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'thick belt' thickness


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My current 'thick belt' has printed on the outside 20 x 900, which is in millimetres.

However a while back the rear of my fan pulley shed (with a delightful musical metallic 'ring') a large piece the size of half the circle. Makes me suspect the belt is wider than Triumph intended.

I'm about to begin the adventure of finding one about 350mm in circumference to run just from the fan pulley to the alternator (wide pulleys), and will see how an electric water pump performs.

Can't find any reference to the fan belt width in my books.

Does anyone know the correct width for the 'wide' fan belt?

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Hi Jim,

 

The 20mm width belt is the correct original width, as it tended to sit up in the pulleys a bit.

 

Fatigue and fracture of the back sheave of the crankshaft pulley is not uncommon, and has been one of those little TR peccadilloes for donkey's years.

 

To determine a correct length for your short fanbelt, you could use the old one and just keep cutting it down until you get fitting butt joints, then tape it together as a template. If you position your alternator about half way along the locking slide, then you can use a slightly shorter or longer belt, depending on what's available.

 

A short 20mm width belt might be hard to source, but a 17mm width belt is usable, and just sits a bit lower in the pulleys. Bearing shops often have a good selection of wider section belts. Also Cummins diesel use various wide cogged belts, or find a supplier for Dayco Top Dog Gold Label cogged belts which supply in 20mm, or Gates which have 19mm wide belts. (If using a 17mm belt you will need a slightly shorter one than a 20mm).

 

Good luck with the treasure hunt, and let me know if you are in strife and I'll see what I can dig up down here, as there are many potential suppliers near my office.

 

Caio,

 

Viv.

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My current 'thick belt' has printed on the outside 20 x 900, which is in millimetres.

However a while back the rear of my fan pulley shed (with a delightful musical metallic 'ring') a large piece the size of half the circle. Makes me suspect the belt is wider than Triumph intended.

I'm about to begin the adventure of finding one about 350mm in circumference to run just from the fan pulley to the alternator (wide pulleys), and will see how an electric water pump performs.

Can't find any reference to the fan belt width in my books.

Does anyone know the correct width for the 'wide' fan belt?

 

Hi Jim,

 

You have the right size belt. I suspect excessive belt tension, a classic way to ruin pulleys.

Concerning electric pumps, lucky you, the best supplier is Davies Craig, from downunder.

 

http://www.daviescraig.com.au/main/display.asp

 

Cheers,

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Thanks Viv and BF,

 

I wondered if the PO had been forced to buy a compromise belt, it looks quite new. Thought that 1.9 or 1.8mm might be the original size but now know otherwise.

Lot of forum members mightn't know that Davies Craig invented the thermatic fan, fitted one to my HQ Holden in the mid 70's, and immediately got an extra 1 mile to the gallon. In a fit of altruism (? stupidity) they didn't apply for a patent and now everybody has one on their new car.

They have patented their electric water pumps as far as I know. Slow learners, but they do learn.

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many thanks Chris. That tells me that I can go for thicknesses between 20mm and 17mm without any disasters.

With the water pump pulley out of the circuit my length will be round 340mm.

I've found that the Xmas break is not a good time to go searching for one.

So far I have learnt that I'm going to have to get it via an industrial engineering shop, not an automotive source. All the part number cross referencing is about car models, not about width and circumference. These days most of the shops can't afford to carry a huge stock on the shelves and only have what sells quickly.

 

it will have to wait a while, I'm currently in a little Qld fishing village doing the 'carer' bit, and won't get back to what passes for civilization over here for another week or two.

 

Ps. was chuffed to see you got a chapter in one of the Kas Kastener books.

Edited by littlejim
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many thanks Chris. That tells me that I can go for thicknesses between 20mm and 17mm without any disasters.

With the water pump pulley out of the circuit my length will be round 340mm.

I've found that the Xmas break is not a good time to go searching for one.

So far I have learnt that I'm going to have to get it via an industrial engineering shop....

 

Hi Jim,

 

I would not go thru this aggravation. The thick belt consumes 5-7 bhp in its original size. A 17/340 belt will be even more rigid and will consume more power, making the whole change useless.

The small belt/pulley kit will be far more simple and will also eliminate the hassle associated with ruptured belt on the road, i.e. dismantling engine silent-blocks, then lifting the engine to allow space for belt removal.

Cheers,

 

PS: Chris Marx's upper engine stabilizing device is a good idea. I will try it myself.

Edited by Badfrog
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Hi Chris,

your 'upper engine stabilization' device looks interesting.

Apart from the 'bl**ding obvious' (to quote Basil) what does it achieve?

Is it just a solid strut or has it got damping?

Does it impart vibration into the body?

 

Rgds

 

Roger

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Apart from the 'bl**ding obvious' (to quote Basil) what does it achieve? - prevents rotation of the block

Is it just a solid strut or has it got damping? - yes and yes

Does it impart vibration into the body? - yes

 

 

To make this clear - this is a fan belt thread and not an other weird engine parts thread ;-)

Edited by MadMarx
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If I may ask... What is your radiator attached to at the top? I see that the mounting bracket on the cross tube is empty.

 

Richard,

 

I use an Opel Manta radiator. The upper attachment is mounted at the signal horn screws. The long rods disturb so I removed them.

 

Cheers

Chris

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When considering how to reduce sideways movement of the engine, I decided not to go for a solution like Marx's because that imposes an undesirable load on the bodywork, even though the strut is at the ideal (90 degrees) angle to the engine. Hence, I went for a strut which puts the forces into the chassis, as described in TRaction 130 and Section G3 of the Technicalities CD - although not at the ideal angle to the engine, I feel much happier with a connection to the chassis.

Ian Cornish

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Steel studding between a bracket on engine and a bracket bolted to left-hand end of cross-tube/chassis connection. Studding has pairs of rubber (could be polyurethane) bushes astride each bracket and clamped by nyloc nuts and washers, so, by adjusting the compression on the bushes, one can adjust the stiffness of the mounting.

The advantages to my mind were:

(1) no modifications whatsoever required to bodywork or chassis,

(2) forces fed into the chassis,

(3) adjustability of stiffness.

I had to make two brackets (dimensioned drawings in the article) from pieces of steel which I had lying around in the garage, and I bought studding, washers and nuts from a hardware store (B&Q probably). The rubber bushes came from Revington. A few bolts need to be replaced with longer ones, to accommodate the thickness of the brackets - these I had lying about!

If you don't have TRaction or the CD and are interested, e-mail me (ifcornish@btinterent.com) and I'll scan and send the article to you (offer open to any TR4/4A people).

I don't think it would work as well (if at all) on a TR2/3/3A because the chassis is narrower, so the angle would not be as advantageous.

 

Ian

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