virtually invisible in
people's mirrors and you'll be "squeezed out" often. 40" minimum would be good. OTOH if it's for the track then
yes, the lower the better.
|
|
|
Cita
|
| posted on 16/8/04 at 08:51 PM |
|
|
You can move the front wheels as far back as where your knee's are if you're not running into width problems though.
You can also pinch something from the engine bay 'cause 30 inch seems more than enough.
All in my very humble opinion though.
|
|
|
JoelP
|
| posted on 16/8/04 at 08:55 PM |
|
|
thanks for the comments so far guys.
kb. it will be a mix of track and road, probably more road though cos its free! you comments about feet make sense, thanks.
cita. im off to measure the zx9 lump now. I need to leave a little extra room for the gubbins required to make the engines work together. Might flip
one around, so the exhausts are both on the outside, one engine chained and one cogged to reverse the spin.
more comments welcome.
[Edited on 16/8/04 by JoelP]
|
|
|
Cita
|
| posted on 16/8/04 at 09:23 PM |
|
|
Just an idea:why not place the engine's in tandem on top of each other?
It may seem stupid at first but it will save a lot of fiddling around with the power supply to the diff or axle.
The bottom engine can be placed real low in the frame so the CG will be not that bad.
|
|
|
alister667
|
| posted on 16/8/04 at 09:26 PM |
|
|
I read a book about the original 750MC racers. For some of their middy layouts they have the engine basically where the passenger sits, but if you
require it to be a 2 seater you can forget that!
All the best
http://members.lycos.co.uk/alister667/
|
|
|
kb58
|
| posted on 16/8/04 at 09:27 PM |
|
|
About the 30" for the engine and 12" for the back wishbones, can't those overlap some?
Since it's for the street I'd really consider "scrunching it up" some and making it taller, 45" or so. Getting taken
out by an SUV is no fun, they have a hard enough time seeing out as it is...
|
|
|
niceperson709
|
| posted on 16/8/04 at 09:28 PM |
|
|
TextOrangecolor=White]TextWhite[/color]
best wishes
Iain
|
|
|
Cita
|
| posted on 16/8/04 at 09:30 PM |
|
|
KB are you talking about length or height?
|
|
|
Cita
|
| posted on 16/8/04 at 09:31 PM |
|
|
Thank you very much Ian
|
|
|
niceperson709
|
| posted on 16/8/04 at 09:41 PM |
|
|
TextTextOrange
I am just wondering how you are going to syncronise two engines and seperate gearboxes ? And have you considered the transmission losses in your
proposed set up? seems like a wrong headed aproach to me that looses lots of the virtues of a bike engine in a car . or is it a desire to have a
bigger lot of whirring bits than any one else on the road? Any way if you stick to one engine there is always the posibility that as the cylinder
head and carbs/ injectors would be on the left that you could have an asymetrical cockpit and have a smaller/ shorter space for your passengerand have
the shorter wheelbase you desire.
best wishes
Iain
|
|
|
JoelP
|
| posted on 16/8/04 at 09:44 PM |
|
|
well, heres my advances and changes.
from the centre of the rear wheels to the bulkhead in front of the engines, is now 36 inches. the engine is about 20 inches long. i have spun one
round, i figure if im gonna work out a chain drive for one i may as well work out a pair of cogs for the other! plus, the off side engine (uk drivers
side) would've needed the cog extending out from the engine to clear the block, as the chain would head the wrong way to usual. so that that bit
sorted. PLus the exhausts will both be ouside, and the carbs both (all?) inside.
so that 30 inches used. By raising the cockpit/rollbar bit to 36 inches, and making the pedals almost touch the steering rack, ive managed to get the
centre of the front wheels to 54 infront of the engine bulkhead. hence total wheelbase is now 90 inches, the ratio is 1.66
the cockpit is 48 inches wide at the back of the seat, but it narrows continually to 24 inches wide at the front, which is the width between the two
top front bone pivots. this is wider than book dimensions (i guess 'book' dimensions went out of the window hours ago though!), but this
allows some space for feet near the rack. the drivers feet will point into the middle of the car a little, and the passanger will have no footwell. or
at least, the driver has priority!
the reason for the odd cockpit layout is that i never liked the way that book chassis have a kink in the side under the scuttle. its a pet hate. seems
to be unbraced and as such will add a little flex to the chassis. My way it ends up like a 2 part chassis, namely a front suspension box, the cockpit
with straight sides, and the engine/diff area on the back.
Rear drive is via a simple LSD, probably freelander origin, and a de dion rear axle. Its easy to link it up to the chassis.
Having an integral roof will allow a much stronger roll bar, or a thinner/smaller one, however i decide. plus the chassis will benefit from the extra
bracing.
it does look very odd in profile, being 36 inches high and only 90 long, but i guess bodywork will cover that.
seats will be foam on the floor, shaped to be supportive. Fuel tank will be squeezed wherever it will fit, ideally between driver and passanger, but
maybe not. The wheels will be 13 inch ally ones (maybe magnesium if funds allow) and cut slicks for road.
i feel motivated now! just need to wait for the remortgage (litereally!) in a few weeks.
there will be a few posts coming up soon about the correct use of bearings on the prop, as the drive will be transmitted from the engines to a prop
via the chain and cog, and the prop to the diff as usual. bearings will be used to hold the free ends in place.
oh yeah, rosejoints all round i think. Anyone know how wide the brackets will need to be roughly to take 1/2x1/2 roses?
more input welcome of course, ridicule too if you feel the need!
|
|
|
JoelP
|
| posted on 16/8/04 at 09:47 PM |
|
|
cheers iain, the real reason behind the choice of drivetrain is twofold. One, to see if i can. And two, linked to that, one day it will be a pair of
turbo'd busas. Hence this car is 'proof of concept' sort of stuff.
i appreciate what you are saying, about the main bike advantage (weight) being squandered. Still, it will be a laugh, unique, and like poo off a wet
shovel!
