How Do You Calculate an Extension Spring's Load?
Pono ʻoe i kahi pūnāwai e huki me ka ikaika kikoʻī, aka, ua pau kou helu ana. ʻO nā ʻāpana ke ʻike ʻole ʻia a paʻa paha, a pilikia ʻoe i kahi hoʻolālā i hilinaʻi ʻole a hāʻule loa paha.
Ua helu ʻia ka haʻawe holoʻokoʻa o kahi pūnāwai hoʻonui me kēia ʻano: Haawe = (Ka helu puna × ka mamao hele) + ʻO ka hoʻomau mua[^1]n](https://www.acxesspring.com/initial-tension-in-extension-springs.html?srsltid=AfmBOoqIOZdbYGa2dxloEt1N1MVBsBVWbRRAne-8F6W4-_GoP9_Vgr3o)[^2]. ʻO kēia ke kumu o ka ikaika mai ka hoʻopololei ʻana a me ka ikaika i hoʻokomo mua ʻia i loko o ka pūnāwai.
I koʻu 14 makahiki o ke kōkua ʻana i nā ʻenekinia e hoʻolālā i nā punawai maʻamau, ʻO ke kumu maʻamau o ka hewa ʻo ka poina ʻana i kekahi ʻāpana o ia ʻano maʻalahi. Nui ka poʻe e nānā wale ana i ka nui o ka puna a me ka lōʻihi o ka lōʻihi, hoʻowahāwahā loa i ka haʻalulu mua. ʻO kēia ikaika huna ʻo ia ka ʻokoʻa ma waena o kahi mīkini e manaʻo e pane a me ka mea i manaʻo ʻole ʻia a maʻalahi. E wehewehe mākou pehea e loaʻa ai kēia helu i kēlā me kēia manawa.
What's the Fundamental Formula for Spring Load?
Ua helu ʻoe i ka ikaika me ka hoʻohana wale ʻana i ka helu puna a me ka mamao. I kēia manawa, ʻoi aku ka ikaika o kāu prototype kino e hana ma mua o kāu i manaʻo ai, e hoolei ana i kou manao holookoa.
ʻO ke kumu kūpono Haawe = (Ka helu puna × huakaʻi) + ʻO ka hoʻomau mua. Pono ʻoe e hoʻohui i ka hoʻomaka mua-hoʻouka (ʻO ka hoʻomau mua) i ka ikaika i hanaia ma ke kikoo ana (Ka helu puna × huakaʻi) e imi i ka ikaika holookoa maoli.
Ke hoʻomanaʻo nei au i ka hana ʻana me kahi hoʻomaka e hoʻomohala ana i kahi ʻāpana hana hoʻoikaika kino. ʻO kā lākou hoʻolālā i hilinaʻi i kahi puna e hāʻawi ai i kahi maʻalahi, hoʻonui kūʻē. He weliweli ko lākou mau prototypes mua. Aia kahi "wahi make" i ka hoʻomaka ʻana o ka huki ʻana ma mua o ke kū ʻana o kekahi kūʻē maoli. Ua poina loa iā lākou e pili ana i ka haʻalulu mua i kā lākou helu ʻana. Ua helu wale lākou i ka helu puna. Ua hoʻolālā hou mākou i ka pūnāwai me kahi waiwai hoʻopaʻapaʻa mua. Ua hōʻoia kēia i ka mea hoʻohana i ke kū'ē koke, a ʻo ka nui o ka ukana ma ka hoʻonui piha ʻana i kūpono i kā lākou pahuhopu. ʻO kēlā hoʻololi hoʻokahi i manaʻo ai ka huahana i ka ʻoihana a me ke kūlana kiʻekiʻe.
Nā Kiʻi ʻekolu
E helu i ka ukana, pono ʻoe e hoʻomaopopo i ʻekolu mau waiwai like ʻole. He kuleana koʻikoʻi kēlā me kēia i ka hana hope o ka puna.
- Kāleka kōkuhi (k)[^ 3]: This is the spring's stiffness, ana i ka ikaika no ka wae o ka mamao (E.g., lbs/inihi a i ʻole N/mm). Hōʻike ia iā ʻoe i ka nui o ka ikaika hou e pono ai no kēlā me kēia ʻīniha a i ʻole millimeter āu e hohola ai i ka pūnāwai.
- Huahele (X)[^4]: ʻO kēia ka lōʻihi o ka pūnāwai mai kona hoʻomaha ʻana, aiʻole "noa," lōʻihi.
