Technical Advice needed!

[jmillf]

Hey guys.

I am currently doing my final year project at uni; an electric conversion of a small two door hatch. Now i am at the stage where i have to modify the rear brakes from drum to disc brakes. The problem is that i dont have alot of room to work with. The measurement that i am working with is 79mm. So i have to find a brake caliper that is kess than 79mm wide. Options i have:

• Find a performance motorbike caliper that fits and manufacture a brake disc.
• Do the above as well as upgrading the front brakes.
• Maybe find ATV or fourwheeler performance brakes.

I dont think i am confident that the motorbike brakes and the stock front brakes will stop the car as efficienetly.

Also a drum brake conversion, is it as simple as replacing and installing stock brake lines. etc

So if any braking experts can help that would be great.

Thanks guys

[The Yeti]

need a little more info sorry

79mm I dont see as too bigger issue I think if you look at some of the smapp hatchs you'll find that isnt to bigger deal (may have to shave some of the cooling webing but that would be it

why cant you use the drums though, also you do know you will need to boost the discs dont you? I dont know what your doing to boost the front (No engine means no vacume, you could run a hydro boost type system or even a mechaical vacume pump off some rotating shaft some there, simular to how diesel engines are configured)

what sort of car are we talking?

[jmillf]

The reason i cant use drum is because the electric motors that are being used actually sit inside the rim, slightly resembles the drum brake. The engine is being removed as well as the transmission. So not sure about boosting, haven thought about that.

The car is a Holden Barina 2 door around 950 kg.

[Riksta]

Sounds like an interesting project, got any pics you can share?

[The Yeti]

Why can't you use the drive motors as brakes this way they could act as regenerative ?

[The Yeti]

Also ment to ask AC or DC ?

[cs123]

Can the motors in the rear be used to perform a braking function?

[The Yeti]

That's what I recon but I guess we'll need to hear back from the OP

[hawke]

Many race cars use Lockhead LD 19 or 20 callipers. They are small and light. I suspect that they may be smaller than 79 mm, however, you may need to google some drawings for them.

As far as discs go, I have got some good advice from DBA if you can give them the dimensions you want. They recently put me onto some Nissan Micra rear disks, which then with minor machining, fitted into my application.

If you are going from drums to disks, you may need to fiddle with the line pressure between front and rear. Disks typically need more line pressure. You will need to consider the relationship between the piston areas front and rear, both in the disk and master cylinders. This is often determined in race cars by using seperate front and rear cylinders, and altering the mechanical advantage between the two by moving the piviot point.

For a road car, you may not need this level of adjustability, but for a project, you may get credit points.

[damo76]

well the car is front wheel drive, it depends on what setup you have on the rear axle. if you are using a drive axle on the rear, the brakes dont have to be in the rims, if you know what i mean. Bit hard typing this stuff.
Good fun project though, i once put a 2 litre izuzu engine and gemini 5 spead in a 82 suzuki siera, the drive shaft was only 170mm yoke to yoke but it fit.
You can make anything fit

[jmillf]

Originally Posted by hawke

This is often determined in race cars by using seperate front and rear cylinders, and altering the mechanical advantage between the two by moving the piviot point.

For a road car, you may not need this level of adjustability, but for a project, you may get credit points.

This seems like a good idea.

Ok the motors are DC.

They cant be used as brakes, already gone over budget for the motors.

Sorry no photos available.

Ok looked at the Lockheed calipers and they look pretty solid. The thing is i have to model them up and do a FEA analysis on them as a part of the assessment.

Any other incites. Keep them coming, cheers guys

[jmillf]

Found some pretty pictures.

[Yellow_Festiva]

Originally Posted by jmillf

The reason i cant use drum is because the electric motors that are being used actually sit inside the rim, slightly resembles the drum brake. The engine is being removed as well as the transmission. So not sure about boosting, haven thought about that.

The car is a Holden Barina 2 door around 950 kg.

What Barina exactly? By that weight I may guess it's the Opel sourced one with the roundish headlights?? Came in 3 models, City, Swing and Joy??? Mum had the Swing, was around a 1994 model.

Wild guess, but if so, the GSi model could have had the rear discs as it was pushing 80kw and was the 'hot hatch' of the line up.

If it is earlier, was there a Barina based on the Swift (or visa versa?)? Again, the Gti model probably had discs on the rear.

I'm guessing you have a budget.. adapting something off the shelf that fits with minimal mods is what you are after.