[Edited on 16/8/04 by JoelP]
|
|
|
niceperson709
|
| posted on 16/8/04 at 10:03 PM |
|
|
best of luck you guys in blighty have MUCH MORE SCOPE than us residents of the antipodies to build something out ragious for the road . here we are
much more restricted , all of our cars have to meet Current emission and design requirements and bike engines are forbiden in a car.but the othe side
of the coin is our weather is better most of the time , at least where we live in Queens land
best wishes
Iain
|
|
|
JoelP
|
| posted on 16/8/04 at 10:05 PM |
|
|
horses for courses!
|
|
|
ady8077
|
| posted on 17/8/04 at 11:56 AM |
|
|
Hi JoelP
Have you seen how Z cars use twin engines in their mini ? Looks very compact
http://www.zcars.org.uk/mini/mini_twin_rl.htm
Adrian
|
|
|
JoelP
|
| posted on 17/8/04 at 05:46 PM |
|
|
theres some interesting jiggery pokery going on in that transfer box! looks complex. shame i cant make that sort of thing...
|
|
|
sgraber
|
| posted on 17/8/04 at 07:01 PM |
|
|
You could save a lot of aggravation if both your engines had the output shaft pointing rearwards. Then you could have the LH engine mated directly to
the driveshaft and the right one could use a chain drive to transfer power over to the driveshaft.
Kinda like this (except longer so you can fit the driveshaft onto the output of the other engine):
What do you think? That way you wouldn't have to revese the rotation of the right side engine via a secondary gearbox.
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
|
|
|
JoelP
|
| posted on 17/8/04 at 08:05 PM |
|
|
thats exactly what i was going to do in the first place! i decided to switch one engine round to save the length of the sprocket extension, as
shown in your picture. it would also put both exhausts on the outside of the car. Maybe this isnt such a problem. I had initially decided use a chain
drive to link each engine to a central freespinning prop, with the diff at one end and a bearing at the other. I like the idea of having one engine
straight onto the prop, however on a UK car this would put the engines over toward the drivers side, and a less favourable weight distribution.
im gonna go out and measure the block, and imagine two side by side. I've only got one engine so far...
cheers for the input!
|
|
|
sgraber
|
| posted on 17/8/04 at 08:18 PM |
|
|
Do the halfshafts need to be the same length exactly? Theres no steering back there after all so you shouldn't get noticeable torque steer
effect. If you can shift the differential and both engines over to the right side by say 10-20cm you can shift the weight balance to the center
better. It seems like that packaging should work...
I assume you will run the 2 headers into one centralized resonator and then out the back from there? That would probably sound incredible anyways! I
can see that you will probably have to bespoke the headers/ exhaust anyways...
Steve Graber
http://www.grabercars.com/
"Quickness through lightness"
|
|
|
JoelP
|
| posted on 17/8/04 at 09:13 PM |
|
|
steve, thats an awesome idea, moving the diff over to one side.... why didnt i think of that?!
|
|
|
liam.mccaffrey
|
| posted on 17/8/04 at 09:29 PM |
|
|
back to the twin bike transfer box again
unless i am missing something there is nothing crazy or complex about it in fact if it is this one
i was amazed at how simple it was!
linky thing
as ever i am pleased to be proven wrong
please if someone could tell me what is special about it
it costs £2500
[Edited on 17/8/04 by liam.mccaffrey]
Build Blog
Build Photo Album
|
|
|
JoelP
|
| posted on 17/8/04 at 09:33 PM |
|
|
steve.
moving the diff over affects the de dion bar, but this isnt the end of the world.
Liam, any idea how that thing gets oiled? Would a splash system work, with say an inch of oil in the bottom? seems to be simple cogs, bearings and
machining involved.
if you could throw a diff into this transfer box, then you would have an excellent piece of kit
[Edited on 17/8/04 by JoelP]
|
|
|
liam.mccaffrey
|
| posted on 17/8/04 at 09:40 PM |
|
|
i think it has its own seperate oil system, this is implied on the website
all the gears are off the shelf, bearings no probs, machining no probs lathe and miller, only thing would be the casting not too difficult if you are
in a serious mood.
if the worst comes to the worst you could fabricate something and tidy it up by machining. stuff £2500 i bet i could make that for £800
please someone tell me i am talking through my arse(tell us why it can't be done)
[Edited on 17/8/04 by liam.mccaffrey]
Build Blog
Build Photo Album
|
|
|
JoelP
|
| posted on 17/8/04 at 09:46 PM |
|
|
leave it a day for any experts to comment. Id bet a lot less than £800 too. The housing wouldnt need machining i think. the two end plates i would
outsource to someone competent. simply flat steel, maybe just 10mm, with large holes drilled to take the bearings. Maybe 50mm? stick bearings in, weld
cogs to thinner bars, maybe 25 or 30mm, stick these into the inner race. make a triangular housing out of 10mm by 100mm bar, grind it nearly flat, and
fill the gaps with gasket sealant. Tap holes to hold it all together. I would weld mountings onto the end plates. not sure how to seal the outputs and
inputs, but it cant be rocket science...
|
|
|
