Sunday 29 October 2017

Nearly Throttled

Yes, yes, I know this seems to be taking an age, but the throttle bodies are nearly finished - as long as the engine starts when it is finished.
The majority of the reason it's taking so long is that usually I have a clear plan & drawings - often a CAD model of what I need to make or do, this time apart from working out the lever geometry in CAD, I'm winging it - making it up as I go a long, so parts have been scrapped, re-modelled, changed into other parts & slowly (very slowly) a working system is emerging from the fog. I've also taken the opportunity to improve things as I go.

I've trimmed all the "flags" which will become levers on the throttle bodies, I've lowered the airbox so (hopefully) it won't rub on the underside of the bonnet, that meant trimming all four trumpets to clear the airbox top skin. I had to re-make the cable mounting as I realised the bonnet would foul what I'd made, fortunately work was having a clear-out & several exquisite lightweight machinings were being scrapped before I liberated them & was able to work them into the new cable mount design - which is better than the old one in a number of ways.
Still can't turn pictures sideways
I've also modified the pulley to take a longer return spring mounting so I can fit two return springs, so (assuming the enjoined works), I won't have a repeat of the "stuck-wide-open-throttle-on-the-M25" incident from this year's Rogue Runners trip.

I'm now just waiting for the arrival of the turnbuckles & I can set up the main shaft, drill & trim the levers & adjust, fit the new cables & go for the start.

Sunday 22 October 2017

Cable Man

After a day in the garage making small metallic bits & bobs, (which is one of my favourite ways to spend a day) the No.1 throttle body is now worked by the cable. I’ve made up all the “master” levers & all the “slave” levers, some of them had to be cranked to gain enough space for the turnbuckles, but I've left a load of metal on them as I don’t know where I’ll want the hole until the new turnbuckles arrive – probably Weds.

So at the moment they look like flags & hit all sorts of bits of throttle body as they travel, but once I have the hole location, I'll be cutting all the excess off.

Also on todays list was the cable hanger, which is riveted to the extrusion which is bolted to No. 1 throttle body. At the moment it's hanging out in space, but when it's all finished the airbox will sit behind it in this photo taking away some of the visual impact (which is good).

Cable relaxed
I need to order another two cable inners as the ones I have are less than straight & frayed, I also need another bracket riveted to the airbox to support the cable outers & then I can go for the start & see if all this cunningness has paid off.

Cable pulled - butterfly open

Saturday 21 October 2017

The First Of The Links

This is at idle.
On the excuse that I was going to make up a part to stop the exhaust knocking on Mrs Blatter's car, I went out to the garage & removed the airbox from its’ backplate, then removed the back plate, with them safely separated I was able to trim parts of the backplate & airbox & seal up the hole where the air temp sensor goes as it was in the way of the linkage.

This is at Wide Open Throttle
I then dismantled the throttle bodies from each other, which was a bit daunting, but gave me space to work out the geometry for the levers. I made up a couple of prototype levers & attached one of the pushrods. After messing about a bit I was able to make something that fully opens & closes the butterfly from the cable pulley, but at fully open the lever passes through one of the mountings, so I’ve ordered some shorter turnbuckles which should sort the problem out, but so far it’s working, it’s smooth & it has the rising-rate mechanism I was looking for, so when the geometry is finalised, there’s every possibility it might work!

Thursday 12 October 2017

A Little Progress

I've been trying to do a little to the car every day, so to recap the last few days:-

I took off the original Suzuki pulley & found it had a second job driving a return spring, so I made up a "washer" with the tabs needed to do the same job, if you look at the picture, there's a vee between the top of the bracket & the spring, well the washer / spring is above the point of the vee.

I've also made an aluminium angle to act as a stop for the cable outers & made up a "peg" screwed into the engine block to anchor the main return spring. So far the movement seems pretty smooth, but the next job is to connect the new shaft up to the Throttle Bodies & disconnect each TB from the next.

Sunday 8 October 2017


Today's stint in the garage revolved around (see what I did there?) fitting the pulley to the end of the shaft for the new throttle linkage. I cut away some of the alloy bracket so the pulley could rotate, then when I was happy with that, I trial fitted it on the car.

AH! The pulley fouled the alternator in a serious way. The options were to move the alternator (no good as the alternator pulley needs to be where it is for other reasons). Dramatically reduce the size of the throttle pulley (not ideal as gearing it up was part of the reason for doing this in the first place). Rotating the pulley by 90 deg on the shaft (it'd work, but the cables would come in from above, possibly fouling the bonnet). Or move the shaft outboard so the pulley centre moves away from the alternator - which is what I decided to do.

Having done it, the pulley just clears, but a little filing will give a practical gap.

The next thing is to make up the levers that will operate the throttle bodies, then I can get all the geometry finalised.

Saturday 7 October 2017

Snail Mail

Obviously I'll need a something to rotate the shaft from the last post. At the moment the throttle pedal is too sensitive, so the thing-to-rotate-the-shaft needs to be lower geared than the Suzuki motorcycle quadrant currently fitted. It also needs to be a "snail" quadrant i.e. lower geared at the start of the travel to allow for finer control with small throttle openings, then getting higher geared as the pedal get's further through it's travel. I measured the Suzuki quadrant & the gearing at idle was 1/2 that at Wide Open Throttle (WOT) so I copied that, but also doubled the gearing throughout the range. No idea if it'll give the results I'm after, but it's a start.

It's a piece of alloy the width of the cable, with a piece of thin stainless either side, then repeated so I can run two cables. Here's what it looks like:-

On the car, the M6 bolt lower right will be replaced by the shaft & the cable nipples will go in the hole bottom left (I need to cut a small slot to make that work). At the moment it weighs 81g which I'd like to reduce tomorrow if I get a chance.

Friday 6 October 2017

Winter Upgrades Begin

With the car officially off the road for winter maintenance & upgrades it was time to start cutting metal. I took the throttle bodies off the car & fitted an alloy angle to the existing strip that holds the throttle bodies in a lump, this angle locates two old aircraft rod ends chosen because they are self aligning & can be adjusted for position. They support a length of 6mm studding which will be the main shaft, to this will be fitted the levers that will move the levers on the throttle bodies

Then cut, drilled & fitted an alloy channel across the end, fitted it with another bearing to support the shaft, next job is to make up the twin pulleys & the cunning return springs. When I have all the elements positioned, I'll cut away the metal that's not doing anything, making it look techie & loosing a lot of the weight.
So far so good.