Another timing belt question

[AndrewWebber]

I sensed at yesterdays 'Burroughs meeting', you were a man on a mission.

Great work

Andy

[Hawaiis0]

Needless to say, Stu's gauge had the flat blade - but not any longer - Hope you don't mind Stu. Though I say it myself, I think I did a pretty decent job reprofiling it.

Tony

Where's Bash? Never around when you need him!

[malrig]

I have finally worked out a measurement from the Draper/Neilsen gauge that I'm happy to stand by and post on here.
When Tony visited we were quickly able to establish that my cambelt is pretty much spot on in terms of tension, according to the Burroughs gauge. As a second double check, Tony had also pre-tested the Burroughs gauge at a trusted Esprit builder's premises before coming over to mine, so we were happy that we have a well tensioned belt as a check for the Neilsen gauge.
The reason for the delay in posting is that I was getting inconsistent readings from the Neilsen gauge at first, and was on the point of suggesting that it's not a good option, and people should steer clear. I've now done a few checks on different days with very consistent results. People with experience of "Gauge R&R" will get my concerns.
Key information for success and to use this advice :
1. Engine to be stone cold - 10-20 degrees C.
2. Engine has run for a few minutes to bed in the cambelt.
3. ALWAYS wind the dial in from the loose position to the required tension setting : i.e. start at approx 25 on the scale and wind it straight in to 16.0, then take the reading. NEVER make small adjustments to the dial and expect a good reading.

The readings on the gauge for a correctly tensioned belt are :
"Tension setting" = 16.0
"Optimum tension" = 14.0
This equates to a side force on the cambelt of 5.5DaN and a deflection of 1.5mm.
See picture


Happily this does relate to the Burroughs. We crudely checked that, and the side load is 10DaN (10 kgf) with a deflection of 4mm.
The span of the legs on the Neilsen is 50mm against a span of 75mm on the Burroughs, hence the deflection should be 2.667mm for a force of 10DaN.
The Neilsen gauge only goes up to 7.9DaN, so a further reduction is required. I applied a simple ratio of 0.75 to both deflection and force.
I first tried 7.5DaN for 2mm deflection, which equates to :
"Tension setting" = 14.0
"Optimum tension" = 13.5
I recommend this as a secondary check only. The gauge is more difficult to read when the dial approaches the same position as the sliding scale.
Picture below

I then applied a ratio of 0.55 to get to a point where the gauge is easier to read. That gave the 5.5DaN and 1.5mm numbers which match with my recommended settings of 16.0/14.0.

Hopefully this is helpful, and may save a few people some money if they can't borrow a Burroughs gauge. My Neilsen gauge cost £16.50 delivered from ebay, so a lot cheaper than alternatives, and a good option if you're not changing cambelts very often.
Happy to be challenged, and/or clarify if I haven't been clear with any of this.

Cheers,
Malcolm.

[RED BARON]

I have just replaced my Belts on my 1990 SE's. I have used this Setting Gage on 6 times on changing my Belts, even though I do very little Mileage between MOT's. As the Gage doesn't come with Setting Instructions I had to go to the Manufacture who sent them to me from Japan. On the Chart it show to set the Gage to 15.1 to give a 12.5 Tension reading on the top of the Belt. I have found this in my case has worked. So isn't a long way from your findings. Just thought I would put my 2 penance in.

[malrig]

Interesting - that's a lot looser than my advice below.
You're getting a 3mm deflection with a force of 5.0 DaN, whereas I'm getting 1.5mm with a force of 5.5 DaN.
It would be interesting to double check yours with a Burroughs gauge if you ever get the chance.

[dancroft1984]

Where on the belt are people taking these readings? I'm assuming the "top" run of the belt between the timing wheel and inlet cam?
Going to buy myself a draper/nielsen or Krikit gauge (can't afford a Borroughs right now!)
I tried with a guitar tuner in this part of the belt, got 128Hz, but I think it may be tight.

[MetBlue]

The Burroughs gauge is used between the Inlet and the Exhaust cam shaft pulley.

[Pete Boole]

Auxiliary and inlet he means!

Pete

[Hawaiis0]

Auxiliary and inlet he means!

Pete

Thin line - starting to grade us

Hope the final paper isnt too bad!

[Pete Boole]

Auxiliary and inlet he means!

Pete

Thin line - starting to grade us

Hope the final paper isnt too bad!

Pete

[mbracing]

Hi from Italy
What is the best source in Europe (or UK) to buy the best quality timing belt and eventually the tensioner for a 1979 Elite 501?
Regards
mbracing

[rbgosling]

Hi from Italy
What is the best source in Europe (or UK) to buy the best quality timing belt and eventually the tensioner for a 1979 Elite 501?
Regards
mbracing

Welcome to the forum! Do tell us more about yourself and your car - there's a section for new introductions here: viewforum.php?f=11

I've no idea where you'd look for parts outside the UK. I get all my parts from Lotusbits (who are local to me, and also have a massive stock of used parts) and SJ Sportscars (who have a much better website for online ordering). Classic Team Lotus, and PNM Engineering, are also good sources of parts. When it comes to timing belts, and most common parts, I'd suspect whoever you buy it from it'll still be the same belt.

[CJG in WOB]

Within the EU, there is also Brammer here in Germany.