- ʻO ka hoʻomau mua[^ 2] (IT): ʻO kēia ka ikaika i hoʻopili ʻia i ka pūnāwai i ka wā hana. It's the load you must apply just to separate the coils before it even starts to stretch.
| Hoʻololi | hōʻailona | wehewehe |
|---|---|---|
| Kāleka kōkuhi | k | ʻO ka ʻoʻoleʻa o ka pūnāwai. |
| Ka mamao hele | X | Pehea ka lōʻihi o ka pūnāwai mai kona lōʻihi manuahi. |
| ʻO ka hoʻomau mua[^ 2] | IT | 'Ōlelo ikaika i kau mua ʻia[^5] e paa ana i na wili i ka hoomaha. |
No ke aha ʻO ka hoʻomau mua[^ 2] ka hewa mau loa?
Your spring isn't engaging when you need it to. Aia kahi lag i ʻike ʻia ma mua o ka hoʻomaka ʻana e huki, ʻo ia ke kumu o ke ʻano kūlike ʻole i kāu hui mechanical[^6].
ʻO kēia lag ma muli o ka haʻahaʻa haʻahaʻa a i ʻole ka helu kuhi mua ʻana. ʻO kēia ikaika pre-loading ka mea hoʻololi pinepine i nānā ʻole ʻia, akā naʻe, hoʻoholo ia i ka ukana e pono ai ma mua o ka hoʻomaka ʻana o ka pūnāwai, directly impacting the system's responsiveness.
One of the clearest examples I've seen was for a simple screen door closer. A hardware company came to us because their new door closers weren't working. The doors wouldn't fully latch shut. The spring they designed had a strong enough spring rate, but it had almost no initial tension. This meant that for the last few inches of travel, as the spring got shorter, the load dropped to almost zero. There was no final "snap" to pull the door into the latch. We manufactured a new spring with the same rate but added a significant amount of initial tension. That small change provided the constant pull needed to latch the door securely every time.
Where Initial Tension Comes From
Initial tension is not an accident; it is a feature intentionally created during the manufacturing process.
- ʻO ke Kaʻina wili: As the spring wire is being coiled on a machine, it is twisted slightly. ʻO kēia torsional stress[^7] ʻo ia ka mea e kaomi paʻa ai nā ʻōwili i kekahi i kekahi.
- Hana: Pono kēia ikaika i kūkulu ʻia no nā noi he nui. Mālama ʻo ia i nā hui, pale i ka haʻalulu mai ka haʻalulu, a hōʻoiaʻiʻo a paʻa paʻa ka mīkini[^8] ma kona kulana hoomaha. ʻO ka huina ikaika o kāu pūnāwai ʻo ia ka huina o kēia ikaika mua a me ka ikaika mai ka hohola ʻana.
| Aspect | He Puna me ke Kiekie Kiekie | He Puna me ka Haahaa ʻO ka hoʻomau mua[^ 2] |
|---|---|---|
| I ka hoomaha | Paʻa paʻa loa nā ʻōwili. | Hoʻopā ʻia nā wili akā maʻalahi ka hoʻokaʻawale ʻana. |
| Huki Hoʻomaka | Pono ka ikaika nui no ka hoʻomaka ʻana e hoʻopololei. | Pono liʻiliʻi ka ikaika no ka hoʻomaka ʻana i ke kikoo. |
| Hoʻohana maʻamau | Pani puka, trampolines, ʻōnaehana hiki ke hoʻihoʻi ʻia. | Nā mea kani paʻakikī, ʻōnaehana hoʻohālikelike. |
Pehea ʻoe e hoʻopili ai i ke kumu hoʻohālike i kahi pilikia o ka honua maoli?
Me he mea lā ʻaʻole maopopo. You're not confident about how to plug in your own numbers and get a reliable answer for your specific application, hoʻopaneʻe i kāu papahana.
Hiki iā ʻoe ke hoʻohana i ke ʻano ma kahi maʻalahi, kaʻina hana ʻanuʻu. Ka mua, define your spring's properties (uku, haʻalulu mua, lōʻihi lōʻihi). A laila, e hoʻoholo i kou lōʻihi hana e helu i ka huakaʻi. ʻO ka hope loa, e hoʻokomo i kēia mau waiwai i loko o ke ʻano.
