free hit
counters
HTD pulleys vs trapezoid pulleys - Page 2 - Engine/Ancilliaries - The Lotus Forums #ForTheOwners Jump to content


HTD pulleys vs trapezoid pulleys


Recommended Posts


Upgrade today to remove Google ads and support TLF.
  • Replies 46
  • Created
  • Last Reply

Top Posters In This Topic

Top Posters In This Topic

Popular Posts

If you do keep your trapezoidal pullies, remember there's a stronger blue belt option, the Gates T104RB

The Jensen Healey engine had a fixed tensioner and suffered the issue with the start on very cold mornings causing belt to jump teeth. So they very quickly designed the spring tensioner and added belt

My 82 Turbo engine, now rebuilt with HTD setup and fixed tensioner.  Other photo shows drilling jig for tensioner mounting hole.  

Posted Images

Anyone know if the HTD pulleys and associated belt can be used with the semi-/automatic tensioner?

Link to post
Share on other sites

I very much doubt there'd be any issue in running the HTD's with the semi-auto rig. AFAIK, one distinct advantage in the newer cog profile is in greater certainty of meshing, as compared to the original Gilmer type.

  • Like 1
Link to post
Share on other sites
12 hours ago, Fridge said:

Anyone know if the HTD pulleys and associated belt can be used with the semi-/automatic tensioner?

I am thinking about converting the auto tensioner into a manual one to avoid drilling so with a bit of luck I can let the engine in the car. 

Link to post
Share on other sites
6 hours ago, lotus-62 said:

I am thinking about converting the auto tensioner into a manual one to avoid drilling so with a bit of luck I can let the engine in the car. 

Hi, I've been thinking about such a mod..Some sort of threaded rod passing through the adjuster. How were you planning to do it?

On 25/02/2021 at 08:17, Escape said:

I think most (if not all) engines now use an automatic tensioner. But that could be for ease of fitting more than reliability.

Interestingly, I've replaced the timing belt on a Land Rover earlier this week and found the keyway in the drivepulley to be about twice as wide as the key itself. This is intentional, to allow some freedom on kickback and avoid shock loads or slack on the belt. I know Gates has developped pulleys with varying diameter (only very slightly) to further smoothen the load on the belt.

Filip

 

19 hours ago, RichardJGC said:

My 82 Turbo engine, now rebuilt with HTD setup and fixed tensioner. 
Other photo shows drilling jig for tensioner mounting hole.

 

14ACC55E-BF29-4620-8DE5-7EC43E6F2723.jpeg

372BD0B9-82E3-4599-B40E-AF99486A7875.jpeg

Excellent and thankyou 

 Lovely looking engine !

  • Thanks 1
Link to post
Share on other sites
2 hours ago, PrecisionMike said:
2 hours ago, PrecisionMike said:

Hi, I've been thinking about such a mod..Some sort of threaded rod passing through the adjuster. How were you planning to do it?

same way, replacing the spring with a solid something but will have a better look when I take it of, maybe a one piece with tread 

 

Link to post
Share on other sites
On 28/02/2021 at 19:00, 910Esprit said:

Why not just replace the internal springs with a distance piece?

I have been considering this too but feel some small range of spring compliance would be beneficial in coping with thermal expansion and contraction.  I will give the matter further thought and post my solution when ready.

Link to post
Share on other sites

Consideration of harmonics compounding components flexing may be in order. Would the risk of jumped teeth be reduced with use of the fixed tensioner, that having precluded opportunity for crank flex permitting the belt to elude the auto-adjust process at certain RPM? As I see it the fundamental theory of a synchronous ( i.e.toothed ) belt system amounts to a low inertia geartrain, thereby eliminating one potential contributor to disharmony between the synchronised components. Pretty deep water for my level of education, I'll admit. 

Link to post
Share on other sites

Both methods work. The original design, for Jensen, suffered from cold-start issues, this was investigated and fixed.

Then later on, Lotus moved to the HTD belt and lower-cost fixed tensioner which also works.

I dont think there is a need to over-think this or swap between one and the other.

Link to post
Share on other sites
1 hour ago, Andyww said:

I dont think there is a need to over-think this or swap between one and the other.

Think that's absolutely true and there are no issues with with a well maintened 'legacy' trapeziodal belt system.   But you should remember to treat the tensioner assembly itself as a service item when you do the belt.

Link to post
Share on other sites
2 hours ago, Andyww said:

I dont think there is a need to over-think this or swap between one and the other.

the trapezoidal tooth shape results in high stress concentrations at the belt-pulley interface, which can lead to high wear rates when the transmitted torque or speed is high.  (inlet cam pully due to the very short contact area between the belt and pulley)

the curvilinear (HTD) tooth profile was developed to alleviate the stress concentrations found in trapezoidal profiles and improve on torque and speed capabilities.   (the tradeoff, however, is that curvilinear designs have higher backlash than trapezoidal profiles) 

 

a quick google search found me the above information, sounds good to me. 

Link to post
Share on other sites
  • Gold FFM

Given the limited use most Lotus get and the short service intervals, I don't think the wear rate is an issue.

I'm with Andy and Steve, the standard system works well enough if maintained properly. Which is why I kept the trapezoidal belt on the Excel, couldn't justify doing all the mods/expenses to fit a HTD belt.

Filip 

I have made many mistakes in my life. Buying a multiple Lotus is not one of them.

