bonnet struts

[Keith Clements]

A casualty of the Le Mans trip on Amy's SC was a bonnet strut that sheared at the square hole in the inner tube that holds the bonnet up with the plunger pin.

I found some suitable 15mm tube at Serco and made a new inner tube. The tube is removed by knocking or drilling out the pin holding the bottom plug in the outer tube. Take care as the spring will pop out.

The springs were straightened as a couple had been distorted.

The springs are separated by a rod with brass ring in the centre. One of these was missing on the other side so I turned one up in the lathe. This needed to be carefully fitted to make sure it travelled smoothly inside the inner tube. A previous repair required reaming out some weld inside the inner tube.

The inner tube has a stop ring braised onto its bottom end. I made up a ring and welded it to the new tube. The lathe smoothed off the inner tube at its top end, where the stop bracket is pinned, to make sure it passed through the sleeve on the outer tube.

The outer tube has a brass sleeve that has worn. I made a shim and stuck it in with Loctite. I could have made a new sleeve but fitting it would have been a lot of work.

The location of the hole to accept the locking pin was measured and set up in the mill. It is 20 deg off the horizontal plane of the pin holding the end stop. I used a 7mm drill to create a slightly oval hole rather than a square hole. Its location was checked in situ once the strut was assembled.

[RichardMc]

Well done on fixing that, a massively over complicated piece of engineering as usual. I’m experimenting with two gas struts as an alternative. They need to go from the chassis rail near the bulkhead to the bonnet fixing points so I’m using a Munsen ring on each side to clamp to the chassis tube. They are a meter long and rated at 100 Newton each, which by my calculations will lift the bonnet. I checked NXH and the downward force at the front is 20Kg with all the lights and bright work fitted. I think someone has looked at this before but they were trying to use the original bottom mount, which won’t work as the struts need to be angled.
It might not work, I’m fitting it to my Jupiter first because it’s in bits and easier to do without the wings fitted. If it works Geoff is going to use it on his Jupiter because his Jowett mechanism has been replaced with an ‘interesting’ alternative that is quite dangerous! If it does work I’ll post a proper description and a parts list.

[Keith Clements]

Good luck. We did think about doing this when rebuilding the car in 2009 and also looked at the boot mechanism. Since what we had just worked, we stuck with original.
I think Drummond has made all new mechanisms.

[Chris Spencer]

Drummond fabricates new Jupiter bonnet struts - still spring assisted but far superior to the originals - The originals are simply not worth the effort or faff when compared to a new set

[RichardMc]

A quick update for anyone that’s interested in an alternative to the bonnet strut arrangement on their Jupiter. The reason behind the mod is twofold, firstly my original strut is in pretty bad shape and secondly the elder (and wiser I’m told) Mr McAuley isn’t quite as fit as he used to be and lifting a 20Kg bonnet on his Jupiter doesn’t help. After some calculations and measurements to make sure everything fits I bit the bullet and ordered a set of gas struts and the various fixings. These were fitted to my Jupiter and conclusively proved my calculations were wrong! Back to the equation to work out why. I had divided the total load by two, because two struts, but I had also divided the weight by two, because two struts, earlier in the equation. I should have spotted that.

I chose to fit rose joints to each end of the strut to compensate for any alignment issues, these are the RE-10 M8 options on the Metrol website, I also opted for dust covers which came assembled.

The chassis fixing is a 2” Munsen ring, which isn’t actually 2” as advertised but 50mm so it needs a bit of opening up. The Munsen rings came with a 10mm thread but the bolts for the rose joints on the end of the strut are 8mm. I got some M10 to M8 thread reducers from Amazon, these have an M8 inner thread and a Chinese version of M10 outer thread, sort of M10 ish, so they needed a die running over them before they would fit.

The Munsen ring clamps to the chassis rail ‘just’ in front of the bulkhead, basically as close as it will go before it touches the foot well. The other end fixes to the existing bonnet mounts, these needed opening up a bit to take the M8 bolt. I fitted M8 nylock nuts to keep everything secure.

The result is a bonnet that slowly opens once you undo the front catches (and rear ones if you have them) and comes to a gentle stop in the fully open position. On the white Jupiter it needs a little push at the end because the 175 tyres rub slightly on the wing in the fully open position but other than that the only other adjustments were the wiring loom on the near side that needed fixing to the top suspension mount to keep it out of the way and the aftermarket washer bottle on the off side needed moving inboard slightly to clear the strut.
I’ve put a video on YouTube, the short-link is https://t.ly/YwNLx

Parts List:- https://motioncontrol.metrol.com/
NS-FF-10-425 Fixed Force Gas Strut CODE: NS-FF-10-425
Force required 2 x 200N
Rod end fitting 2 x RE10 - M8 Rose Eye End, 36mm length, 8mm eye
Rod end bracket 2 x none
Body end fitting 2 x RE10 - M8 Rose Eye End, 36mm length, 8mm eye
Body end bracket 2 x none
Accessories 2 x Dust Cover

Subtotal £65.70
Shipping £6.95
Tax £14.53
Grand Total £87.18

2 x Munsen Ring 2" £9.90 Amazon
Pack M10/M8 thread reducer £9.69 Amazon
Pack M8 Set Screw / Nuts £9.50 Screwfix

About £120 and two hours work. If anyone needs two 100 Newton struts, that won't work on a Jupiter, just let me know!

[Keith Clements]

Good work Rich,
Would you need to recalculate strut strength if inner wings were fitted or not fitted on the bonnet?
Would those spare struts work on the SC boot or are they the wrong length or strength?
If not, can you suggest a design for the SC boot and/or the Javelin boot?

[RichardMc]

Not sure about the inner wings, I'll have a look. The fixing at the bonnet should be OK because this is where the standard rod fits but the inboard one might be pretty close. It does clear the suspension top mount and I assume the inner wing doesn't reach this area because it would catch. I've got some inner wings so I'll have a go next week.
The left over struts are too long for the boot using the standard mounts but I could probably find something on the Metrol site that would work. Leave it with me!

I might have a go at Lambo doors next

[jowettgeoff]

Very kind of Rich to equip my Jup with his bonnet strut solution. I can now amuse myself by opening and closing the bonnet with one finger. It's quite cathartic, but I suppose I'll get bored with it eventually...

[Keith Clements]

At least you will not get trapped like I did in Cortina High Street!


More pics in my personal album on JT.

[jowettgeoff]

Nice shot!

Amazing what you used to do Keith to attract attention from Cortina's young ladies...