Interesting job... I have toyed with the idea of making an EV Festiva. Space and time constraints seem to always get in the way. As well as the fact anything decent will cost $20k+ to build.

[The Yeti]

Originally Posted by Yellow_Festiva

What Barina exactly? By that weight I may guess it's the Opel sourced one with the roundish headlights?? Came in 3 models, City, Swing and Joy??? Mum had the Swing, was around a 1994 model.

Wild guess, but if so, the GSi model could have had the rear discs as it was pushing 80kw and was the 'hot hatch' of the line up.

If it is earlier, was there a Barina based on the Swift (or visa versa?)? Again, the Gti model probably had discs on the rear.

I'm guessing you have a budget.. adapting something off the shelf that fits with minimal mods is what you are after.

.

I cant add to that, as that would be my way of looking at it also

we then need to consider boosting the system

your using indevidaul drive motors, but is there somthing that will be turning all the time? an electric hydroboost will be expencive if your over budget, but if youve got somthing thats always turning you could run a drive for a vacume pump stolen from the back of an alternator on a diesel motor, or perhaps you could look at pulling it of a drive moter with an accumulator in the system?

[lockieoc]

Originally Posted by jmillf

Found some pretty pictures.

So is that roughly how you want the disc to be positioned?
Does it have to be that exact mounting PCD?
I know of some discs that you could use that are similar in style but with a slightly different mounting PCD.

[hawke]

You may find this page the Pegasus catalogue relevent:

https://www.pegasusautoracing.com/2012/127.pdf

If pegasus dont list it, it doesnt exist.

[jmillf]

Yellow_Festiva, Yeh thats the idea of the project is to keep costs down and have a EV that could retail around $20,000. Majority of EV at the moment are all over $30,000; iMiEV, Volt etc

lockieoc, yeh this is how i want the disc to be set up. What have you got in mind for a different mounting option?

The Yeti, no i dont think i have something turning all the time, the motors are all that comes to mind but they are not constantly turning. As i said haven really thought of boosting, should really do some research into 'boosting'

I am kind of leaning toward also upgrading the front disc brakes. Once i have decided on the caliper, just have to design a mounting bracket.

[The Yeti]

Originally Posted by jmillf

The Yeti, no i dont think i have something turning all the time, the motors are all that comes to mind but they are not constantly turning. As i said haven really thought of boosting, should really do some research into 'boosting'

I am kind of leaning toward also upgrading the front disc brakes. Once i have decided on the caliper, just have to design a mounting bracket.

if it has disc brakes they will require boosting or it will feel like your trying to stop on ice. I dont know if you have room to lift the master cyilnder up to enable you to have a longer pedal?

As the vacume booster currently on the car is no longer usable perhaps you can move the master cylinder up giving you room for a longer peddle (longer leaver)

or perhaps fabricate some sort of mechanical advantage system in between the pedel and the mastercylinder

Failing that this would do the same thing http://www.autoworksparts.com/electr...ke_booster.htm

and if you do some looking arround you would be able to find somthing in an exisiting car way cheeper

[lockieoc]

Originally Posted by jmillf

[B]

lockieoc, yeh this is how i want the disc to be set up. What have you got in mind for a different mounting option?

Depends,
What sort of diameter are we talking?
Also, does it have to be solid?
Would a thin, vented rotor work? Around 16mm thick?

[The Yeti]

http://www.ebay.com/itm/2001-AUDI-A4...sories&vxp=mtr

If you grab sotmhing like this you use the existing booster and this gives it vacume required

[jmillf]

lockieoc, the thing is if i increase the size of the disc to a slim rotor i am taking away from the room that i have to find a caliper. The disc that has been manufactured can be scrapped, off the top of my head it is 9-10mm. So an extra 6mm isnt that much. If i do this the caliper width would have to fit in around 72mm. What rotor have you got in mind? Can you tell me the difference between rotor and disc in terms of stopping the car.

The Yeti, ok so will this solve my boosting problem? Is it as simple as plug and play with the existing booster and master cylinder? Little bit of modification?

Appreciate the help fellas, keep it coming

[The Yeti]

Originally Posted by jmillf

The Yeti, ok so will this solve my boosting problem? Is it as simple as plug and play with the existing booster and master cylinder? Little bit of modification?

