When you click on links to various merchants on this site and make a purchase, this can result in this site earning a commission. Affiliate programs and affiliations include, but are not limited to, the eBay Partner Network.
Since this has been brought back to life, I'd like to apologize for not responding to those who have reached out to me.
I never actually got the custom component quoted. My overall concern with the project, is the total cost of the assembly (OMP tow strap + custom machined component + labor + shipping + headaches/liability/time dealing with people).
Based on the low production volume there are no savings or economy of scale for machining or on the OMP strap it self. Some rough estimates on my part put this strap at $300-500 each, which seems high, but it is the reality of the situation. I haven't done a market study or poll to see if there is a tolerable price point. Again, I did not set out to do this as business, but more of a I want this, it doesn't exist for the 997 and I can make it happen, so I did it. As some have pointed out this could also be done for the rear, which would actually be pretty cool too.
Given the community interest and the fact that I would like to give back to our RL 997 GT3 forum, I will submit this part for quote and I'll update this thread. Once I have an accurate quote, I'll be able to get a better grasp of pricing the Tow Strap Assembly.
For good measure some pics from Buttonwillow a couple of weeks ago, tow strap is not just for "show".
Why not simply take the OEM tow hook and cut it off at the proper length and then drill and tap it for the 7/16-20 threads of the eye bolt / OMP strap assembly?? Would be cheap and relatively painless....
Definitely good thinking, and do-able. Which might be a possible solution for some here.
Some of my initial thoughts are:
Assume we use the OEM tow hook, it's some kind of steel, it's cast then machined, let's say we say saw/cut off the loop end.
1. You need to be able to hold the work piece to, cut to length and drill and tap. Unfortunately the major diameter of the knuckle threads are the largest OD on the OEM tow hook and I don't like clamping or work holding on threads (it's not accurate/concentric and not much clamping surface area). But does it need to be accurate? I'm pretty confident, that I could do it with hand drill if I really wanted to, but that's not me. Most likely anyone that would be doing this in some limited production would design/fabricate a holding fixture to do it this way.
2. You'd still need to some flats so that you could tighten one part against the other and possibly to the chassis or fabricate a Female knuckle thread (nut).
3. Tiny bit concerned about the wall thickness/material properties on the OEM tow hook, given that there was no intent to drill and tap. In the section view below, gives you an idea of what it would look like by modifying the OEM tow hook.
Bottom line is yes, it could be done, if you're willing to "hack and whack" or don't have access to machines. Depending on labor rate/who is doing the work, I'm not sure if it would be much cheaper than a custom threaded adapter that is CNC machined.
Providing/selling the adapter is probably the cheapest and easiest thing that I could do and leave it up to the individual to source the OMP tow strap, disassemble, reassemble and figure out clocking.
I officially sent out the drawing for quote today, hoping to get a price per part quote soon.
I checked the LeBlonde at the shop and 8TPI should be no problem. I might turn one of these for fun on the manual lathe..but, I also promised myself I'd never single point thread by hand again
Powerhound got me thinking...just eyeballing the OMP tow hook it appears that you might be able to cut off the existing threads and cut a new set of ACME threads on the larger OD. Or, is that material not solid?
1. You need to be able to hold the work piece to, cut to length and drill and tap. Unfortunately the major diameter of the knuckle threads are the largest OD on the OEM tow hook and I don't like clamping or work holding on threads (it's not accurate/concentric and not much clamping surface area). But does it need to be accurate? I'm pretty confident, that I could do it with hand drill if I really wanted to, but that's not me. Most likely anyone that would be doing this in some limited production would design/fabricate a holding fixture to do it this way.
Depending on the OD of the adapter you might be able to stick it in a collet. If it's too large, either a simple clamping fixture. Or, a tap some stock to accept the ACME side of your adapter.
Depending on the OD of the adapter you might be able to stick it in a collet. If it's too large, either a simple clamping fixture. Or, a tap some stock to accept the ACME side of your adapter.
You could definetly back feed it into a 5C collet. Not that I really looked too hared, but find the correct tap might be difficult. It's not a ACME thread unfortunately.
Originally Posted by ngng
I checked the LeBlonde at the shop and 8TPI should be no problem. I might turn one of these for fun on the manual lathe..but, I also promised myself I'd never single point thread by hand again
Powerhound got me thinking...just eyeballing the OMP tow hook it appears that you might be able to cut off the existing threads and cut a new set of ACME threads on the larger OD. Or, is that material not solid?
To make it the right length I think you'd need to cut of the existing male threads and then also cut off the 7/16 threaded portion. At that point, just make your own part. Again, some 3rd party companies are cutting male ACME threads for these tow hooks, which appear to engage and work with the threads to some extent, but OEM is not an ACME profile. ACME is 29° and square profile, DIN 405 is 30° and round profile. Yeah, the cutting loads on the tool for ACME or DIN 405 are pretty big, doing it without power feed might be really challenging.
Yeah, I need to buy the insert but it's not high on my list of things to do. Just got a Bridgeport for the shop that needs to be set up and I have Cup tow hooks already 🤣
To add to this thread, I just installed a tow strap made for BMWs by Turner Motorsports. It's beautifully machined from a single billet piece of steel and uses the same oddball 20 x 1/8 thread as Porsche uses. For the rear the 55mm (on a 996 anyway) works perfect for the OEM bumper. They also sell a 75mm version but judging by the picture in post #25 the 55mm version I used would be the perfect length in the front. I folded the strap over for a more compact set up and secured it with a zip tie which can be quickly pulled off if needed. One could also sew on a small patch of velcro instead to fold it up onto itself like the OMP one. In any case, for the $90 I spent on this it can't be beat and the quality is top notch. Of course for the purists, it doesn't have the OMP logo.....
05-21-2021, 02:55 PM
