Rocky Mountain Hammer 725 steel
Ok I know RM no longer makes the Hammer 29 HT. I have the last model year they made in 2009 of the geared version and I'm curious about the 725 Reynolds steel that was used for the frame...
Having had a Niner MCR9 that was made out of 853, I would say that 853 is a bit more springy where 725 feels a little stiffer. In my search on the Internets, it seems like 725 is fairly rare (which adds to the cool factor)! How does it compare to the more widely used 853?
Last edited by AK47; 10-13-2012 at 12:07 AM.
Reason: wrong steel type
753 - Heat-Treated Manganese-Molybdenum. Essentially 531 made with reduced wall thickness and heat treated to increase tensile strength. UTS: 1080-1280 MPa (70-83 Tsi, 157-186 ksi) The 753 tubeset was the first heat-treated tubeset in the race bicycle industry, based on the same alloy as 531. Used mainly in lugged and fillet-brazed framesets, Reynolds implemented a Certification procedure for builders who wished to use the tubing, as it helped builders understand the requirement to avoid overheating the thin wall tubes. Most builders used silver-brazing for the fabrication of frames, due to the low melting point, so that 753 tubing was not annealed inadvertantly.
725 - Using an industry standard alloy with mechanical properties similar to our famous 753 brand, Reynolds mandrel butt and heat-treat this alloy so that thinner walls can be used compared to non-heat-treated steels. 725 can be TIG welded and used within our "Designer Select" combinations including 853 and 631 tubes. UTS: 1080-1280 MPa, density 7.78gm/cc. Based on a 0.3% carbon steel alloy which has been heat-treated and back-tempered for increased ductility. The chromium content promotes hardenability and resistance to oxidation. The molybdenum works in conjunction with the chrome to stabilize the alloy and maintain strength after heat-treatment and in use.
853 - Seamless air-hardening heat-treated. UTS: 1250-1400 MPa, density 7.78 g/cm3. Heat-treatment to the 853 specification raises the yield strength for the entire tube, increasing dent and impact resistance. Reynolds introduced the 853 tubeset which is air-hardening, the problem of reduced strength because of overheating during brazing or welding was greatly diminished, so most builders quickly abandoned 753 in favor of the air-hardening 853.
Last edited by rockyuphill; 10-13-2012 at 06:41 AM.
Reason: added another steel type