 

Link to post
Share on other sites
On 15/01/2021 at 18:23, snowrx said:

If you do keep your trapezoidal pullies, remember there's a stronger blue belt option, the Gates T104RB

IMG_0032 small.JPG

looking at the gates racing website I get a warning:   "This part is not compatible with your vehicle"  funny as it is on yours

 

Link to post
Share on other sites

Gates will not support vehicles they have not qualified the belts on even if the size matches.

I spoke to them a few years ago about any blue belt for the Ferrari 3x8 V8 engines which use the same tooth dimensions as the Lotus belts but are shorter. I asked them if they made a blue belt in the length I specified. They absolutely refused to continue the discussion and pretty much put the phone down.

  • Like 1
Link to post
Share on other sites

If I remember, the T104RB was specified for the 300ZX Nissan engine.  The 133 tooth count was the same in a cross-reference, and I assumed someone must be racing a 300ZX, so I looked for better belts for that and came up with the T104RB.  It's worked so far, fits the pullies well, and feels sturdier than the others, but no guarantees!  

If the HTD pullies were priced better, I'd go with them, but this was an inexpensive upgrade for the time being. Rockauto.com lists them under $60USD. 

  • Like 1
Link to post
Share on other sites
1 hour ago, snowrx said:

If I remember, the T104RB was specified for the 300ZX Nissan engine.  The 133 tooth count was the same in a cross-reference, and I assumed someone must be racing a 300ZX, so I looked for better belts for that and came up with the T104RB.  It's worked so far, fits the

1 hour ago, snowrx said:

If I remember, the T104RB was specified for the 300ZX Nissan engine.  The 133 tooth count was the same in a cross-reference, and I assumed someone must be racing a 300ZX, so I looked for better belts for that and came up with the T104RB.  It's worked so far, fits the pullies well, and feels sturdier than the others, but no guarantees!  

If the HTD pullies were priced better, I'd go with them, but this was an inexpensive upgrade for the time being. Rockauto.com lists them under $60USD. 

pullies well, and feels sturdier than the others, but no guarantees!  

If the HTD pullies were priced better, I'd go with them, but this was an inexpensive upgrade for the time being. Rockauto.com lists them under $60USD. 

On 27/02/2021 at 16:50, PrecisionMike said:

Please dont get me wrong, I love lotus and I've owned mine for thirty years....I'm nit sure lotus had a strategy for solving an early belt jump problem.....I think in the early days thet lurched through a field of iterations in hope that the "next mod" would fix it. I've worked on various high reving Ferrari, alfa and Landis all of whom use auto damped tensioners!! Who really knows?????? We need a direct line to CABC!

Thanks snowrs...do you mean Nissan 200....I had a 300 zx twin turbo years ago (fantastic machine...some to rag stole it and burnt it) and that was a v6 with a single cambelt 6 yards long! 

Link to post
Share on other sites
4 hours ago, snowrx said:

If I remember, the T104RB was specified for the 300ZX Nissan engine.  The 133 tooth count was the same in a cross-reference, 

how wide is that blue gates belt? 

Link to post
Share on other sites
8 hours ago, PrecisionMike said:

Thanks snowrs...do you mean Nissan 200....I had a 300 zx twin turbo years ago (fantastic machine...some to rag stole it and burnt it) and that was a v6 with a single cambelt 6 yards long! 

I thought the same thing, kinda short for a V6; but the listing showed 300x, 200zx, Pathfinder, Maxima, Quest, D21, Infiniti M40 all starting about 1994 with a 3.0 6cyl using that belt size.

Link to post
Share on other sites
On 08/03/2021 at 18:01, drdoom said:

Consideration of harmonics compounding components flexing may be in order. Would the risk of jumped teeth be reduced with use of the fixed tensioner, that having precluded opportunity for crank flex permitting the belt to elude the auto-adjust process at certain RPM? As I see it the fundamental theory of a synchronous ( i.e.toothed ) belt system amounts to a low inertia geartrain, thereby eliminating one potential contributor to disharmony between the synchronised components. Pretty deep water for my level of education, I'll admit. 

Spot on! As a mechanical engineer but not an expert in vibration and harmonics this is the root of the matter. There are two scenarios to design for a) the harmonics and resonance that may cause excessive deflection in belt runs and b) the loss of tension caused by counter clockwise rotation which can occur during engine switch off. Where there is a potential for resonance, dampers are usually employed and for the kick back situation I observe that many tensioners in high reving motorcycle engines often have a one way device which allows forward motion of the tensioner but limited reward motion. As an expreiment I've rotated my engine backwards through 10 degrees and it is shocking how the tension on the drive side disappears, leaving the belt slack for the next engine start event. If that slack is not enough to cause belt creep ( which it appears not to be) then it's not an issue. For that situation, the fixed tensioner is theoretically better .....Its all a compromise and the point has been well made here that overthinking the issue is a real danger and that for well maintained set ups both solutions are ok.

I do observe from work on various "modern" machinery with a cam belt however,  that the use of hydraulically damped spring loaded tensioners seem common.

 

  • Like 1
Link to post
Share on other sites

Join the conversation

You can post now and register later. If you have an account, sign in now to post with your account.

Guest
Reply to this topic...

×   Pasted as rich text.   Paste as plain text instead

  Only 75 emoji are allowed.

×   Your link has been automatically embedded.   Display as a link instead

×   Your previous content has been restored.   Clear editor

×   You cannot paste images directly. Upload or insert images from URL.



Upgrade today to remove Google ads and support TLF.


×
×
  • Create New...