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MG Midget and Sprite Technical - Phantom Grip ?

At a hillclimb yesterday a halfshaft broke (at the hub end. I have a phantom grip fitted. why did i loose ALL drive?

any ideas?
danny

Sounds like you need to contact Phantom Grip for an explanation. If the unit is working properly you should have still had drive to the good side.
Bill Young

Are you using the road spec or race spec springs in the Phantom Grip?
How long has it been installed?
What diff oil and additives are you using?
If you have old/weak springs,and have done a fair bit of wheel spinning i.e. polished the surfaces of the blocks, and have a slippy oil additive, these will all affect it's ability to grip.
David Smith(davidDOTsmithATstonesDOTcom

My understanding is that an LSD does just that: "limits" the slip. Doesn't eradicate it, with no drive to one side it can't cope. You'd need a welded diff for that.

Max T

What is going on with all the half shafts in the last 2 months...this is like the 8th thread where someone has had a broken shaft.....definatly afraid of driving my car now for fear my car might get the "halfshaft virus"


prop
Prop

I'm running standard springs, i couldn't clamp the assy together with the heavy springs.
i'm using 75w90 oil.
its done about 100 road miles and about the same on track.
i was getting alot of wheel spin in 2nd which suprised me..
danny

From looking at the Phantom grip details it looks to be that they increase the load and therefore friction on the sun gear thrust washers and present 2 additional friction faces between the PG and sun wheels. The literature doesn't say much but mentions a rocking action so I think maybe the 2 halves rotate relative to each other due to the differential action and then may wedge the planet gears outward to increase the friction at their thrust washers. Looks like a cheap solution but I expect hard on the thrust washers if used regularly, especially the phenolic ones if fitted. Danny do you know if all the thrust washers were in good order when the PG was fitted, I would expect its functioning to suffer somewhat if the thrusts were significantly worn.
David Billington

An LSD will put more load onto the halfshaft with the best grip, and with a reasonably powerful engine, the halfshaft is likely to go quite easily - as I found out after fitting a Tran-X LSD! This was with 'toughened' halfshafts - it now has Peter May's EN24 shafts, and so far??

Unless the LSD has a very high pre-load, it can only provide a relative low level of drive, as the name suggests.
Richard Wale

washers were new..
danny

Danny,

You said you had trouble compressing the PG with the heavy springs, as the installation details mention a strap to be removed each side once installed is this a 2nd hand PG.
David Billington

was about to ask the same as DB, I use the race version and have swapped it between diffs with no problem. I compress it in the vice, replace the two straps, fit to diff then remove the straps.
David Smith(davidDOTsmithATstonesDOTcom

it was new, you build the unit up on the bench,or vice, putting in the little clips you mention, then put it in the diff, pulling the clips out.

I couldn't compress the heavy springs enough to fit the clips (they were coil bound) I made slightly larger clips, but the assembly would not fit into the gears.
danny

Danny,

Did you get new bronze thrust for the sun gears, if so from where?. This was discussed awhile back and I wondered about punching them but wanted to verify the new thickness.
David Billington

it was 2 years ago but i think i got fibre and bronze washers from moss?
danny

There are quite a few topics in the archives this one I contributed to http://www2.mgcars.org.uk/cgi-bin/gen5?runprog=mgbbs&access=&mode=archiveth&subject=97&subjectar=97&thread=2008011811244021816

The springs force the blocks of the Phantom Grip into contact with the bevel gears creating friction which 'limits slip'. They are effective but as has been said they rely on a tightly controlled clearance (With clamps compressing the springs)to achieve the correct force on the gears. Wear of the fibre washers increases the clearance and effectiveness of the device. I think my washers have worn so am still looking for some PB ones.

John Turner (Midget & MGB)

yep, it would be good to revive this subject as I want some PB thrust washers too.
David Smith(davidDOTsmithATstonesDOTcom

Well the thread John mentioned ended with me querying if anyone had info on what the thickness should be rather than relying on measuring old thrust washers and there was no more. A look now at Moss http://www.moss-europe.co.uk/Shop/ViewProducts.aspx?PlateIndexID=956&SortOrder=68#top mentions 0.035" for late carrier and Sprite I, Sprite II, Sprite III, midget I, Midget II, anyone know the differences between diffs, are later ones 1500 different in any significant way, the part seems to have the same number ATA7039 but I can't view the later model info as Moss site is rubbish with Firefox.

I have made an enquiry about 6' x 1' 0.9mm (0.0354") PB102 rolled bronze sheet to get an idea of price but haven't heard back yet.
David Billington

DaveB,

Still interested in PB thrust washers

John
John Turner (Midget & MGB)

can't find the old thread but IIRC I dug out a new fibre thrust and posted the thickness as measured...
David Smith(davidDOTsmithATstonesDOTcom

From the previous thread, dimensions are Bronze OD 2 1/8" x ID 1 5/16" x 0.035"
Fibre OD 55mm x ID 35mm x 0.031"
John
John Turner (Midget & MGB)

I'm fairly busy at the moment but will get some info on material price and see what I can do regarding making the punches and dies to make them if the material price is acceptable. I have material for the tooling. The ones I have here measured 0.035" IIRC so are not measurably worn, I have another diff with bronze thrusts also, and may have some from stripped diffs in my mothers garage. If some were required urgently I might be able to provide a set or 2 depending on what I find.
David Billington

thanks David, I don't have an urgent need but would like to put a few sets away for future requirements.
David Smith(davidDOTsmithATstonesDOTcom

This thread was discussed between 19/05/2008 and 20/05/2008

MG Midget and Sprite Technical index

This thread is from the archive. The Live MG Midget and Sprite Technical BBS is active now.