Pretty much, all you need is a 12v DC power supply so when you turn the car on it is on, this will supply vacume (cau you actualy supply a vacume? as a vacume is a negative? ) any who this conects to the vacume port on the booster and your brakes should work as they did when the IC engine was running

[jmillf]

The Yeti Ok so just did a quick research, that electric brake vacum will just replace the action of the vacum made by the engine. So that vacum hose from the booster is plugged into the pump.

[jmillf]

Originally Posted by The Yeti

Pretty much, all you need is a 12v DC power supply so when you turn the car on it is on, this will supply vacume (cau you actualy supply a vacume? as a vacume is a negative? ) any who this conects to the vacume port on the booster and your brakes should work as they did when the IC engine was running

Haha ok awesome will definitely get on to this, better schedule an appointment with my supervisor haha.

Ok so if the front disc brakes are kept stock and i manage to mount the Lockheed caliper/other aftermarket caliper with a fabricated disc/rotor, do you think this will be an effective braking option for the prototype?

[Yellow_Festiva]

The only other mounting option I can think of is disc brakes that are mounted on a drive shaft (as in the shaft to each wheel after the diff).. Some cars have them, can't remember the correct terminology...'inboard' brakes or something???

Only problem is, your rear wheels don't have a shaft to speak of. Bugger....

In terms of stopping the car efficiently, what weight surplus will your vehicle have at the end of the job? The engine / transmission hardware you remove will weigh around 150-200kg at a guess. How much over the stock weight will your vehicle be?

I know you have already settled on your donor vehicle, but perhaps if you chose a cheap 'AWD' vehicle (Honda HRV / Holden Cruze??) you can apply the same principles to the front as you are applying to the back.

This is, assuming you are maintaining some sort of drive shaft to each of the front wheels???

Have you investigated how your suspension will be set up? Sounds like you will be adding a lot more weight to each corner below the springs / dampers?

[jmillf]

Originally Posted by Yellow_Festiva

The only other mounting option I can think of is disc brakes that are mounted on a drive shaft (as in the shaft to each wheel after the diff).. Some cars have them, can't remember the correct terminology...'inboard' brakes or something???

Only problem is, your rear wheels don't have a shaft to speak of. Bugger....

In terms of stopping the car efficiently, what weight surplus will your vehicle have at the end of the job? The engine / transmission hardware you remove will weigh around 150-200kg at a guess. How much over the stock weight will your vehicle be?

I know you have already settled on your donor vehicle, but perhaps if you chose a cheap 'AWD' vehicle (Honda HRV / Holden Cruze??) you can apply the same principles to the front as you are applying to the back.

This is, assuming you are maintaining some sort of drive shaft to each of the front wheels???

Have you investigated how your suspension will be set up? Sounds like you will be adding a lot more weight to each corner below the springs / dampers?

I am apart of the intitial investigation of electric motors, weight distribution and braking components. I can have a chat to the other guys in charge of the suspension see what they say. But yeh i agree with you that there will be a bit more wight involved with the rear suspension.

Yeh we are removing engine and transmission, but we are adding a large battery pack which wont be as heavy as the engine but will be fairly heavy. Will get some potential weights of the final prototype.

[jmillf]

lockieoc Can you tell me the difference between rotor and disc in terms of stopping the car. Thin solid disc vs vented rotor? Is it just cooling of the disc

[Yellow_Festiva]

Originally Posted by jmillf

lockieoc Can you tell me the difference between rotor and disc in terms of stopping the car. Thin solid disc vs vented rotor?

From my basic knowledge a 'disc' and 'rotor' is the same thing.

Thin solid disc is not as efficient at dispersing heat. They were generally used as a basic brake set up in economy / older cars. Prob 8-13mm in width?????????

A vented disk / rotor is thicker, perhaps 16-28mm as it is essentially 2 solid rotors joined together with a space in the middle to help cooling / heat dissipation. More common these days and are a better performing rotor.. I think even my Festiva had front vented rotors???

Solid rotors would be lighter as there is less in them.

Anyway, this is my basic understanding… I’m sure I’ll be corrected if It’s wrong!

[jmillf]

Yeh thats what i though better to dissipate the heat. Think i wont need the performance from the vented rotors think the 10 mm solid will be fine.

[The Yeti]

If your worried about heat on a solid disc just cross drill it

But I wouldn't loose any sleep on that its a small car and you'll find a lot of small cars run / ran solid rear discs, hell XJ6 series I jags had them front and rear