Ua hana pū mākou me kahi ʻenekinia kaʻa e hoʻolālā ana i kahi latch i hoʻopiha ʻia i ka pūnāwai no kahi ʻāpana mīkina lima.. Ua pololei loa nā kikoʻī. Pono e paʻa ka laka akā maʻalahi hoʻi e wehe. Ua hāʻawi mai ka ʻenekinia iā mākou i ka ukana pololei a lākou e pono ai ma ke kūlana paʻa piha. Ua hoʻohana mākou i ke ʻano helu helu ukana i hope. Ua ʻike mākou i ka ukana e pono ai a me ka mamao o ka huakaʻi, no laila hiki iā mākou ke hana i hope e kuhikuhi i ka hui kūpono o ka helu puna a me ka ʻāʻī mua. ʻO kēia "design-by-calculation" Ua mālama ʻo approach i ka nui o ka hoʻāʻo a me ka hewa me nā prototypes kino a loaʻa iā lākou i ka hopena, ʻoi aku ka wikiwiki o ka hana.
He laʻana helu ʻanuʻu
Let's walk through a complete example.
E noʻonoʻo ʻoe he pūnāwai me nā kikoʻī aʻe:
- Lōʻihi lōʻihi (L₀): 2 iniha
- Kāleka kōkuhi (k)[^ 3]: 10 lbs/inihi
- ʻO ka hoʻomau mua (IT): 5 lbs
Ninau: He aha ka nui o ka ukana i ka wā e hoʻolōʻihi ʻia ai ka pūnāwai (L₁) o 6 iniha?
-
E helu i ka mamao huakaʻi (X):
Travel = Extended Length - Free Length
X = 6 inches - 2 inches = 4 inches -
E helu i ka haawe mai ke kau ana:
Load from Travel = Spring Rate × Travel
Load from Travel = 10 lbs/inch × 4 inches = 40 lbs -
E helu i ka Haawe Huina:
Total Load = Load from Travel + [Initial Tension](https://www.acxesspring.com/initial-tension-in-extension-springs.html?srsltid=AfmBOoqIOZdbYGa2dxloEt1N1MVBsBVWbRRAne-8F6W4-_GoP9_Vgr3o)[^2]
Total Load = 40 lbs + 5 lbs = 45 lbs
ʻO ka pane hope loa 45 lbs.
| ʻanuʻu | Heluhelu | Ka hopena |
|---|---|---|
| 1. Huli Huahele (X)[^4] | 6" (L₁) - 2" (L₀) |
4 inches |
| 2. E huli i ka ukana mai ka huakaʻi | 10 lbs/inch (k) * 4" (X) |
40 lbs |
| 3. E imi i ka Haawe Huina | 40 lbs + 5 lbs (IT) |
45 lbs |
Hopena
To calculate an extension spring's load, pono ʻoe e hoʻohana i ke ʻano piha. E hoʻohui mau i ka ʻāʻī mua i ka ikaika i hana ʻia e ka helu puna a huakaʻi no ka hopena pololei.
[^1]: He mea koʻikoʻi ka hoʻomaopopo ʻana i kēia ʻano kumu no ka hoʻolālā ʻana a me ka hana pono o ka puna.
[^ 2]: E aʻo pehea e pili ai ka ʻāʻī mua i ka hana puna a me ka pane ʻana i nā ʻōnaehana mechanical.
[^ 3]: E ʻike i ke ʻano o ka hopena o ka pūnāwai i ka ʻoʻoleʻa a me ka hiki ke hoʻouka o nā pūnāwai.
[^4]: ʻO ka hoʻomaopopo ʻana i ka mamao o ka huakaʻi ke kī nui e hōʻoia i ka holo pono ʻana o kāu pūnāwai.
[^5]: E ʻimi i ke koʻikoʻi o ka ikaika i hoʻouka mua ʻia i ka hoʻokō ʻana i ka ʻano punawai i makemake ʻia.
[^6]: E aʻo pehea e hiki ai i ka helu ʻana o ka hoʻoili puna pono ke hoʻonui i ka hilinaʻi o nā hui mechanical.
[^7]: He mea nui ka hoʻomaopopo ʻana i ke koʻikoʻi torsional no ka hōʻoia ʻana i ka maikaʻi a me ka hana o nā pūnāwai.
[^8]: E aʻo e pili ana i ke koʻikoʻi o nā pūnāwai i ka mālama ʻana i ka paʻa a me ka hana ʻana i nā mea hana.